Support reading and writing application data as json

Controlled by feature flags.
Also write last deployed session when preparing a session

5 files changed, 272 insertions, 14 deletions

diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/application/ApplicationCuratorDatabase.java b/configserver/src/main/java/com/yahoo/vespa/config/server/application/ApplicationCuratorDatabase.java
index bd2bad4db93..70b8dc5f51a 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/application/ApplicationCuratorDatabase.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/application/ApplicationCuratorDatabase.java
@@ -23,9 +23,11 @@ import java.time.Duration;
 import java.time.Instant;
 import java.util.List;
 import java.util.Optional;
+import java.util.OptionalLong;
 import java.util.concurrent.ExecutorService;
 import java.util.function.UnaryOperator;
 
+import static com.yahoo.vespa.curator.transaction.CuratorOperations.setData;
 import static java.util.stream.Collectors.toUnmodifiableMap;
 
 /**
@@ -72,13 +74,18 @@ public class ApplicationCuratorDatabase {
     /**
      * Creates a node for the given application, marking its existence.
      */
-    public void createApplication(ApplicationId id) {
+    public void createApplication(ApplicationId id, boolean writeAsJson) {
         if ( ! id.tenant().equals(tenant))
             throw new IllegalArgumentException("Cannot write application id '" + id + "' for tenant '" + tenant + "'");
-        try (Lock lock = lock(id)) {
-            if (curator.exists(applicationPath(id))) return;
 
-            curator.create(applicationPath(id));
+        try (Lock lock = lock(id)) {
+            if (writeAsJson) {
+                var applicationData = new ApplicationData(id, OptionalLong.empty(), OptionalLong.empty());
+                curator.set(applicationPath(id), applicationData.toJson());
+            } else {
+                if (curator.exists(applicationPath(id))) return;
+                curator.create(applicationPath(id));
+            }
             modifyReindexing(id, ApplicationReindexing.empty(), UnaryOperator.identity());
         }
     }
@@ -89,8 +96,32 @@ public class ApplicationCuratorDatabase {
      * @param applicationId An {@link ApplicationId} that represents an active application.
      * @param sessionId session id belonging to the application package for this application id.
      */
-    public Transaction createWriteActiveTransaction(Transaction transaction, ApplicationId applicationId, long sessionId) {
-        return transaction.add(CuratorOperations.setData(applicationPath(applicationId).getAbsolute(), Utf8.toAsciiBytes(sessionId)));
+    public Transaction createWriteActiveTransaction(Transaction transaction, ApplicationId applicationId, long sessionId, boolean writeAsJson) {
+        String path = applicationPath(applicationId).getAbsolute();
+        return transaction.add(writeAsJson
+                                       ? setData(path, new ApplicationData(applicationId, OptionalLong.of(sessionId), OptionalLong.of(sessionId)).toJson())
+                                       : setData(path, Utf8.toAsciiBytes(sessionId)));
+    }
+
+    /**
+     * Returns a transaction which writes the given session id as the currently active for the given application.
+     *
+     * @param applicationId An {@link ApplicationId} that represents an active application.
+     * @param sessionId session id belonging to the application package for this application id.
+     */
+    public Transaction createWritePrepareTransaction(Transaction transaction,
+                                                     ApplicationId applicationId,
+                                                     long sessionId,
+                                                     OptionalLong activeSessionId,
+                                                     boolean writeAsJson) {
+
+        // Needs to read or be supplied current active session id, to avoid overwriting a newer session id.
+
+        String path = applicationPath(applicationId).getAbsolute();
+        if (writeAsJson)
+            return transaction.add(setData(path, new ApplicationData(applicationId, activeSessionId, OptionalLong.of(sessionId)).toJson()));
+        else
+            return transaction;  // Do nothing, as there is nothing to write in this case
     }
 
     /**
@@ -112,6 +143,46 @@ public class ApplicationCuratorDatabase {
     }
 
     /**
+     * Returns application data for the given application.
+     * Returns Optional.empty() if application not found or no application data exists.
+     */
+    public Optional<ApplicationData> applicationData(ApplicationId id) {
+        return applicationData(id, false);
+    }
+
+    /**
+     * Returns application data for the given application.
+     * Returns Optional.empty() if application not found or no application data exists.
+     */
+    public Optional<ApplicationData> applicationData(ApplicationId id, boolean readAsJson) {
+        Optional<byte[]> data = curator.getData(applicationPath(id));
+        if (data.isEmpty() || data.get().length == 0) return Optional.empty();
+
+        if (readAsJson) {
+            try {
+                return Optional.of(ApplicationData.fromBytes(data.get()));
+            } catch (IllegalArgumentException e) {
+                return applicationDataOldFormat(id, readAsJson);
+            }
+        } else {
+            return applicationDataOldFormat(id, readAsJson);
+        }
+    }
+
+    /**
+     * Returns application data for the given application.
+     * Returns Optional.empty() if application not found or no application data exists.
+     */
+    public Optional<ApplicationData> applicationDataOldFormat(ApplicationId id, boolean readAsJson) {
+        Optional<byte[]> data = curator.getData(applicationPath(id));
+        if (data.isEmpty() || data.get().length == 0) return Optional.empty();
+
+        return Optional.of(new ApplicationData(id,
+                                               OptionalLong.of(data.map(bytes -> Long.parseLong(Utf8.toString(bytes))).get()),
+                                               OptionalLong.empty()));
+    }
+
+    /**
      * List the active applications of a tenant in this config server.
      *
      * @return a list of {@link ApplicationId}s that are active.
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/application/ApplicationData.java b/configserver/src/main/java/com/yahoo/vespa/config/server/application/ApplicationData.java
new file mode 100644
index 00000000000..868ea060fba
--- /dev/null
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/application/ApplicationData.java
@@ -0,0 +1,72 @@
+package com.yahoo.vespa.config.server.application;
+
+import com.yahoo.config.provision.ApplicationId;
+import com.yahoo.slime.Cursor;
+import com.yahoo.slime.Slime;
+import com.yahoo.slime.SlimeUtils;
+
+import java.io.IOException;
+import java.util.OptionalLong;
+
+import static com.yahoo.slime.SlimeUtils.optionalLong;
+
+/**
+ * Data class for application id, active session and last deployed session
+ *
+ * @author hmusum
+ */
+public class ApplicationData {
+
+    private static final String APPLICATION_ID_FIELD = "applicationId";
+    private static final String ACTIVE_SESSION_FIELD = "activeSession";
+    private static final String LAST_DEPLOYED_SESSION_FIELD = "lastDeployedSession";
+
+    private final ApplicationId applicationId;
+    private final OptionalLong activeSession;
+    private final OptionalLong lastDeployedSession;
+
+    ApplicationData(ApplicationId applicationId, OptionalLong activeSession, OptionalLong lastDeployedSession) {
+        this.applicationId = applicationId;
+        this.activeSession = activeSession;
+        this.lastDeployedSession = lastDeployedSession;
+    }
+
+    static ApplicationData fromBytes(byte[] data) {
+        return fromSlime(SlimeUtils.jsonToSlime(data));
+    }
+
+    static ApplicationData fromSlime(Slime slime) {
+        Cursor cursor = slime.get();
+        return new ApplicationData(ApplicationId.fromSerializedForm(cursor.field(APPLICATION_ID_FIELD).asString()),
+                                   optionalLong(cursor.field(ACTIVE_SESSION_FIELD)),
+                                   optionalLong(cursor.field(LAST_DEPLOYED_SESSION_FIELD)));
+    }
+
+    public byte[] toJson() {
+        try {
+            Slime slime = new Slime();
+            toSlime(slime.setObject());
+            return SlimeUtils.toJsonBytes(slime);
+        } catch (IOException e) {
+            throw new RuntimeException("Serialization of application data to json failed", e);
+        }
+    }
+
+    public ApplicationId applicationId() { return applicationId; }
+
+    public OptionalLong activeSession() { return activeSession; }
+
+    public OptionalLong lastDeployedSession() { return lastDeployedSession; }
+
+    @Override
+    public String toString() {
+        return "application '" + applicationId + "', active session " + activeSession + ", last deployed session " + lastDeployedSession;
+    }
+
+    private void toSlime(Cursor object) {
+        object.setString(APPLICATION_ID_FIELD, applicationId.serializedForm());
+        activeSession.ifPresent(session -> object.setLong(ACTIVE_SESSION_FIELD, session));
+        lastDeployedSession.ifPresent(session -> object.setLong(LAST_DEPLOYED_SESSION_FIELD, session));
+    }
+
+}
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java b/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
index af29f6e8530..538534d0040 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/application/TenantApplications.java
@@ -27,7 +27,9 @@ import com.yahoo.vespa.curator.CompletionTimeoutException;
 import com.yahoo.vespa.curator.Curator;
 import com.yahoo.vespa.curator.Lock;
 import com.yahoo.vespa.curator.transaction.CuratorTransaction;
+import com.yahoo.vespa.flags.BooleanFlag;
 import com.yahoo.vespa.flags.FlagSource;
+import com.yahoo.vespa.flags.Flags;
 import com.yahoo.vespa.flags.ListFlag;
 import com.yahoo.vespa.flags.PermanentFlags;
 import org.apache.curator.framework.CuratorFramework;
@@ -41,6 +43,7 @@ import java.util.Collection;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Optional;
+import java.util.OptionalLong;
 import java.util.Set;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
@@ -76,6 +79,8 @@ public class TenantApplications implements RequestHandler, HostValidator {
     private final TenantFileSystemDirs tenantFileSystemDirs;
     private final String serverId;
     private final ListFlag<String> incompatibleVersions;
+    private final BooleanFlag writeApplicationDataAsJson;
+    private final BooleanFlag readApplicationDataAsJson;
 
     public TenantApplications(TenantName tenant, Curator curator, StripedExecutor<TenantName> zkWatcherExecutor,
                               ExecutorService zkCacheExecutor, Metrics metrics, ConfigActivationListener configActivationListener,
@@ -97,6 +102,8 @@ public class TenantApplications implements RequestHandler, HostValidator {
         this.clock = clock;
         this.serverId = configserverConfig.serverId();
         this.incompatibleVersions = PermanentFlags.INCOMPATIBLE_VERSIONS.bindTo(flagSource);
+        this.writeApplicationDataAsJson = Flags.WRITE_APPLICATION_DATA_AS_JSON.bindTo(flagSource);
+        this.readApplicationDataAsJson = Flags.READ_APPLICATION_DATA_AS_JSON.bindTo(flagSource);
     }
 
     /** The curator backed ZK storage of this. */
@@ -123,6 +130,14 @@ public class TenantApplications implements RequestHandler, HostValidator {
         return database().activeSessionOf(id);
     }
 
+    /**
+     * Returns application data for the given application.
+     * Returns Optional.empty if application not found or no application data exists.
+     */
+    public Optional<ApplicationData> applicationData(ApplicationId id) {
+        return database().applicationData(id, readApplicationDataAsJson.value());
+    }
+
     public boolean sessionExistsInFileSystem(long sessionId) {
         return Files.exists(Paths.get(tenantFileSystemDirs.sessionsPath().getAbsolutePath(), String.valueOf(sessionId)));
     }
@@ -134,14 +149,31 @@ public class TenantApplications implements RequestHandler, HostValidator {
      * @param sessionId session id belonging to the application package for this application id.
      */
     public Transaction createWriteActiveTransaction(Transaction transaction, ApplicationId applicationId, long sessionId) {
-        return database().createWriteActiveTransaction(transaction, applicationId, sessionId);
+        return database().createWriteActiveTransaction(transaction, applicationId, sessionId, writeApplicationDataAsJson.value());
+    }
+
+    /**
+     * Returns a transaction which writes the given session id as the last deployed for the given application.
+     *
+     * @param applicationId An {@link ApplicationId} that represents an active application.
+     * @param sessionId session id belonging to the application package for this application id.
+     */
+    public Transaction createWritePrepareTransaction(Transaction transaction,
+                                                     ApplicationId applicationId,
+                                                     long sessionId,
+                                                     Optional<Long> activeSessionId) {
+        return database().createWritePrepareTransaction(transaction,
+                                                        applicationId,
+                                                        sessionId,
+                                                        activeSessionId.map(OptionalLong::of).orElseGet(OptionalLong::empty),
+                                                        writeApplicationDataAsJson.value());
     }
 
     /**
      * Creates a node for the given application, marking its existence.
      */
     public void createApplication(ApplicationId id) {
-        database().createApplication(id);
+        database().createApplication(id, writeApplicationDataAsJson.value());
     }
 
     /**
diff --git a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionRepository.java b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionRepository.java
index 3144665ec91..44a656a1579 100644
--- a/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionRepository.java
+++ b/configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionRepository.java
@@ -39,6 +39,7 @@ import com.yahoo.vespa.config.server.tenant.TenantRepository;
 import com.yahoo.vespa.config.server.zookeeper.SessionCounter;
 import com.yahoo.vespa.config.server.zookeeper.ZKApplication;
 import com.yahoo.vespa.curator.Curator;
+import com.yahoo.vespa.curator.transaction.CuratorTransaction;
 import com.yahoo.vespa.flags.BooleanFlag;
 import com.yahoo.vespa.flags.FlagSource;
 import com.yahoo.vespa.flags.Flags;
@@ -239,14 +240,22 @@ public class SessionRepository {
                 throw new UnknownVespaVersionException("Vespa version '" + version + "' not known by this config server");
         });
 
-        applicationRepo.createApplication(params.getApplicationId()); // TODO jvenstad: This is wrong, but it has to be done now, since preparation can change the application ID of a session :(
-        logger.log(Level.FINE, "Created application " + params.getApplicationId());
+        ApplicationId applicationId = params.getApplicationId();
+        applicationRepo.createApplication(applicationId); // TODO jvenstad: This is wrong, but it has to be done now, since preparation can change the application ID of a session :(
+        logger.log(Level.FINE, "Created application " + applicationId);
         long sessionId = session.getSessionId();
         SessionZooKeeperClient sessionZooKeeperClient = createSessionZooKeeperClient(sessionId);
         Optional<CompletionWaiter> waiter = params.isDryRun()
                 ? Optional.empty()
                 : Optional.of(sessionZooKeeperClient.createPrepareWaiter());
-        Optional<ApplicationVersions> activeApplicationVersions = activeApplicationVersions(params.getApplicationId());
+        Optional<ApplicationVersions> activeApplicationVersions = activeApplicationVersions(applicationId);
+        try (var transaction = new CuratorTransaction(curator)) {
+            applicationRepo.createWritePrepareTransaction(transaction,
+                                                          applicationId,
+                                                          sessionId,
+                                                          getActiveSessionId(applicationId))
+                    .commit();
+        }
         ConfigChangeActions actions = sessionPreparer.prepare(applicationRepo, logger, params,
                                                               activeApplicationVersions, now, getSessionAppDir(sessionId),
                                                               session.getApplicationPackage(), sessionZooKeeperClient)
@@ -277,6 +286,7 @@ public class SessionRepository {
                                                             timeoutBudget,
                                                             deployLogger,
                                                             created);
+        applicationRepo.createApplication(applicationId);
         write(existingSession, session, applicationId, created);
         return session;
     }
@@ -293,9 +303,10 @@ public class SessionRepository {
                                                             ApplicationId applicationId,
                                                             TimeoutBudget timeoutBudget,
                                                             DeployLogger deployLogger) {
-        applicationRepo.createApplication(applicationId);
-        return createSessionFromApplication(applicationDirectory, applicationId, false, timeoutBudget,
+        LocalSession session = createSessionFromApplication(applicationDirectory, applicationId, false, timeoutBudget,
                                             deployLogger, clock.instant());
+        applicationRepo.createApplication(applicationId);
+        return session;
     }
 
     /**
diff --git a/configserver/src/test/java/com/yahoo/vespa/config/server/application/ApplicationCuratorDatabaseTest.java b/configserver/src/test/java/com/yahoo/vespa/config/server/application/ApplicationCuratorDatabaseTest.java
index cbdb462c35e..8d1b22c94c5 100644
--- a/configserver/src/test/java/com/yahoo/vespa/config/server/application/ApplicationCuratorDatabaseTest.java
+++ b/configserver/src/test/java/com/yahoo/vespa/config/server/application/ApplicationCuratorDatabaseTest.java
@@ -3,13 +3,17 @@ package com.yahoo.vespa.config.server.application;
 
 import com.yahoo.config.provision.ApplicationId;
 import com.yahoo.vespa.curator.mock.MockCurator;
+import com.yahoo.vespa.curator.transaction.CuratorTransaction;
 import org.junit.Test;
 
 import java.time.Instant;
 import java.util.Optional;
+import java.util.OptionalLong;
 
 import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.fail;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
 /**
  * @author jonmv
@@ -35,4 +39,72 @@ public class ApplicationCuratorDatabaseTest {
         assertEquals(reindexing, db.readReindexingStatus(id).orElseThrow());
     }
 
+    @Test
+    public void testReadingAndWritingApplicationData() {
+        ApplicationId id = ApplicationId.defaultId();
+        MockCurator curator = new MockCurator();
+        ApplicationCuratorDatabase db = new ApplicationCuratorDatabase(id.tenant(), curator);
+
+        assertEquals(Optional.empty(), db.applicationData(id));
+
+        db.createApplication(id, false);
+        assertEquals(Optional.empty(), db.applicationData(id)); // still empty, as no data has been written to node
+
+        db.createApplication(id, true);
+        try {
+            Optional<ApplicationData> applicationData = db.applicationData(id);
+            fail("Expected exception, got " + applicationData);
+        } catch (NumberFormatException e) {
+            // expected
+        }
+
+        // Can be read as json, but no active session or last deployed session
+        Optional<ApplicationData> applicationData = db.applicationData(id, true);
+        assertTrue(applicationData.isPresent());
+        assertEquals(id, applicationData.get().applicationId());
+        assertFalse(applicationData.get().activeSession().isPresent());
+        assertFalse(applicationData.get().lastDeployedSession().isPresent());
+
+        // Prepare session 2, no active session
+        try (var t = db.createWritePrepareTransaction(new CuratorTransaction(curator), id, 2, OptionalLong.empty(), false)) {
+            t.commit();
+        }
+        // Activate session 2, last deployed session not present (not writing json)
+        try (var t = db.createWriteActiveTransaction(new CuratorTransaction(curator), id, 2, false)) {
+            t.commit();
+        }
+        // Can be read as session id only
+        applicationData = db.applicationData(id, false);
+        assertTrue(applicationData.isPresent());
+        assertEquals(id, applicationData.get().applicationId());
+        assertTrue(applicationData.get().activeSession().isPresent());
+        assertEquals(2, applicationData.get().activeSession().getAsLong());
+        assertFalse(applicationData.get().lastDeployedSession().isPresent());
+
+        // Prepare session 3, last deployed session is still 2
+        try (var t = db.createWritePrepareTransaction(new CuratorTransaction(curator), id, 3, OptionalLong.of(2), true)) {
+            t.commit();
+        }
+        // Can be read as json, active session is still 2 and last deployed session is 3
+        applicationData = db.applicationData(id, true);
+        assertTrue(applicationData.isPresent());
+        assertEquals(id, applicationData.get().applicationId());
+        assertTrue(applicationData.get().activeSession().isPresent());
+        assertEquals(2, applicationData.get().activeSession().getAsLong());
+        assertTrue(applicationData.get().lastDeployedSession().isPresent());
+        assertEquals(3, applicationData.get().lastDeployedSession().getAsLong());
+
+        try (var t = db.createWriteActiveTransaction(new CuratorTransaction(curator), id, 3, true)) {
+            t.commit();
+        }
+        // Can be read as json, active session and last deployed session present
+        applicationData = db.applicationData(id, true);
+        assertTrue(applicationData.isPresent());
+        assertEquals(id, applicationData.get().applicationId());
+        assertTrue(applicationData.get().activeSession().isPresent());
+        assertEquals(3, applicationData.get().activeSession().getAsLong());
+        assertTrue(applicationData.get().lastDeployedSession().isPresent());
+        assertEquals(3, applicationData.get().lastDeployedSession().getAsLong());
+    }
+
 }