161. Stackdriver Logging

Maven coordinates, using Spring Cloud GCP BOM:


Gradle coordinates:

dependencies {
    compile group: 'org.springframework.cloud', name: 'spring-cloud-gcp-starter-logging'

Stackdriver Logging is the managed logging service provided by Google Cloud Platform.

This module provides support for associating a web request trace ID with the corresponding log entries. It does so by retrieving the X-B3-TraceId value from the Mapped Diagnostic Context (MDC), which is set by Spring Cloud Sleuth. If Spring Cloud Sleuth isn’t used, the configured TraceIdExtractor extracts the desired header value and sets it as the log entry’s trace ID. This allows grouping of log messages by request, for example, in the Google Cloud Console Logs viewer.


Due to the way logging is set up, the GCP project ID and credentials defined in application.properties are ignored. Instead, you should set the GOOGLE_CLOUD_PROJECT and GOOGLE_APPLICATION_CREDENTIALS environment variables to the project ID and credentials private key location, respectively. You can do this easily if you’re using the Google Cloud SDK, using the gcloud config set project [YOUR_PROJECT_ID] and gcloud auth application-default login commands, respectively.

161.1 Web MVC Interceptor

For use in Web MVC-based applications, TraceIdLoggingWebMvcInterceptor is provided that extracts the request trace ID from an HTTP request using a TraceIdExtractor and stores it in a thread-local, which can then be used in a logging appender to add the trace ID metadata to log messages.


If Spring Cloud GCP Trace is enabled, the logging module disables itself and delegates log correlation to Spring Cloud Sleuth.

LoggingWebMvcConfigurer configuration class is also provided to help register the TraceIdLoggingWebMvcInterceptor in Spring MVC applications.

Applications hosted on the Google Cloud Platform include trace IDs under the x-cloud-trace-context header, which will be included in log entries. However, if Sleuth is used the trace ID will be picked up from the MDC.

161.2 Logback Support

Currently, only Logback is supported and there are 2 possibilities to log to Stackdriver via this library with Logback: via direct API calls and through JSON-formatted console logs.

161.2.1 Log via API

A Stackdriver appender is available using org/springframework/cloud/gcp/autoconfigure/logging/logback-appender.xml. This appender builds a Stackdriver Logging log entry from a JUL or Logback log entry, adds a trace ID to it and sends it to Stackdriver Logging.

STACKDRIVER_LOG_NAME and STACKDRIVER_LOG_FLUSH_LEVEL environment variables can be used to customize the STACKDRIVER appender.

Your configuration may then look like this:

  <include resource="org/springframework/cloud/gcp/autoconfigure/logging/logback-appender.xml" />

  <root level="INFO">
    <appender-ref ref="STACKDRIVER" />

If you want to have more control over the log output, you can further configure the appender. The following properties are available:

PropertyDefault ValueDescription



The Stackdriver Log name. This can also be set via the STACKDRIVER_LOG_NAME environmental variable.



If a log entry with this level is encountered, trigger a flush of locally buffered log to Stackdriver Logging. This can also be set via the STACKDRIVER_LOG_FLUSH_LEVEL environmental variable.

161.2.2 Log via Console

For Logback, a org/springframework/cloud/gcp/autoconfigure/logging/logback-json-appender.xml file is made available for import to make it easier to configure the JSON Logback appender.

Your configuration may then look something like this:

  <include resource="org/springframework/cloud/gcp/autoconfigure/logging/logback-json-appender.xml" />

  <root level="INFO">
    <appender-ref ref="CONSOLE_JSON" />

If your application is running on Google Kubernetes Engine, Google Compute Engine or Google App Engine Flexible, your console logging is automatically saved to Google Stackdriver Logging. Therefore, you can just include org/springframework/cloud/gcp/autoconfigure/logging/logback-json-appender.xml in your logging configuration, which logs JSON entries to the console. The trace id will be set correctly.

If you want to have more control over the log output, you can further configure the appender. The following properties are available:

PropertyDefault ValueDescription


If not set, default value is determined in the following order:

  1. SPRING_CLOUD_GCP_LOGGING_PROJECT_ID Environmental Variable.
  2. Value of DefaultGcpProjectIdProvider.getProjectId()

This is used to generate fully qualified Stackdriver Trace ID format: projects/[PROJECT-ID]/traces/[TRACE-ID].

This format is required to correlate trace between Stackdriver Trace and Stackdriver Logging.

If projectId is not set and cannot be determined, then it’ll log traceId without the fully qualified format.



Should the traceId be included



Should the spanId be included



Should the severity be included



Should the thread name be included



Should all MDC properties be included. The MDC properties X-B3-TraceId, X-B3-SpanId and X-Span-Export provided by Spring Sleuth will get excluded as they get handled separately



Should the name of the logger be included



Should the formatted log message be included.



Should the stacktrace be appended to the formatted log message. This setting is only evaluated if includeFormattedMessage is true



Should the logging context be included



Should the log message with blank placeholders be included



Should the stacktrace be included as a own field

This is an example of such an Logback configuration:

<configuration >
  <property name="projectId" value="${projectId:-${GOOGLE_CLOUD_PROJECT}}"/>

  <appender name="CONSOLE_JSON" class="ch.qos.logback.core.ConsoleAppender">
    <encoder class="ch.qos.logback.core.encoder.LayoutWrappingEncoder">
      <layout class="org.springframework.cloud.gcp.logging.StackdriverJsonLayout">


161.3 Sample

A Sample Spring Boot Application is provided to show how to use the Cloud logging starter.