Gracefully drain SSE stream before shutdown (#97)

* Assert SSE result events in integration test

* Gracefully drain SSE stream before shutdown

* Only stop on faults once assembly finished

* Bump version to 2.2.1

Author: kvz

CHANGELOG.md

@@ -1,3 +1,8 @@
+### 2.2.1 / 2025-10-27
+
+- Ensure the SSE client drains pending events before shutdown while still tolerating transient network faults prior to completion.
+- Prevent duplicate `assembly_finished` callbacks by only stopping once and leaving reconnect handling to the client until completion.
+
 ### 2.2.0 / 2025-10-27
 
 - Prevent the SSE client from reconnecting after `assembly_finished`, eliminating spurious `assembly_error` callbacks and timeouts.

CONTRIBUTING.md

@@ -40,8 +40,9 @@ High-level checklist for maintainers:
 
 1. Bump the version in `src/main/resources/java-sdk-version/version.properties` and update `CHANGELOG.md`.
 2. Merge the release branch into `main`.
-3. Create a git tag for `main` that matches the new version
-4. Publish a GitHub release (include the changelog). This triggers the release workflow.
+3. Create a git tag for `main` that matches the new versions
+4. Publish a GitHub release (include the changelog). This triggers the release workflow. (via the GitHub UI, `gh release creates v1.0.1 --title "v1.0.1" --notes-file <(cat CHANGELOG.md section)`)
 5. Wait for Sonatype to sync the artifact (this can take a few hours).
 
 The required signing keys and credentials are stored as GitHub secrets. If you need access or spot an issue with the release automation, please reach out to the Transloadit team via the issue tracker or support channels.
+

src/main/java/com/transloadit/sdk/EventsourceRunnable.java

@@ -6,6 +6,7 @@
 import com.launchdarkly.eventsource.EventSource;
 import com.launchdarkly.eventsource.FaultEvent;
 import com.launchdarkly.eventsource.MessageEvent;
+import com.launchdarkly.eventsource.ReadyState;
 import com.launchdarkly.eventsource.RetryDelayStrategy;
 import com.launchdarkly.eventsource.StartedEvent;
 import com.launchdarkly.eventsource.StreamEvent;
@@ -28,6 +29,8 @@ class EventsourceRunnable implements Runnable {
     protected EventSource eventSource;
 
     protected Transloadit transloadit;
+    protected boolean stopRequested;
+    protected boolean assemblyFinishedNotified;
 
     /**
      * Constructor for {@link EventsourceRunnable}. It creates a new {@link EventSource} instance, wrapped in a
@@ -64,16 +67,21 @@ class EventsourceRunnable implements Runnable {
     @Override
     public void run() {
         this.assemblyFinished = false;
+        this.stopRequested = false;
+        this.assemblyFinishedNotified = false;
         try {
             eventSource.start();
         } catch (StreamException e) {
             assemblyListener.onError(e);
+            stopRequested = true;
         }
 
-        while (!assemblyFinished) {
+        while (!stopRequested) {
+            boolean processedEvent = false;
             Iterable<StreamEvent> events = eventSource.anyEvents();
             Iterator<StreamEvent> eventIterator = events.iterator();
-            if (eventIterator.hasNext()) {
+            while (eventIterator.hasNext()) {
+                processedEvent = true;
                 StreamEvent streamEvent = eventIterator.next();
                 if (streamEvent instanceof MessageEvent) {
                     handleMessageEvent((MessageEvent) streamEvent);
@@ -85,7 +93,24 @@ public void run() {
                     handleFaultEvent((FaultEvent) streamEvent);
                 }
             }
+
+            if (!processedEvent) {
+                ReadyState state = eventSource.getState();
+                if (state == ReadyState.CLOSED || state == ReadyState.SHUTDOWN) {
+                    stopRequested = true;
+                }
+                if (!stopRequested) {
+                    try {
+                        Thread.sleep(25);
+                    } catch (InterruptedException interruptedException) {
+                        Thread.currentThread().interrupt();
+                        stopRequested = true;
+                    }
+                }
+            }
         }
+
+        shutdownEventSource();
     }
 
     /**
@@ -101,22 +126,22 @@ protected void handleMessageEvent(MessageEvent messageEvent) {
         String eventName = messageEvent.getEventName();
         String data = messageEvent.getData();
 
-        if (assemblyFinished) {
-            shutdownEventSource();
-            return;
-        }
-
         // Check if the event is a message event without
         if (eventName.equals("message")) {
             switch (data) {
                 case "assembly_finished":
                     assemblyFinished = true;
-                    try {
-                        assemblyListener.onAssemblyFinished(transloadit.getAssemblyByUrl(response.getSslUrl()));
-                    } catch (RequestException  | LocalOperationException e) {
-                        assemblyListener.onError(e);
-                    } finally {
-                        shutdownEventSource();
+                    stopRequested = true;
+                    if (!assemblyFinishedNotified) {
+                        assemblyFinishedNotified = true;
+                        try {
+                            assemblyListener.onAssemblyFinished(transloadit.getAssemblyByUrl(response.getSslUrl()));
+                        } catch (RequestException  | LocalOperationException e) {
+                            assemblyListener.onError(e);
+                        }
+                    }
+                    if (eventSource != null) {
+                        eventSource.stop();
                     }
                     break;
                 case "assembly_upload_meta_data_extracted":
@@ -146,10 +171,10 @@ protected void handleMessageEvent(MessageEvent messageEvent) {
 
                 case "assembly_error":
                     if (assemblyFinished) {
-                        shutdownEventSource();
                         break;
                     }
                     assemblyListener.onError(new RequestException(data));
+                    stopRequested = true;
                     shutdownEventSource();
                     break;
 
@@ -178,6 +203,7 @@ protected void handleStartedEvent(StartedEvent startedEvent) {
 
     protected void handleFaultEvent(FaultEvent faultEvent) {
         if (assemblyFinished) {
+            stopRequested = true;
             shutdownEventSource();
         }
         // Debug output, uncomment if needed

src/main/resources/java-sdk-version/version.properties

@@ -1 +1 @@
-versionNumber='2.2.0'
+versionNumber='2.2.1'

src/test/java/com/transloadit/sdk/integration/AssemblySseIntegrationTest.java

@@ -19,6 +19,7 @@
 import java.util.Map;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ExecutionException;
+import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicReference;
@@ -51,6 +52,8 @@ void sseStreamShouldCloseWithoutErrorsAfterAssemblyFinished() throws Exception {
             AtomicReference<AssemblyResponse> finishedResponse = new AtomicReference<>();
             CompletableFuture<Void> finishedFuture = new CompletableFuture<>();
             CompletableFuture<Exception> errorFuture = new CompletableFuture<>();
+            CountDownLatch resultLatch = new CountDownLatch(1);
+            AtomicReference<JSONArray> resultPayload = new AtomicReference<>();
 
             AssemblyListener listener = new AssemblyListener() {
                 @Override
@@ -97,6 +100,14 @@ public void onAssemblyProgress(JSONObject progress) {
 
                 @Override
                 public void onAssemblyResultFinished(JSONArray result) {
+                    System.out.println("[AssemblySseIntegrationTest] assembly_result_finished payload=" + result);
+                    if (result != null && result.length() >= 2) {
+                        String stepName = result.optString(0, null);
+                        if ("resize".equals(stepName)) {
+                            resultPayload.compareAndSet(null, cloneJsonArray(result));
+                            resultLatch.countDown();
+                        }
+                    }
                 }
             };
 
@@ -120,6 +131,12 @@ public void onAssemblyResultFinished(JSONArray result) {
             assertTrue(completed.isFinished(), "Assembly should be finished");
             assertEquals("ASSEMBLY_COMPLETED", completed.json().optString("ok"));
 
+            boolean resultSeen = resultLatch.await(2, TimeUnit.MINUTES);
+            assertTrue(resultSeen, "Timed out waiting for assembly_result_finished event");
+            JSONArray resizePayload = resultPayload.get();
+            assertNotNull(resizePayload, "Resize SSE payload missing");
+            assertEquals("resize", resizePayload.optString(0));
+
             try {
                 Exception unexpected = errorFuture.get(30, TimeUnit.SECONDS);
                 fail("Unexpected SSE error after completion: " + unexpected);
@@ -134,6 +151,10 @@ public void onAssemblyResultFinished(JSONArray result) {
         }
     }
 
+    private static JSONArray cloneJsonArray(JSONArray array) {
+        return array == null ? null : new JSONArray(array.toString());
+    }
+
     private static Path createTempUpload() throws IOException {
         Path file = Files.createTempFile("transloadit-sse-test", ".jpg");
         URL source = new URL("https://demos.transloadit.com/inputs/chameleon.jpg");