System Log Monitor

System Log Monitor is a problem daemon in node problem detector. It monitors specified system daemon log and detects problems following predefined rules.

The System Log Monitor matches problems according to a set of predefined rule list in the configuration files. ( config/kernel-monitor.json as an example). The rule list is extensible.

Supported sources

System Log Monitor currently supports file-based logs, journald, and kmsg. Additional sources can be added by implementing a new log watcher.

Add New NodeConditions

To support new node conditions, you can extend the conditions field in the configuration file with new condition definition:

{
  "type": "NodeConditionType",
  "reason": "CamelCaseDefaultNodeConditionReason",
  "message": "arbitrary default node condition message"
}

Detect New Problems

To detect new problems, you can extend the rules field in the configuration file with new rule definition:

{
  "type": "temporary/permanent",
  "condition": "NodeConditionOfPermanentIssue",
  "reason": "CamelCaseShortReason",
  "pattern": "regexp matching the issue in the log",
  "patternGeneratedMessageSuffix": "Please check the network connectivity and ensure that all required services are running. For more details, see our documentation at https://example.com/docs/troubleshooting."
}

Note that the pattern must match to the end of the line excluding the tailing newline character, and multi-line pattern is supported.

Log Watchers

System log monitor supports different log management tools with different log watchers:

filelog: Log watcher for arbitrary file based log.
journald: Log watcher for journald.
kmsg: Log watcher for the kernel ring buffer device, /dev/kmsg. Set plugin in the configuration file to specify log watcher.

Plugin Configuration

Log watcher specific configurations are configured in pluginConfig.

journald
- source: The SYSLOG_IDENTIFIER of the log to watch.
filelog:
- timestamp: The regular expression used to match timestamp in the log line. Submatch is supported, but only the last result will be used as the actual timestamp.
- message: The regular expression used to match message in the log line. Submatch is supported, but only the last result will be used as the actual message.
- timestampFormat: The format of the timestamp. The format string is the time 2006-01-02T15:04:05Z07:00 in the expected format. (See golang timestamp format)
kmsg: No configuration for now.

Change Log Path

Log on different OS distros may locate in different path. The logPath field in the configuration file is the log path. You can always configure logPath to match your OS distro.

filelog: logPath is the path of log file, e.g. /var/log/kern.log for kernel log.
journald: logPath is the journal log directory, usually /var/log/journal.

New Log Watcher

System log monitor uses Log Watcher to support different log management tools. It is easy to implement a new log watcher.

Metrics Reporting

By setting the boolean metricsReporting at top level, you can choose to enable or disable metrics reporting of System Log Monitor. If you omit the field, it will be set to true by default.

Temporary problems will be reported as counter metrics, such as below example:

# HELP problem_counter Number of times a specific type of problem have occurred.
# TYPE problem_counter counter
problem_counter{reason="TaskHung"} 2

Permanent problems will be reported as both gauge metrics and counter metrics, such as below example:

# HELP problem_counter Number of times a specific type of problem have occurred.
# TYPE problem_counter counter
problem_counter{reason="DockerHung"} 1
# HELP problem_gauge Whether a specific type of problem is affecting the node or not.
# TYPE problem_gauge gauge
problem_gauge{condition="KernelDeadlock",reason="DockerHung"} 1