feat: using dynamic ThreadPoolExecutor for reconcile and workflow executor services

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/ConfigurationService.java

@@ -3,8 +3,7 @@
 import java.time.Duration;
 import java.util.Optional;
 import java.util.Set;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
+import java.util.concurrent.*;
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -75,24 +74,49 @@ default boolean checkCRDAndValidateLocalModel() {
     return false;
   }
 
-  int DEFAULT_RECONCILIATION_THREADS_NUMBER = 10;
+  int DEFAULT_RECONCILIATION_THREADS_NUMBER = 200;
+  int MIN_DEFAULT_RECONCILIATION_THREADS_NUMBER = 10;
 
   /**
-   * Retrieves the maximum number of threads the operator can spin out to dispatch reconciliation
-   * requests to reconcilers
+   * The maximum number of threads the operator can spin out to dispatch reconciliation requests to
+   * reconcilers
    *
    * @return the maximum number of concurrent reconciliation threads
    */
   default int concurrentReconciliationThreads() {
     return DEFAULT_RECONCILIATION_THREADS_NUMBER;
   }
 
+  /**
+   * The minimum number of threads the operator starts in the thread pool for reconciliations.
+   *
+   * @return the minimum number of concurrent reconciliation threads
+   */
+  default int minConcurrentReconciliationThreads() {
+    return MIN_DEFAULT_RECONCILIATION_THREADS_NUMBER;
+  }
+
   int DEFAULT_WORKFLOW_EXECUTOR_THREAD_NUMBER = DEFAULT_RECONCILIATION_THREADS_NUMBER;
+  int MIN_DEFAULT_WORKFLOW_EXECUTOR_THREAD_NUMBER = MIN_DEFAULT_RECONCILIATION_THREADS_NUMBER;
 
+  /**
+   * Retrieves the maximum number of threads the operator can spin out to be used in the workflows.
+   *
+   * @return the maximum number of concurrent workflow threads
+   */
   default int concurrentWorkflowExecutorThreads() {
     return DEFAULT_WORKFLOW_EXECUTOR_THREAD_NUMBER;
   }
 
+  /**
+   * The minimum number of threads the operator starts in the thread pool for workflows.
+   *
+   * @return the minimum number of concurrent workflow threads
+   */
+  default int minConcurrentWorkflowExecutorThreads() {
+    return MIN_DEFAULT_WORKFLOW_EXECUTOR_THREAD_NUMBER;
+  }
+
   /**
    * Used to clone custom resources. It is strongly suggested that implementors override this method
    * since the default implementation creates a new {@link Cloner} instance each time this method is
@@ -136,11 +160,15 @@ default Metrics getMetrics() {
   }
 
   default ExecutorService getExecutorService() {
-    return Executors.newFixedThreadPool(concurrentReconciliationThreads());
+    return new ThreadPoolExecutor(minConcurrentReconciliationThreads(),
+        concurrentReconciliationThreads(),
+        1, TimeUnit.MINUTES, new LinkedBlockingDeque<>());
   }
 
   default ExecutorService getWorkflowExecutorService() {
-    return Executors.newFixedThreadPool(concurrentWorkflowExecutorThreads());
+    return new ThreadPoolExecutor(minConcurrentWorkflowExecutorThreads(),
+        concurrentWorkflowExecutorThreads(),
+        1, TimeUnit.MINUTES, new LinkedBlockingDeque<>());
   }
 
   default boolean closeClientOnStop() {

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/ConfigurationServiceOverrider.java

@@ -19,7 +19,9 @@ public class ConfigurationServiceOverrider {
   private Config clientConfig;
   private Boolean checkCR;
   private Integer concurrentReconciliationThreads;
+  private Integer minConcurrentReconciliationThreads;
   private Integer concurrentWorkflowExecutorThreads;
+  private Integer minConcurrentWorkflowExecutorThreads;
   private Cloner cloner;
   private Integer timeoutSeconds;
   private Boolean closeClientOnStop;
@@ -56,6 +58,16 @@ public ConfigurationServiceOverrider withConcurrentWorkflowExecutorThreads(int t
     return this;
   }
 
+  public ConfigurationServiceOverrider withMinConcurrentReconciliationThreads(int threadNumber) {
+    this.minConcurrentReconciliationThreads = threadNumber;
+    return this;
+  }
+
+  public ConfigurationServiceOverrider withMinConcurrentWorkflowExecutorThreads(int threadNumber) {
+    this.minConcurrentWorkflowExecutorThreads = threadNumber;
+    return this;
+  }
+
   public ConfigurationServiceOverrider withResourceCloner(Cloner cloner) {
     this.cloner = cloner;
     return this;
@@ -149,6 +161,18 @@ public int concurrentWorkflowExecutorThreads() {
             : original.concurrentWorkflowExecutorThreads();
       }
 
+      @Override
+      public int minConcurrentReconciliationThreads() {
+        return minConcurrentReconciliationThreads != null ? minConcurrentReconciliationThreads
+            : original.minConcurrentReconciliationThreads();
+      }
+
+      @Override
+      public int minConcurrentWorkflowExecutorThreads() {
+        return minConcurrentWorkflowExecutorThreads != null ? minConcurrentWorkflowExecutorThreads
+            : original.minConcurrentWorkflowExecutorThreads();
+      }
+
       @Override
       public int getTerminationTimeoutSeconds() {
         return timeoutSeconds != null ? timeoutSeconds : original.getTerminationTimeoutSeconds();