Log4j 2 configuration file Add logging dependency SDK-specific errors and warnings Request/response summary logging Debug-level SDK logging Enable wire logging

Logging with the SDK for Java 2.x

The AWS SDK for Java 2.x uses SLF4J, which is an abstraction layer that enables the use of any one of several logging systems at runtime.

Supported logging systems include the Java Logging Framework and Apache Log4j 2, among others. This topic shows you how to use Log4j 2 as the logging system for working with the SDK.

Log4j 2 configuration file

You typically use a configuration file, namedlog4j2.xml with Log4j 2. Example configuration files are shown below. To learn more about the values used in the configuration file, see the manual for Log4j configuration.

The log4j2.xml file needs to be on the classpath when your application starts up. For a Maven project, put the file in the <project-dir>/src/main/resources directory.

The log4j2.xml configuration file specifies properties such as logging level, where logging output is sent (for example, to a file or to the console), and the format of the output. The logging level specifies the level of detail that Log4j 2 outputs. Log4j 2 supports the concept of multiple logging hierarchies. The logging level is set independently for each hierarchy. The main logging hierarchy that you use with the AWS SDK for Java 2.x is software.amazon.awssdk.

Add logging dependency

To configure the Log4j 2 binding for SLF4J in your build file, use the following.

Use 2.20.0 for the minimum version of the log4j-slf4j2-impl artifact. For the latest version, use the version published to Maven central. Replace VERSION with version you'll use.

SDK-specific errors and warnings

We recommend that you always leave the "software.amazon.awssdk" logger hierarchy set to "WARN" to catch any important messages from the SDK's client libraries. For example, if the Amazon S3 client detects that your application hasn’t properly closed an InputStream and could be leaking resources, the S3 client reports it through a warning message to the logs. This also ensures that messages are logged if the client has any problems handling requests or responses.

The following log4j2.xml file sets the rootLogger to "WARN", which causes warning and error-level messages from all loggers in the application to be output, including those in the "software.amazon.awssdk" hierarchy. Alternatively, you can explicitly set the "software.amazon.awssdk" logger hierarchy to "WARN" if <Root level="ERROR"> is used.

Example Log4j2.xml configuration file

This configuration will log messages at the "ERROR" and "WARN" levels to the console for all logger hierarchies.


<Configuration status="WARN">
 <Appenders>
  <Console name="ConsoleAppender" target="SYSTEM_OUT">
   <PatternLayout pattern="%d{YYYY-MM-dd HH:mm:ss} [%t] %-5p %c:%L - %m%n" />
  </Console>
 </Appenders>

 <Loggers>
  <Root level="WARN">
   <AppenderRef ref="ConsoleAppender"/>
  </Root>
 </Loggers>
</Configuration>

Request/response summary logging

Every request to an AWS service generates a unique AWS request ID that is useful if you run into an issue with how an AWS service is handling a request. AWS request IDs are accessible programmatically through SdkServiceException objects in the SDK for any failed service call, and can also be reported through the "DEBUG" log level of the "software.amazon.awssdk.request" logger.

The following log4j2.xml file enables a summary of requests and responses.


<Configuration status="WARN">
 <Appenders>
  <Console name="ConsoleAppender" target="SYSTEM_OUT">
   <PatternLayout pattern="%d{YYYY-MM-dd HH:mm:ss} [%t] %-5p %c:%L - %m%n" />
  </Console>
 </Appenders>

 <Loggers>
  <Root level="ERROR">
   <AppenderRef ref="ConsoleAppender"/>
  </Root>
  <Logger name="software.amazon.awssdk" level="WARN" />
  <Logger name="software.amazon.awssdk.request" level="DEBUG" />
 </Loggers>
</Configuration>

Here is an example of the log output:


2022-09-23 16:02:08 [main] DEBUG software.amazon.awssdk.request:85 - Sending Request: DefaultSdkHttpFullRequest(httpMethod=POST, protocol=https, host=dynamodb.us-east-1.amazonaws.com, encodedPath=/, headers=[amz-sdk-invocation-id, Content-Length, Content-Type, User-Agent, X-Amz-Target], queryParameters=[])
2022-09-23 16:02:08 [main] DEBUG software.amazon.awssdk.request:85 - Received successful response: 200, Request ID: QS9DUMME2NHEDH8TGT9N5V53OJVV4KQNSO5AEMVJF66Q9ASUAAJG, Extended Request ID: not available

If you are interested in only the request ID use <Logger name="software.amazon.awssdk.requestId" level="DEBUG" />.

Debug-level SDK logging

If you need more detail about what the SDK is doing, you can set the logging level of the software.amazon.awssdk logger to DEBUG. At this level, the SDK outputs a large amount of detail, so we recommend that you set this level to resolve errors using integration tests.

At this logging level, the SDK logs information about configuration, credentials resolution, execution interceptors, high-level TLS activity, request signing, and much more.

The following is a sampling of statements that are output by the SDK at DEBUG level for a S3Client#listBuckets() call.


DEBUG s.a.a.r.p.AwsRegionProviderChain:57 - Unable to load region from software.amazon.awssdk.regions.providers.SystemSettingsRegionProvider@324dcd31:Unable to load region from system settings. Region must be specified either via environment variable (AWS_REGION) or  system property (aws.region).
DEBUG s.a.a.c.i.h.l.ClasspathSdkHttpServiceProvider:85 - The HTTP implementation loaded is software.amazon.awssdk.http.apache.ApacheSdkHttpService@a23a01d
DEBUG s.a.a.c.i.ExecutionInterceptorChain:85 - Creating an interceptor chain that will apply interceptors in the following order: [software.amazon.awssdk.core.internal.interceptor.HttpChecksumValidationInterceptor@69b2f8e5, software.amazon.awssdk.awscore.interceptor.HelpfulUnknownHostExceptionInterceptor@6331250e, software.amazon.awssdk.awscore.eventstream.EventStreamInitialRequestInterceptor@a10c1b5, software.amazon.awssdk.awscore.interceptor.TraceIdExecutionInterceptor@644abb8f, software.amazon.awssdk.services.s3.auth.scheme.internal.S3AuthSchemeInterceptor@1a411233, software.amazon.awssdk.services.s3.endpoints.internal.S3ResolveEndpointInterceptor@70325d20, software.amazon.awssdk.services.s3.endpoints.internal.S3RequestSetEndpointInterceptor@7c2327fa, software.amazon.awssdk.services.s3.internal.handlers.StreamingRequestInterceptor@4d847d32, software.amazon.awssdk.services.s3.internal.handlers.CreateBucketInterceptor@5f462e3b, software.amazon.awssdk.services.s3.internal.handlers.CreateMultipartUploadRequestInterceptor@3d7fa3ae, software.amazon.awssdk.services.s3.internal.handlers.DecodeUrlEncodedResponseInterceptor@58065f0c, software.amazon.awssdk.services.s3.internal.handlers.GetBucketPolicyInterceptor@3605c4d3, software.amazon.awssdk.services.s3.internal.handlers.S3ExpressChecksumInterceptor@585c13de, software.amazon.awssdk.services.s3.internal.handlers.AsyncChecksumValidationInterceptor@187eb9a8, software.amazon.awssdk.services.s3.internal.handlers.SyncChecksumValidationInterceptor@726a6b94, software.amazon.awssdk.services.s3.internal.handlers.EnableTrailingChecksumInterceptor@6ad11a56, software.amazon.awssdk.services.s3.internal.handlers.ExceptionTranslationInterceptor@522b2631, software.amazon.awssdk.services.s3.internal.handlers.GetObjectInterceptor@3ff57625, software.amazon.awssdk.services.s3.internal.handlers.CopySourceInterceptor@1ee29c84, software.amazon.awssdk.services.s3.internal.handlers.ObjectMetadataInterceptor@7c8326a4]
DEBUG s.a.a.u.c.CachedSupplier:85 - (SsoOidcTokenProvider()) Cached value is stale and will be refreshed.
...
DEBUG s.a.a.c.i.ExecutionInterceptorChain:85 - Creating an interceptor chain that will apply interceptors in the following order: [software.amazon.awssdk.core.internal.interceptor.HttpChecksumValidationInterceptor@51351f28, software.amazon.awssdk.awscore.interceptor.HelpfulUnknownHostExceptionInterceptor@21618fa7, software.amazon.awssdk.awscore.eventstream.EventStreamInitialRequestInterceptor@15f2eda3, software.amazon.awssdk.awscore.interceptor.TraceIdExecutionInterceptor@34cf294c, software.amazon.awssdk.services.sso.auth.scheme.internal.SsoAuthSchemeInterceptor@4d7aaca2, software.amazon.awssdk.services.sso.endpoints.internal.SsoResolveEndpointInterceptor@604b1e1d, software.amazon.awssdk.services.sso.endpoints.internal.SsoRequestSetEndpointInterceptor@62566842]
...
DEBUG s.a.a.request:85 - Sending Request: DefaultSdkHttpFullRequest(httpMethod=GET, protocol=https, host=portal.sso.us-east-1.amazonaws.com, encodedPath=/federation/credentials, headers=[amz-sdk-invocation-id, User-Agent, x-amz-sso_bearer_token], queryParameters=[role_name, account_id])
DEBUG s.a.a.c.i.h.p.s.SigningStage:85 - Using SelectedAuthScheme: smithy.api#noAuth
DEBUG s.a.a.h.a.i.c.SdkTlsSocketFactory:366 - Connecting socket to portal.sso.us-east-1.amazonaws.com/18.235.195.183:443 with timeout 2000
...
DEBUG s.a.a.requestId:85 - Received successful response: 200, Request ID: bb4f40f4-e920-4b5c-8648-58f26e7e08cd, Extended Request ID: not available
DEBUG s.a.a.request:85 - Received successful response: 200, Request ID: bb4f40f4-e920-4b5c-8648-58f26e7e08cd, Extended Request ID: not available
DEBUG s.a.a.u.c.CachedSupplier:85 - (software.amazon.awssdk.services.sso.auth.SsoCredentialsProvider@b965857) Successfully refreshed cached value. Next Prefetch Time: 2024-04-25T22:03:10.097Z. Next Stale Time: 2024-04-25T22:05:30Z
DEBUG s.a.a.c.i.ExecutionInterceptorChain:85 - Interceptor 'software.amazon.awssdk.services.s3.endpoints.internal.S3RequestSetEndpointInterceptor@7c2327fa' modified the message with its modifyHttpRequest method.
...
DEBUG s.a.a.c.i.h.p.s.SigningStage:85 - Using SelectedAuthScheme: aws.auth#sigv4
...
DEBUG s.a.a.a.s.Aws4Signer:85 - AWS4 Canonical Request: GET
...
DEBUG s.a.a.h.a.a.i.s.DefaultV4RequestSigner:85 - AWS4 String to sign: AWS4-HMAC-SHA256
20240425T210631Z
20240425/us-east-1/s3/aws4_request
aafb7784627fa7a49584256cb746279751c48c2076f813259ef767ecce304d64
DEBUG s.a.a.h.a.i.c.SdkTlsSocketFactory:366 - Connecting socket to s3.us-east-1.amazonaws.com/52.217.41.86:443 with timeout 2000
...

The following log4j2.xml file configures the previous output.


<Configuration status="WARN">
    <Appenders>
        <Console name="ConsoleAppender" target="SYSTEM_OUT">
            <PatternLayout pattern="%-5p %c{1.}:%L - %m%n" />
        </Console>
    </Appenders>

    <Loggers>
        <Root level="WARN">
            <AppenderRef ref="ConsoleAppender"/>
        </Root>
        <Logger name="software.amazon.awssdk" level="DEBUG" />
    </Loggers>
</Configuration>

Enable wire logging

It can be useful to see the exact requests and responses that the SDK for Java 2.x sends and receives. If you need access to this information, you can temporarily enable it by adding the necessary configuration depending on the HTTP client the service client uses.

By default, synchronous service clients, such as the S3Client, use an underlying Apache HttpClient, and asynchronous service clients, such as the S3AsyncClient, use a Netty non-blocking HTTP client.

Here is a breakdown of HTTP clients you can use for the two categories of service clients:

Synchronous HTTP Clients	Asynchronous HTTP Clients
ApacheHttpClient (default)	NettyNioAsyncHttpClient (default)
UrlConnectionHttpClient	AwsCrtAsyncHttpClient
AwsCrtHttpClient

Consult the appropriate tab below for configuration settings you need to add depending on the underlying HTTP client.

Warning

We recommend you only use wire logging for debugging purposes. Disable it in your production environments because it can log sensitive data. It logs the full request or response without encryption, even for an HTTPS call. For large requests (e.g., to upload a file to Amazon S3) or responses, verbose wire logging can also significantly impact your application’s performance.

ApacheHttpClient

Add the "org.apache.http.wire" logger to the log4j2.xml configuration file and set the level to "DEBUG".

The following log4j2.xml file turns on full wire logging for the Apache HttpClient.


<Configuration status="WARN">
 <Appenders>
  <Console name="ConsoleAppender" target="SYSTEM_OUT">
   <PatternLayout pattern="%d{YYYY-MM-dd HH:mm:ss} [%t] %-5p %c:%L - %m%n" />
  </Console>
 </Appenders>

 <Loggers>
  <Root level="WARN">
   <AppenderRef ref="ConsoleAppender"/>
  </Root>
  <Logger name="software.amazon.awssdk" level="WARN" />
  <Logger name="software.amazon.awssdk.request" level="DEBUG" />
  <Logger name="org.apache.http.wire" level="DEBUG" />
 </Loggers>
</Configuration>

An additional Maven dependency on the log4j-1.2-api artifact is required for wire logging with Apache since it uses 1.2 under the hood.

The full set of Maven dependencies for log4j 2, including wire logging for the Apache HTTP client are shown in the following build file snippets.

Maven


...
<dependencyManagement>
    ...
    <dependencies>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-bom</artifactId>
            <version>VERSION</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
     </dependencies>
</dependencyManagement>
...
<!-- The following is needed for Log4j2 with SLF4J -->
<dependency>
   <groupId>org.apache.logging.log4j</groupId>
   <artifactId>log4j-slf4j2-impl</artifactId>
</dependency>

<!-- The following is needed for Apache HttpClient wire logging -->
<dependency>
   <groupId>org.apache.logging.log4j</groupId>
   <artifactId>log4j-1.2-api</artifactId>
</dependency>
...

Gradle–Kotlin DSL


...
dependencies {
    ...
    implementation(platform("org.apache.logging.log4j:log4j-bom:VERSION"))
    implementation("org.apache.logging.log4j:log4j-slf4j2-impl")
    implementation("org.apache.logging.log4j:log4j-1.2-api")
}
...

Use 2.20.0 for the minimum version of the log4j-bom artifact. For the latest version, use the version published to Maven central. Replace VERSION with version you'll use.

UrlConnectionHttpClient

To log details for service clients that use the UrlConnectionHttpClient, first create a logging.properties file with the following contents:


handlers=java.util.logging.ConsoleHandler
java.util.logging.ConsoleHandler.level=FINEST
sun.net.www.protocol.http.HttpURLConnection.level=ALL

Set the following JVM system property with the full path of the logging.properties:


-Djava.util.logging.config.file=/full/path/to/logging.properties

This configuration will log the only the headers of the request and response, for example:


<Request>  FINE: sun.net.www.MessageHeader@35a9782c11 pairs: {GET /fileuploadtest HTTP/1.1: null}{amz-sdk-invocation-id: 5f7e707e-4ac5-bef5-ba62-00d71034ffdc}{amz-sdk-request: attempt=1; max=4}{Authorization: AWS4-HMAC-SHA256 Credential=<deleted>/20220927/us-east-1/s3/aws4_request, SignedHeaders=amz-sdk-invocation-id;amz-sdk-request;host;x-amz-content-sha256;x-amz-date;x-amz-te, Signature=e367fa0bc217a6a65675bb743e1280cf12fbe8d566196a816d948fdf0b42ca1a}{User-Agent: aws-sdk-java/2.17.230 Mac_OS_X/12.5 OpenJDK_64-Bit_Server_VM/25.332-b08 Java/1.8.0_332 vendor/Amazon.com_Inc. io/sync http/UrlConnection cfg/retry-mode/legacy}{x-amz-content-sha256: UNSIGNED-PAYLOAD}{X-Amz-Date: 20220927T133955Z}{x-amz-te: append-md5}{Host: tkhill-test1.s3.amazonaws.com}{Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2}{Connection: keep-alive}
<Response> FINE: sun.net.www.MessageHeader@70a36a6611 pairs: {null: HTTP/1.1 200 OK}{x-amz-id-2: sAFeZDOKdUMsBbkdjyDZw7P0oocb4C9KbiuzfJ6TWKQsGXHM/dFuOvr2tUb7Y1wEHGdJ3DSIxq0=}{x-amz-request-id: P9QW9SMZ97FKZ9X7}{Date: Tue, 27 Sep 2022 13:39:57 GMT}{Last-Modified: Tue, 13 Sep 2022 14:38:12 GMT}{ETag: "2cbe5ad4a064cedec33b452bebf48032"}{x-amz-transfer-encoding: append-md5}{Accept-Ranges: bytes}{Content-Type: text/plain}{Server: AmazonS3}{Content-Length: 67}

To see the request/response bodies, add -Djavax.net.debug=all to the JVM properties. This additional property logs a great deal of information, including all SSL information.

Within the log console or log file, search for "GET" or "POST" to quickly go to the section of the log containing actual requests and responses. Search for "Plaintext before ENCRYPTION" for requests and "Plaintext after DECRYPTION" for responses to see the full text of the headers and bodies.

NettyNioAsyncHttpClient

If your asynchronous service client uses the default NettyNioAsyncHttpClient, add two additional loggers to your log4j2.xml file to log HTTP headers and request/response bodies.


<Logger name="io.netty.handler.logging" level="DEBUG" />
<Logger name="io.netty.handler.codec.http2.Http2FrameLogger" level="DEBUG" />

Here is a complete log4j2.xml example:


<Configuration status="WARN">
    <Appenders>
        <Console name="ConsoleAppender" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{YYYY-MM-dd HH:mm:ss} [%t] %-5p %c:%L - %m%n" />
        </Console>
    </Appenders>

    <Loggers>
        <Root level="WARN">
            <AppenderRef ref="ConsoleAppender"/>
        </Root>
        <Logger name="software.amazon.awssdk" level="WARN" />
        <Logger name="software.amazon.awssdk.request" level="DEBUG" />
        <Logger name="io.netty.handler.logging" level="DEBUG" />
        <Logger name="io.netty.handler.codec.http2.Http2FrameLogger" level="DEBUG" />
    </Loggers>
</Configuration>

These settings log all header details and request/response bodies.

AwsCrtAsyncHttpClient/AwsCrtHttpClient

If you have configured your service client to use an instance of an AWS CRT-based HTTP client, you can log details by setting JVM system properties or programmatically.

Log to a file at "Debug" level

Using system properties:


-Daws.crt.log.level=Trace 
-Daws.crt.log.destination=File 
-Daws.crt.log.filename=<path to file>

Programmatically:


import software.amazon.awssdk.crt.Log;

// Execute this statement before constructing the SDK service client.
Log.initLoggingToFile(Log.LogLevel.Trace, "<path to file>");

Log to the console at "Debug" level

Using system properties:


-Daws.crt.log.level=Trace 
-Daws.crt.log.destination=Stdout

Programmatically:


import software.amazon.awssdk.crt.Log;

// Execute this statement before constructing the SDK service client.
Log.initLoggingToStdout(Log.LogLevel.Trace);

For security reasons, at the "Trace" level the AWS CRT-based HTTP clients log only response headers. Request headers, request bodies, and response bodies are not logged.

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Document Conventions

Retries

Set the JVM TTL for DNS name lookups