Incorrect ELASTIC_HOSTS variable in Logstash container

[thibaut_a]

Hi, I have a docker compose file with which I start 3 ES nodes (+ 1 for the setup), 1 Kibana, and 1 Logstash. The 4th ones works well when I deploy, but Logstash crashes. Here is the error I get from logs:

[2024-03-18T11:59:04,717][ERROR][logstash.agent           ] Failed to execute action {:action=>LogStash::PipelineAction::Create/pipeline_id:main, :exception=>"Java::JavaLang::IllegalStateException", :message=>"Unable to configure plugins: Illegal character in scheme name at index 0: \"https://es01:9200,https://es02:9200,https://es03:9200\"", :backtrace=>["org.logstash.config.ir.CompiledPipeline.<init>(CompiledPipeline.java:120)", "org.logstash.execution.AbstractPipelineExt.initialize(AbstractPipelineExt.java:186)", "org.logstash.execution.AbstractPipelineExt$INVOKER$i$initialize.call(AbstractPipelineExt$INVOKER$i$initialize.gen)", "org.jruby.internal.runtime.methods.JavaMethod$JavaMethodN.call(JavaMethod.java:846)", "org.jruby.ir.runtime.IRRuntimeHelpers.instanceSuper(IRRuntimeHelpers.java:1229)", "org.jruby.ir.instructions.InstanceSuperInstr.interpret(InstanceSuperInstr.java:131)", "org.jruby.ir.interpreter.InterpreterEngine.processCall(InterpreterEngine.java:361)", "org.jruby.ir.interpreter.StartupInterpreterEngine.interpret(StartupInterpreterEngine.java:72)", "org.jruby.internal.runtime.methods.MixedModeIRMethod.INTERPRET_METHOD(MixedModeIRMethod.java:128)", "org.jruby.internal.runtime.methods.MixedModeIRMethod.call(MixedModeIRMethod.java:115)", "org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:329)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:87)", "org.jruby.RubyClass.newInstance(RubyClass.java:911)", "org.jruby.RubyClass$INVOKER$i$newInstance.call(RubyClass$INVOKER$i$newInstance.gen)", "org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:329)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:87)", "org.jruby.ir.instructions.CallBase.interpret(CallBase.java:549)", "org.jruby.ir.interpreter.InterpreterEngine.processCall(InterpreterEngine.java:361)", "org.jruby.ir.interpreter.StartupInterpreterEngine.interpret(StartupInterpreterEngine.java:72)", "org.jruby.ir.interpreter.InterpreterEngine.interpret(InterpreterEngine.java:92)", "org.jruby.internal.runtime.methods.MixedModeIRMethod.INTERPRET_METHOD(MixedModeIRMethod.java:238)", "org.jruby.internal.runtime.methods.MixedModeIRMethod.call(MixedModeIRMethod.java:225)", "org.jruby.internal.runtime.methods.DynamicMethod.call(DynamicMethod.java:226)", "org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:393)", "org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:206)", "org.jruby.ir.interpreter.InterpreterEngine.processCall(InterpreterEngine.java:325)", "org.jruby.ir.interpreter.StartupInterpreterEngine.interpret(StartupInterpreterEngine.java:72)", "org.jruby.ir.interpreter.Interpreter.INTERPRET_BLOCK(Interpreter.java:116)", "org.jruby.runtime.MixedModeIRBlockBody.commonYieldPath(MixedModeIRBlockBody.java:136)", "org.jruby.runtime.IRBlockBody.call(IRBlockBody.java:66)", "org.jruby.runtime.IRBlockBody.call(IRBlockBody.java:58)", "org.jruby.runtime.Block.call(Block.java:143)", "org.jruby.RubyProc.call(RubyProc.java:309)", "org.jruby.internal.runtime.RubyRunnable.run(RubyRunnable.java:107)", "java.base/java.lang.Thread.run(Thread.java:833)"]}
[2024-03-18T11:59:04,747][INFO ][logstash.runner          ] Logstash shut down.
[2024-03-18T11:59:04,755][FATAL][org.logstash.Logstash    ] Logstash stopped processing because of an error: (SystemExit) exit
org.jruby.exceptions.SystemExit: (SystemExit) exit
        at org.jruby.RubyKernel.exit(org/jruby/RubyKernel.java:790) ~[jruby.jar:?]
        at org.jruby.RubyKernel.exit(org/jruby/RubyKernel.java:753) ~[jruby.jar:?]
        at usr.share.logstash.lib.bootstrap.environment.<main>(/usr/share/logstash/lib/bootstrap/environment.rb:91) ~[?:?]

I want to specify my 3 hosts ES nodes in the ELASTIC_HOSTS variable. I tried a lot of combinations but each one I defined fails at the end (some times as a string, some as an array, with single/double quotes, with(out) backslashes, ...). I didn't find anything on the Internet too.

Logstash service:

  logstash01:
    depends_on:
      es01:
        condition: service_healthy
      es02:
        condition: service_healthy
      es03:
        condition: service_healthy
      kibana:
        condition: service_healthy
    image: docker.elastic.co/logstash/logstash:${STACK_VERSION}
    labels:
      co.elastic.logs/module: logstash
    user: root
    volumes:
      - certs:/usr/share/logstash/certs
      - logstashdata01:/usr/share/logstash/data
      - "./logstash_ingest_data/:/usr/share/logstash/ingest_data/"
      - "./logstash.conf:/usr/share/logstash/pipeline/logstash.conf:ro"
    ports:
      - ${BEATS_PORT}:5044
      - 5000:5000
      - 9600:9600
    environment:
      - xpack.monitoring.enabled=false
      - ELASTIC_USER=elastic
      - ELASTIC_PASSWORD=${ELASTIC_PASSWORD}
      ### WIP ###
      - ELASTIC_HOSTS="https://es01:9200,https://es02:9200,https://es03:9200"
      ##########
    deploy:
      resources:
        limits:
          memory: 1G

logstash.conf output:

output {
  elasticsearch {
    index => "logstash-%{+YYYY.MM.dd}"
    hosts=> "${ELASTIC_HOSTS}"
    user=> "${ELASTIC_USER}"
    password=> "${ELASTIC_PASSWORD}"
    cacert=> "certs/ca/ca.crt"
  }
}

If I only put es01 as host, it works but I want to add load balancing between nodes.

Thank you in advance to anyone having an idea.
Thibaut

[thibaut_a]

Actually, I found the answer totally randomly (I was looking for a solution for some days).

For those asking, you can set the variable like this :

      - ELASTIC_HOSTS=https://es01:9200 https://es02:9200 https://es03:9200

It's not intuitive at all but at least, it works.