Logback RollingPolicy with S3 upload

logback-s3-rolling-policy automatically uploads rolled log files to S3.

There are 2 rolling policies which can be used:

• S3FixedWindowRollingPolicy
• S3TimeBasedRollingPolicy

logback-s3-rolling-policy was forked from logback-s3 (https://github.com/shuwada/logback-s3) but transfered into a new project because changes were getting too big.

Index

• Requirements
• Usage
• Configuration
  • logback.xml variables
  • web.xml
  • logback.xml rolling policy examples
• AWS Credentials
• Libraries

Requirements

• Java 17

Configuration

logback.xml variables

Whether you implement one of any available S3 policies, the following extra variables (on top of Logback's) can be used:

• s3BucketName The S3 bucket name to upload your log files to (mandatory).
• awsAccessKey Your AWS access key. If not provided it falls back to the AWS SDK default provider chain.
• awsSecretKey Your AWS secret key. If not provided it falls back to the AWS SDK default provider chain.
• s3FolderName The S3 folder name in your S3 bucket to put the log files in. This variable supports dates, just put your pattern between %d{}. Example: %d{yyyy/MM/dd}.
• shutdownHookType Defines which type of shutdown hook you want to use. This variable is mandatory when you use rolloverOnExit. Defaults to NONE. Possible values are:
  • NONE This will not add a shutdown hook. Please note that your most up to date log file won't be uploaded to S3!
  • JVM_SHUTDOWN_HOOK This will add a runtime shutdown hook. If you're using a webapplication, please use the SERVLET_CONTEXT, as the JVM shutdown hook is not really safe to use here.
  • SERVLET_CONTEXT This will register a shutdown hook to the context destroyed method of RollingPolicyContextListener. Don't forget to actually add the context listener to you web.xml. (see below)
• rolloverOnExit Whether to rollover when your application is being shut down or not. Boolean value, defaults to false. If this is set to false, and you have defined a shutdownHookType, then the log file will be uploaded as is.
• prefixTimestamp Whether to prefix the uploaded filename with a timestamp formatted as yyyyMMdd_HHmmss or not. Boolean value, defaults to false.
• prefixIdentifier Whether to prefix the uploaded filename with an identifier or not. Boolean value, defaults to false. If running on an AWS EC2 instance, the instance ID will be used. If not running on an AWS EC2 instance, the hostname address will be used. If the hostname address can't be used, a UUID will be used.

web.xml

If you're using the shutdown hook SERVLET_CONTEXT as defined above, you'll need to add the context listener class to your web.xml:

<listener>
   <listener-class>ch.qos.logback.core.rolling.shutdown.RollingPolicyContextListener</listener-class>
</listener>

Run-time variables

As of version 1.3 you can set run-time variables. For now you can only add an extra S3 folder.

Just use CustomData.extraS3Folder.set("extra_folder_name"); somewhere in your code before the upload occurs. You can always change this value during run-time and it will be picked up on the next upload. set to null to ignore.

logback.xml rolling policy examples

An example logback.xml appender for each available policy using RollingFileAppender.

• ch.qos.logback.core.rolling.S3FixedWindowRollingPolicy:

<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
  <file>logs/myapp.log</file>
  <encoder>
    <pattern>[%d] %-8relative %22c{0} [%-5level] %msg%xEx{3}%n</pattern>
  </encoder>
  <rollingPolicy class="ch.qos.logback.core.rolling.S3FixedWindowRollingPolicy">
    <fileNamePattern>logs/myapp.%i.log.gz</fileNamePattern>
    <awsAccessKey>ACCESS_KEY</awsAccessKey>
    <awsSecretKey>SECRET_KEY</awsSecretKey>
    <s3BucketName>myapp-logging</s3BucketName>
    <s3FolderName>logs/%d{yyyy/MM/dd}</s3FolderName>
    <rolloverOnExit>true</rolloverOnExit>
    <shutdownHookType>SERVLET_CONTEXT</shutdownHookType>
    <prefixTimestamp>true</prefixTimestamp>
    <prefixIdentifier>true</prefixIdentifier>
  </rollingPolicy>
  <triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
    <maxFileSize>10MB</maxFileSize>
  </triggeringPolicy>
</appender>

In this example you'll find the logs at myapp-logging/logs/2015/08/18/.

• ch.qos.logback.core.rolling.S3TimeBasedRollingPolicy:

<appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
  <file>logs/myapp.log</file>
  <encoder>
    <pattern>[%d] %-8relative %22c{0} [%-5level] %msg%xEx{3}%n</pattern>
  </encoder>
  <rollingPolicy class="ch.qos.logback.core.rolling.S3TimeBasedRollingPolicy">
    <!-- Rollover every minute -->
    <fileNamePattern>logs/myapp.%d{yyyy-MM-dd_HH-mm}.%i.log.gz</fileNamePattern>
    <awsAccessKey>ACCESS_KEY</awsAccessKey>
    <awsSecretKey>SECRET_KEY</awsSecretKey>
    <s3BucketName>myapp-logging</s3BucketName>
    <s3FolderName>log</s3FolderName>
    <rolloverOnExit>true</rolloverOnExit>
    <shutdownHookType>SERVLET_CONTEXT</shutdownHookType>
    <prefixTimestamp>false</prefixTimestamp>
    <prefixIdentifier>true</prefixIdentifier>
    <timeBasedFileNamingAndTriggeringPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP">
      <maxFileSize>10MB</maxFileSize>
    </timeBasedFileNamingAndTriggeringPolicy>
  </rollingPolicy>
</appender>

In this example you'll find the logs at myapp-logging/log/.

AWS Credentials

It is a good idea to create an IAM user only allowed to upload S3 object to a specific S3 bucket. It improves the control and reduces the risk of unauthorized access to your S3 bucket.

The following is an example IAM policy.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Action": [
        "s3:PutObject"
      ],
      "Sid": "Stmt1378251801000",
      "Resource": [
        "arn:aws:s3:::myapp-logging/log/*"
      ],
      "Effect": "Allow"
    }
  ]
}

Libraries

This project uses the following libraries:

• com.amazonaws:aws-java-sdk:1.12.688
• ch.qos.logback:logback-classic:1.4.14
• com.google.guava:guava:33.1.0-jre
• jakarta.servlet:jakarta.servlet-ap:6.0.0 (scope provided)
• org.jetbrains:annotations:15.0 (scope provided)