feat(nats-connection): implement named executor thread factories (#1254)

* feat(nats-connection): implement named executor thread factories

* Refactor executor creation to use configurable thread factories PR#1254

* Fix executor tests PR#1254

---------

Co-authored-by: Scott Fauerbach <scottfauerbach@gmail.com>

src/main/java/io/nats/client/Options.java

@@ -38,6 +38,7 @@
 import java.util.*;
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Supplier;
 
 import static io.nats.client.support.Encoding.*;
 import static io.nats.client.support.NatsConstants.*;
@@ -226,6 +227,11 @@ public class Options {
      */
     public static final boolean DEFAULT_DISCARD_MESSAGES_WHEN_OUTGOING_QUEUE_FULL = false;
 
+    /**
+     * Default supplier for creating a single-threaded executor service.
+     */
+    public static final Supplier<ExecutorService> DEFAULT_SINGLE_THREAD_EXECUTOR = Executors::newSingleThreadExecutor;
+
     // ----------------------------------------------------------------------------------------------------
     // ENVIRONMENT PROPERTIES
     // ----------------------------------------------------------------------------------------------------
@@ -644,6 +650,8 @@ public class Options {
     private final boolean traceConnection;
 
     private final ExecutorService executor;
+    private final ThreadFactory connectThreadFactory;
+    private final ThreadFactory callbackThreadFactory;
     private final ServerPool serverPool;
     private final DispatcherFactory dispatcherFactory;
 
@@ -759,6 +767,8 @@ public static class Builder {
         private StatisticsCollector statisticsCollector = null;
         private String dataPortType = DEFAULT_DATA_PORT_TYPE;
         private ExecutorService executor;
+        private ThreadFactory connectThreadFactory;
+        private ThreadFactory callbackThreadFactory;
         private List<java.util.function.Consumer<HttpRequest>> httpRequestInterceptors;
         private Proxy proxy;
 
@@ -1553,6 +1563,28 @@ public Builder executor(ExecutorService executor) {
             return this;
         }
 
+        /**
+         * Sets custom thread factory for the executor service
+         *
+         * @param threadFactory the thread factory to use for the executor service
+         * @return the Builder for chaining
+         */
+        public Builder connectThreadFactory(ThreadFactory threadFactory) {
+            this.connectThreadFactory = threadFactory;
+            return this;
+        }
+
+        /**
+         * Sets custom thread factory for the executor service
+         *
+         * @param threadFactory the thread factory to use for the executor service
+         * @return the Builder for chaining
+         */
+        public Builder callbackThreadFactory(ThreadFactory threadFactory) {
+            this.callbackThreadFactory = threadFactory;
+            return this;
+        }
+
         /**
          * Add an HttpRequest interceptor which can be used to modify the HTTP request when using websockets
          *
@@ -1914,6 +1946,8 @@ public Builder(Options o) {
             this.dataPortType = o.dataPortType;
             this.trackAdvancedStats = o.trackAdvancedStats;
             this.executor = o.executor;
+            this.callbackThreadFactory = o.callbackThreadFactory;
+            this.connectThreadFactory = o.connectThreadFactory;
             this.httpRequestInterceptors = o.httpRequestInterceptors;
             this.proxy = o.proxy;
 
@@ -1979,6 +2013,8 @@ private Options(Builder b) {
         this.dataPortType = b.dataPortType;
         this.trackAdvancedStats = b.trackAdvancedStats;
         this.executor = b.executor;
+        this.callbackThreadFactory = b.callbackThreadFactory;
+        this.connectThreadFactory = b.connectThreadFactory;
         this.httpRequestInterceptors = b.httpRequestInterceptors;
         this.proxy = b.proxy;
 
@@ -2002,6 +2038,22 @@ public ExecutorService getExecutor() {
         return this.executor;
     }
 
+    /**
+     * @return the callback executor, see {@link Builder#callbackThreadFactory(ThreadFactory) callbackThreadFactory()} in the builder doc
+     */
+    public ExecutorService getCallbackExecutor() {
+        return this.callbackThreadFactory == null ?
+                DEFAULT_SINGLE_THREAD_EXECUTOR.get() : Executors.newSingleThreadExecutor(this.callbackThreadFactory);
+    }
+
+    /**
+     * @return the connect executor, see {@link Builder#connectThreadFactory(ThreadFactory) connectThreadFactory()} in the builder doc
+     */
+    public ExecutorService getConnectExecutor() {
+        return this.connectThreadFactory == null ?
+                DEFAULT_SINGLE_THREAD_EXECUTOR.get() : Executors.newSingleThreadExecutor(this.connectThreadFactory);
+    }
+
     /**
      * @return the list of HttpRequest interceptors.
      */

src/main/java/io/nats/client/impl/NatsConnection.java

@@ -157,8 +157,8 @@ class NatsConnection implements Connection {
 
         timeTraceLogger.trace("creating executors");
         this.executor = options.getExecutor();
-        this.callbackRunner = Executors.newSingleThreadExecutor();
-        this.connectExecutor = Executors.newSingleThreadExecutor();
+        this.callbackRunner = options.getCallbackExecutor();
+        this.connectExecutor = options.getConnectExecutor();
 
         timeTraceLogger.trace("creating reader and writer");
         this.reader = new NatsConnectionReader(this);

src/test/java/io/nats/client/OptionsTests.java

@@ -32,10 +32,7 @@
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
 import java.util.*;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.Future;
-import java.util.concurrent.TimeUnit;
+import java.util.concurrent.*;
 
 import static io.nats.client.Options.*;
 import static io.nats.client.support.Encoding.base64UrlEncodeToString;
@@ -980,6 +977,30 @@ public void testDefaultExecutor() throws Exception {
         assertTrue(name.startsWith(Options.DEFAULT_THREAD_NAME_PREFIX));
     }
 
+    @Test
+    public void testCallbackExecutor() throws ExecutionException, InterruptedException, TimeoutException {
+        ThreadFactory threadFactory = r -> new Thread(r, "test");
+        Options options = new Options.Builder()
+                .callbackThreadFactory(threadFactory)
+                .build();
+        Future<?> callbackFuture = options.getCallbackExecutor().submit(() -> {
+            assertEquals("test", Thread.currentThread().getName());
+        });
+        callbackFuture.get(5, TimeUnit.SECONDS);
+    }
+
+    @Test
+    public void testConnectExecutor() throws ExecutionException, InterruptedException, TimeoutException {
+        ThreadFactory threadFactory = r -> new Thread(r, "test");
+        Options options = new Options.Builder()
+                .connectThreadFactory(threadFactory)
+                .build();
+        Future<?> connectFuture = options.getConnectExecutor().submit(() -> {
+            assertEquals("test", Thread.currentThread().getName());
+        });
+        connectFuture.get(5, TimeUnit.SECONDS);
+    }
+
     String[] schemes = new String[]   { "NATS", "unk",  "tls",  "opentls",  "ws",   "wss", "nats"};
     boolean[] secures = new boolean[] { false,  false,  true,   true,       false,  true,  false};
     boolean[] wses = new boolean[]    { false,  false,  false,  false,      true,   true,  false};