Help Center/ MapReduce Service/ User Guide (Kuala Lumpur Region)/ MRS Cluster Component Operation Guide/ Using Flink/ Flink Log Overview
Updated on 2022-08-12 GMT+08:00
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Flink Log Overview

Log Description

Log path:
  • Run logs of a Flink job: ${BIGDATA_DATA_HOME}/hadoop/data${i}/nm/containerlogs/application_${appid}/container_{$contid}

    The logs of executing tasks are stored in the preceding path. After the execution is complete, the Yarn configuration determines whether these logs are gathered to the HDFS directory.

  • FlinkResource run logs: /var/log/Bigdata/flink/flinkResource

Log archive rules:

  1. FlinkResource run logs:
    • By default, service logs are backed up each time when the log size reaches 20 MB. A maximum of 20 logs can be reserved without being compressed.

      For versions earlier than MRS 3.x, The executor logs are backed up each time when the log size reaches 30 MB. A maximum of 20 logs can be reserved without being compressed.

    • You can set the log size and number of compressed logs on the Manager page or modify the corresponding configuration items in log4j-cli.properties, log4j.properties, and log4j-session.properties in /opt/client/Flink/flink/conf/ on the client. /opt/client is the client installation directory.
    Table 1 FlinkResource log list

    Type

    Name

    Description

    FlinkResource run logs

    checkService.log

    Health check log

    kinit.log

    Initialization log

    postinstall.log

    Service installation log

    prestart.log

    Prestart script log

    start.log

    Startup log

Log Level

Table 2 describes the log levels supported by Flink. The priorities of log levels are ERROR, WARN, INFO, and DEBUG in descending order. Logs whose levels are higher than or equal to the specified level are printed. The number of printed logs decreases as the specified log level increases.

Table 2 Log levels

Level

Description

ERROR

Error information about the current event processing

WARN

Exception information about the current event processing

INFO

Normal running status information about the system and events

DEBUG

System information and system debugging information

To modify log levels, perform the following steps:

  1. Go to the All Configurations page of Flink by referring to Modifying Cluster Service Configuration Parameters.
  2. On the menu bar on the left, select the log menu of the target role.
  3. Select a desired log level.
  4. Save the configuration. In the displayed dialog box, click OK to make the configurations take effect.
  • After the configuration is complete, you do not need to restart the service. Download the client again for the configuration to take effect.
  • You can also change the configuration items corresponding to the log level in log4j-cli.properties, log4j.properties, and log4j-session.properties in /opt/client/Flink/flink/conf/ on the client. /opt/client is the client installation directory.
  • When a job is submitted using a client, a log file is generated in the log folder on the client. The default umask value is 0022. Therefore, the default log permission is 644. To change the file permission, you need to change the umask value. For example, to change the umask value of user omm:
    • Add umask 0026 to the end of the /home/omm/.baskrc file.
    • Run the source /home/omm/.baskrc command to make the file permission take effect.

Log Format

Table 3 Log formats

Type

Format

Example

Run log

<yyyy-MM-dd HH:mm:ss,SSS>|<Log level>|<Name of the thread that generates the log>|<Message in the log>|<Location where the log event occurs>

2019-06-27 21:30:31,778 | INFO | [flink-akka.actor.default-dispatcher-3] | TaskManager container_e10_1498290698388_0004_02_000007 has started. | org.apache.flink.yarn.YarnFlinkResourceManager (FlinkResourceManager.java:368)
Parent topic: Using Flink