feat: implement grpc reconnect for inprocess mode

Signed-off-by: Bernd Warmuth <[email protected]>

Author: Bernd Warmuth

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/grpc/GrpcConnector.java

@@ -1,6 +1,5 @@
 package dev.openfeature.contrib.providers.flagd.resolver.grpc;
 
-import com.google.common.annotations.VisibleForTesting;
 import dev.openfeature.contrib.providers.flagd.FlagdOptions;
 import dev.openfeature.contrib.providers.flagd.resolver.common.ChannelBuilder;
 import dev.openfeature.contrib.providers.flagd.resolver.common.ChannelMonitor;
@@ -125,8 +124,7 @@ public GrpcConnector(
      * @param onConnectionEvent   a consumer to handle connection events
      * @param eventStreamObserver a consumer to handle the event stream
      */
-    @VisibleForTesting
-    GrpcConnector(
+    public GrpcConnector(
             final FlagdOptions options,
             final Function<ManagedChannel, T> stub,
             final Function<ManagedChannel, K> blockingStub,

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/process/InProcessResolver.java

@@ -57,7 +57,7 @@ public InProcessResolver(
             FlagdOptions options,
             final Supplier<Boolean> connectedSupplier,
             Consumer<ConnectionEvent> onConnectionEvent) {
-        this.flagStore = new FlagStore(getConnector(options));
+        this.flagStore = new FlagStore(getConnector(options, onConnectionEvent));
         this.deadline = options.getDeadline();
         this.onConnectionEvent = onConnectionEvent;
         this.operator = new Operator();
@@ -160,14 +160,14 @@ public ProviderEvaluation<Value> objectEvaluation(String key, Value defaultValue
                 .build();
     }
 
-    static Connector getConnector(final FlagdOptions options) {
+    static Connector getConnector(final FlagdOptions options, Consumer<ConnectionEvent> onConnectionEvent) {
         if (options.getCustomConnector() != null) {
             return options.getCustomConnector();
         }
         return options.getOfflineFlagSourcePath() != null
                         && !options.getOfflineFlagSourcePath().isEmpty()
                 ? new FileConnector(options.getOfflineFlagSourcePath())
-                : new GrpcStreamConnector(options);
+                : new GrpcStreamConnector(options, onConnectionEvent);
     }
 
     private <T> ProviderEvaluation<T> resolve(Class<T> type, String key, EvaluationContext ctx) {

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/process/storage/connector/grpc/GrpcStreamConnector.java

@@ -1,28 +1,25 @@
 package dev.openfeature.contrib.providers.flagd.resolver.process.storage.connector.grpc;
 
 import dev.openfeature.contrib.providers.flagd.FlagdOptions;
-import dev.openfeature.contrib.providers.flagd.resolver.common.ChannelBuilder;
-import dev.openfeature.contrib.providers.flagd.resolver.common.backoff.GrpcStreamConnectorBackoffService;
+import dev.openfeature.contrib.providers.flagd.resolver.common.ConnectionEvent;
+import dev.openfeature.contrib.providers.flagd.resolver.grpc.GrpcConnector;
 import dev.openfeature.contrib.providers.flagd.resolver.process.storage.connector.Connector;
 import dev.openfeature.contrib.providers.flagd.resolver.process.storage.connector.QueuePayload;
 import dev.openfeature.contrib.providers.flagd.resolver.process.storage.connector.QueuePayloadType;
 import dev.openfeature.flagd.grpc.sync.FlagSyncServiceGrpc;
-import dev.openfeature.flagd.grpc.sync.FlagSyncServiceGrpc.FlagSyncServiceBlockingStub;
-import dev.openfeature.flagd.grpc.sync.FlagSyncServiceGrpc.FlagSyncServiceStub;
 import dev.openfeature.flagd.grpc.sync.Sync.GetMetadataRequest;
 import dev.openfeature.flagd.grpc.sync.Sync.GetMetadataResponse;
 import dev.openfeature.flagd.grpc.sync.Sync.SyncFlagsRequest;
 import dev.openfeature.flagd.grpc.sync.Sync.SyncFlagsResponse;
 import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import io.grpc.Context;
 import io.grpc.Context.CancellableContext;
-import io.grpc.ManagedChannel;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.function.Consumer;
 import lombok.extern.slf4j.Slf4j;
-import org.slf4j.event.Level;
 
 /**
  * Implements the {@link Connector} contract and emit flags obtained from flagd sync gRPC contract.
@@ -36,42 +33,34 @@ public class GrpcStreamConnector implements Connector {
 
     private final AtomicBoolean shutdown = new AtomicBoolean(false);
     private final BlockingQueue<QueuePayload> blockingQueue = new LinkedBlockingQueue<>(QUEUE_SIZE);
-    private final ManagedChannel channel;
-    private final FlagSyncServiceStub serviceStub;
-    private final FlagSyncServiceBlockingStub serviceBlockingStub;
     private final int deadline;
-    private final int streamDeadlineMs;
     private final String selector;
-    private final int retryBackoffMillis;
+    private final GrpcConnector<
+                    FlagSyncServiceGrpc.FlagSyncServiceStub, FlagSyncServiceGrpc.FlagSyncServiceBlockingStub>
+            grpcConnector;
+    private final LinkedBlockingQueue<GrpcResponseModel> streamReceiver;
 
     /**
-     * Construct a new GrpcStreamConnector.
-     *
-     * @param options flagd options
+     * Creates a new GrpcStreamConnector responsible for observing the event stream.
      */
-    public GrpcStreamConnector(final FlagdOptions options) {
-        channel = ChannelBuilder.nettyChannel(options);
-        serviceStub = FlagSyncServiceGrpc.newStub(channel);
-        serviceBlockingStub = FlagSyncServiceGrpc.newBlockingStub(channel);
+    public GrpcStreamConnector(final FlagdOptions options, Consumer<ConnectionEvent> onConnectionEvent) {
         deadline = options.getDeadline();
-        streamDeadlineMs = options.getStreamDeadlineMs();
         selector = options.getSelector();
-        retryBackoffMillis = options.getRetryBackoffMs();
+        streamReceiver = new LinkedBlockingQueue<>(QUEUE_SIZE);
+        grpcConnector = new GrpcConnector<>(
+                options,
+                FlagSyncServiceGrpc::newStub,
+                FlagSyncServiceGrpc::newBlockingStub,
+                onConnectionEvent,
+                stub -> stub.syncFlags(SyncFlagsRequest.getDefaultInstance(), new GrpcStreamHandler(streamReceiver)));
     }
 
     /** Initialize gRPC stream connector. */
-    public void init() {
+    public void init() throws Exception {
+        grpcConnector.initialize();
         Thread listener = new Thread(() -> {
             try {
-                observeEventStream(
-                        blockingQueue,
-                        shutdown,
-                        serviceStub,
-                        serviceBlockingStub,
-                        selector,
-                        deadline,
-                        streamDeadlineMs,
-                        retryBackoffMillis);
+                observeEventStream(blockingQueue, shutdown, selector, deadline);
             } catch (InterruptedException e) {
                 log.warn("gRPC event stream interrupted, flag configurations are stale", e);
                 Thread.currentThread().interrupt();
@@ -96,37 +85,17 @@ public void shutdown() throws InterruptedException {
         if (shutdown.getAndSet(true)) {
             return;
         }
-
-        try {
-            if (this.channel != null && !this.channel.isShutdown()) {
-                this.channel.shutdown();
-                this.channel.awaitTermination(this.deadline, TimeUnit.MILLISECONDS);
-            }
-        } finally {
-            if (this.channel != null && !this.channel.isShutdown()) {
-                this.channel.shutdownNow();
-                this.channel.awaitTermination(this.deadline, TimeUnit.MILLISECONDS);
-                log.warn(String.format("Unable to shut down channel by %d deadline", this.deadline));
-            }
-        }
+        this.grpcConnector.shutdown();
     }
 
     /** Contains blocking calls, to be used concurrently. */
-    static void observeEventStream(
+    void observeEventStream(
             final BlockingQueue<QueuePayload> writeTo,
             final AtomicBoolean shutdown,
-            final FlagSyncServiceStub serviceStub,
-            final FlagSyncServiceBlockingStub serviceBlockingStub,
             final String selector,
-            final int deadline,
-            final int streamDeadlineMs,
-            int retryBackoffMillis)
+            final int deadline)
             throws InterruptedException {
 
-        final BlockingQueue<GrpcResponseModel> streamReceiver = new LinkedBlockingQueue<>(QUEUE_SIZE);
-        final GrpcStreamConnectorBackoffService backoffService =
-                new GrpcStreamConnectorBackoffService(retryBackoffMillis);
-
         log.info("Initializing sync stream observer");
 
         while (!shutdown.get()) {
@@ -143,15 +112,10 @@ static void observeEventStream(
             }
 
             try (CancellableContext context = Context.current().withCancellation()) {
-                FlagSyncServiceStub localServiceStub = serviceStub;
-                if (streamDeadlineMs > 0) {
-                    localServiceStub = localServiceStub.withDeadlineAfter(streamDeadlineMs, TimeUnit.MILLISECONDS);
-                }
-
-                localServiceStub.syncFlags(syncRequest.build(), new GrpcStreamHandler(streamReceiver));
 
                 try {
-                    metadataResponse = serviceBlockingStub
+                    metadataResponse = grpcConnector
+                            .getResolver()
                             .withDeadlineAfter(deadline, TimeUnit.MILLISECONDS)
                             .getMetadata(metadataRequest.build());
                 } catch (Exception e) {
@@ -164,27 +128,18 @@ static void observeEventStream(
 
                 while (!shutdown.get()) {
                     final GrpcResponseModel response = streamReceiver.take();
-
                     if (response.isComplete()) {
                         log.info("Sync stream completed");
-                        // The stream is complete, this isn't really an error but we should try to
+                        // The stream is complete, this isn't really an error, but we should try to
                         // reconnect
                         break;
                     }
 
                     Throwable streamException = response.getError();
                     if (streamException != null || metadataException != null) {
-                        long retryDelay = backoffService.getCurrentBackoffMillis();
-
-                        // if we are in silent recover mode, we should not expose the error to the client
-                        if (backoffService.shouldRetrySilently()) {
-                            logExceptions(Level.INFO, streamException, metadataException, retryDelay);
-                        } else {
-                            logExceptions(Level.ERROR, streamException, metadataException, retryDelay);
-                            if (!writeTo.offer(new QueuePayload(
-                                    QueuePayloadType.ERROR, "Error from stream or metadata", metadataResponse))) {
-                                log.error("Failed to convey ERROR status, queue is full");
-                            }
+                        if (!writeTo.offer(new QueuePayload(
+                                QueuePayloadType.ERROR, "Error from stream or metadata", metadataResponse))) {
+                            log.error("Failed to convey ERROR status, queue is full");
                         }
 
                         // close the context to cancel the stream in case just the metadata call failed
@@ -199,34 +154,10 @@ static void observeEventStream(
                     if (!writeTo.offer(new QueuePayload(QueuePayloadType.DATA, data, metadataResponse))) {
                         log.error("Stream writing failed");
                     }
-
-                    // reset backoff if we succeeded in a retry attempt
-                    backoffService.reset();
                 }
             }
-
-            // check for shutdown and avoid sleep
-            if (!shutdown.get()) {
-                log.debug("Stream failed, retrying in {}ms", backoffService.getCurrentBackoffMillis());
-                backoffService.waitUntilNextAttempt();
-            }
         }
 
         log.info("Shutdown invoked, exiting event stream listener");
     }
-
-    private static void logExceptions(
-            Level logLevel, Throwable streamException, Exception metadataException, long retryDelay) {
-        if (streamException != null) {
-            log.atLevel(logLevel)
-                    .setCause(streamException)
-                    .log("Error initializing stream, retrying in {}ms", retryDelay);
-        }
-
-        if (metadataException != null) {
-            log.atLevel(logLevel)
-                    .setCause(metadataException)
-                    .log("Error initializing metadata, retrying in {}ms", retryDelay);
-        }
-    }
 }

providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/resolver/process/InProcessResolverTest.java

@@ -67,9 +67,9 @@ public void connectorSetup() {
                 .build();
 
         // then
-        assertInstanceOf(GrpcStreamConnector.class, InProcessResolver.getConnector(forGrpcOptions));
-        assertInstanceOf(FileConnector.class, InProcessResolver.getConnector(forOfflineOptions));
-        assertInstanceOf(MockConnector.class, InProcessResolver.getConnector(forCustomConnectorOptions));
+        assertInstanceOf(GrpcStreamConnector.class, InProcessResolver.getConnector(forGrpcOptions, e -> {}));
+        assertInstanceOf(FileConnector.class, InProcessResolver.getConnector(forOfflineOptions, e -> {}));
+        assertInstanceOf(MockConnector.class, InProcessResolver.getConnector(forCustomConnectorOptions, e -> {}));
     }
 
     @Test