Dead letter queue not working with logtash output mongo

Hi everyone,

I intend to use dead letter queue on log event failure from sending log into mongodb use logtash.
My config includes:

logtash.yml ""

pipeline.batch.delay: 10

pipeline.batch.size: 10

pipeline.ecs_compatibility: disabled

dead_letter_queue.enable: true


- backup_elastics
  pipeline.ecs_compatibility: disabled
  path.config: "/usr/share/logstash/pipeline/dead-letter-queue.conf"

- "read-file-log"
  pipeline.ecs_compatibility: disabled
  path.config: "/usr/share/logstash/pipeline/read-file.conf"

with config 2 pipelines, one for send log into mongodb

    file {
        type => "dummylog"
        path => ["/home/data/*.log"]

    if [type] == "dummylog" {
      mongodb {
        collection => "logtash_mongodb"
        database => "dmp_log"
        uri => "mongodb://logtash:logtash@mongodb:27017/dmp_log"
        codec => "json"
    stdout {
      codec => rubydebug

the second will write into elastics if any failed log event

input {
  dead_letter_queue {
    id => "backup_elastics"
    pipeline_id => "read-file-log"
    commit_offsets => true
    path => "/usr/share/logstash/data/dead_letter_queue/"

output {
  elasticsearch {
    hosts => [ "elasticsearch:9200" ]
    index => "logs-%{+YYYY.MM.dd}"
    manage_template => false
  stdout {
    codec => rubydebug

but when mongo got problem, it's not send into the dead letter queue.

logtash-mongo-logstash-1       | [WARN ] 2022-10-07 04:59:56.849 [[read-file-log]>worker1] mongodb - Failed to send event to MongoDB, retrying in 3 seconds {:event=>#<LogStash::Event:0x31ec7696>, :exception=>#<Mongo::Error::NoServerAvailable: No server is available matching preference: #<Mongo::ServerSelector::Primary:0x7a355ad8 @tag_sets=[], @server_selection_timeout=30, @options={:database=>"dmp_log", :user=>"logtash", :password=>"logtash"}>>}

I'm using logtash 7.17.6, logtash output mongodb version 3.1.5.
So any config above wrong? or how can i catch the error from first pipeline(logtash-mongodb) to process failed event?

Thank you.

According to the documentation the DLQ is only supported by the elasticsearch output. Any output could be modified to use a dlq_writer, but that has only been done for the elasticsearch output.

1 Like

yes, thank you
i miss the note below

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