When you have a container with both feed and query, you risk that during warmup the throughput optimized

feed pipeline will overwhelm the search pipeline during warmup.
Here we add an option to enforce a soft start of the feed pipeline, by gradually increasing max number of feed threads.
It might not be the perfect solution as mesages will pile up in the dynamic throttle policy, but that should have a builtin
softstart already. So I think this might a good fit.

2 files changed, 21 insertions, 3 deletions

diff --git a/vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/ClientFeederV3.java b/vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/ClientFeederV3.java
index ec5fc0cad07..d537e873600 100644
--- a/vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/ClientFeederV3.java
+++ b/vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/ClientFeederV3.java
@@ -57,8 +57,8 @@ class ClientFeederV3 {
     private final Object monitor = new Object();
     private final StreamReaderV3 streamReaderV3;
     private final AtomicInteger ongoingRequests = new AtomicInteger(0);
-    private String hostName;
-    private AtomicInteger threadsAvailableForFeeding;
+    private final String hostName;
+    private final AtomicInteger threadsAvailableForFeeding;
 
     ClientFeederV3(
             ReferencedResource<SharedSourceSession> sourceSession,
diff --git a/vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/FeedHandlerV3.java b/vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/FeedHandlerV3.java
index 37803d96714..1b342363046 100644
--- a/vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/FeedHandlerV3.java
+++ b/vespaclient-container-plugin/src/main/java/com/yahoo/vespa/http/server/FeedHandlerV3.java
@@ -43,6 +43,9 @@ public class FeedHandlerV3 extends LoggingRequestHandler {
     protected final ReplyHandler feedReplyHandler;
     private final Metric metric;
     private final Object monitor = new Object();
+    private int remainingThreadsForFeedingAllowance;
+    private final long msBetweenBumpingMaxThreads;
+    private long nextTimeToAllocateAnotherThread;
     private final AtomicInteger threadsAvailableForFeeding;
     private static final Logger log = Logger.getLogger(FeedHandlerV3.class.getName());
 
@@ -60,10 +63,20 @@ public class FeedHandlerV3 extends LoggingRequestHandler {
         this.metric = parentCtx.getMetric();
         // 40% of the threads can be blocking on feeding before we deny requests.
         if (threadpoolConfig != null) {
-            threadsAvailableForFeeding = new AtomicInteger(Math.max((int) (0.4 * threadpoolConfig.maxthreads()), 1));
+            remainingThreadsForFeedingAllowance = Math.max((int) (0.4 * threadpoolConfig.maxthreads()), 1);
+            if (threadpoolConfig.softStartSeconds() > 0.0) {
+                threadsAvailableForFeeding = new AtomicInteger(0);
+                msBetweenBumpingMaxThreads = (long)threadpoolConfig.softStartSeconds() * 1000 / remainingThreadsForFeedingAllowance;
+            } else {
+                threadsAvailableForFeeding = new AtomicInteger(remainingThreadsForFeedingAllowance);
+                remainingThreadsForFeedingAllowance = 0;
+                msBetweenBumpingMaxThreads = 0;
+            }
         } else {
             log.warning("No config for threadpool, using 200 for max blocking threads for feeding.");
             threadsAvailableForFeeding = new AtomicInteger(200);
+            remainingThreadsForFeedingAllowance = 0;
+            msBetweenBumpingMaxThreads = 0;
         }
     }
 
@@ -78,6 +91,11 @@ public class FeedHandlerV3 extends LoggingRequestHandler {
         String clientId = clientId(request);
         ClientFeederV3 clientFeederV3;
         synchronized (monitor) {
+            if ((remainingThreadsForFeedingAllowance > 0) && (System.currentTimeMillis() > nextTimeToAllocateAnotherThread)) {
+                threadsAvailableForFeeding.incrementAndGet();
+                remainingThreadsForFeedingAllowance --;
+                nextTimeToAllocateAnotherThread = System.currentTimeMillis() + msBetweenBumpingMaxThreads;
+            }
             if (! clientFeederByClientId.containsKey(clientId)) {
                 SourceSessionParams sourceSessionParams = sourceSessionParams(request);
                 clientFeederByClientId.put(clientId,