I'm using Log4j2 in an AWS Lambda project, and everything works fine when running locally. However, when deploying to Lambda and logging to CloudWatch, I receive the following error:
Here’s the pattern layout in my log4j2.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
<Appenders>
<Lambda name="Lambda" format="${env:AWS_LAMBDA_LOG_FORMAT:-TEXT}">
<LambdaTextFormat>
<PatternLayout pattern="%d{ISO8601} [%t] %-5level %logger - %msg%n"/>
</LambdaTextFormat>
<LambdaJSONFormat>
<JsonTemplateLayout eventTemplateUri="classpath:logback-config.json" />
</LambdaJSONFormat>
</Lambda>
</Appenders>
<Loggers>
<Root level="${env:AWS_LAMBDA_LOG_LEVEL:-INFO}">
<AppenderRef ref="Lambda" />
</Root>
</Loggers>
</Configuration>
and build.gradle dependencies
implementation 'com.amazonaws:aws-lambda-java-core:1.2.1'
implementation 'com.amazonaws:aws-lambda-java-events:3.11.0'
implementation 'com.amazonaws:aws-lambda-java-log4j2:1.6.0'
implementation 'software.amazon.awssdk:s3:2.20.112'
implementation 'software.amazon.awssdk:core:2.20.0'
implementation 'software.amazon.awssdk:ssm:2.20.0'
implementation 'software.amazon.awssdk:lambda:2.20.0'
implementation '.apache.logging.log4j:log4j-slf4j-impl:2.24.3'
implementation '.apache.logging.log4j:log4j-core:2.24.3'
implementation '.apache.logging.log4j:log4j-api:2.19.0'
implementation '.apache.logging.log4j:log4j-layout-template-json:2.24.3'
and the error
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| timestamp | message |
|---------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 1741259442561 | INIT_START Runtime Version: java:17.v39 Runtime Version ARN: arn:aws:lambda:us-east-1::runtime:6f7d8c19e520ca92114d1fccd25e3ede3da8a01faa3fcd6e6a1218b56d944593 |
| 1741259443119 | 2025-03-06T11:10:43.113934328Z main ERROR Unrecognized format specifier [d] |
| 1741259443120 | 2025-03-06T11:10:43.120584259Z main ERROR Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. |
| 1741259443124 | 2025-03-06T11:10:43.124700878Z main ERROR Unrecognized format specifier [thread] |
| 1741259443125 | 2025-03-06T11:10:43.124934783Z main ERROR Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. |
| 1741259443125 | 2025-03-06T11:10:43.125096532Z main ERROR Unrecognized format specifier [level] |
| 1741259443125 | 2025-03-06T11:10:43.125206983Z main ERROR Unrecognized conversion specifier [level] starting at position 35 in conversion pattern. |
| 1741259443125 | 2025-03-06T11:10:43.125370997Z main ERROR Unrecognized format specifier [logger] |
| 1741259443125 | 2025-03-06T11:10:43.125476937Z main ERROR Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern. |
| 1741259443125 | 2025-03-06T11:10:43.125588790Z main ERROR Unrecognized format specifier [msg] |
| 1741259443125 | 2025-03-06T11:10:43.125706041Z main ERROR Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern. |
| 1741259443125 | 2025-03-06T11:10:43.125833587Z main ERROR Unrecognized format specifier [n] |
| 1741259443125 | 2025-03-06T11:10:43.125927525Z main ERROR Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. |
| 1741259443156 | 2025-03-06T11:10:43.156795171Z main ERROR Unrecognized format specifier [d] |
| 1741259443157 | 2025-03-06T11:10:43.156992848Z main ERROR Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157109763Z main ERROR Unrecognized format specifier [thread] |
| 1741259443157 | 2025-03-06T11:10:43.157196547Z main ERROR Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157292534Z main ERROR Unrecognized format specifier [level] |
| 1741259443157 | 2025-03-06T11:10:43.157385179Z main ERROR Unrecognized conversion specifier [level] starting at position 35 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157515572Z main ERROR Unrecognized format specifier [logger] |
| 1741259443157 | 2025-03-06T11:10:43.157599552Z main ERROR Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157691427Z main ERROR Unrecognized format specifier [msg] |
| 1741259443157 | 2025-03-06T11:10:43.157779528Z main ERROR Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157864428Z main ERROR Unrecognized format specifier [n] |
| 1741259443157 | 2025-03-06T11:10:43.157940035Z main ERROR Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. |
| 1741259443315 | START RequestId: b003f85b-8b31-4e70-9628-dd03607219da Version: $LATEST |
| 1741259443700 | %d [%thread] %-5level %logger - %msg%n2025-03-06T11:10:43.700301498Z main ERROR Unrecognized format specifier [d] |
| 1741259443700 | 2025-03-06T11:10:43.700471652Z main ERROR Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. |
| 1741259443700 | 2025-03-06T11:10:43.700581914Z main ERROR Unrecognized format specifier [thread] |
| 1741259443700 | 2025-03-06T11:10:43.700684369Z main ERROR Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. |
| 1741259443700 | 2025-03-06T11:10:43.700787373Z main ERROR Unrecognized format specifier [level] |
| 1741259443700 | 2025-03-06T11:10:43.700868065Z main ERROR Unrecognized conversion specifier [level] starting at position 35 in conversion pattern. |
| 1741259443701 | 2025-03-06T11:10:43.700988647Z main ERROR Unrecognized format specifier [logger] |
| 1741259443701 | 2025-03-06T11:10:43.701071281Z main ERROR Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern. |
| 1741259443701 | 2025-03-06T11:10:43.701182242Z main ERROR Unrecognized format specifier [msg] |
| 1741259443701 | 2025-03-06T11:10:43.701262817Z main ERROR Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern. |
| 1741259443701 | 2025-03-06T11:10:43.701354991Z main ERROR Unrecognized format specifier [n] |
| 1741259443701 | 2025-03-06T11:10:43.701434557Z main ERROR Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702174857Z main ERROR Unrecognized format specifier [d] |
| 1741259443702 | 2025-03-06T11:10:43.702287908Z main ERROR Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702385288Z main ERROR Unrecognized format specifier [thread] |
| 1741259443702 | 2025-03-06T11:10:43.702463104Z main ERROR Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702559185Z main ERROR Unrecognized format specifier [level] |
| 1741259443702 | 2025-03-06T11:10:43.702640991Z main ERROR Unrecognized conversion specifier [level] starting at position 35 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702736245Z main ERROR Unrecognized format specifier [logger] |
| 1741259443702 | 2025-03-06T11:10:43.702814560Z main ERROR Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702905452Z main ERROR Unrecognized format specifier [msg] |
| 1741259443703 | 2025-03-06T11:10:43.702981466Z main ERROR Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern. |
| 1741259443703 | 2025-03-06T11:10:43.703065460Z main ERROR Unrecognized format specifier [n] |
| 1741259443703 | 2025-03-06T11:10:43.703142907Z main ERROR Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. |
| 1741259458361 | %d [%thread] %-5level %logger - %msg%n%d [%thread] %-5level %logger - %msg%n |
| 1741259463396 | %d [%thread] %-5level %logger - %msg%n%d [%thread] %-5level %logger - %msg%n |
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
What I’ve tried:
I tested with a simplified pattern (without %msg) and it works fine. I ensured that the dependencies are packaged correctly for Lambda. I’ve updated all dependencies to the latest versions. I’ve also tried testing with %logger and %t specifiers, which work fine locally but not in the lambda.
Question: What could be causing this issue with the %msg specifier when running on AWS Lambda, and how can I resolve it? Is there any Lambda-specific configuration I need to adjust?
I'm using Log4j2 in an AWS Lambda project, and everything works fine when running locally. However, when deploying to Lambda and logging to CloudWatch, I receive the following error:
Here’s the pattern layout in my log4j2.xml file:
<?xml version="1.0" encoding="UTF-8"?>
<Configuration>
<Appenders>
<Lambda name="Lambda" format="${env:AWS_LAMBDA_LOG_FORMAT:-TEXT}">
<LambdaTextFormat>
<PatternLayout pattern="%d{ISO8601} [%t] %-5level %logger - %msg%n"/>
</LambdaTextFormat>
<LambdaJSONFormat>
<JsonTemplateLayout eventTemplateUri="classpath:logback-config.json" />
</LambdaJSONFormat>
</Lambda>
</Appenders>
<Loggers>
<Root level="${env:AWS_LAMBDA_LOG_LEVEL:-INFO}">
<AppenderRef ref="Lambda" />
</Root>
</Loggers>
</Configuration>
and build.gradle dependencies
implementation 'com.amazonaws:aws-lambda-java-core:1.2.1'
implementation 'com.amazonaws:aws-lambda-java-events:3.11.0'
implementation 'com.amazonaws:aws-lambda-java-log4j2:1.6.0'
implementation 'software.amazon.awssdk:s3:2.20.112'
implementation 'software.amazon.awssdk:core:2.20.0'
implementation 'software.amazon.awssdk:ssm:2.20.0'
implementation 'software.amazon.awssdk:lambda:2.20.0'
implementation '.apache.logging.log4j:log4j-slf4j-impl:2.24.3'
implementation '.apache.logging.log4j:log4j-core:2.24.3'
implementation '.apache.logging.log4j:log4j-api:2.19.0'
implementation '.apache.logging.log4j:log4j-layout-template-json:2.24.3'
and the error
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| timestamp | message |
|---------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 1741259442561 | INIT_START Runtime Version: java:17.v39 Runtime Version ARN: arn:aws:lambda:us-east-1::runtime:6f7d8c19e520ca92114d1fccd25e3ede3da8a01faa3fcd6e6a1218b56d944593 |
| 1741259443119 | 2025-03-06T11:10:43.113934328Z main ERROR Unrecognized format specifier [d] |
| 1741259443120 | 2025-03-06T11:10:43.120584259Z main ERROR Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. |
| 1741259443124 | 2025-03-06T11:10:43.124700878Z main ERROR Unrecognized format specifier [thread] |
| 1741259443125 | 2025-03-06T11:10:43.124934783Z main ERROR Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. |
| 1741259443125 | 2025-03-06T11:10:43.125096532Z main ERROR Unrecognized format specifier [level] |
| 1741259443125 | 2025-03-06T11:10:43.125206983Z main ERROR Unrecognized conversion specifier [level] starting at position 35 in conversion pattern. |
| 1741259443125 | 2025-03-06T11:10:43.125370997Z main ERROR Unrecognized format specifier [logger] |
| 1741259443125 | 2025-03-06T11:10:43.125476937Z main ERROR Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern. |
| 1741259443125 | 2025-03-06T11:10:43.125588790Z main ERROR Unrecognized format specifier [msg] |
| 1741259443125 | 2025-03-06T11:10:43.125706041Z main ERROR Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern. |
| 1741259443125 | 2025-03-06T11:10:43.125833587Z main ERROR Unrecognized format specifier [n] |
| 1741259443125 | 2025-03-06T11:10:43.125927525Z main ERROR Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. |
| 1741259443156 | 2025-03-06T11:10:43.156795171Z main ERROR Unrecognized format specifier [d] |
| 1741259443157 | 2025-03-06T11:10:43.156992848Z main ERROR Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157109763Z main ERROR Unrecognized format specifier [thread] |
| 1741259443157 | 2025-03-06T11:10:43.157196547Z main ERROR Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157292534Z main ERROR Unrecognized format specifier [level] |
| 1741259443157 | 2025-03-06T11:10:43.157385179Z main ERROR Unrecognized conversion specifier [level] starting at position 35 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157515572Z main ERROR Unrecognized format specifier [logger] |
| 1741259443157 | 2025-03-06T11:10:43.157599552Z main ERROR Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157691427Z main ERROR Unrecognized format specifier [msg] |
| 1741259443157 | 2025-03-06T11:10:43.157779528Z main ERROR Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern. |
| 1741259443157 | 2025-03-06T11:10:43.157864428Z main ERROR Unrecognized format specifier [n] |
| 1741259443157 | 2025-03-06T11:10:43.157940035Z main ERROR Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. |
| 1741259443315 | START RequestId: b003f85b-8b31-4e70-9628-dd03607219da Version: $LATEST |
| 1741259443700 | %d [%thread] %-5level %logger - %msg%n2025-03-06T11:10:43.700301498Z main ERROR Unrecognized format specifier [d] |
| 1741259443700 | 2025-03-06T11:10:43.700471652Z main ERROR Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. |
| 1741259443700 | 2025-03-06T11:10:43.700581914Z main ERROR Unrecognized format specifier [thread] |
| 1741259443700 | 2025-03-06T11:10:43.700684369Z main ERROR Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. |
| 1741259443700 | 2025-03-06T11:10:43.700787373Z main ERROR Unrecognized format specifier [level] |
| 1741259443700 | 2025-03-06T11:10:43.700868065Z main ERROR Unrecognized conversion specifier [level] starting at position 35 in conversion pattern. |
| 1741259443701 | 2025-03-06T11:10:43.700988647Z main ERROR Unrecognized format specifier [logger] |
| 1741259443701 | 2025-03-06T11:10:43.701071281Z main ERROR Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern. |
| 1741259443701 | 2025-03-06T11:10:43.701182242Z main ERROR Unrecognized format specifier [msg] |
| 1741259443701 | 2025-03-06T11:10:43.701262817Z main ERROR Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern. |
| 1741259443701 | 2025-03-06T11:10:43.701354991Z main ERROR Unrecognized format specifier [n] |
| 1741259443701 | 2025-03-06T11:10:43.701434557Z main ERROR Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702174857Z main ERROR Unrecognized format specifier [d] |
| 1741259443702 | 2025-03-06T11:10:43.702287908Z main ERROR Unrecognized conversion specifier [d] starting at position 16 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702385288Z main ERROR Unrecognized format specifier [thread] |
| 1741259443702 | 2025-03-06T11:10:43.702463104Z main ERROR Unrecognized conversion specifier [thread] starting at position 25 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702559185Z main ERROR Unrecognized format specifier [level] |
| 1741259443702 | 2025-03-06T11:10:43.702640991Z main ERROR Unrecognized conversion specifier [level] starting at position 35 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702736245Z main ERROR Unrecognized format specifier [logger] |
| 1741259443702 | 2025-03-06T11:10:43.702814560Z main ERROR Unrecognized conversion specifier [logger] starting at position 47 in conversion pattern. |
| 1741259443702 | 2025-03-06T11:10:43.702905452Z main ERROR Unrecognized format specifier [msg] |
| 1741259443703 | 2025-03-06T11:10:43.702981466Z main ERROR Unrecognized conversion specifier [msg] starting at position 54 in conversion pattern. |
| 1741259443703 | 2025-03-06T11:10:43.703065460Z main ERROR Unrecognized format specifier [n] |
| 1741259443703 | 2025-03-06T11:10:43.703142907Z main ERROR Unrecognized conversion specifier [n] starting at position 56 in conversion pattern. |
| 1741259458361 | %d [%thread] %-5level %logger - %msg%n%d [%thread] %-5level %logger - %msg%n |
| 1741259463396 | %d [%thread] %-5level %logger - %msg%n%d [%thread] %-5level %logger - %msg%n |
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
What I’ve tried:
I tested with a simplified pattern (without %msg) and it works fine. I ensured that the dependencies are packaged correctly for Lambda. I’ve updated all dependencies to the latest versions. I’ve also tried testing with %logger and %t specifiers, which work fine locally but not in the lambda.
Question: What could be causing this issue with the %msg specifier when running on AWS Lambda, and how can I resolve it? Is there any Lambda-specific configuration I need to adjust?
Share Improve this question asked Mar 6 at 11:18 ShimakShimak 891 silver badge7 bronze badges1 Answer
Reset to default 0A transformer should be added to gradle
shadowJar {
transform(Log4j2PluginsCacheFileTransformer)
}