feat: add gRPC keepalive

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/Config.java

@@ -18,6 +18,7 @@ public final class Config {
 
     static final int DEFAULT_DEADLINE = 500;
     static final int DEFAULT_MAX_CACHE_SIZE = 1000;
+    static final long DEFAULT_KEEP_ALIVE = 0;
 
     static final String RESOLVER_ENV_VAR = "FLAGD_RESOLVER";
     static final String HOST_ENV_VAR_NAME = "FLAGD_HOST";
@@ -32,6 +33,7 @@ public final class Config {
     static final String DEADLINE_MS_ENV_VAR_NAME = "FLAGD_DEADLINE_MS";
     static final String SOURCE_SELECTOR_ENV_VAR_NAME = "FLAGD_SOURCE_SELECTOR";
     static final String OFFLINE_SOURCE_PATH = "FLAGD_OFFLINE_FLAG_SOURCE_PATH";
+    static final String KEEP_ALIVE_ENV_VAR_NAME = "FLAGD_KEEP_ALIVE";
 
     static final String RESOLVER_RPC = "rpc";
     static final String RESOLVER_IN_PROCESS = "in-process";
@@ -64,6 +66,14 @@ static int fallBackToEnvOrDefault(String key, int defaultValue) {
         }
     }
 
+    static long fallBackToEnvOrDefault(String key, long defaultValue) {
+        try {
+            return System.getenv(key) != null ? Long.parseLong(System.getenv(key)) : defaultValue;
+        } catch (Exception e) {
+            return defaultValue;
+        }
+    }
+
     static Resolver fromValueProvider(Function<String, String> provider) {
         final String resolverVar = provider.apply(RESOLVER_ENV_VAR);
         if (resolverVar == null) {

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/FlagdOptions.java

@@ -93,6 +93,14 @@ public class FlagdOptions {
     @Builder.Default
     private String selector = fallBackToEnvOrDefault(Config.SOURCE_SELECTOR_ENV_VAR_NAME, null);
 
+    /**
+     * gRPC client KeepAlive in milliseconds. Disabled with 0.
+     * Defaults to 0 (disabled).
+     * 
+     **/
+    @Builder.Default
+    private long keepAlive = fallBackToEnvOrDefault(Config.KEEP_ALIVE_ENV_VAR_NAME, Config.DEFAULT_KEEP_ALIVE);
+
     /**
      * File source of flags to be used by offline mode.
      * Setting this enables the offline mode of the in-process provider.

providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/common/ChannelBuilder.java

@@ -13,6 +13,7 @@
 
 import javax.net.ssl.SSLException;
 import java.io.File;
+import java.util.concurrent.TimeUnit;
 
 /**
  * gRPC channel builder helper.
@@ -36,6 +37,9 @@ public static ManagedChannel nettyChannel(final FlagdOptions options) {
 
             return NettyChannelBuilder
                     .forAddress(new DomainSocketAddress(options.getSocketPath()))
+                    // keepAliveTime: Long.MAX_VALUE disables keepAlive; very small values are increased automatically
+                    .keepAliveTime(options.getKeepAlive() == 0 ? Long.MAX_VALUE : options.getKeepAlive(),
+                            TimeUnit.MILLISECONDS)
                     .eventLoopGroup(new EpollEventLoopGroup())
                     .channelType(EpollDomainSocketChannel.class)
                     .usePlaintext()

providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/FlagdOptionsTest.java

@@ -3,7 +3,6 @@
 import dev.openfeature.contrib.providers.flagd.resolver.process.storage.MockConnector;
 import dev.openfeature.contrib.providers.flagd.resolver.process.storage.connector.Connector;
 import io.opentelemetry.api.OpenTelemetry;
-import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 import org.junitpioneer.jupiter.SetEnvironmentVariable;
 import org.mockito.Mockito;
@@ -33,6 +32,7 @@ void TestDefaults() {
         assertNull(builder.getCustomConnector());
         assertNull(builder.getOfflineFlagSourcePath());
         assertEquals(Resolver.RPC, builder.getResolverType());
+        assertEquals(0, builder.getKeepAlive());
     }
 
     @Test
@@ -53,6 +53,7 @@ void TestBuilderOptions() {
                 .openTelemetry(openTelemetry)
                 .customConnector(connector)
                 .resolverType(Resolver.IN_PROCESS)
+                .keepAlive(1000)
                 .build();
 
         assertEquals("https://hosted-flagd", flagdOptions.getHost());
@@ -67,6 +68,7 @@ void TestBuilderOptions() {
         assertEquals(openTelemetry, flagdOptions.getOpenTelemetry());
         assertEquals(connector, flagdOptions.getCustomConnector());
         assertEquals(Resolver.IN_PROCESS, flagdOptions.getResolverType());
+        assertEquals(1000, flagdOptions.getKeepAlive());
     }
 
 

providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/resolver/grpc/GrpcConnectorTest.java

@@ -5,6 +5,7 @@
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyInt;
+import static org.mockito.ArgumentMatchers.anyLong;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.ArgumentMatchers.argThat;
 import static org.mockito.Mockito.doAnswer;
@@ -277,6 +278,7 @@ private NettyChannelBuilder getMockChannelBuilderSocket() {
         when(mockChannelBuilder.eventLoopGroup(any(EventLoopGroup.class))).thenReturn(mockChannelBuilder);
         when(mockChannelBuilder.channelType(any(Class.class))).thenReturn(mockChannelBuilder);
         when(mockChannelBuilder.usePlaintext()).thenReturn(mockChannelBuilder);
+        when(mockChannelBuilder.keepAliveTime(anyLong(), any())).thenReturn(mockChannelBuilder);
         when(mockChannelBuilder.build()).thenReturn(null);
         return mockChannelBuilder;
     }