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    Setting Up Cloud Logging for Java

    You can write logs to Cloud Logging from Java applications by using the Logback appender or a java.util.logging handler , or by using the Cloud Logging library for Java directly.

    The Cloud Logging agent does not have to be installed to use the Cloud Logging library for Java.

    Before you begin

    1. Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.

    2. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

      Go to project selector

    3. Verify that billing is enabled for your Google Cloud project .

    4. Enable the Cloud Logging API.

      Enable the API

    5. In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

      Go to project selector

    6. Verify that billing is enabled for your Google Cloud project .

    7. Enable the Cloud Logging API.

      Enable the API

    Logback appender for Cloud Logging

    Using the Logback appender, you can use Cloud Logging with the SLF4J logging facade.

    Installing the dependency

    If you are using Maven , add the following to your pom.xml file. For more information about BOMs, see The Google Cloud Platform Libraries BOM .

     <dependency>
  <groupId>com.google.cloud</groupId>
  <artifactId>google-cloud-logging-logback</artifactId>
  <version>0.131.11-alpha</version>
</dependency>

    If you are using Gradle , add the following to your dependencies:

     implementation 'com.google.cloud:google-cloud-logging-logback:0.131.11-alpha'

    If you are using sbt , add the following to your dependencies:

     libraryDependencies += "com.google.cloud" % "google-cloud-logging-logback" % "0.131.11-alpha"

    Logback configuration

    Logback can be configured programmatically or using a script expressed in XML or Groovy.

    You can customize the minimum severity threshold, log name, or provide additional enhancers. This is a sample Logback configuration in XML format:

     < configuration 
>  
< appender 
  
 name 
 = 
 "CLOUD" 
  
 class 
 =" 
 com 
 . 
 google 
 . 
 cloud 
 . 
 logging 
 . 
 logback 
 . 
 LoggingAppender 
 " 
> <!-- Optional : filter logs at or above a level --> 
 <filter class=" 
 ch 
 . 
 qos 
 . 
 logback 
 . 
 classic 
 . 
 filter 
 . 
 ThresholdFilter 
 " 
> <level>INFO</level> 
 </filter> 
 <log>application.log</log> <!-- Optional : default java.log --> 
 <resourceType>gae_app</resourceType> <!-- Optional : default: auto-detected, fallback: global --> 
 <enhancer>com.example.logging.logback.enhancers.ExampleEnhancer</enhancer> <!-- Optional --> 
 <flushLevel>WARN</flushLevel> <!-- Optional : default ERROR --> 
 </appender> 
 <root level=" 
 info 
 " 
> <appender-ref ref=" 
 CLOUD 
 " / 
> </root> 
< /configuration 
>

    Example

    Once you have configured Logback to use the Cloud Logging Logback appender, you can now redirect logs using the SLF4J logging API. Provide Google Cloud configuration if you plan to run the example locally or outside of Google Cloud. This snippet shows how to log using SLF4J facade within your application:

      import 
  
 org.slf4j.Logger 
 ; 
 import 
  
 org.slf4j.LoggerFactory 
 ; 
 public 
  
 class 
 Quickstart 
  
 { 
  
 private 
  
 static 
  
 final 
  
 Logger 
  
 logger 
  
 = 
  
 LoggerFactory 
 . 
 getLogger 
 ( 
 Quickstart 
 . 
 class 
 ); 
  
 public 
  
 static 
  
 void 
  
 main 
 ( 
 String 
 [] 
  
 args 
 ) 
  
 { 
  
 logger 
 . 
 info 
 ( 
 "Logging INFO with Logback" 
 ); 
  
 logger 
 . 
 error 
 ( 
 "Logging ERROR with Logback" 
 ); 
  
 } 
 }

    The java.util.logging handler

    You can also use the Cloud Logging API using a default Java Logging API handler .

    Installing the dependency

    If you are using Maven with a BOM, add the following to your pom.xml file:

     <dependencyManagement>  
<dependencies>  
<dependency>  
<groupId>com.google.cloud</groupId>  
<artifactId>libraries-bom</artifactId>  
<version>26.55.0</version>  
<type>pom</type>  
<scope>import</scope>  
</dependency>  
</dependencies>
</dependencyManagement>

<dependencies>  
<dependency>  
<groupId>com.google.cloud</groupId>  
<artifactId>google-cloud-logging</artifactId>  
</dependency>  
<!--  
...
</dependencies>

    If you are using Maven without a BOM, add this to your dependencies:

     <dependency>  
<groupId>com.google.cloud</groupId>  
<artifactId>google-cloud-logging</artifactId>  
<version>3.21.3</version>
</dependency>

    If you are using Gradle , add the following to your dependencies:

     implementation platform('com.google.cloud:libraries-bom:26.65.0')

implementation 'com.google.cloud:google-cloud-logging'

    If you are using sbt , add the following to your dependencies:

     libraryDependencies += "com.google.cloud" % "google-cloud-logging" % "3.23.3"

    If you're using Visual Studio Code, IntelliJ, or Eclipse, you can add client libraries to your project using the following IDE plugins:

    The plugins provide additional functionality, such as key management for service accounts. Refer to each plugin's documentation for details.

    java.util.logging configuration

    Logging handlers can be added programmatically or by using a configuration file. The path to the configuration file must be provided to your application as a system property: -Djava.util.logging.config.file=/path/to/logging.properties

    Here is an example of a configuration file:

      # 
  
 To 
  
 use 
  
 this 
  
 configuration 
 , 
  
 add 
  
 to 
  
 system 
  
 properties 
  
 : 
  
 - 
 Djava 
 . 
 util 
 . 
 logging 
 . 
 config 
 . 
 file 
 = 
 "/path/to/file" 
 # 
 . 
 level 
  
 = 
  
 INFO 
 # 
  
 it 
  
 is 
  
 recommended 
  
 that 
  
 io 
 . 
 grpc 
  
 and 
  
 sun 
 . 
 net 
  
 logging 
  
 level 
  
 is 
  
 kept 
  
 at 
  
 INFO 
  
 level 
 , 
 # 
  
 as 
  
 both 
  
 these 
  
 packages 
  
 are 
  
 used 
  
 by 
  
 Cloud 
  
 internals 
  
 and 
  
 can 
  
 result 
  
 in 
  
 verbose 
  
 / 
  
 initialization 
  
 problems 
 . 
 io 
 . 
 grpc 
 . 
 netty 
 . 
 level 
 = 
 INFO 
 sun 
 . 
 net 
 . 
 level 
 = 
 INFO 
 com 
 . 
 example 
 . 
 logging 
 . 
 jul 
 . 
 Quickstart 
 . 
 handlers 
 = 
 com 
 . 
 google 
 . 
 cloud 
 . 
 logging 
 . 
 LoggingHandler 
 # 
  
 default 
  
 : 
  
 java 
 . 
 log 
 com 
 . 
 google 
 . 
 cloud 
 . 
 logging 
 . 
 LoggingHandler 
 . 
 log 
 = 
 custom_log 
 # 
  
 default 
  
 : 
  
 INFO 
 com 
 . 
 google 
 . 
 cloud 
 . 
 logging 
 . 
 LoggingHandler 
 . 
 level 
 = 
 FINE 
 # 
  
 default 
  
 : 
  
 ERROR 
 com 
 . 
 google 
 . 
 cloud 
 . 
 logging 
 . 
 LoggingHandler 
 . 
 flushLevel 
 = 
 ERROR 
 # 
  
 default 
  
 : 
  
 auto 
 - 
 detected 
 , 
  
 fallback 
  
 "global" 
 com 
 . 
 google 
 . 
 cloud 
 . 
 logging 
 . 
 LoggingHandler 
 . 
 resourceType 
 = 
 container 
 # 
  
 custom 
  
 formatter 
 com 
 . 
 google 
 . 
 cloud 
 . 
 logging 
 . 
 LoggingHandler 
 . 
 formatter 
 = 
 java 
 . 
 util 
 . 
 logging 
 . 
 SimpleFormatter 
 java 
 . 
 util 
 . 
 logging 
 . 
 SimpleFormatter 
 . 
 format 
 =% 
 3 
 $s 
 : 
  
 % 
 5 
 $s 
 % 
 6 
 $s 
 # 
 optional 
  
 enhancers 
  
 ( 
 to 
  
 add 
  
 additional 
  
 fields 
 , 
  
 labels 
 ) 
 com 
 . 
 google 
 . 
 cloud 
 . 
 logging 
 . 
 LoggingHandler 
 . 
 enhancers 
 = 
 com 
 . 
 example 
 . 
 logging 
 . 
 jul 
 . 
 enhancers 
 . 
 ExampleEnhancer

    Example

    Provide Google Cloud configuration if you plan to run the example locally or outside of Google Cloud. This snippet shows you how to log using java.util.logging :

      import 
  
 java.util.logging.Logger 
 ; 
 public 
  
 class 
 Quickstart 
  
 { 
  
 private 
  
 static 
  
 final 
  
 Logger 
  
 logger 
  
 = 
  
 Logger 
 . 
 getLogger 
 ( 
 Quickstart 
 . 
 class 
 . 
 getName 
 ()); 
  
 public 
  
 static 
  
 void 
  
 main 
 ( 
 String 
 [] 
  
 args 
 ) 
  
 { 
  
 logger 
 . 
 info 
 ( 
 "Logging INFO with java.util.logging" 
 ); 
  
 logger 
 . 
 severe 
 ( 
 "Logging ERROR with java.util.logging" 
 ); 
  
 } 
 }

    Common Configuration

    The following sections cover configuration that is common to the java.util.logging handler and the Logback appender for Cloud Logging.

    Defaults

    The Logback appender and java.util.logging handler use the following defaults to instantiate a Cloud Logging client:

    • Log name : java.log

    • Minimum threshold to log : INFO

    • Flush severity : ERROR

    The Cloud Logging library for Java batches messages by size and time since last write. Batches with logging requests at or above the flush severity are immediately written out.

    Monitored resource detection

    All logs sent via the Cloud Logging libraries require a monitored resource type to identify your application.

    The Logback appender and the java.util.logging handler provide automatic resource type detection of your App Engine, Compute Engine, and Google Kubernetes Engine applications.

    A global monitored resource is used as the default in other environments.

    You can override the monitored resource type to a valid type in the Logback appender Configuration or the java.util.logging Handler Configuration .

    Additional fields and labels

    Using the Logback appender and the java.util.logging handler, you can add or update fields on a LogEntry object using an instance of LoggingEnhancer .

    The enhancers must be configured as shown in the Logback appender configuration or the java.util.logging handler configuration :

      import 
  
 com.google.cloud.logging. LogEntry 
 
 ; 
 import 
  
 com.google.cloud.logging. LoggingEnhancer 
 
 ; 
 // Add / update additional fields to the log entry 
 public 
  
 class 
 ExampleEnhancer 
  
 implements 
  
  LoggingEnhancer 
 
  
 { 
  
 @Override 
  
 public 
  
 void 
  
 enhanceLogEntry 
 ( 
  LogEntry 
 
 . 
 Builder 
  
 logEntry 
 ) 
  
 { 
  
 // add additional labels 
  
 logEntry 
 . 
  addLabel 
 
 ( 
 "test-label-1" 
 , 
  
 "test-value-1" 
 ); 
  
 } 
 }

    Use of custom labels might not be supported for your configuration. For example, Dataflow logs don't include these labels.

    For more information on installation, see the documentation for the Cloud Logging library for Java. You can also report issues using the issue tracker .

    Write logs with the Cloud Logging client library

    For information on using the Cloud Logging client library for Java directly, see Cloud Logging Client Libraries .

    Run on Google Cloud

    For an application to write logs by using the Cloud Logging library for Java, the service account for the underlying resource must have the Logs Writer ( roles/logging.logWriter ) IAM role. Most Google Cloud environments automatically configure the default service account to have this role.

    App Engine

    Cloud Logging is automatically enabled for App Engine, and your app's default service account has the IAM permissions by default to write log entries.

    App Engine standard environment, by default , uses the java.util.logging.Logger API; this writes to Cloud Logging directly and is easy to configure.

    For further details, see App Engine documentation on Reading and Writing Application Logs .

    App Engine flexible environment

    On App Engine flexible environment , java.util.logging uses the ConsoleHandler by default, and sends logs to stdout and stderr .

    The Jetty Runtime is bundled with the Cloud Logging library for Java.

    The java.util.logging handler can be used to log directly to Cloud Logging by providing the logging.properties in your app.yaml as shown here:

       
 env_variables 
 : 
  
 JETTY_ARGS 
 : 
  
 - 
 Djava 
 . 
 util 
 . 
 logging 
 . 
 config 
 . 
 file 
 = 
 WEB 
 - 
 INF 
 / 
 logging 
 . 
 properties

    Trace ID logging is available on Jetty runtimes if you are using the java.util.logging handler or the Logback appender.

    When running on App Engine flexible environment, a TraceLoggingEnhancer instance adds a thread-safe trace ID to every log entry using the label trace_id .

    Google Kubernetes Engine (GKE)

    GKE automatically grants the default service account the Logs Writer ( roles/logging.logWriter ) IAM role. If you use Workload Identity Federation for GKE with this default service account to let workloads access specific Google Cloud APIs, then no additional configuration is required. However, if you use Workload Identity Federation for GKE with a custom IAM service account, then ensure that the custom service account has the role of Logs Writer ( roles/logging.logWriter ).

    If needed, you can also use the following command to add the logging.write access scope when creating the cluster:

     gcloud  
container  
clusters  
create  
example-cluster-name  
 \ 
  
--scopes  
https://www.googleapis.com/auth/logging.write

    Compute Engine

    When using Compute Engine VM instances, add the cloud-platform access scope to each instance. When creating a new instance through the Google Cloud console, you can do this in the Identity and API accesssection of the Create Instancepanel. Use the Compute Engine default service account or another service account of your choice, and select Allow full access to all Cloud APIsin the Identity and API accesssection. Whichever service account you select, ensure that it has been granted the Logs Writer role in the IAM & Adminsection of the Google Cloud console.

    Run locally and elsewhere

    To use the Cloud Logging library for Java outside of Google Cloud, including running the library on your own workstation, on your data center's computers, or on the VM instances of another cloud provider, you must set up Application Default Credentials (ADC) in your local environment to authenticate to the Cloud Logging library for Java.

    For more information, see Set up ADC for on-premises or another cloud provider .

    View the logs

    In the Google Cloud console, go to the Logs Explorer page:

    Go to Logs Explorer

    If you use the search bar to find this page, then select the result whose subheading is Logging .

    In the Logs Explorer, you must specify one or more resources, but the resource selection might not be obvious. Here are some tips to help you get started:

    • If you are deploying your application to App Engine or using the App Engine-specific libraries, set your resource to GAE Application.

    • If you are deploying your application on Compute Engine, set the resource to GCE VM Instance.

    • If you are deploying your application on Google Kubernetes Engine, your cluster's logging configuration determines the resource type of the log entries. For a detailed discussion on the Legacy Google Cloud Observability and the Google Cloud Observability Kubernetes Monitoring solutions, and how those options affect the resource type, see Migrating to Google Cloud Observability Kubernetes Monitoring .

    • If your application is using the Cloud Logging API directly, the resource is dependent on the API and your configuration. For example, in your application, you can specify a resource or use a default resource.

    • If you don't see any logs in the Logs Explorer, to see all log entries, switch to the advanced query mode and use an empty query.

      1. To switch to the advanced query mode, click menu(&blacktriangledown;) at the top of the Logs Explorer and then select Convert to advanced filter.
      2. Clear the content that appears in the filter box.
      3. Click Submit Filter.

      You can examine the individual entries to identify your resources.

    For additional information, see Using the Logs Explorer .
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