How to Troubleshoot an Apache Storm Topology

Apache Storm is a real-time, fault-tolerant, event-based streaming framework and platform that runs your code in a highly parallelized way on distributed nodes. It’s all about Spouts (processing units to read from data sources) and Bolts (general processing units). Storm is often used to read data from Apache Kafka and write the results back to Kafka or to a data store. Apache Storm and Apache Kafka are the work horses of the cyber security platform Apache Metron. Storm is also being used internally by the Streaming Analytics Manager (SAM)

This article guides you through the debugging process and points you to the places you need to tweak your configuration to get your topology up and running in a kerberized environment in case certain errors occur. For basic information on how to authenticate your application check out the reference implementation by Pierre Villard on his Github page.

Storm_logo

Prerequisites

I assume that you start from a certain point:

  • Your Storm cluster and the services you communicate with (Kafka, Zookeeper, HBase) is up and running as well as secure, i.e., the authentication happens through the Kerberos protocol.
  • Your Storm cluster is configured to run topologies as the OS user corresponding to the Kerberos principal who submitted the topology. (See: “Run worker processes as user who submitted the topology” in the excellent article of the Storm documentation)
  • Your topology (written in Java) is ready to be deployed and authentication is put in place.

Debugging Process

  • Use the Storm UI to check if the topology’s workers are throwing any errors and on which machine they are running! The worker’s log files are stored on the machine the worker is running in  /var/log/storm/workers-artifacts/<topology-name><unique-id>/<port-number>/worker.log.
  • Check the input data and output data of your Storm topology. In case you are using Kafka, connect via the Kafka console consumer and read from the input and the output topic of your topology! If you don’t see any events in the input Kafka topic, you should check upstream for errors. If you do see input events, but no output events, refer to your topology logs described in the item above. If you do see output events, check if they have the expected format (data format, number and kind of fields are correct, fields contain data that makes sense as opposed to null values)

Screen Shot 2018-07-16 at 19.49.37

# List Kafka topics:
bin/kafka-topics.sh --zookeeper <zookeeper.hostname>:<zookeeper.port> --list

# print messages as they are written on stdout from input topic
bin/kafka-console-consumer.sh --bootstrap-server <kafka.broker.hostname>:<kafka.broker.port> --topic input

# print messages as they are written on stdout from output topic
bin/kafka-console-consumer.sh --bootstrap-server <kafka.broker.hostname>:<kafka.broker.port> --topic output

Possible Error Scenarios

Authentication Errors Exception

Caused by: javax.security.auth.login.LoginException: Could not login: the client is being asked for a password, but the Kafka client code does not currently support obtaining a password from the user. not available to garner authentication information from the user

Your topology is being submitted and the supervisor tries to start and initialize the Spouts and Bolts in the worker process based on the configuration you provided. When this error occurs the worker process is killed and the supervisor tries to spawn a new worker process. On the machine the worker is supposed to run, you can see a worker process popping up with a certain PID (ps aux | grep <topology_name>). A few seconds later this process is killed and a process exactly as the old one is started with a different PID. You can also tail the worker log and see this error message. Soon afterwards the “Worker has died” message appears. This can happen for various reasons:

  • The OS user running the topology does not have the permission to read the keytabs configured in the jaas config file. Check with ps aux or top which user is running and check if the keytab has the correct POSIX attributes. Usually it should be read-only by the owning user (-r– — — <topology-user><topology-user>)
  • The jaas configuration points to the wrong keytabs to be used for authentication and the OS user does not have permission to those. Check with ps aux which jaas file is configured. You might find an option there. Check if this jaas config file has the desired authentication options configured. If not configure your own and pass it to the topology.
-Djava.security.auth.login.config=/etc/storm/conf/client_jaas.conf

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