Write structured logs

Demonstrates how to write a log entry.

Explore further

For detailed documentation that includes this code sample, see the following:

• Using .NET logging frameworks or calling the API

Code sample

C#

To learn how to install and use the client library for Logging, see Logging client libraries.

To authenticate to Logging, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

private void WriteLogEntry(string logId)
{
    var client = LoggingServiceV2Client.Create();
    LogName logName = new LogName(s_projectId, logId);
    var jsonPayload = new Struct()
    {
        Fields =
        {
            { "name", Value.ForString("King Arthur") },
            { "quest", Value.ForString("Find the Holy Grail") },
            { "favorite_color", Value.ForString("Blue") }
        }
    };
    LogEntry logEntry = new LogEntry
    {
        LogNameAsLogName = logName,
        Severity = LogSeverity.Info,
        JsonPayload = jsonPayload
    };
    MonitoredResource resource = new MonitoredResource { Type = "global" };
    IDictionary<string, string> entryLabels = new Dictionary<string, string>
    {
        { "size", "large" },
        { "color", "blue" }
    };
    client.WriteLogEntries(logName, resource, entryLabels,
        new[] { logEntry }, _retryAWhile);
    Console.WriteLine($"Created log entry in log-id: {logId}.");
}

Go

To learn how to install and use the client library for Logging, see Logging client libraries.

To authenticate to Logging, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import (
	"context"
	"log"

	"cloud.google.com/go/logging"
)

func structuredWrite(projectID string) {
	ctx := context.Background()
	client, err := logging.NewClient(ctx, projectID)
	if err != nil {
		log.Fatalf("Failed to create logging client: %v", err)
	}
	defer client.Close()
	const name = "log-example"
	logger := client.Logger(name)
	defer logger.Flush() // Ensure the entry is written.

	logger.Log(logging.Entry{
		// Log anything that can be marshaled to JSON.
		Payload: struct{ Anything string }{
			Anything: "The payload can be any type!",
		},
		Severity: logging.Debug,
	})
}

Java

To learn how to install and use the client library for Logging, see Logging client libraries.

To authenticate to Logging, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import com.google.cloud.MonitoredResource;
import com.google.cloud.logging.LogEntry;
import com.google.cloud.logging.Logging;
import com.google.cloud.logging.LoggingOptions;
import com.google.cloud.logging.Payload.JsonPayload;
import com.google.cloud.logging.Severity;
import com.google.common.collect.ImmutableMap;
import java.util.Collections;
import java.util.Map;

public class WriteLogEntry {

  public static void main(String[] args) throws Exception {
    // TODO(developer): Optionally provide the logname as an argument
    String logName = args.length > 0 ? args[0] : "test-log";

    // Instantiates a client
    try (Logging logging = LoggingOptions.getDefaultInstance().getService()) {
      Map<String, String> payload =
          ImmutableMap.of(
              "name", "King Arthur", "quest", "Find the Holy Grail", "favorite_color", "Blue");
      LogEntry entry =
          LogEntry.newBuilder(JsonPayload.of(payload))
              .setSeverity(Severity.INFO)
              .setLogName(logName)
              .setResource(MonitoredResource.newBuilder("global").build())
              .build();

      // Writes the log entry asynchronously
      logging.write(Collections.singleton(entry));

      // Optional - flush any pending log entries just before Logging is closed
      logging.flush();
    }
    System.out.printf("Wrote to %s\n", logName);
  }
}

Node.js

To learn how to install and use the client library for Logging, see Logging client libraries.

To authenticate to Logging, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

const {Logging} = require('@google-cloud/logging');
const logging = new Logging();

/**
 * TODO(developer): Uncomment the following line and replace with your values.
 */
// const logName = 'my-log';
const log = logging.log(logName);

// A text log entry
const text_entry = log.entry('Hello world!');

// A json log entry with additional context
const metadata = {
  severity: 'WARNING',
  labels: {
    foo: 'bar',
  },
  // A default log resource is added for some GCP environments
  // This log resource can be overwritten per spec:
  // https://cloud.google.com/logging/docs/reference/v2/rest/v2/MonitoredResource
  resource: {
    type: 'global',
  },
};

const message = {
  name: 'King Arthur',
  quest: 'Find the Holy Grail',
  favorite_color: 'Blue',
};

const json_Entry = log.entry(metadata, message);

async function writeLogEntry() {
  // Asynchronously write the log entry
  await log.write(text_entry);

  // Asynchronously batch write the log entries
  await log.write([text_entry, json_Entry]);

  // Let the logging library dispatch logs
  log.write(text_entry);

  console.log(`Wrote to ${logName}`);
}
writeLogEntry();

PHP

To learn how to install and use the client library for Logging, see Logging client libraries.

To authenticate to Logging, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

use Google\Cloud\Logging\LoggingClient;
use Google\Cloud\Logging\Logger;

/** Write a log message via the Stackdriver Logging API.
 *
 * @param string $projectId The Google project ID.
 * @param string $loggerName The name of the logger.
 * @param string $message The log message.
 */
function write_log($projectId, $loggerName, $message)
{
    $logging = new LoggingClient(['projectId' => $projectId]);
    $logger = $logging->logger($loggerName, [
        'resource' => [
            'type' => 'gcs_bucket',
            'labels' => [
                'bucket_name' => 'my_bucket'
            ]
        ]
    ]);
    $entry = $logger->entry($message, [
        'severity' => Logger::INFO
    ]);
    $logger->write($entry);
    printf("Wrote a log to a logger '%s'." . PHP_EOL, $loggerName);
}

Python

To learn how to install and use the client library for Logging, see Logging client libraries.

To authenticate to Logging, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

def write_entry(logger_name):
    """Writes log entries to the given logger."""
    logging_client = logging.Client()

    # This log can be found in the Cloud Logging console under 'Custom Logs'.
    logger = logging_client.logger(logger_name)

    # Make a simple text log
    logger.log_text("Hello, world!")

    # Simple text log with severity.
    logger.log_text("Goodbye, world!", severity="WARNING")

    # Struct log. The struct can be any JSON-serializable dictionary.
    logger.log_struct(
        {
            "name": "King Arthur",
            "quest": "Find the Holy Grail",
            "favorite_color": "Blue",
        },
        severity="INFO",
    )

    print("Wrote logs to {}.".format(logger.name))

Ruby

To learn how to install and use the client library for Logging, see Logging client libraries.

To authenticate to Logging, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

require "google/cloud/logging"

logging = Google::Cloud::Logging.new

entry = logging.entry
# payload = "The data you want to log"
entry.payload = payload
# log_name = "The name of the log to write to"
entry.log_name = log_name
entry.severity = :NOTICE
entry.resource.type = "gae_app"
entry.resource.labels[:module_id] = "default"
entry.resource.labels[:version_id] = "20160101t163030"

logging.write_entries entry
puts "Wrote payload: #{entry.payload} to log: #{entry.log_name}"

What's next

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