Exception in ReadChannelOnceAsync method unexpectedly pauses the consumer.

[jheisong]

Problem Description
An exception occurred in the ReadChannelOnceAsync method of the Silverback.Messaging.Broker.Kafka.ConsumerChannelsManager class. The exception was logged but caused the consumer to pause. We have error policies implemented in the OnError method, using a specialization of RetryableErrorPolicyBase, but this specific exception (System.Threading.Channels.ChannelClosedException) was not captured by the configured policy.

We would like to understand how this exception can be externally captured so we can implement an action to handle it.

This behavior has caused unexpected interruptions in the message flow and requires manual intervention to restart the consumer.

Steps to Reproduce
Currently, we are unable to consistently reproduce the issue. However, this behavior has been observed multiple times in the production environment.

Expected
The consumer should automatically restart and continue processing messages even after such an exception. Alternatively, we should be able to capture the exception within the error policies.

Actual
The consumer is paused after the exception, and no automatic recovery occurs, even with error policies configured.

Versions Used:
Silverback.Integration.HealthChecks: 4.5.1
Silverback.Integration.Newtonsoft: 4.5.1
Framework: .NET 8.0

Error Policy Configuration:
.OnError(policy)
Using a specialization of RetryableErrorPolicyBase.

Logs:
{
"attributes": {
"MessageTemplate": "Fatal error occurred processing the consumed message. The consumer will be stopped. | consumerId: {consumerId}, endpointName: {endpointName}",
"Level": "Fatal",
"Properties": {
"ExceptionDetail": {
"Type": "System.Threading.Channels.ChannelClosedException",
"Message": "The channel has been closed.",
"HResult": -2146233079,
"TargetSite": "Void Throw()",
"Source": "System.Private.CoreLib"
},
"ApplicationName": "",
"MachineName": "",
"ThreadId": 67,
"consumerId": "",
"endpointName": "*",
"EventId": {
"Id": 1023,
"Name": "Silverback.Integration_ConsumerFatalError"
},
"SourceContext": "Silverback.Messaging.Broker.KafkaConsumer"
},
"error": {
"stack": "System.Threading.Channels.ChannelClosedException: The channel has been closed.\n at System.Threading.Channels.AsyncOperation1.GetResult(Int16 token)\n at Silverback.Messaging.Broker.Kafka.ConsumerChannelsManager.ReadChannelOnceAsync(Int32 channelIndex, CancellationToken cancellationToken)\n at Silverback.Messaging.Broker.Kafka.ConsumerChannelsManager.ReadChannelAsync(Int32 channelIndex, CancellationToken cancellationToken)", "kind": "System.Threading.Channels.ChannelClosedException", "message": "The channel has been closed." }, "Timestamp": "2025-01-06T23:58:00.0751329+00:00", "Exception": "System.Threading.Channels.ChannelClosedException: The channel has been closed.\n at System.Threading.Channels.AsyncOperation1.GetResult(Int16 token)\n at Silverback.Messaging.Broker.Kafka.ConsumerChannelsManager.ReadChannelOnceAsync(Int32 channelIndex, CancellationToken cancellationToken)\n at Silverback.Messaging.Broker.Kafka.ConsumerChannelsManager.ReadChannelAsync(Int32 channelIndex, CancellationToken cancellationToken)"
}
}

Questions

1. Is this the expected behavior for this exception (ChannelClosedException)?
2. How can we configure Silverback to capture this exception and automatically restart the consumer, avoiding it being paused?
   3 . Are there any configurations or best practices to prevent consumer interruptions due to uncaptured exceptions?

Thank you for your attention and support! ;)

[BEagle1984]

Thank you for reporting this issue. This is indeed a bug; such an exception should not occur, and in the worst case, the consumer should be able to recover gracefully. I encountered this behavior previously and believed it had been resolved.

Could you provide more details about your consumer configuration? For instance:

Are you batch consuming?
How many partitions are you working with?
Are partitions processed together or independently?
Additionally, how frequently does this issue occur? Have you noticed any specific triggers, such as a rebalance during a deployment, unusually high load, or any other notable patterns?

Lastly, is it possible for you to upgrade to version 4.6.0? There was a minor adjustment to channel handling between versions 4.5.1 and 4.6.0, which might influence this behavior.

[jheisong]

Thank you very much for your attention and clarifications.

Batch Consumption: No.
Number of Partitions: 5.
Partition Processing: Partitions are processed independently.

Frequency of the Issue:
It happens sporadically. These errors occur at this level without being encapsulated by the FatalExceptionLoggerConsumerBehavior. However, they are rare and sporadic events relative to the message volume.

Observed Triggers:
No unusual behavior has been observed in our ecosystem at the moment.

Current Version:
We have upgraded to version 4.6.0 and are redeploying the application.

We have also set up some monitoring rules to identify exceptions with the same pattern, containing the message "The consumer will be stopped." and where the SourceContext is not FatalExceptionLoggerConsumerBehavior. I will monitor the situation over the next few days and provide updates here with more details if it happens again.

If you need further details, I am at your disposal.

Thank you again for your support and collaboration.