Allow non-existing instances when appropriate

5 files changed, 252 insertions, 205 deletions

diff --git a/config-model-api/abi-spec.json b/config-model-api/abi-spec.json
index 315b03c301a..d08cda06e5d 100644
--- a/config-model-api/abi-spec.json
+++ b/config-model-api/abi-spec.json
@@ -329,7 +329,7 @@
       "public"
     ],
     "methods": [
-      "public void <init>(java.util.List, java.util.Optional, java.lang.String)",
+      "public void <init>(java.util.List, java.util.Optional, java.util.Optional, java.util.Optional, java.lang.String)",
       "public void <init>(java.util.Optional, com.yahoo.config.application.api.DeploymentSpec$UpgradePolicy, java.util.Optional, java.util.List, java.util.List, java.lang.String, java.util.Optional, java.util.Optional, com.yahoo.config.application.api.Notifications, java.util.List)",
       "public java.util.Optional globalServiceId()",
       "public com.yahoo.config.application.api.DeploymentSpec$UpgradePolicy upgradePolicy()",
@@ -341,12 +341,12 @@
       "public java.util.List zones()",
       "public java.util.Optional athenzDomain()",
       "public java.util.Optional athenzService(com.yahoo.config.provision.Environment, com.yahoo.config.provision.RegionName)",
+      "public java.util.Optional athenzService(com.yahoo.config.provision.InstanceName, com.yahoo.config.provision.Environment, com.yahoo.config.provision.RegionName)",
       "public com.yahoo.config.application.api.Notifications notifications()",
       "public java.util.List endpoints()",
       "public java.lang.String xmlForm()",
       "public boolean includes(com.yahoo.config.provision.Environment, java.util.Optional)",
-      "public com.yahoo.config.application.api.DeploymentInstanceSpec instance(java.lang.String)",
-      "public com.yahoo.config.application.api.DeploymentInstanceSpec instance(com.yahoo.config.provision.InstanceName)",
+      "public java.util.Optional instance(com.yahoo.config.provision.InstanceName)",
       "public com.yahoo.config.application.api.DeploymentInstanceSpec requireInstance(java.lang.String)",
       "public com.yahoo.config.application.api.DeploymentInstanceSpec requireInstance(com.yahoo.config.provision.InstanceName)",
       "public java.util.List instances()",
diff --git a/config-model-api/src/main/java/com/yahoo/config/application/api/DeploymentSpec.java b/config-model-api/src/main/java/com/yahoo/config/application/api/DeploymentSpec.java
index 71af050174b..9b0454cffee 100644
--- a/config-model-api/src/main/java/com/yahoo/config/application/api/DeploymentSpec.java
+++ b/config-model-api/src/main/java/com/yahoo/config/application/api/DeploymentSpec.java
@@ -47,11 +47,18 @@ public class DeploymentSpec {
                                                                   List.of());
 
     private final List<Step> steps;
+
+    // Attributes which can be set on the root tag and which must be available outside of any particular instance
     private final Optional<Integer> majorVersion;
+    private final Optional<AthenzDomain> athenzDomain;
+    private final Optional<AthenzService> athenzService;
+
     private final String xmlForm;
 
     public DeploymentSpec(List<Step> steps,
                           Optional<Integer> majorVersion,
+                          Optional<AthenzDomain> athenzDomain,
+                          Optional<AthenzService> athenzService,
                           String xmlForm) {
         if (singleInstance(steps)) { // TODO: Remove this clause after November 2019
             var singleInstance = (DeploymentInstanceSpec)steps.get(0);
@@ -61,6 +68,8 @@ public class DeploymentSpec {
             this.steps = List.copyOf(completeSteps(steps));
         }
         this.majorVersion = majorVersion;
+        this.athenzDomain = athenzDomain;
+        this.athenzService = athenzService;
         this.xmlForm = xmlForm;
         validateTotalDelay(steps);
     }
@@ -81,6 +90,8 @@ public class DeploymentSpec {
                                                 notifications,
                                                 endpoints)),
              majorVersion,
+             athenzDomain,
+             athenzService,
              xmlForm);
     }
 
@@ -137,7 +148,7 @@ public class DeploymentSpec {
     }
 
     // TODO: Remove after October 2019
-    private DeploymentInstanceSpec defaultInstance() {
+    private DeploymentInstanceSpec singleInstance() {
         if (singleInstance(steps)) return (DeploymentInstanceSpec)steps.get(0);
         throw new IllegalArgumentException("This deployment spec does not support the legacy API " +
                                            "as it has multiple instances: " +
@@ -145,56 +156,74 @@ public class DeploymentSpec {
     }
 
     // TODO: Remove after October 2019
-    public Optional<String> globalServiceId() { return defaultInstance().globalServiceId(); }
+    public Optional<String> globalServiceId() { return singleInstance().globalServiceId(); }
 
     // TODO: Remove after October 2019
-    public UpgradePolicy upgradePolicy() { return defaultInstance().upgradePolicy(); }
+    public UpgradePolicy upgradePolicy() { return singleInstance().upgradePolicy(); }
 
     /** Returns the major version this application is pinned to, or empty (default) to allow all major versions */
     public Optional<Integer> majorVersion() { return majorVersion; }
 
     // TODO: Remove after November 2019
-    public boolean canUpgradeAt(Instant instant) { return defaultInstance().canUpgradeAt(instant); }
+    public boolean canUpgradeAt(Instant instant) { return singleInstance().canUpgradeAt(instant); }
 
     // TODO: Remove after November 2019
-    public boolean canChangeRevisionAt(Instant instant) { return defaultInstance().canChangeRevisionAt(instant); }
+    public boolean canChangeRevisionAt(Instant instant) { return singleInstance().canChangeRevisionAt(instant); }
 
     // TODO: Remove after November 2019
-    public List<ChangeBlocker> changeBlocker() { return defaultInstance().changeBlocker(); }
+    public List<ChangeBlocker> changeBlocker() { return singleInstance().changeBlocker(); }
 
     /** Returns the deployment steps of this in the order they will be performed */
     public List<Step> steps() {
-        if (singleInstance(steps)) return defaultInstance().steps(); // TODO: Remove line after November 2019
+        if (singleInstance(steps)) return singleInstance().steps(); // TODO: Remove line after November 2019
         return steps;
     }
 
     // TODO: Remove after November 2019
     public List<DeclaredZone> zones() {
-        return defaultInstance().steps().stream()
-                                       .flatMap(step -> step.zones().stream())
-                                       .collect(Collectors.toList());
+        return singleInstance().steps().stream()
+                               .flatMap(step -> step.zones().stream())
+                               .collect(Collectors.toList());
     }
 
-    // TODO: Remove after November 2019
-    public Optional<AthenzDomain> athenzDomain() { return defaultInstance().athenzDomain(); }
+    /** Returns the Athenz domain set on the root tag, if any */
+    public Optional<AthenzDomain> athenzDomain() { return athenzDomain; }
 
+    /** Returns the Athenz service to use for the given environment and region, if any */
     // TODO: Remove after November 2019
     public Optional<AthenzService> athenzService(Environment environment, RegionName region) {
-        return defaultInstance().athenzService(environment, region);
+        Optional<AthenzService> service = Optional.empty();
+        if (singleInstance(steps))
+            service = singleInstance().athenzService(environment, region);
+        if (service.isPresent())
+            return service;
+        return this.athenzService;
+    }
+
+    /**
+     * Returns the Athenz service to use for the given instance, environment and region, if any.
+     * This returns the default set on  the deploy tag (if any) if nothing is set for this particular
+     * combination of instance, environment and region, and also if that combination is not specified
+     * at all in services.
+     */
+    public Optional<AthenzService> athenzService(InstanceName instanceName, Environment environment, RegionName region) {
+        Optional<DeploymentInstanceSpec> instance = instance(instanceName);
+        if (instance.isEmpty()) return this.athenzService;
+        return instance.get().athenzService(environment, region).or(() -> this.athenzService);
     }
 
     // TODO: Remove after November 2019
-    public Notifications notifications() { return defaultInstance().notifications(); }
+    public Notifications notifications() { return singleInstance().notifications(); }
 
     // TODO: Remove after November 2019
-    public List<Endpoint> endpoints() { return defaultInstance().endpoints(); }
+    public List<Endpoint> endpoints() { return singleInstance().endpoints(); }
 
     /** Returns the XML form of this spec, or null if it was not created by fromXml, nor is empty */
     public String xmlForm() { return xmlForm; }
 
     // TODO: Remove after November 2019
     public boolean includes(Environment environment, Optional<RegionName> region) {
-        return defaultInstance().deploysTo(environment, region);
+        return singleInstance().deploysTo(environment, region);
     }
 
     // TODO: Remove after November 2019
@@ -202,31 +231,25 @@ public class DeploymentSpec {
         return steps.size() == 1 && steps.get(0) instanceof DeploymentInstanceSpec;
     }
 
-    /** Returns the instance step containing the given instance name, or null if not present */
-    public DeploymentInstanceSpec instance(String name) {
-        return instance(InstanceName.from(name));
-    }
-
-    /** Returns the instance step containing the given instance name, or null if not present */
-    public DeploymentInstanceSpec instance(InstanceName name) {
+    /** Returns the instance step containing the given instance name */
+    public Optional<DeploymentInstanceSpec> instance(InstanceName name) {
         for (DeploymentInstanceSpec instance : instances()) {
             if (instance.name().equals(name))
-                return instance;
+                return Optional.of(instance);
         }
-        return null;
+        return Optional.empty();
     }
 
-    /** Returns the instance step containing the given instance name, or throws an IllegalArgumentException if not present */
     public DeploymentInstanceSpec requireInstance(String name) {
         return requireInstance(InstanceName.from(name));
     }
 
     public DeploymentInstanceSpec requireInstance(InstanceName name) {
-        DeploymentInstanceSpec instance = instance(name);
-        if (instance == null)
+        Optional<DeploymentInstanceSpec> instance = instance(name);
+        if (instance.isEmpty())
             throw new IllegalArgumentException("No instance '" + name + "' in deployment.xml'. Instances: " +
                                                instances().stream().map(spec -> spec.name().toString()).collect(Collectors.joining(",")));
-        return instance;
+        return instance.get();
     }
 
     /** Returns the steps of this which are instances */
diff --git a/config-model-api/src/main/java/com/yahoo/config/application/api/xml/DeploymentSpecXmlReader.java b/config-model-api/src/main/java/com/yahoo/config/application/api/xml/DeploymentSpecXmlReader.java
index cb645813290..59b31985376 100644
--- a/config-model-api/src/main/java/com/yahoo/config/application/api/xml/DeploymentSpecXmlReader.java
+++ b/config-model-api/src/main/java/com/yahoo/config/application/api/xml/DeploymentSpecXmlReader.java
@@ -108,6 +108,8 @@ public class DeploymentSpecXmlReader {
 
         return new DeploymentSpec(steps,
                                   optionalIntegerAttribute(majorVersionTag, root),
+                                  stringAttribute(athenzDomainAttribute, root).map(AthenzDomain::from),
+                                  stringAttribute(athenzServiceAttribute, root).map(AthenzService::from),
                                   xmlForm);
     }
 
diff --git a/config-model-api/src/test/java/com/yahoo/config/application/api/DeploymentSpecTest.java b/config-model-api/src/test/java/com/yahoo/config/application/api/DeploymentSpecTest.java
index b75801de7ea..c6035ac8d46 100644
--- a/config-model-api/src/test/java/com/yahoo/config/application/api/DeploymentSpecTest.java
+++ b/config-model-api/src/test/java/com/yahoo/config/application/api/DeploymentSpecTest.java
@@ -3,6 +3,7 @@ package com.yahoo.config.application.api;
 
 import com.google.common.collect.ImmutableSet;
 import com.yahoo.config.provision.Environment;
+import com.yahoo.config.provision.InstanceName;
 import com.yahoo.config.provision.RegionName;
 import org.junit.Test;
 
@@ -39,14 +40,14 @@ public class DeploymentSpecTest {
         StringReader r = new StringReader(specXml);
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
         assertEquals(specXml, spec.xmlForm());
-        assertEquals(1, spec.instance("default").steps().size());
+        assertEquals(1, spec.requireInstance("default").steps().size());
         assertFalse(spec.majorVersion().isPresent());
-        assertTrue(spec.instance("default").steps().get(0).deploysTo(Environment.test));
-        assertTrue(spec.instance("default").includes(Environment.test, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
-        assertFalse(spec.instance("default").includes(Environment.staging, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.prod, Optional.empty()));
-        assertFalse(spec.instance("default").globalServiceId().isPresent());
+        assertTrue(spec.requireInstance("default").steps().get(0).deploysTo(Environment.test));
+        assertTrue(spec.requireInstance("default").includes(Environment.test, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
+        assertFalse(spec.requireInstance("default").includes(Environment.staging, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.prod, Optional.empty()));
+        assertFalse(spec.requireInstance("default").globalServiceId().isPresent());
     }
 
     @Test
@@ -60,7 +61,7 @@ public class DeploymentSpecTest {
         StringReader r = new StringReader(specXml);
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
         assertEquals(specXml, spec.xmlForm());
-        assertEquals(1, spec.instance("default").steps().size());
+        assertEquals(1, spec.requireInstance("default").steps().size());
         assertTrue(spec.majorVersion().isPresent());
         assertEquals(6, (int)spec.majorVersion().get());
     }
@@ -76,14 +77,14 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(2, spec.instance("default").steps().size());
-        assertTrue(spec.instance("default").steps().get(0).deploysTo(Environment.test));
-        assertTrue(spec.instance("default").steps().get(1).deploysTo(Environment.staging));
-        assertTrue(spec.instance("default").includes(Environment.test, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
-        assertTrue(spec.instance("default").includes(Environment.staging, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.prod, Optional.empty()));
-        assertFalse(spec.instance("default").globalServiceId().isPresent());
+        assertEquals(2, spec.requireInstance("default").steps().size());
+        assertTrue(spec.requireInstance("default").steps().get(0).deploysTo(Environment.test));
+        assertTrue(spec.requireInstance("default").steps().get(1).deploysTo(Environment.staging));
+        assertTrue(spec.requireInstance("default").includes(Environment.test, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
+        assertTrue(spec.requireInstance("default").includes(Environment.staging, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.prod, Optional.empty()));
+        assertFalse(spec.requireInstance("default").globalServiceId().isPresent());
     }
 
     @Test
@@ -100,27 +101,27 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(4, spec.instance("default").steps().size());
+        assertEquals(4, spec.requireInstance("default").steps().size());
 
-        assertTrue(spec.instance("default").steps().get(0).deploysTo(Environment.test));
+        assertTrue(spec.requireInstance("default").steps().get(0).deploysTo(Environment.test));
 
-        assertTrue(spec.instance("default").steps().get(1).deploysTo(Environment.staging));
+        assertTrue(spec.requireInstance("default").steps().get(1).deploysTo(Environment.staging));
 
-        assertTrue(spec.instance("default").steps().get(2).deploysTo(Environment.prod, Optional.of(RegionName.from("us-east1"))));
-        assertFalse(((DeploymentSpec.DeclaredZone)spec.instance("default").steps().get(2)).active());
+        assertTrue(spec.requireInstance("default").steps().get(2).deploysTo(Environment.prod, Optional.of(RegionName.from("us-east1"))));
+        assertFalse(((DeploymentSpec.DeclaredZone)spec.requireInstance("default").steps().get(2)).active());
 
-        assertTrue(spec.instance("default").steps().get(3).deploysTo(Environment.prod, Optional.of(RegionName.from("us-west1"))));
-        assertTrue(((DeploymentSpec.DeclaredZone)spec.instance("default").steps().get(3)).active());
+        assertTrue(spec.requireInstance("default").steps().get(3).deploysTo(Environment.prod, Optional.of(RegionName.from("us-west1"))));
+        assertTrue(((DeploymentSpec.DeclaredZone)spec.requireInstance("default").steps().get(3)).active());
 
-        assertTrue(spec.instance("default").includes(Environment.test, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
-        assertTrue(spec.instance("default").includes(Environment.staging, Optional.empty()));
-        assertTrue(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("us-east1"))));
-        assertTrue(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("us-west1"))));
-        assertFalse(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("no-such-region"))));
-        assertFalse(spec.instance("default").globalServiceId().isPresent());
+        assertTrue(spec.requireInstance("default").includes(Environment.test, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
+        assertTrue(spec.requireInstance("default").includes(Environment.staging, Optional.empty()));
+        assertTrue(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("us-east1"))));
+        assertTrue(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("us-west1"))));
+        assertFalse(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("no-such-region"))));
+        assertFalse(spec.requireInstance("default").globalServiceId().isPresent());
 
-        assertEquals(DeploymentSpec.UpgradePolicy.defaultPolicy, spec.instance("default").upgradePolicy());
+        assertEquals(DeploymentSpec.UpgradePolicy.defaultPolicy, spec.requireInstance("default").upgradePolicy());
     }
 
     @Test
@@ -140,7 +141,7 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertCorrectFirstInstance(spec.instance("default"));
+        assertCorrectFirstInstance(spec.requireInstance("default"));
     }
 
     @Test
@@ -166,9 +167,9 @@ public class DeploymentSpecTest {
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
 
-        assertCorrectFirstInstance(spec.instance("instance1"));
+        assertCorrectFirstInstance(spec.requireInstance("instance1"));
 
-        DeploymentInstanceSpec instance2 = spec.instance("instance2");
+        DeploymentInstanceSpec instance2 = spec.requireInstance("instance2");
         assertEquals(1, instance2.steps().size());
         assertEquals(1, instance2.zones().size());
 
@@ -193,8 +194,8 @@ public class DeploymentSpecTest {
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
 
-        assertCorrectFirstInstance(spec.instance("instance1"));
-        assertCorrectFirstInstance(spec.instance("instance2"));
+        assertCorrectFirstInstance(spec.requireInstance("instance1"));
+        assertCorrectFirstInstance(spec.requireInstance("instance2"));
     }
 
     private void assertCorrectFirstInstance(DeploymentInstanceSpec instance) {
@@ -237,7 +238,7 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(spec.instance("default").globalServiceId(), Optional.of("query"));
+        assertEquals(spec.requireInstance("default").globalServiceId(), Optional.of("query"));
     }
 
     @Test(expected=IllegalArgumentException.class)
@@ -281,7 +282,7 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals("qrs", spec.instance("default").globalServiceId().get());
+        assertEquals("qrs", spec.requireInstance("default").globalServiceId().get());
     }
 
     @Test
@@ -300,7 +301,7 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals("canary", spec.instance("default").upgradePolicy().toString());
+        assertEquals("canary", spec.requireInstance("default").upgradePolicy().toString());
     }
 
     @Test
@@ -317,8 +318,8 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals("conservative", spec.instance("instance1").upgradePolicy().toString());
-        assertEquals("canary", spec.instance("instance2").upgradePolicy().toString());
+        assertEquals("conservative", spec.requireInstance("instance1").upgradePolicy().toString());
+        assertEquals("canary", spec.requireInstance("instance2").upgradePolicy().toString());
     }
 
     @Test
@@ -349,7 +350,7 @@ public class DeploymentSpecTest {
 
     @Test
     public void testEmpty() {
-        assertFalse(DeploymentSpec.empty.instance("default").globalServiceId().isPresent());
+        assertFalse(DeploymentSpec.empty.requireInstance("default").globalServiceId().isPresent());
         assertEquals(DeploymentSpec.UpgradePolicy.defaultPolicy, DeploymentSpec.empty.upgradePolicy());
         assertTrue(DeploymentSpec.empty.steps().isEmpty());
         assertEquals("<deployment version='1.0'/>", DeploymentSpec.empty.xmlForm());
@@ -371,7 +372,7 @@ public class DeploymentSpecTest {
                 "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        DeploymentSpec.ParallelZones parallelZones = ((DeploymentSpec.ParallelZones) spec.instance("default").steps().get(3));
+        DeploymentSpec.ParallelZones parallelZones = ((DeploymentSpec.ParallelZones) spec.requireInstance("default").steps().get(3));
         assertEquals(2, parallelZones.zones().size());
         assertEquals(RegionName.from("us-central-1"), parallelZones.zones().get(0).region().get());
         assertEquals(RegionName.from("us-east-3"), parallelZones.zones().get(1).region().get());
@@ -546,23 +547,23 @@ public class DeploymentSpecTest {
                 "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(2, spec.instance("default").changeBlocker().size());
-        assertTrue(spec.instance("default").changeBlocker().get(0).blocksVersions());
-        assertFalse(spec.instance("default").changeBlocker().get(0).blocksRevisions());
-        assertEquals(ZoneId.of("UTC"), spec.instance("default").changeBlocker().get(0).window().zone());
+        assertEquals(2, spec.requireInstance("default").changeBlocker().size());
+        assertTrue(spec.requireInstance("default").changeBlocker().get(0).blocksVersions());
+        assertFalse(spec.requireInstance("default").changeBlocker().get(0).blocksRevisions());
+        assertEquals(ZoneId.of("UTC"), spec.requireInstance("default").changeBlocker().get(0).window().zone());
 
-        assertTrue(spec.instance("default").changeBlocker().get(1).blocksVersions());
-        assertTrue(spec.instance("default").changeBlocker().get(1).blocksRevisions());
-        assertEquals(ZoneId.of("CET"), spec.instance("default").changeBlocker().get(1).window().zone());
+        assertTrue(spec.requireInstance("default").changeBlocker().get(1).blocksVersions());
+        assertTrue(spec.requireInstance("default").changeBlocker().get(1).blocksRevisions());
+        assertEquals(ZoneId.of("CET"), spec.requireInstance("default").changeBlocker().get(1).window().zone());
 
-        assertTrue(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-18T14:15:30.00Z")));
-        assertFalse(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-18T15:15:30.00Z")));
-        assertFalse(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-18T16:15:30.00Z")));
-        assertTrue(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-18T17:15:30.00Z")));
+        assertTrue(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-18T14:15:30.00Z")));
+        assertFalse(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-18T15:15:30.00Z")));
+        assertFalse(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-18T16:15:30.00Z")));
+        assertTrue(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-18T17:15:30.00Z")));
 
-        assertTrue(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-23T09:15:30.00Z")));
-        assertFalse(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-23T08:15:30.00Z"))); // 10 in CET
-        assertTrue(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-23T10:15:30.00Z")));
+        assertTrue(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-23T09:15:30.00Z")));
+        assertFalse(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-23T08:15:30.00Z"))); // 10 in CET
+        assertTrue(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-23T10:15:30.00Z")));
     }
 
     @Test
@@ -582,13 +583,13 @@ public class DeploymentSpecTest {
 
         String inheritedChangeBlocker = "change blocker revision=false version=true window=time window for hour(s) [15, 16] on [monday, tuesday] in UTC";
 
-        assertEquals(2, spec.instance("instance1").changeBlocker().size());
-        assertEquals(inheritedChangeBlocker, spec.instance("instance1").changeBlocker().get(0).toString());
+        assertEquals(2, spec.requireInstance("instance1").changeBlocker().size());
+        assertEquals(inheritedChangeBlocker, spec.requireInstance("instance1").changeBlocker().get(0).toString());
         assertEquals("change blocker revision=true version=true window=time window for hour(s) [10] on [saturday] in CET",
-                     spec.instance("instance1").changeBlocker().get(1).toString());
+                     spec.requireInstance("instance1").changeBlocker().get(1).toString());
 
-        assertEquals(1, spec.instance("instance2").changeBlocker().size());
-        assertEquals(inheritedChangeBlocker, spec.instance("instance2").changeBlocker().get(0).toString());
+        assertEquals(1, spec.requireInstance("instance2").changeBlocker().size());
+        assertEquals(inheritedChangeBlocker, spec.requireInstance("instance2").changeBlocker().get(0).toString());
     }
 
     @Test
@@ -603,8 +604,16 @@ public class DeploymentSpecTest {
                 "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(spec.instance("instance1").athenzDomain().get().value(), "domain");
-        assertEquals(spec.instance("instance1").athenzService(Environment.prod, RegionName.from("us-west-1")).get().value(), "service");
+        assertEquals("domain", spec.athenzDomain().get().value());
+        assertEquals("service", spec.athenzService(InstanceName.from("instance1"),
+                                                            Environment.prod,
+                                                            RegionName.from("us-west-1")).get().value());
+        assertEquals("service", spec.athenzService(InstanceName.from("non-existent"),
+                                                   Environment.prod,
+                                                   RegionName.from("us-west-1")).get().value());
+        assertEquals("domain", spec.requireInstance("instance1").athenzDomain().get().value());
+        assertEquals("service", spec.requireInstance("instance1").athenzService(Environment.prod,
+                                                                                         RegionName.from("us-west-1")).get().value());
     }
 
     @Test
@@ -619,8 +628,11 @@ public class DeploymentSpecTest {
                 "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(spec.instance("default").athenzDomain().get().value(), "domain");
-        assertEquals(spec.instance("default").athenzService(Environment.prod, RegionName.from("us-west-1")).get().value(), "service");
+        assertEquals(spec.requireInstance("default").athenzDomain().get().value(), "domain");
+        assertEquals(spec.requireInstance("default").athenzService(Environment.prod, RegionName.from("us-west-1")).get().value(), "service");
+        assertEquals(Optional.empty(), spec.athenzService(InstanceName.from("non-existent"),
+                                                          Environment.prod,
+                                                          RegionName.from("us-west-1")));
     }
 
     @Test
@@ -636,8 +648,18 @@ public class DeploymentSpecTest {
                 "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(spec.instance("default").athenzDomain().get().value(), "domain");
-        assertEquals(spec.instance("default").athenzService(Environment.prod, RegionName.from("us-west-1")).get().value(), "prod-service");
+        assertEquals(spec.requireInstance("default").athenzDomain().get().value(), "domain");
+        assertEquals(spec.athenzService(InstanceName.from("default"),
+                                        Environment.prod,
+                                        RegionName.from("us-west-1")).get().value(),
+                     "prod-service");
+        assertEquals(spec.requireInstance("default").athenzService(Environment.prod,
+                                                                   RegionName.from("us-west-1")).get().value(),
+                     "prod-service");
+        assertEquals(spec.athenzService(InstanceName.from("non-existent"),
+                                        Environment.prod,
+                                        RegionName.from("us-west-1")).get().value(),
+                     "service");
     }
 
     @Test(expected = IllegalArgumentException.class)
@@ -673,7 +695,7 @@ public class DeploymentSpecTest {
         assertEquals(Notifications.none(),
                      DeploymentSpec.fromXml("<deployment>" +
                                             "   <instance id='default'/>" +
-                                            "</deployment>").instance("default").notifications());
+                                            "</deployment>").requireInstance("default").notifications());
     }
 
     @Test
@@ -683,7 +705,7 @@ public class DeploymentSpecTest {
                                                      "      <notifications/>" +
                                                      "   </instance>" +
                                                      "</deployment>");
-        assertEquals(Notifications.none(), spec.instance("default").notifications());
+        assertEquals(Notifications.none(), spec.requireInstance("default").notifications());
     }
 
     @Test
@@ -697,10 +719,10 @@ public class DeploymentSpecTest {
                                                      "      </notifications>" +
                                                      "   </instance>" +
                                                      "</deployment>");
-        assertEquals(ImmutableSet.of(author), spec.instance("default").notifications().emailRolesFor(failing));
-        assertEquals(ImmutableSet.of(author), spec.instance("default").notifications().emailRolesFor(failingCommit));
-        assertEquals(ImmutableSet.of("john@dev", "jane@dev"), spec.instance("default").notifications().emailAddressesFor(failingCommit));
-        assertEquals(ImmutableSet.of("jane@dev"), spec.instance("default").notifications().emailAddressesFor(failing));
+        assertEquals(ImmutableSet.of(author), spec.requireInstance("default").notifications().emailRolesFor(failing));
+        assertEquals(ImmutableSet.of(author), spec.requireInstance("default").notifications().emailRolesFor(failingCommit));
+        assertEquals(ImmutableSet.of("john@dev", "jane@dev"), spec.requireInstance("default").notifications().emailAddressesFor(failingCommit));
+        assertEquals(ImmutableSet.of("jane@dev"), spec.requireInstance("default").notifications().emailAddressesFor(failing));
     }
 
     @Test
@@ -723,11 +745,11 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        DeploymentInstanceSpec instance1 = spec.instance("instance1");
+        DeploymentInstanceSpec instance1 = spec.requireInstance("instance1");
         assertEquals(Set.of(author), instance1.notifications().emailRolesFor(failing));
         assertEquals(Set.of("john@operator"), instance1.notifications().emailAddressesFor(failing));
 
-        DeploymentInstanceSpec instance2 = spec.instance("instance2");
+        DeploymentInstanceSpec instance2 = spec.requireInstance("instance2");
         assertEquals(Set.of(author), instance2.notifications().emailRolesFor(failingCommit));
         assertEquals(Set.of("mary@dev"), instance2.notifications().emailAddressesFor(failingCommit));
     }
@@ -752,11 +774,11 @@ public class DeploymentSpecTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        DeploymentInstanceSpec instance1 = spec.instance("instance1");
+        DeploymentInstanceSpec instance1 = spec.requireInstance("instance1");
         assertEquals(Set.of(author), instance1.notifications().emailRolesFor(failing));
         assertEquals(Set.of("john@operator"), instance1.notifications().emailAddressesFor(failing));
 
-        DeploymentInstanceSpec instance2 = spec.instance("instance2");
+        DeploymentInstanceSpec instance2 = spec.requireInstance("instance2");
         assertEquals(Set.of(author), instance2.notifications().emailRolesFor(failingCommit));
         assertEquals(Set.of("mary@dev"), instance2.notifications().emailAddressesFor(failingCommit));
     }
@@ -771,9 +793,9 @@ public class DeploymentSpecTest {
                                                      "      </prod>" +
                                                      "   </instance>" +
                                                      "</deployment>");
-        assertEquals(Optional.of("d-1-4-20"), spec.instance("default").steps().get(0).zones().get(0).testerFlavor());
-        assertEquals(Optional.empty(), spec.instance("default").steps().get(1).zones().get(0).testerFlavor());
-        assertEquals(Optional.of("d-2-8-50"), spec.instance("default").steps().get(2).zones().get(0).testerFlavor());
+        assertEquals(Optional.of("d-1-4-20"), spec.requireInstance("default").steps().get(0).zones().get(0).testerFlavor());
+        assertEquals(Optional.empty(), spec.requireInstance("default").steps().get(1).zones().get(0).testerFlavor());
+        assertEquals(Optional.of("d-2-8-50"), spec.requireInstance("default").steps().get(2).zones().get(0).testerFlavor());
     }
 
     @Test
@@ -781,7 +803,7 @@ public class DeploymentSpecTest {
         assertEquals(Collections.emptyList(),
                      DeploymentSpec.fromXml("<deployment>" +
                                             "   <instance id='default'/>" +
-                                            "</deployment>").instance("default").endpoints());
+                                            "</deployment>").requireInstance("default").endpoints());
     }
 
     @Test
@@ -791,7 +813,7 @@ public class DeploymentSpecTest {
                                           "      <endpoints/>" +
                                           "   </instance>" +
                                           "</deployment>");
-        assertEquals(Collections.emptyList(), spec.instance("default").endpoints());
+        assertEquals(Collections.emptyList(), spec.requireInstance("default").endpoints());
     }
 
     @Test
@@ -814,15 +836,15 @@ public class DeploymentSpecTest {
 
         assertEquals(
                 List.of("foo", "nalle", "default"),
-                spec.instance("default").endpoints().stream().map(Endpoint::endpointId).collect(Collectors.toList())
+                spec.requireInstance("default").endpoints().stream().map(Endpoint::endpointId).collect(Collectors.toList())
         );
 
         assertEquals(
                 List.of("bar", "frosk", "quux"),
-                spec.instance("default").endpoints().stream().map(Endpoint::containerId).collect(Collectors.toList())
+                spec.requireInstance("default").endpoints().stream().map(Endpoint::containerId).collect(Collectors.toList())
         );
 
-        assertEquals(Set.of(RegionName.from("us-east")), spec.instance("default").endpoints().get(0).regions());
+        assertEquals(Set.of(RegionName.from("us-east")), spec.requireInstance("default").endpoints().get(0).regions());
     }
 
     @Test
@@ -880,7 +902,7 @@ public class DeploymentSpecTest {
     }
 
     private static Set<String> endpointRegions(String endpointId, DeploymentSpec spec) {
-        return spec.instance("default").endpoints().stream()
+        return spec.requireInstance("default").endpoints().stream()
                 .filter(endpoint -> endpoint.endpointId().equals(endpointId))
                 .flatMap(endpoint -> endpoint.regions().stream())
                 .map(RegionName::value)
@@ -899,7 +921,7 @@ public class DeploymentSpecTest {
                   "   </instance>" +
                   "</deployment>";
 
-        return DeploymentSpec.fromXml(xml).instance("default").endpoints().stream()
+        return DeploymentSpec.fromXml(xml).requireInstance("default").endpoints().stream()
                              .map(Endpoint::endpointId)
                              .collect(Collectors.toList());
     }
diff --git a/config-model-api/src/test/java/com/yahoo/config/application/api/DeploymentSpecWithoutInstanceTest.java b/config-model-api/src/test/java/com/yahoo/config/application/api/DeploymentSpecWithoutInstanceTest.java
index 33ef3f4bea8..ad5c6375aa6 100644
--- a/config-model-api/src/test/java/com/yahoo/config/application/api/DeploymentSpecWithoutInstanceTest.java
+++ b/config-model-api/src/test/java/com/yahoo/config/application/api/DeploymentSpecWithoutInstanceTest.java
@@ -40,11 +40,11 @@ public class DeploymentSpecWithoutInstanceTest {
         assertEquals(1, spec.steps().size());
         assertFalse(spec.majorVersion().isPresent());
         assertTrue(spec.steps().get(0).deploysTo(Environment.test));
-        assertTrue(spec.instance("default").includes(Environment.test, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
-        assertFalse(spec.instance("default").includes(Environment.staging, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.prod, Optional.empty()));
-        assertFalse(spec.instance("default").globalServiceId().isPresent());
+        assertTrue(spec.requireInstance("default").includes(Environment.test, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
+        assertFalse(spec.requireInstance("default").includes(Environment.staging, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.prod, Optional.empty()));
+        assertFalse(spec.requireInstance("default").globalServiceId().isPresent());
     }
 
     @Test
@@ -71,13 +71,13 @@ public class DeploymentSpecWithoutInstanceTest {
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
         assertEquals(2, spec.steps().size());
-        assertTrue(spec.instance("default").steps().get(0).deploysTo(Environment.test));
-        assertTrue(spec.instance("default").steps().get(1).deploysTo(Environment.staging));
-        assertTrue(spec.instance("default").includes(Environment.test, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
-        assertTrue(spec.instance("default").includes(Environment.staging, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.prod, Optional.empty()));
-        assertFalse(spec.instance("default").globalServiceId().isPresent());
+        assertTrue(spec.requireInstance("default").steps().get(0).deploysTo(Environment.test));
+        assertTrue(spec.requireInstance("default").steps().get(1).deploysTo(Environment.staging));
+        assertTrue(spec.requireInstance("default").includes(Environment.test, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
+        assertTrue(spec.requireInstance("default").includes(Environment.staging, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.prod, Optional.empty()));
+        assertFalse(spec.requireInstance("default").globalServiceId().isPresent());
     }
 
     @Test
@@ -92,27 +92,27 @@ public class DeploymentSpecWithoutInstanceTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(4, spec.instance("default").steps().size());
+        assertEquals(4, spec.requireInstance("default").steps().size());
 
-        assertTrue(spec.instance("default").steps().get(0).deploysTo(Environment.test));
+        assertTrue(spec.requireInstance("default").steps().get(0).deploysTo(Environment.test));
 
-        assertTrue(spec.instance("default").steps().get(1).deploysTo(Environment.staging));
+        assertTrue(spec.requireInstance("default").steps().get(1).deploysTo(Environment.staging));
 
-        assertTrue(spec.instance("default").steps().get(2).deploysTo(Environment.prod, Optional.of(RegionName.from("us-east1"))));
-        assertFalse(((DeploymentSpec.DeclaredZone)spec.instance("default").steps().get(2)).active());
+        assertTrue(spec.requireInstance("default").steps().get(2).deploysTo(Environment.prod, Optional.of(RegionName.from("us-east1"))));
+        assertFalse(((DeploymentSpec.DeclaredZone)spec.requireInstance("default").steps().get(2)).active());
 
-        assertTrue(spec.instance("default").steps().get(3).deploysTo(Environment.prod, Optional.of(RegionName.from("us-west1"))));
-        assertTrue(((DeploymentSpec.DeclaredZone)spec.instance("default").steps().get(3)).active());
+        assertTrue(spec.requireInstance("default").steps().get(3).deploysTo(Environment.prod, Optional.of(RegionName.from("us-west1"))));
+        assertTrue(((DeploymentSpec.DeclaredZone)spec.requireInstance("default").steps().get(3)).active());
 
-        assertTrue(spec.instance("default").includes(Environment.test, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
-        assertTrue(spec.instance("default").includes(Environment.staging, Optional.empty()));
-        assertTrue(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("us-east1"))));
-        assertTrue(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("us-west1"))));
-        assertFalse(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("no-such-region"))));
-        assertFalse(spec.instance("default").globalServiceId().isPresent());
+        assertTrue(spec.requireInstance("default").includes(Environment.test, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
+        assertTrue(spec.requireInstance("default").includes(Environment.staging, Optional.empty()));
+        assertTrue(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("us-east1"))));
+        assertTrue(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("us-west1"))));
+        assertFalse(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("no-such-region"))));
+        assertFalse(spec.requireInstance("default").globalServiceId().isPresent());
         
-        assertEquals(DeploymentSpec.UpgradePolicy.defaultPolicy, spec.instance("default").upgradePolicy());
+        assertEquals(DeploymentSpec.UpgradePolicy.defaultPolicy, spec.requireInstance("default").upgradePolicy());
     }
 
     @Test
@@ -130,29 +130,29 @@ public class DeploymentSpecWithoutInstanceTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(5, spec.instance("default").steps().size());
-        assertEquals(4, spec.instance("default").zones().size());
+        assertEquals(5, spec.requireInstance("default").steps().size());
+        assertEquals(4, spec.requireInstance("default").zones().size());
 
-        assertTrue(spec.instance("default").steps().get(0).deploysTo(Environment.test));
+        assertTrue(spec.requireInstance("default").steps().get(0).deploysTo(Environment.test));
 
-        assertTrue(spec.instance("default").steps().get(1).deploysTo(Environment.staging));
+        assertTrue(spec.requireInstance("default").steps().get(1).deploysTo(Environment.staging));
 
-        assertTrue(spec.instance("default").steps().get(2).deploysTo(Environment.prod, Optional.of(RegionName.from("us-east1"))));
-        assertFalse(((DeploymentSpec.DeclaredZone)spec.instance("default").steps().get(2)).active());
+        assertTrue(spec.requireInstance("default").steps().get(2).deploysTo(Environment.prod, Optional.of(RegionName.from("us-east1"))));
+        assertFalse(((DeploymentSpec.DeclaredZone)spec.requireInstance("default").steps().get(2)).active());
 
-        assertTrue(spec.instance("default").steps().get(3) instanceof DeploymentSpec.Delay);
-        assertEquals(3 * 60 * 60 + 30 * 60, spec.instance("default").steps().get(3).delay().getSeconds());
+        assertTrue(spec.requireInstance("default").steps().get(3) instanceof DeploymentSpec.Delay);
+        assertEquals(3 * 60 * 60 + 30 * 60, spec.requireInstance("default").steps().get(3).delay().getSeconds());
 
-        assertTrue(spec.instance("default").steps().get(4).deploysTo(Environment.prod, Optional.of(RegionName.from("us-west1"))));
-        assertTrue(((DeploymentSpec.DeclaredZone)spec.instance("default").steps().get(4)).active());
+        assertTrue(spec.requireInstance("default").steps().get(4).deploysTo(Environment.prod, Optional.of(RegionName.from("us-west1"))));
+        assertTrue(((DeploymentSpec.DeclaredZone)spec.requireInstance("default").steps().get(4)).active());
 
-        assertTrue(spec.instance("default").includes(Environment.test, Optional.empty()));
-        assertFalse(spec.instance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
-        assertTrue(spec.instance("default").includes(Environment.staging, Optional.empty()));
-        assertTrue(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("us-east1"))));
-        assertTrue(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("us-west1"))));
-        assertFalse(spec.instance("default").includes(Environment.prod, Optional.of(RegionName.from("no-such-region"))));
-        assertFalse(spec.instance("default").globalServiceId().isPresent());
+        assertTrue(spec.requireInstance("default").includes(Environment.test, Optional.empty()));
+        assertFalse(spec.requireInstance("default").includes(Environment.test, Optional.of(RegionName.from("region1"))));
+        assertTrue(spec.requireInstance("default").includes(Environment.staging, Optional.empty()));
+        assertTrue(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("us-east1"))));
+        assertTrue(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("us-west1"))));
+        assertFalse(spec.requireInstance("default").includes(Environment.prod, Optional.of(RegionName.from("no-such-region"))));
+        assertFalse(spec.requireInstance("default").globalServiceId().isPresent());
     }
 
     @Test
@@ -167,7 +167,7 @@ public class DeploymentSpecWithoutInstanceTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(spec.instance("default").globalServiceId(), Optional.of("query"));
+        assertEquals(spec.requireInstance("default").globalServiceId(), Optional.of("query"));
     }
 
     @Test(expected=IllegalArgumentException.class)
@@ -205,7 +205,7 @@ public class DeploymentSpecWithoutInstanceTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals("qrs", spec.instance("default").globalServiceId().get());
+        assertEquals("qrs", spec.requireInstance("default").globalServiceId().get());
     }
 
     @Test
@@ -222,7 +222,7 @@ public class DeploymentSpecWithoutInstanceTest {
         );
 
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals("canary", spec.instance("default").upgradePolicy().toString());
+        assertEquals("canary", spec.requireInstance("default").upgradePolicy().toString());
     }
 
     @Test
@@ -251,7 +251,7 @@ public class DeploymentSpecWithoutInstanceTest {
 
     @Test
     public void testEmpty() {
-        assertFalse(DeploymentSpec.empty.instance("default").globalServiceId().isPresent());
+        assertFalse(DeploymentSpec.empty.requireInstance("default").globalServiceId().isPresent());
         assertEquals(DeploymentSpec.UpgradePolicy.defaultPolicy, DeploymentSpec.empty.upgradePolicy());
         assertTrue(DeploymentSpec.empty.steps().isEmpty());
         assertEquals("<deployment version='1.0'/>", DeploymentSpec.empty.xmlForm());
@@ -271,7 +271,7 @@ public class DeploymentSpecWithoutInstanceTest {
                         "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        DeploymentSpec.ParallelZones parallelZones = ((DeploymentSpec.ParallelZones) spec.instance("default").steps().get(3));
+        DeploymentSpec.ParallelZones parallelZones = ((DeploymentSpec.ParallelZones) spec.requireInstance("default").steps().get(3));
         assertEquals(2, parallelZones.zones().size());
         assertEquals(RegionName.from("us-central-1"), parallelZones.zones().get(0).region().get());
         assertEquals(RegionName.from("us-east-3"), parallelZones.zones().get(1).region().get());
@@ -339,23 +339,23 @@ public class DeploymentSpecWithoutInstanceTest {
                 "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(2, spec.instance("default").changeBlocker().size());
-        assertTrue(spec.instance("default").changeBlocker().get(0).blocksVersions());
-        assertFalse(spec.instance("default").changeBlocker().get(0).blocksRevisions());
-        assertEquals(ZoneId.of("UTC"), spec.instance("default").changeBlocker().get(0).window().zone());
-
-        assertTrue(spec.instance("default").changeBlocker().get(1).blocksVersions());
-        assertTrue(spec.instance("default").changeBlocker().get(1).blocksRevisions());
-        assertEquals(ZoneId.of("CET"), spec.instance("default").changeBlocker().get(1).window().zone());
-
-        assertTrue(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-18T14:15:30.00Z")));
-        assertFalse(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-18T15:15:30.00Z")));
-        assertFalse(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-18T16:15:30.00Z")));
-        assertTrue(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-18T17:15:30.00Z")));
-
-        assertTrue(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-23T09:15:30.00Z")));
-        assertFalse(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-23T08:15:30.00Z"))); // 10 in CET
-        assertTrue(spec.instance("default").canUpgradeAt(Instant.parse("2017-09-23T10:15:30.00Z")));
+        assertEquals(2, spec.requireInstance("default").changeBlocker().size());
+        assertTrue(spec.requireInstance("default").changeBlocker().get(0).blocksVersions());
+        assertFalse(spec.requireInstance("default").changeBlocker().get(0).blocksRevisions());
+        assertEquals(ZoneId.of("UTC"), spec.requireInstance("default").changeBlocker().get(0).window().zone());
+
+        assertTrue(spec.requireInstance("default").changeBlocker().get(1).blocksVersions());
+        assertTrue(spec.requireInstance("default").changeBlocker().get(1).blocksRevisions());
+        assertEquals(ZoneId.of("CET"), spec.requireInstance("default").changeBlocker().get(1).window().zone());
+
+        assertTrue(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-18T14:15:30.00Z")));
+        assertFalse(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-18T15:15:30.00Z")));
+        assertFalse(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-18T16:15:30.00Z")));
+        assertTrue(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-18T17:15:30.00Z")));
+
+        assertTrue(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-23T09:15:30.00Z")));
+        assertFalse(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-23T08:15:30.00Z"))); // 10 in CET
+        assertTrue(spec.requireInstance("default").canUpgradeAt(Instant.parse("2017-09-23T10:15:30.00Z")));
     }
 
     @Test
@@ -368,8 +368,8 @@ public class DeploymentSpecWithoutInstanceTest {
                 "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(spec.instance("default").athenzDomain().get().value(), "domain");
-        assertEquals(spec.instance("default").athenzService(Environment.prod, RegionName.from("us-west-1")).get().value(), "service");
+        assertEquals(spec.requireInstance("default").athenzDomain().get().value(), "domain");
+        assertEquals(spec.requireInstance("default").athenzService(Environment.prod, RegionName.from("us-west-1")).get().value(), "service");
     }
 
     @Test
@@ -383,8 +383,8 @@ public class DeploymentSpecWithoutInstanceTest {
                 "</deployment>"
         );
         DeploymentSpec spec = DeploymentSpec.fromXml(r);
-        assertEquals(spec.instance("default").athenzDomain().get().value(), "domain");
-        assertEquals(spec.instance("default").athenzService(Environment.prod, RegionName.from("us-west-1")).get().value(), "prod-service");
+        assertEquals(spec.requireInstance("default").athenzDomain().get().value(), "domain");
+        assertEquals(spec.requireInstance("default").athenzService(Environment.prod, RegionName.from("us-west-1")).get().value(), "prod-service");
     }
 
     @Test(expected = IllegalArgumentException.class)
@@ -414,7 +414,7 @@ public class DeploymentSpecWithoutInstanceTest {
     @Test
     public void noNotifications() {
         assertEquals(Notifications.none(),
-                     DeploymentSpec.fromXml("<deployment />").instance("default").notifications());
+                     DeploymentSpec.fromXml("<deployment />").requireInstance("default").notifications());
     }
 
     @Test
@@ -422,7 +422,7 @@ public class DeploymentSpecWithoutInstanceTest {
         DeploymentSpec spec = DeploymentSpec.fromXml("<deployment>\n" +
                                                      "  <notifications />" +
                                                      "</deployment>");
-        assertEquals(Notifications.none(), spec.instance("default").notifications());
+        assertEquals(Notifications.none(), spec.requireInstance("default").notifications());
     }
 
     @Test
@@ -434,10 +434,10 @@ public class DeploymentSpecWithoutInstanceTest {
                                                      "    <email address=\"jane@dev\"/>\n" +
                                                      "  </notifications>\n" +
                                                      "</deployment>");
-        assertEquals(ImmutableSet.of(author), spec.instance("default").notifications().emailRolesFor(failing));
-        assertEquals(ImmutableSet.of(author), spec.instance("default").notifications().emailRolesFor(failingCommit));
-        assertEquals(ImmutableSet.of("john@dev", "jane@dev"), spec.instance("default").notifications().emailAddressesFor(failingCommit));
-        assertEquals(ImmutableSet.of("jane@dev"), spec.instance("default").notifications().emailAddressesFor(failing));
+        assertEquals(ImmutableSet.of(author), spec.requireInstance("default").notifications().emailRolesFor(failing));
+        assertEquals(ImmutableSet.of(author), spec.requireInstance("default").notifications().emailRolesFor(failingCommit));
+        assertEquals(ImmutableSet.of("john@dev", "jane@dev"), spec.requireInstance("default").notifications().emailAddressesFor(failingCommit));
+        assertEquals(ImmutableSet.of("jane@dev"), spec.requireInstance("default").notifications().emailAddressesFor(failing));
     }
 
     @Test
@@ -448,20 +448,20 @@ public class DeploymentSpecWithoutInstanceTest {
                                                      "    <region active=\"false\">us-north-7</region>\n" +
                                                      "  </prod>\n" +
                                                      "</deployment>");
-        assertEquals(Optional.of("d-1-4-20"), spec.instance("default").steps().get(0).zones().get(0).testerFlavor());
-        assertEquals(Optional.empty(), spec.instance("default").steps().get(1).zones().get(0).testerFlavor());
-        assertEquals(Optional.of("d-2-8-50"), spec.instance("default").steps().get(2).zones().get(0).testerFlavor());
+        assertEquals(Optional.of("d-1-4-20"), spec.requireInstance("default").steps().get(0).zones().get(0).testerFlavor());
+        assertEquals(Optional.empty(), spec.requireInstance("default").steps().get(1).zones().get(0).testerFlavor());
+        assertEquals(Optional.of("d-2-8-50"), spec.requireInstance("default").steps().get(2).zones().get(0).testerFlavor());
     }
 
     @Test
     public void noEndpoints() {
-        assertEquals(Collections.emptyList(), DeploymentSpec.fromXml("<deployment />").instance("default").endpoints());
+        assertEquals(Collections.emptyList(), DeploymentSpec.fromXml("<deployment />").requireInstance("default").endpoints());
     }
 
     @Test
     public void emptyEndpoints() {
         var spec = DeploymentSpec.fromXml("<deployment><endpoints/></deployment>");
-        assertEquals(Collections.emptyList(), spec.instance("default").endpoints());
+        assertEquals(Collections.emptyList(), spec.requireInstance("default").endpoints());
     }
 
     @Test
@@ -482,15 +482,15 @@ public class DeploymentSpecWithoutInstanceTest {
 
         assertEquals(
                 List.of("foo", "nalle", "default"),
-                spec.instance("default").endpoints().stream().map(Endpoint::endpointId).collect(Collectors.toList())
+                spec.requireInstance("default").endpoints().stream().map(Endpoint::endpointId).collect(Collectors.toList())
         );
 
         assertEquals(
                 List.of("bar", "frosk", "quux"),
-                spec.instance("default").endpoints().stream().map(Endpoint::containerId).collect(Collectors.toList())
+                spec.requireInstance("default").endpoints().stream().map(Endpoint::containerId).collect(Collectors.toList())
         );
 
-        assertEquals(Set.of(RegionName.from("us-east")), spec.instance("default").endpoints().get(0).regions());
+        assertEquals(Set.of(RegionName.from("us-east")), spec.requireInstance("default").endpoints().get(0).regions());
     }
 
     @Test
@@ -516,7 +516,7 @@ public class DeploymentSpecWithoutInstanceTest {
     }
 
     private static Set<String> endpointRegions(String endpointId, DeploymentSpec spec) {
-        return spec.instance("default").endpoints().stream()
+        return spec.requireInstance("default").endpoints().stream()
                 .filter(endpoint -> endpoint.endpointId().equals(endpointId))
                 .flatMap(endpoint -> endpoint.regions().stream())
                 .map(RegionName::value)