Reliable Kafka Output Plugin config

I'm wondering about a way how to make output to Kafka reliable. I am new to Kafka, so I'm sorry about any logical errors.

I use Logstash 5.4.0 and Kafka with a matching Zookeeper. The Kafka setup is rather simple with a single instance and single broker.

My basic idea is to parse events from pseudo-log files on file system and send them to Kafka in a reliable manner.

I thought about network issues, Kafka being down, etc. So I added retries etc. to my Kafka output plugin config. The basic test scenario involving stdin/stdout was:

  • fire up both Kafka and Logstash
  • Logstash emits events based on stdin input
  • read events from a Kafka topic with a simple stdout consumer
  • stop Kafka
  • keep emitting events in Logstash - they should be retrying, right?
  • start Kafka again
  • read events from start of the Kafka topic - retried should be present, right?

After I start the Kafka no new events are shown. Thus it seems to me like the retry policy doesn't take effect.

Pipeline setup:

 input { stdin { } }
 output {
    kafka {
       codec => plain {
          format => "%{message}"
       topic_id => "test"
       client_id => "test_console_client"
       bootstrap_servers => "kafka:9092"
       acks => "all"
       retries => 999 
       retry_backoff_ms => 10000
       block_on_buffer_full => true

I've tried to examine the pipeline's internals through _node/stats/pipeline. I got equal no. of "in" and "out" events for the Kafka plugin even when the Kafka was down.

Is my setup wrong? Is the testing idea flawed?

Thanks in advance!

The cause is a setting called The default is set to 60 000ms. After this timeout the message is dropped.

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