3. Logging to AWS CloudWatch

To log to AWS CloudWatch there are two modifications required:

  1. adding org.slf4j.bridge.SLF4JBridgeHandler to logging bean:

logging () {
    rootHandlers = [ 'java.util.logging.ConsoleHandler', 'java.util.logging.FileHandler', 'org.slf4j.bridge.SLF4JBridgeHandler' ]
}

  1. Add appender configuration to logback.xml configuration file:

<appender name="ASYNC_AWS_LOGS" class="ca.pjer.logback.AwsLogsAppender">

    <!-- Nice layout pattern -->
    <layout>
        <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%20(%thread)] %logger{5}.%method\(\): %msg %n</pattern>
    </layout>

    <!-- Hardcoded Log Group Name -->
    <logGroupName>/kangaroo-logs/${VHOST}</logGroupName>

    <!-- Log Stream Name UUID Prefix -->
    <logStreamUuidPrefix>${EXTERNAL_IP}/</logStreamUuidPrefix>

    <!-- Hardcoded AWS region -->
    <!-- So even when running inside an AWS instance in us-west-1, logs will go to us-west-2 -->
    <logRegion>us-west-2</logRegion>

    <!-- Maximum number of events in each batch (50 is the default) -->
    <!-- will flush when the event queue has 50 elements, even if still in quiet time (see maxFlushTimeMillis) -->
    <maxBatchLogEvents>50</maxBatchLogEvents>

    <!-- Maximum quiet time in millisecond (0 is the default) -->
    <!-- will flush when met, even if the batch size is not met (see maxBatchLogEvents) -->
    <maxFlushTimeMillis>30000</maxFlushTimeMillis>

    <!-- Maximum block time in millisecond (5000 is the default) -->
    <!-- when > 0: this is the maximum time the logging thread will wait for the logger, -->
    <!-- when == 0: the logging thread will never wait for the logger, discarding events while the queue is full -->
    <maxBlockTimeMillis>5000</maxBlockTimeMillis>

    <!-- Retention value for log groups, 0 for infinite see -->
    <!-- https://docs.aws.amazon.com/AmazonCloudWatchLogs/latest/APIReference/API_PutRetentionPolicy.html for other -->
    <!-- possible values -->

    <retentionTimeDays>60</retentionTimeDays>
</appender>

and it to root logger configuration:

<root level="WARN">
    <appender-ref ref="ASYNC_AWS_LOGS"/>