Logging and viewing logs in Cloud Run

This page describes the logs available when using Cloud Run, and how to view and write logs.

Cloud Run has several types of logs, and these are automatically sent to Cloud Logging:

View logs

Both of the console methods of viewing logs examine the same logs stored in Cloud Logging, but the Cloud Logging Logs Explorer provides more details and more filtering capabilities.

View logs in Cloud Run

View logs for a service

View logs for a job

View logs for a worker pool

View service logs using Google Cloud CLI

You can use Google Cloud CLI to view tailing logs or read existing logs for a Cloud Run service in the command line By default, the logs are formatted in a single-line format optimized for the console.

To tail logs, you need to install the log-streaming component in Google Cloud CLI. If the component isn't installed, you will be prompted to install it when required.

View tailing logs in the command line

For a Cloud Run service, you can tail logs in real-time from your Cloud Run service directly in the command-line:

Read logs in the command line

View logs in Cloud Logging

View service logs in Cloud Code

Read logs programmatically

If you want to read the logs programmatically, you can use one of these methods:

Instance scaling logs format and contents

When new instances start for your Cloud Run service, Cloud Logging includes log entries under the varlog/system log name explaining why each instance was created. The log entry follows this format:

Write container logs

When you write logs from your service, job, or worker pool, they will be picked up automatically by Cloud Logging so long as the logs are written to any of these locations:

Most developers are expected to write logs using standard output and standard error.

Reason	Description
`MANUAL_OR_CUSTOMER_MIN_INSTANCE`	Instance started because of customer-configured minimum instances or manual scaling.
`AUTOSCALING`	Instance started due to configured scaling factors (such as CPU utilization, request throughput, and so forth) or not enough existing capacity for current traffic.
`DEPLOYMENT_ROLLOUT`	Instance started due to traffic shifting between revisions due to deployment, traffic split adjustment, or deployment health check.

The container logs written to these supported locations are automatically associated with the Cloud Run service, revision, and location, the Cloud Run worker pool, revision, and location, or with the Cloud Run job. Exceptions contained in these logs are captured by and reported in Error Reporting.

The integrated logging balances reliability and resource usage, and should work for most applications. Writing log entries using integrated logging does not consume quota for the number of entries.write requests per minute of the Cloud Logging API.

Use simple text vs structured JSON in logs

When you write logs, you can send a simple text string or send a single line of serialized JSON, also called "structured" data. This is picked up and parsed by Cloud Logging and is placed into jsonPayload. In contrast, the simple text message is placed in textPayload.

Write structured logs

The following snippet shows how to write structured log entries. It also shows how to correlate log messages with the corresponding request log.

Node.js


// Uncomment and populate this variable in your code:
// const project = 'The project ID of your function or Cloud Run service';

// Build structured log messages as an object.
const globalLogFields = {};

// Add log correlation to nest all log messages beneath request log in Log Viewer.
// (This only works for HTTP-based invocations where `req` is defined.)
if (typeof req !== 'undefined') {
  const traceHeader = req.header('X-Cloud-Trace-Context');
  if (traceHeader && project) {
    const [trace] = traceHeader.split('/');
    globalLogFields['logging.googleapis.com/trace'] =
      `projects/${project}/traces/${trace}`;
  }
}

// Complete a structured log entry.
const entry = Object.assign(
  {
    severity: 'NOTICE',
    message: 'This is the default display field.',
    // Log viewer accesses 'component' as 'jsonPayload.component'.
    component: 'arbitrary-property',
  },
  globalLogFields
);

// Serialize to a JSON string and output.
console.log(JSON.stringify(entry));

Python

# Uncomment and populate this variable in your code:
# PROJECT = 'The project ID of your Cloud Run service';

# Build structured log messages as an object.
global_log_fields = {}

# Add log correlation to nest all log messages.
# This is only relevant in HTTP-based contexts, and is ignored elsewhere.
# (In particular, non-HTTP-based Cloud Functions.)
request_is_defined = "request" in globals() or "request" in locals()
if request_is_defined and request:
    trace_header = request.headers.get("X-Cloud-Trace-Context")

    if trace_header and PROJECT:
        trace = trace_header.split("/")
        global_log_fields[
            "logging.googleapis.com/trace"
        ] = f"projects/{PROJECT}/traces/{trace[0]}"

# Complete a structured log entry.
entry = dict(
    severity="NOTICE",
    message="This is the default display field.",
    # Log viewer accesses 'component' as jsonPayload.component'.
    component="arbitrary-property",
    **global_log_fields,
)

print(json.dumps(entry))

Go

The structure for each log entry is provided by an Entry type:


// Entry defines a log entry.
type Entry struct {
	Message  string `json:"message"`
	Severity string `json:"severity,omitempty"`
	Trace    string `json:"logging.googleapis.com/trace,omitempty"`

	// Logs Explorer allows filtering and display of this as `jsonPayload.component`.
	Component string `json:"component,omitempty"`
}

// String renders an entry structure to the JSON format expected by Cloud Logging.
func (e Entry) String() string {
	if e.Severity == "" {
		e.Severity = "INFO"
	}
	out, err := json.Marshal(e)
	if err != nil {
		log.Printf("json.Marshal: %v", err)
	}
	return string(out)
}

When an Entry struct is logged, the String method is called to marshal it to the JSON format expected by Cloud Logging:


func init() {
	// Disable log prefixes such as the default timestamp.
	// Prefix text prevents the message from being parsed as JSON.
	// A timestamp is added when shipping logs to Cloud Logging.
	log.SetFlags(0)
}

func indexHandler(w http.ResponseWriter, r *http.Request) {
	// Uncomment and populate this variable in your code:
	// projectID = "The project ID of your Cloud Run service"

	// Derive the traceID associated with the current request.
	var trace string
	if projectID != "" {
		traceHeader := r.Header.Get("X-Cloud-Trace-Context")
		traceParts := strings.Split(traceHeader, "/")
		if len(traceParts) > 0 && len(traceParts[0]) > 0 {
			trace = fmt.Sprintf("projects/%s/traces/%s", projectID, traceParts[0])
		}
	}

	log.Println(Entry{
		Severity:  "NOTICE",
		Message:   "This is the default display field.",
		Component: "arbitrary-property",
		Trace:     trace,
	})

	fmt.Fprintln(w, "Hello Logger!")
}

Java

Enable JSON logging with Logback and SLF4J by configuring the Logging Logback appender in your logback.xml configuration:

// Add log correlation to nest all log messages beneath request log in Log Viewer.
// TODO(developer): delete this code if you're creating a Cloud
//                  Function and it is *NOT* triggered by HTTP.
String traceHeader = req.headers("x-cloud-trace-context");
if (traceHeader != null && project != null) {
  String trace = traceHeader.split("/")[0];
  MDC.put(
      "logging.googleapis.com/trace",
      String.format("projects/%s/traces/%s", project, trace));
}
// -- End log correlation code --

// Create a structured log entry using MDC (Mapped Diagnostic Context) keys.
// For instantiating the "logger" variable, see
// https://cloud.google.com/run/docs/logging#run_manual_logging-java
MDC.put("component", "arbitrary-property");

logger.info("This is the default display field.");

// Clear MDC at the end of the request to avoid resource leaks
MDC.clear();

Configure the LoggingAppender to redirect logs to standard output (stdout) in structured JSON format for Cloud Run to capture. For more details, review Logback configuration.

<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 -->
    <!-- Redirect logs to stdout in JSON format for Cloud Run to capture -->
    <redirectToStdout>true</redirectToStdout>
  </appender>
  <root level="INFO">
    <appender-ref ref="CLOUD"/>
  </root>
</configuration>

This produces the following output log structure:

{"severity":"INFO","time":"YYYY-MM-DDTHH:MM:SS.SSSZ","logging.googleapis.com/labels":{"component":"arbitrary-property","levelName":"INFO","loggerName":"com.example.cloudrun.App","levelValue":"20000"},"logging.googleapis.com/trace_sampled":false,"message":"This is the default display field."}

Special JSON fields in messages

When you provide a structured log as a JSON dictionary, some special fields are stripped from the jsonPayload and are written to the corresponding field in the generated LogEntry as described in the documentation for special fields.

For example, if your JSON includes a severity property, it is removed from the jsonPayload and appears instead as the log entry's severity. The message property is used as the main display text of the log entry if present. For more on special properties read the Logging Resource section below.

Correlate your container logs with a request log (services only)

In the Logs Explorer, logs correlated by the same trace are viewable in "parent-child" format: when you click on the triangle icon at the left of the request log entry, the container logs related to that request show up nested under the request log.

Container logs are not automatically correlated to request logs unless you use a Cloud Logging client library. To correlate container logs with request logs without using a client library, you can use a structured JSON log line that contains a logging.googleapis.com/trace field with the trace identifier extracted from the X-Cloud-Trace-Context header as shown in the above sample for structured logging.

Control request log resource usage (services only)

Request logs are created automatically. Although you cannot control the amount of request logs directly from Cloud Run, you can make use of the logs exclusion feature from Cloud Logging.

A note about logging agents

If you've used Cloud Logging with certain Google Cloud products, such as Compute Engine, you may have used Cloud Logging logging agents. Cloud Run does not use logging agents because it has built-in support for log collection.

Logging resource names

Logging resources

Clicking on a log entry in the Logs Explorer opens up a JSON formatted log entry so you can drill down to the details you want.

All of the fields in a log entry, such as timestamps, severity, and httpRequest are standard, and are described in the documentation for a log entry.

Cloud Run adds additional metadata, so you can identify the source of a log. This includes the (labels that you set on your Cloud Run service) and resource labels that are specific to Cloud Run.

Log entry fields for a service

The following is a list of fields that can be found in the log entry for a Cloud Run service:

Log entry fields for jobs

The following is a list of fields that can be found in the log entry for a Cloud Run job:

Field	Values and notes
`LogEntry.labels.instanceId`	The instance that handled the request.
`LogEntry.labels.run.googleapis.com/base_image_versions`	The base image version that the service uses. Only appears for services deployed from source and if automatic security updates is enabled.
`LogEntry.labels.run.googleapis.com/cloud_event_id`	The CloudEvent ID. Only appears for services receiving events from Eventarc.
`LogEntry.labels.run.googleapis.com/cloud_event_source`	The CloudEvent source. Only appears for services receiving events from Eventarc.
`LogEntry.labels.mylabel`, `LogEntry.labels.mysecondlabel`	The labels that are set by you on the service.
`LogEntry.logName`	Identifies the log, for example, request log, standard error, standard output, etc.
`LogEntry.resource.labels.location`	Identifies the Google Cloud location of the service.
`LogEntry.resource.labels.project_id`	The project the service is deployed to.
`LogEntry.resource.labels.revision_name`	The revision that served the request.
`LogEntry.resource.labels.service_name`	The service that served the request.
`LogEntry.resource.type`	`cloud_run_revision`. The Cloud Run resource type.

LogEntry.labels.mysecondlabel The labels that are set by you on the job. LogEntry.logName Identifies the log, for example, standard error, standard output, etc. LogEntry.resource.labels.location Identifies the Google Cloud location of the job. LogEntry.resource.labels.project_id The project the job is deployed to. LogEntry.resource.labels.job_name The name of the job. LogEntry.labels.execution_name The name of the job execution. LogEntry.labels.task_index The task index. LogEntry.labels.task_attempt How many times this task has been attempted. LogEntry.resource.type cloud_run_job. The Cloud Run resource type.

Log entry fields for worker pools

The following is a list of fields that can be found in the log entry for a Cloud Run worker pool:

LogEntry.labels.mysecondlabel The labels that are set by you on the worker pool. LogEntry.logName Identifies the log, for example, standard error, standard output, etc. LogEntry.resource.labels.location The Google Cloud location of the worker pool. LogEntry.resource.labels.project_id The project the worker pool is deployed to. LogEntry.resource.labels.workerpool_name The name of the worker pool. LogEntry.resource.type cloud_run_workerpool. The Cloud Run resource type.