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Troubleshooting

Counters

As described here, Bruce's web interface provides counter reports that can be used for troubleshooting. Some of Bruce's more interesting counters are as follows:

  • MsgCreate: This is incremented each time Bruce creates a message.
  • MsgDestroy: This is incremented each time Bruce destroys a message. The value MsgCreate - MsgDestroy indicates the total number of messages Bruce is currently holding internally. If the value gets too large, it likely indicates that Kafka isn't keeping up with the volume of messages directed at it.
  • MsgUnprocessedDestroy: This indicates destruction of a message before Bruce has marked it as processed. If this occurs for any reason other than Bruce exiting on a fatal error, then there is a bug in Bruce. On occurrence of this type of event, Bruce will write a syslog message containing a stack trace, which will help track down problems.
  • AckErrorXxx: AckErrorNone indicates a successful ACK from Kafka. All other counters of this type indicate various types of error ACKs received from Kafka, as documented here.
  • XxxInputAgentDiscardXxx and DiscardXxx: These counters are incremented when Bruce discards messages for various reasons.
  • BugXxx: A nonzero value for any counter starting with the prefix Bug indicates a bug in Bruce.
  • MongooseXxx: These counters indicate events related to Bruce's web interface.
  • NoDiscardQuery: This is incremented when Bruce stops getting asked for discard reports at frequent enough intervals. To avoid losing discard information, it is recommended to query Bruce's discard reporting interface at intervals somewhat shorter that Bruce's discard reporting interval.

It is also useful to look in src/bruce/scripts/check_bruce_counters.py to see which counters the script monitors and how it responds to incremented values.

Discard File Logging

For debugging and troubleshooting purposes, it may be helpful to configure Bruce to log discards to local files. To do this, see the --discard_log_path PATH, --discard_log_bad_msg_prefix_size N, --discard_log_max_file_size N, and --discard_log_max_archive_size N command line options, which are documented here. As documented here, a Kafka message consists of a key and a value, either of which may be empty. Each line of the logfile contains information for a single discarded message. The keys and values of the messages are written in base64 encoded form.

Debug Logfiles

As documented here, the --debug_dir DIR, --msg_debug_time_limit N and --msg_debug_byte_limit N command line options configure Bruce's debug logfile mechanism, which causes Bruce to maintain 3 separate logfiles: One for messages received from its input socket, one for messages sent to Kafka, and one for messages that Bruce received a successful ACK for. The --debug_dir DIR option specifies the directory in which these files are placed. To start and stop the logging mechanism, you must send HTTP requests to Bruce's web interface as follows:

  • To start logging for a specific topic, send an HTTP GET to http://bruce_host:9090/msg_debug/add_topic/name_of_topic.
  • To stop logging for a specific topic, send an HTTP GET to http://bruce_host:9090/msg_debug/del_topic/name_of_topic.
  • To start logging for all topics, send an HTTP GET to http://bruce_host:9090/msg_debug/add_all_topics.
  • To stop logging for all topics, send an HTTP GET to http://bruce_host:9090/msg_debug/del_all_topics.
  • To see which topics are currently being logged, send an HTTP GET to http://bruce_host:9090/msg_debug/get_topics.
  • To stop logging and make the debug logfiles empty, send an HTTP GET to http://bruce_host:9090/msg_debug/truncate_files.

Once debug logging is started, it will automatically stop when either the time limit specified by --msg_debug_time_limit N expires or the debug logfile size limit specified by --msg_debug_byte_limit N is reached. As with discard logfiles, keys and values are written in base64 encoded form.

Other Tools

Bruce's queue status interface described here provides per-topic information on messages being processed by Bruce. In cases where Kafka isn't keeping up with the message volume, this may be helpful in identifying specific topics that are placing heavy load on the system. Useful information can also be obtained from Bruce's syslog messages. As documented here, the --log_level LEVEL command line option configures Bruce's logging verbosity.

If you are interested in making custom modifications or contributing to Bruce, information is provided here.

troubleshooting.md: Copyright 2014 if(we), Inc.

troubleshooting.md is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

You should have received a copy of the license along with this work. If not, see http://creativecommons.org/licenses/by-sa/4.0/.