[Question] ClassNotFoundException on kafka-connect startup

I was playing around with Kafka Connect and created a small sample project that setups all needed services + Kafka Connect using Docker Compose. All services start, but logs of kafka-connect are bothering me. I see a lot of ClassNotFoundException when it loads plugins. I did not configure neither CONNECT_PLUGIN_PATH, nor CLASSPATH, did not add volumes with additional plugins, so I supposed that it should work out of the box without these vars. Here is the whole startup log.

Could someone advise what is incorrect in my setup?

[puneetloya]

I had a similar experience using kafka-connect docker image but with kubernetes.

kind: Deployment
metadata:
  name: {{ template "kafka.fullname" . }}-connect
  labels:
    app: {{ include "kafka.name" . | quote }}
    chart: "{{ .Chart.Name }}-{{ .Chart.Version }}"
    release: {{ .Release.Name | quote }}
    heritage: {{ .Release.Service | quote }}
spec:
  selector:
    matchLabels:
      app: {{ include "kafka.name" . | quote }}
  template:
    metadata:
      labels:
        app: {{ include "kafka.name" . | quote }}
    spec:
      containers:
      - name: kafka-connect
        image: confluentinc/cp-kafka-connect:4.1.1-1
        env:
        - name: AWS_ACCESS_KEY_ID
          valueFrom:
            secretKeyRef:
              name: {{ .Values.yyy }}
              key: S3_ACCESS_KEY
        - name: AWS_SECRET_ACCESS_KEY
          valueFrom:
            secretKeyRef:
              name: {{ .Values.xxx }}
              key: S3_SECRET
        - name: COMPONENT
          value: "kafka-connect"
        - name: CONNECT_BOOTSTRAP_SERVERS
          value: {{ template "kafka.fullname" . }}-headless:9092
        - name: CONNECT_SASL_MECHANISM
          value: "PLAIN"
        - name: CONNECT_SECURITY_PROTOCOL
          value: "SASL_PLAINTEXT"
        - name: CONNECT_GROUP_ID
          value: "kafka-connect"
        - name: CONNECT_CONFIG_STORAGE_TOPIC
          value: "connect-configs"
        - name: CONNECT_OFFSET_STORAGE_TOPIC
          value: "connect-offsets"
        - name: CONNECT_STATUS_STORAGE_TOPIC
          value: "connect-status"
        - name: CONNECT_KEY_CONVERTER
          value: "io.confluent.connect.avro.AvroConverter"
        - name: CONNECT_VALUE_CONVERTER
          value: "io.confluent.connect.avro.AvroConverter"
        - name: CONNECT_INTERNAL_KEY_CONVERTER
          value: "org.apache.kafka.connect.json.JsonConverter"
        - name: CONNECT_INTERNAL_VALUE_CONVERTER
          value: "org.apache.kafka.connect.json.JsonConverter"
        - name: CONNECT_REST_ADVERTISED_HOST_NAME
          value: {{ template "kafka.fullname" . }}-connect
        - name: CONNECT_STORE_URL
          value: {{ .Values.connect.s3.endpoint }}
        - name: CONNECT_S3_BUCKET_NAME
          value: {{ .Values.connect.s3.bucket }}
        - name: CONNECT_TOPICS
          value: "organization_ingress_throughput"
        - name: CONNECT_TASKS_MAX
          value: "1"
        - name: CONNECT_SCHEMA_COMPATIBILITY
          value: "NONE"
        - name: CONNECT_CONNECTOR_CLASS
          value: "io.confluent.connect.s3.S3SinkConnector"
        - name: CONNECT_STORAGE_CLASS
          value: "io.confluent.connect.s3.storage.S3Storage"
        - name: CONNECT_FORMAT_CLASS
          value: "io.confluent.connect.s3.format.json.JsonFormat"
        - name: CONNECTOR_NAME
          value: "s3-sink"
        - name: CONNECT_LOG4J_ROOT_LOGLEVEL
          value: "DEBUG"
        # - name: CONNECT_LOG4J_LOGGERS
        #   value: "org.reflections=ERROR"
        - name: CONNECT_KEY_CONVERTER_SCHEMA_REGISTRY_URL
          value: "http://localhost:8081"
        - name: CONNECT_VALUE_CONVERTER_SCHEMA_REGISTRY_URL
          value: "http://localhost:8081"
        - name: CONNECT_PLUGIN_PATH
          value: "/usr/share/java,/etc/kafka-connect/jars" 
        - name: EXTRA_ARGS
          value: "-Djava.security.auth.login.config=client.jaas.conf"

The log is here: https://gist.github.com/puneetloya/33c7d66865892513c7b7d01a01cc2cfa

[liangry]

I solved the problem with the tips: http://mail-archives.apache.org/mod_mbox/kafka-users/201707.mbox/<CABqDk2NgWS0faAyYKdXGs4t=[e-mail]>

If you are running kafka connect with docker image, add this config to /etc/confluent/docker/log4j.properties.template:

log4j.logger.org.reflections=ERROR