Ask questionsPubSub: grpc Uncaught exception in the SynchronizationContext. Panic! - Could not find LoadBalancer pick_first

  1. Specify the API: PubSub
  2. OS type and version: Docker image gradle:5.2-jdk11-slim (also happens with jdk8 and other images)
  3. Java version: jdk11 and jdk8
  4. google-cloud-java version(s): 1.62.0 and above (tested with 1.65.0, too)

Steps to reproduce

  1. Use google-cloud-pubsub library with version 1.62.0 or above as dependency
  2. Create a subscription in own code (see code example below)

Code example

ProjectSubscriptionName subscriptionName = ProjectSubscriptionName.of(projectId, subscriptionId);
try (SubscriptionAdminClient subscriptionAdminClient = SubscriptionAdminClient.create()) {
    subscriptionAdminClient.getSubscription(subscriptionName); // Exception is thrown in this line

Stack trace

Mar 19, 2019 6:20:52 PM io.grpc.internal.ManagedChannelImpl$1 uncaughtException
SEVERE: [io.grpc.internal.ManagedChannelImpl-1] Uncaught exception in the SynchronizationContext. Panic!
java.lang.IllegalStateException: Could not find LoadBalancer pick_first. The build probably threw away META-INF/services/io.grpc.LoadBalancerProvider
        at io.grpc.internal.AutoConfiguredLoadBalancerFactory$AutoConfiguredLoadBalancer.<init>(
        at io.grpc.internal.AutoConfiguredLoadBalancerFactory.newLoadBalancer(
        at io.grpc.internal.ManagedChannelImpl.exitIdleMode(
        at io.grpc.internal.ManagedChannelImpl$ChannelTransportProvider$
        at io.grpc.SynchronizationContext.drain(
        at io.grpc.SynchronizationContext.execute(
        at io.grpc.internal.ManagedChannelImpl$ChannelTransportProvider.get(
        at io.grpc.internal.ClientCallImpl.start(
        at io.grpc.internal.CensusTracingModule$TracingClientInterceptor$1.start(
        at io.grpc.internal.CensusStatsModule$StatsClientInterceptor$1.start(
        at io.grpc.ForwardingClientCall.start(
        at io.grpc.stub.ClientCalls.startCall(
        at io.grpc.stub.ClientCalls.asyncUnaryRequestCall(
        at io.grpc.stub.ClientCalls.futureUnaryCall(
        at my.package.MyClass.start(
        at my.package.App$
        at java.base/

External references such as API reference guides used

  • None

Any additional information below

The error only occurs since google-cloud-pubsub 1.62.0 . When using google-cloud-pubsub 1.61.0 or below, the error does not occur with the same user code.


Answer questions cakism

So happy to have found this thread as I've had exactly the same issue and tried a plethora of increasingly weird things in what can only be described as superstition based coding, but adding the files in the


like above finally did the trick! 🙌

Running a Kotlin project with the Cloud PubSub Java Client Lib in Docker for Mac.


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