Configure parameters to export logs of a deployment - Realtime Compute for Apache Flink

You can view the logs of a deployment on the Diagnostics tab in the Realtime Compute for Apache Flink console. You can also configure parameters to export deployment logs to an external storage, such as Object Storage Service (OSS), Simple Log Service, or Kafka, and specify the level of the logs that you want to export. This topic describes how to configure parameters to export the logs of a deployment to OSS, Simple Log Service, or Kafka.

Precautions

If you do not turn off Allow Log Archives after you configure parameters to export the logs of a deployment to an external storage, the same logs are stored in the external storage and the OSS bucket that you selected when you purchase the workspace. After you turn off Allow Log Archives for a deployment, you cannot view the logs of the deployment in the development console of Realtime Compute for Apache Flink.
After you configure parameters to export the logs of a deployment to OSS, Simple Log Service, or Kafka, you must restart the deployment.
You can specify a key in the ${secret_values.xxxx} format in the log configuration to reference the variables that are configured in the key. For more information, see Manage keys.

Configure parameters to export the logs of a deployment

Go to the Configuration tab.
1. Log on to the management console of Realtime Compute for Apache Flink.
2. Find the workspace that you want to manage and click Console in the Actions column.
3. In the left-side navigation pane, click O&M > Deployments. On the Deployments page, click the name of the desired deployment.
4. In the upper-right corner of the Logging section on the Configuration tab, click Edit.
5. Set Logging Profile to Custom Template.

Configure parameters to export the logs of the deployment.

Copy and paste the deployment code to the code editor based on the storage to which you want to export the logs, and change the values of the specified parameters. If you want to export logs of different levels to different storage systems, you can configure different log filter rules for appenders. For more information, see Configure different log filter rules based on log levels.

Export logs to OSS

<?xml version="1.0" encoding="UTF-8"?>
<Configuration xmlns="http://logging.apache.org/log4j/2.0/config" 
strict="true" packages="com.ververica.platform.logging.appender" status="WARN">  
  <Appenders> 
    <Appender name="StdOut" type="Console"> 
      <Layout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" type="PatternLayout" charset="UTF-8"/> 
    </Appender> 
    <Appender name="RollingFile" type="RollingFile" fileName="${sys:log.file}" filePattern="${sys:log.file}.%i"> 
      <Layout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" type="PatternLayout" charset="UTF-8"/>  
      <Policies> 
        <SizeBasedTriggeringPolicy size="20 MB"/> 
      </Policies>  
      <DefaultRolloverStrategy max="4"/> 
    </Appender>  
    <Appender name="OSS" type="OSS">
      <Layout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" type="PatternLayout" charset="UTF-8"/>  
      
      <!-- The final effective log path is: ${baseUri}/logs/${namespace}/${deploymentId}/{jobId}/ -->
      <Property name="namespace">{{ namespace }}</Property> <!-- Do not modify this line -->
      <Property name="baseUri">oss://YOUR-BUCKET-NAME/</Property>
      <Property name="endpoint">https://YOUR-ENDPOINT</Property> 
      <Property name="accessKeyId">${secret_values.accessKeyId}</Property>
      <Property name="secretAccessKey">${secret_values.accessKeySecret}</Property>
      <Property name="flushIntervalSeconds">10</Property>  
      <Property name="flushIntervalEventCount">100</Property>  
      <Property name="rollingBytes">10485760</Property>  
    </Appender>
   <Appender name="StdOutErrConsoleAppender" type="Console">
     <Layout pattern="%m" type="PatternLayout" charset="UTF-8"/>
   </Appender>
   <Appender name="StdOutFileAppender" type="RollingFile" fileName="${sys:stdout.file}" filePattern="${sys:stdout.file}.%i">
     <Layout pattern="%m" type="PatternLayout" charset="UTF-8"/>
     <Policies>
     <SizeBasedTriggeringPolicy size="1 GB"/>
     </Policies>
     <DefaultRolloverStrategy max="2"/>
   </Appender>
   <Appender name="StdErrFileAppender" type="RollingFile" fileName="${sys:stderr.file}" filePattern="${sys:stderr.file}.%i">
     <Layout pattern="%m" type="PatternLayout" charset="UTF-8"/>
     <Policies>
     <SizeBasedTriggeringPolicy size="1 GB"/>
     </Policies>
     <DefaultRolloverStrategy max="2"/>
   </Appender>
  </Appenders>  
  <Loggers> 
    <Logger level="INFO" name="org.apache.hadoop"/>  
    <Logger level="INFO" name="org.apache.kafka"/>  
    <Logger level="INFO" name="org.apache.zookeeper"/>  
    <Logger level="INFO" name="akka"/>  
    <Logger level="ERROR" name="org.jboss.netty.channel.DefaultChannelPipeline"/>  
    <Logger level="OFF" name="org.apache.flink.runtime.rest.handler.job.JobDetailsHandler"/> 
    <Logger level="ERROR" name="org.apache.flink.fs.osshadoop.shaded.com.aliyun.oss"/>
  <Logger level="INFO" name="StdOutErrRedirector.StdOut" additivity="false">
    <AppenderRef ref="StdOutFileAppender"/>
    <AppenderRef ref="StdOutErrConsoleAppender"/>
  </Logger>
  <Logger level="INFO" name="StdOutErrRedirector.StdErr" additivity="false">
    <AppenderRef ref="StdErrFileAppender"/>
    <AppenderRef ref="StdOutErrConsoleAppender"/>
  </Logger>
    {%- for name, level in userConfiguredLoggers -%} 
      <Logger level="{{ level }}" name="{{ name }}"/> 
    {%- endfor -%}
    <Root level="{{ rootLoggerLogLevel }}"> 
      <AppenderRef ref="StdOut"/>
      <AppenderRef ref="RollingFile"/>  
      <AppenderRef ref="OSS"/> 
    </Root>
  </Loggers> 
</Configuration>

Parameter	Description
YOUR-BUCKET-NAME	Replace the value of this parameter with the name of your OSS bucket.
YOUR-ENDPOINT	Replace the value of this parameter with the endpoint of your OSS. For more information, see Regions and endpoints. Replace the value of this parameter with Endpoint information in the row where VPC Access from ECS (Internal Network) is located.
YOUR-OSS-ACCESSKEYID	Replace the value of the YOUR-OSS-ACCESSKEYID parameter with the AccessKey ID of the account and the value of the YOUR-OSS-ACCESSKEYSECRET parameter with the AccessKey secret of the account that you use to configure OSS. For more information about how to obtain an AccessKey pair, see Obtain an AccessKey pair. To avoid security risks that are caused by plaintext AccessKey pairs, we recommend that you specify the values of the AccessKey pair by using the key management method. For more information, see Manage variables and keys. Note If you configure OSS within an account that is different from the Realtime Compute for Apache Flink account, you must configure these parameters. If you configure OSS within an account that is the same as the Realtime Compute for Apache Flink account, you can delete these parameters.
YOUR-OSS-ACCESSKEYSECRET
flushIntervalSeconds	The time interval at which logs are written to the storage. Unit: seconds.
flushIntervalEventCount	The log count threshold that triggers log synchronization. Each time the number of accumulated logs reaches the value of this parameter, the logs are written to the storage. Note If this parameter and the flushIntervalSeconds parameter are both configured, logs are written to the storage only if one of the conditions is met.
rollingBytes	The size of a log file in OSS. If the size of a log file reaches the value of this parameter, data is written to a new log file.

Export logs to Simple Log Service

<?xml version="1.0" encoding="UTF-8"?>
<Configuration xmlns="http://logging.apache.org/log4j/2.0/config" 
strict="true" packages="com.ververica.platform.logging.appender" status="WARN">  
  <Appenders> 
    <Appender name="StdOut" type="Console"> 
      <Layout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" type="PatternLayout" charset="UTF-8"/> 
    </Appender>  
    <Appender name="RollingFile" type="RollingFile" fileName="${sys:log.file}" filePattern="${sys:log.file}.%i"> 
      <Layout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" type="PatternLayout" charset="UTF-8"/>  
      <Policies> 
        <SizeBasedTriggeringPolicy size="5 MB"/> 
      </Policies>  
      <DefaultRolloverStrategy max="1"/> 
    </Appender>  
    <Appender name="SLS" type="SLS">
      <Layout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" type="PatternLayout" charset="UTF-8"/>  

      <!-- The final effective log path is: ${baseUri}/logs/${namespace}/${deploymentId}/{jobId}/ -->
      <Property name="namespace">{{ namespace }}</Property> <!-- Do not modify this line -->
      <Property name="project">YOUR-SLS-PROJECT</Property>  
      <Property name="logStore">YOUR-SLS-LOGSTORE</Property> 
      <Property name="endpoint">YOUR-SLS-ENDPOINT</Property> 
      <Property name="accessKeyId">${secret_values.accessKeyId}</Property> 
      <Property name="accessKeySecret">${secret_values.accessKeySecret}</Property> 
      <Property name="topic">{{ namespace }}:{{ deploymentId }}:{{ jobId }}</Property>
      <Property name="deploymentName">{{ deploymentName }}</Property>
      <Property name="flushIntervalSeconds">10</Property>
      <Property name="flushIntervalEventCount">100</Property>
    </Appender>
   <Appender name="StdOutErrConsoleAppender" type="Console">
     <Layout pattern="%m" type="PatternLayout" charset="UTF-8"/>
   </Appender>
   <Appender name="StdOutFileAppender" type="RollingFile" fileName="${sys:stdout.file}" filePattern="${sys:stdout.file}.%i">
     <Layout pattern="%m" type="PatternLayout" charset="UTF-8"/>
     <Policies>
     <SizeBasedTriggeringPolicy size="1 GB"/>
     </Policies>
     <DefaultRolloverStrategy max="2"/>
   </Appender>
   <Appender name="StdErrFileAppender" type="RollingFile" fileName="${sys:stderr.file}" filePattern="${sys:stderr.file}.%i">
     <Layout pattern="%m" type="PatternLayout" charset="UTF-8"/>
     <Policies>
     <SizeBasedTriggeringPolicy size="1 GB"/>
     </Policies>
     <DefaultRolloverStrategy max="2"/>
   </Appender>
  </Appenders>  
  <Loggers> 
    <Logger level="INFO" name="org.apache.hadoop"/>  
    <Logger level="INFO" name="org.apache.kafka"/>  
    <Logger level="INFO" name="org.apache.zookeeper"/>  
    <Logger level="INFO" name="akka"/>  
    <Logger level="ERROR" name="org.jboss.netty.channel.DefaultChannelPipeline"/>  
    <Logger level="OFF" name="org.apache.flink.runtime.rest.handler.job.JobDetailsHandler"/> 
    <Logger level="ERROR" name="org.apache.flink.fs.osshadoop.shaded.com.aliyun.oss"/>
  <Logger level="INFO" name="StdOutErrRedirector.StdOut" additivity="false">
    <AppenderRef ref="StdOutFileAppender"/>
    <AppenderRef ref="StdOutErrConsoleAppender"/>
  </Logger>
  <Logger level="INFO" name="StdOutErrRedirector.StdErr" additivity="false">
    <AppenderRef ref="StdErrFileAppender"/>
    <AppenderRef ref="StdOutErrConsoleAppender"/>
  </Logger>
    {%- for name, level in userConfiguredLoggers -%} 
      <Logger level="{{ level }}" name="{{ name }}"/> 
    {%- endfor -%}
    <Root level="{{ rootLoggerLogLevel }}"> 
      <AppenderRef ref="StdOut"/>
      <AppenderRef ref="RollingFile"/>  
      <AppenderRef ref="SLS"/> 
    </Root>
  </Loggers> 
</Configuration>

Note

The namespace, deploymentId, jobId, and deploymentName variables in the code are the variables in Twig templates. You do not need to modify these variables. If you modify one of the preceding variables, an error is reported when you start the deployment.

Parameter	Description
YOUR-SLS-PROJECT	Replace the value of this parameter with the project name of Simple Log Service.
YOUR-SLS-LOGSTORE	Replace the value of this parameter with the Logstore name of Simple Log Service.
YOUR-SLS-ENDPOINT	Replace the value of this parameter with the internal endpoint of the region where Simple Log Service resides. For more information, see Endpoints.
YOUR-SLS-ACCESSKEYID	Replace the value of the YOUR-SLS-ACCESSKEYID parameter with the AccessKey ID of the account and the value of the YOUR-SLS-ACCESSKEYSECRET parameter with the AccessKey secret of the account that you use to configure Simple Log Service. For more information about how to obtain an AccessKey pair, see Obtain an AccessKey pair. To avoid security risks that are caused by plaintext AccessKey pairs, we recommend that you specify the values of the AccessKey pair by using the key management method. For more information, see Manage variables and keys. Note If you configure Simple Log Service within an account that is different from the Realtime Compute for Apache Flink account, you must grant the Realtime Compute for Apache Flink account the permissions to write data to Simple Log Service. For more information, see Create a custom policy. The following sample code provides an example of the policy document. Access Simple Log Service without specifying the access scope of Simple Log Service `{ "Version": "1", "Statement": [ { "Effect": "Allow", "Action": [ "log:Get", "log:PostLogStoreLogs" ], "Resource": "" } ] }` Access Simple Log Service by specifying the access scope of Simple Log Service `{ "Version": "1", "Statement": [ { "Effect": "Allow", "Action": [ "log:PostLogStoreLogs", "log:GetLogStore" ], "Resource": "acs:log:cn-beijing:152940222687****:project/test-vvp-sls/logstore/test-ltest" } ] }`
YOUR-SLS-ACCESSKEYSECRET
flushIntervalSeconds	The time interval at which logs are written to the storage. Unit: seconds.
flushIntervalEventCount	The log count threshold that triggers log synchronization. Each time the number of accumulated logs reaches the value of this parameter, the logs are written to the storage. Note If this parameter and the flushIntervalSeconds parameter are both configured, logs are written to the storage only if one of the conditions is met.

Export logs to Kafka

Note

A Kafka cluster in which the Kerberos authentication is enabled is not supported.

Prerequisites
The KafkaAppender logging plug-in provided by Realtime Compute for Apache Flink is loaded by using the plug-in class loader of Realtime Compute for Apache Flink. Before you use the KafkaAppender logging plug-in, you must specify the path of the package that is used to store the KafkaAppender logging plug-in in the deployment code. In this case, Realtime Compute for Apache Flink can load the KafkaAppender logging plug-in. To export logs to Kafka by using the KafkaAppender logging plug-in, perform one of the following operations:
- Configure parameters to export the logs of all deployments in the current namespace to Kafka
  On the Deployment Defaults tab of the Configurations page in the development console of Realtime Compute for Apache Flink, add the following code to the Other Configuration field:
```
plugin.classloader.parent-first-patterns.additional: com.ververica.platform.logging.appender
```
- Configure parameters to export the logs of the current deployment to Kafka
  On the Deployments page, click the name of the desired deployment. On the Configuration tab of the Deployments page, click Edit in the upper-right corner of the Parameters section and add the following code to the Other Configuration field:
```
plugin.classloader.parent-first-patterns.additional: com.ververica.platform.logging.appender
```

Export logs to Kafka

<?xml version="1.0" encoding="UTF-8"?>
<Configuration xmlns="http://logging.apache.org/log4j/2.0/config" 
strict="true" packages="com.ververica.platform.logging.appender" status="WARN">  
  <Appenders> 
    <Appender name="StdOut" type="Console"> 
      <Layout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" type="PatternLayout"/> 
    </Appender>  
    <Appender name="RollingFile" type="RollingFile" fileName="${sys:log.file}" filePattern="${sys:log.file}.%i"> 
      <Layout pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" type="PatternLayout"/>  
      <Policies> 
        <SizeBasedTriggeringPolicy size="20 MB"/> 
      </Policies>  
      <DefaultRolloverStrategy max="4"/> 
    </Appender>  
    <Appender type="KafkaVVP" name="KafkaVVPAppender" topic="YOUR-TOPIC-NAME">
        <Layout type="PatternLayout" pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n"/>
        <Property name="bootstrap.servers">YOUR-KAFKA-BOOTSTRAP-SERVERS</Property>
         <Property name="acks">YOUR-ACKS-VALUE</Property>
         <Property name="buffer.memory">YOUR-BUFFER-MEMORY-SIZE</Property>
          <Property name="retries">YOUR-RETRIES-NUMBER</Property>
         <Property name="compression.type">YOUR-COMPRESSION-TYPE</Property>
    </Appender>
    <Appender type="Async" name="AsyncAppender">
        <AppenderRef ref="KafkaVVPAppender"/>
    </Appender>
  </Appenders>
  <Loggers> 
    <Logger level="INFO" name="org.apache.hadoop"/>  
    <Logger level="INFO" name="org.apache.kafka"/>  
    <Logger level="INFO" name="org.apache.zookeeper"/>  
    <Logger level="INFO" name="akka"/>  
    <Logger level="ERROR" name="org.jboss.netty.channel.DefaultChannelPipeline"/>  
    <Logger level="OFF" name="org.apache.flink.runtime.rest.handler.job.JobDetailsHandler"/> 
    {%- for name, level in userConfiguredLoggers -%} 
      <Logger level="{{ level }}" name="{{ name }}"/> 
    {%- endfor -%}
    <Root level="{{ rootLoggerLogLevel }}"> 
      <AppenderRef ref="StdOut"/>
      <AppenderRef ref="RollingFile"/>  
      <AppenderRef ref="AsyncAppender"/> 
    </Root>
  </Loggers>
</Configuration>

Parameter	Description
YOUR-TOPIC-NAME	Replace the value of this parameter with the name of the Kafka topic to which you want to write data.
YOUR-KAFKA-BOOTSTRAP-SERVERS	Replace the value of this parameter with the IP addresses or endpoints and port numbers of Kafka brokers to which you want to write data.
YOUR-ACKS-VALUE	Replace the value of this parameter with the number of partition replicas that must receive a message before the producer considers that the message is written to the topic. For more information, see acks.
YOUR-BUFFER-MEMORY-SIZE	Replace the value of this parameter with the size of the producer buffer. Unit: bytes.
YOUR-RETRIES-NUMBER	Replace the value of this parameter with the maximum number of retries allowed after a message fails to be sent.
YOUR-COMPRESSION-TYPE	Replace the value of this parameter with the compression type that can be used by the producer to generate data. The compression type can be none, gzip, snappy, lz4, or zstd.

Note

You can also configure the parameters that are supported by the Apache Kafka client. For more information, see Apache Kafka.

Click Save.
In the upper-right corner of the Deployments page, click Start.

Configure parameters to export the logs of all deployments in a namespace

You can set Logging Profile to Custom Template on the Deployment Defaults tab to enable the logs of all deployments in a namespace to be automatically exported to OSS, Simple Log Service, or Kafka.

Important

After you set Logging Profile to Custom Template, the logs of all deployments that are created in the namespace are stored in OSS, Simple Log Service, or Kafka.

Go to the Deployment Defaults tab.
1. Log on to the Realtime Compute for Apache Flink console.
2. Find the workspace that you want to manage and click Console in the Actions column. In the top navigation bar of the Realtime Compute for Apache Flink development console, select a namespace from the drop-down list.
3. In the left-side navigation pane, click O&M > Configurations.
4. On the Deployment Defaults tab, select a deployment type.
5. In the Logging section, set Logging Profile to Custom Template.
6. Configure parameters to export logs of all deployments in the namespace. For more information, see Configure parameters to export the logs of a deployment.
Click Save Changes.

Configure different log filter rules based on log levels

You can configure different log filter rules for appenders based on log levels by using a ThresholdFilter of Log4j2. Log filter rules provide the following benefits:

Flexibility: You can export logs of different levels to different storage systems based on your business requirements.
Efficiency: Unnecessary log parsing and transmission are reduced to improve system performance.
Clarity: The process of exporting logs of a specific level to a storage system becomes clearer after the configuration of log filter rules. This facilitates log management based on log levels.

Configuration procedure:

In the Logging section of the Configuration tab of a deployment, set Logging Profile to Custom Template.

Add configurations in the field that appears to export the logs of the deployment.

For example, only logs of the INFO level or a higher level can be exported to the development console of Realtime Compute for Apache Flink, and only logs of the ERROR level or a higher level can be exported to Simple Log Service. Sample code:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration xmlns="http://logging.apache.org/log4j/2.0/config" strict="true" status="WARN">
  <Appenders>
    <!-- Console Appender configured to output only INFO level logs -->
    <Appender name="StdOut" type="Console">
      <ThresholdFilter level="INFO" onMatch="ACCEPT" onMismatch="DENY"/>
      <Layout type="PatternLayout" pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" charset="UTF-8"/>
    </Appender>
    
    <!-- RollingFile Appender (no filter shown, logs all levels due to Root level being INFO) -->
    <Appender name="RollingFile" type="RollingFile">
      <!-- Configuration remains unchanged -->
      <!-- ... -->
    </Appender>
    
    <!-- SLS Appender configured to output only ERROR level and above logs -->
    <Appender name="SLS" type="SLS">
      <ThresholdFilter level="ERROR" onMatch="ACCEPT" onMismatch="DENY"/>
      <Layout type="PatternLayout" pattern="%d{yyyy-MM-dd HH:mm:ss,SSS}{GMT+8} %-5p %-60c %x - %m%n" charset="UTF-8"/>
      <!-- SLS specific properties -->
      <Property name="namespace">YOUR_NAMESPACE</Property>
      <Property name="project">YOUR_SLS_PROJECT</Property>
      <Property name="logStore">YOUR_SLS_LOGSTORE</Property>
      <Property name="endpoint">YOUR_SLS_ENDPOINT</Property>
      <!-- Access credentials and other properties -->
      <!-- ... -->
    </Appender>

    <!-- Other Appenders definitions remain unchanged -->
    <!-- ... -->
  </Appenders>
  
  <Loggers>
    <!-- Directly configure loggers for StdOut and SLS with specific levels -->
    <Logger name="StdOutLogger" level="INFO" additivity="false">
      <AppenderRef ref="StdOut"/>
    </Logger>
    
    <Logger name="SLSLogger" level="ERROR" additivity="false">
      <AppenderRef ref="SLS"/>
    </Logger>

    <!-- Other Loggers definitions with their specific configurations -->
    <!-- ... -->

    <!-- Root Logger without specific AppenderRef for SLS and StdOut, to avoid duplicate logging -->
    <Root level="INFO">
      <AppenderRef ref="StdOut"/>
      <AppenderRef ref="RollingFile"/>
      <!-- Exclude SLS from Root to prevent duplicate logging in case of other loggers -->
    </Root>
  </Loggers>
</Configuration>

Description of the parameters and terms in the preceding sample code:

Console Appender: A ThresholdFilter is used to ensure that logs of the INFO level or a higher level are exported to the development console of Realtime Compute for Apache Flink.
SLS Appender: A ThresholdFilter is used to ensure that logs of the ERROR level or a higher level are exported to Simple Log Service. For more information about the specific properties of SLS Appender, see Export logs to Simple Log Service. You must replace the values of parameters such as YOUR_NAMESPACE and YOUR_SLS_PROJECT with the actual information about your Simple Log Service project.
Note
If a custom appender is used as SLS Appender and the type of the custom appender is not SLS, make sure that the type of the custom appender is supported by Realtime Compute for Apache Flink and the custom appender has the logic that is required to connect to Simple Log Service.
StdOutLogger and SLSLogger: Logs are sent to StdOut Appender and SLS Appender based on the log level that you specify.
Root Logger: StdOut Appender and RollingFile Appender are configured for the root logger, but SLS Appender is not configured for the root logger. This avoids repeated sending of logs to Simple Log Service if a specific logger is configured for the logs.

For more information about related operations and how to configure Log4j parameters, see Apache Log4j.

References

A startup error is reported when parameters are configured to export the logs of the deployment to Simple Log Service. For more information, see What do I do if a deployment startup error is reported after I configure parameters to export the logs of the deployment to Simple Log Service?
You can view logs of a deployment. For more information, see View startup logs and operational logs of a deployment.
If an error occurs when a deployment starts or is running, you can view the exception logs of the deployment in the Realtime Compute for Apache Flink console. For more information, see View the exception logs of a deployment.
If you cannot locate an issue based on the logs at the INFO level, you can change the level of the logs to DEBUG. For more information, see Change the log level for a running deployment.
You can view audit events of Realtime Compute for Apache Flink by using ActionTrail. For more information, see View audit events of Realtime Compute for Apache Flink.