The logstash appenders for log4js send NDJSON formatted log events to logstash receivers. This appender uses HTTP to send the events (there is another logstash appender that uses UDP).

npm install log4js @log4js-node/logstash-http

• type - @log4js-node/logstash-http
• url - string - logFaces receiver servlet URL
• application - string (optional) - used to identify your application's logs
• logChannel - string (optional) - also used to identify your application's logs [but in a more specific way]
• logType - string (optional) - used for the type field in the logstash data
• timeout - integer (optional, defaults to 5000ms) - the timeout for the HTTP request.
• agent - http.Agent | https.Agent (optional) - used to configure the requests being sent out if needed.

This appender will also pick up Logger context values from the events, and add them as p_ values in the logFaces event. See the example below for more details.

log4js.configure({
  appenders: {
    logstash: {
      type: "@log4js-node/logstash-http",
      url: "http://localhost:9200/_bulk",
      application: "logstash-log4js",
      logType: "application",
      logChannel: "node",
    },
  },
  categories: {
    default: { appenders: ["logstash"], level: "info" },
  },
});

const logger = log4js.getLogger();
logger.addContext("requestId", "123");
logger.info("some interesting log message");
logger.error("something has gone wrong");

This example will result in two log events being sent to your localhost:9200. Both events will have a context.requestId property with a value of 123.