Salesforce Pub/Sub Connector | io.grpc.StatusRuntimeException: UNAVAILABLE: io exception

SYMPTOM

org.mule.runtime.api.exception.DefaultMuleException: UNAVAILABLE: io exception
Caused by: io.grpc.StatusRuntimeException: UNAVAILABLE: io exception
	at io.grpc.stub.ClientCalls.toStatusRuntimeException(ClientCalls.java:262) ~[grpc-stub-1.45.0.jar:1.45.0]
	at io.grpc.stub.ClientCalls.getUnchecked(ClientCalls.java:243) ~[grpc-stub-1.45.0.jar:1.45.0]
	at io.grpc.stub.ClientCalls.blockingUnaryCall(ClientCalls.java:156) ~[grpc-stub-1.45.0.jar:1.45.0]
	at com.mulesoft.connector.salesforce.pubsub.internal.protobuf.PubSubGrpc$PubSubBlockingStub.getTopic(PubSubGrpc.java:566) ~[mule4-salesforce-pubsub-connector-1.0.1-mule-plugin.jar:?]
	at com.mulesoft.connector.salesforce.pubsub.internal.connection.PubSubConnection.validate(PubSubConnection.java:102) ~[mule4-salesforce-pubsub-connector-1.0.1-mule-plugin.jar:?]
	at com.mulesoft.connector.salesforce.pubsub.internal.source.SubscribeChannelSource.onStart(SubscribeChannelSource.java:137) ~[mule4-salesforce-pubsub-connector-1.0.1-mule-plugin.jar:?]
	at org.mule.runtime.module.extension.internal.runtime.source.legacy.SdkSourceAdapter.onStart(SdkSourceAdapter.java:53) ~[?:?]
	at org.mule.runtime.module.extension.internal.runtime.source.SourceAdapter.start(SourceAdapter.java:430) ~[?:?]
	at org.mule.runtime.module.extension.internal.runtime.source.ExtensionMessageSource.doWork(ExtensionMessageSource.java:581) ~[?:?]
	at org.mule.runtime.module.extension.internal.runtime.source.ExtensionMessageSource.lambda$null$2(ExtensionMessageSource.java:229) ~[?:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) [?:?]
	at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
	at org.mule.service.scheduler.internal.AbstractRunnableFutureDecorator.doRun(AbstractRunnableFutureDecorator.java:113) [mule-service-scheduler-1.4.1/:?]
	at org.mule.service.scheduler.internal.RunnableFutureDecorator.run(RunnableFutureDecorator.java:54) [mule-service-scheduler-1.4.1/:?]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) [?:?]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) [?:?]
	at java.lang.Thread.run(Thread.java:834) [?:?]
Caused by: io.grpc.netty.shaded.io.netty.channel.AbstractChannel$AnnotatedConnectException: Connection timed out: no further information: api.pilot.pubsub.salesforce.com
Caused by: java.net.ConnectException: Connection timed out: no further information
	at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method) ~[?:?]
	at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:779) ~[?:?]
	at io.grpc.netty.shaded.io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:330) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at io.grpc.netty.shaded.io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:334) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at io.grpc.netty.shaded.io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:710) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at io.grpc.netty.shaded.io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:658) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at io.grpc.netty.shaded.io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:584) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at io.grpc.netty.shaded.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:496) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at io.grpc.netty.shaded.io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:986) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at io.grpc.netty.shaded.io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at io.grpc.netty.shaded.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[grpc-netty-shaded-1.45.0.jar:1.45.0]
	at java.lang.Thread.run(Thread.java:834) ~[?:?]

CAUSE

There are two possible causes:

1. There is no connectivity to the gRPC host and port. Telnet connection to gRPC host and port fails.
2. If you are using Salesforce Pub/Sub Connector version 1.0.4 or lower and have a proxy configuration in the General -> Advanced tab of the connector configuration, it is because the connector is not honoring the proxy configuration when validating Pub/Sub API Connection.
 

SOLUTION