Add config for core pool size

2 files changed, 13 insertions, 4 deletions

diff --git a/container-core/src/main/java/com/yahoo/container/handler/threadpool/ContainerThreadPool.java b/container-core/src/main/java/com/yahoo/container/handler/threadpool/ContainerThreadPool.java
index 45b55a8a150..6251f1975dd 100644
--- a/container-core/src/main/java/com/yahoo/container/handler/threadpool/ContainerThreadPool.java
+++ b/container-core/src/main/java/com/yahoo/container/handler/threadpool/ContainerThreadPool.java
@@ -32,9 +32,10 @@ public class ContainerThreadPool extends AbstractComponent implements AutoClosea
     }
 
     public ContainerThreadPool(ThreadpoolConfig threadpoolConfig, Metric metric, ProcessTerminator processTerminator) {
-        int maxNumThreads = computeThreadPoolSize(threadpoolConfig.maxthreads());
+        int maxNumThreads = computeMaximumThreadPoolSize(threadpoolConfig.maxthreads());
+        int coreNumThreads = computeCoreThreadPoolSize(threadpoolConfig.corePoolSize(), maxNumThreads);
         WorkerCompletionTimingThreadPoolExecutor executor =
-                new WorkerCompletionTimingThreadPoolExecutor(maxNumThreads, maxNumThreads,
+                new WorkerCompletionTimingThreadPoolExecutor(coreNumThreads, maxNumThreads,
                         0L, TimeUnit.SECONDS,
                         createQ(threadpoolConfig.queueSize(), maxNumThreads),
                         ThreadFactoryFactory.getThreadFactory(threadpoolConfig.name()),
@@ -79,9 +80,14 @@ public class ContainerThreadPool extends AbstractComponent implements AutoClosea
                 : new ArrayBlockingQueue<>(queueSize);
     }
 
-    private static int computeThreadPoolSize(int maxNumThreads) {
+    private static int computeMaximumThreadPoolSize(int maxNumThreads) {
         return (maxNumThreads <= 0)
                 ? Runtime.getRuntime().availableProcessors() * 4
                 : maxNumThreads;
     }
+
+    private static int computeCoreThreadPoolSize(int corePoolSize, int maxNumThreads) {
+        return Math.min(corePoolSize, maxNumThreads);
+    }
+
 }
diff --git a/container-core/src/main/resources/configdefinitions/threadpool.def b/container-core/src/main/resources/configdefinitions/threadpool.def
index b3202ebfecc..7d57cd3e35c 100644
--- a/container-core/src/main/resources/configdefinitions/threadpool.def
+++ b/container-core/src/main/resources/configdefinitions/threadpool.def
@@ -2,10 +2,13 @@
 
 namespace=container.handler
 
-## Num ber of thread in the thread pool
+## Maximum number of thread in the thread pool
 ## Setting it to 0 or negative number will cause it to be set to #cores * 4
 maxthreads int default=500
 
+# The number of threads to keep in the pool, even if they are idle
+corePoolSize int default=500
+
 ## max queue size
 ## There can be queueSize + maxthreads requests inflight concurrently
 ## The container will start replying 503