Syslog sink

This API is available since LogTape 0.12.0.

If you have a syslog server running, you can use the syslog sink to send log messages to the server using RFC 5424 format via @logtape/syslog package:

Deno

deno add jsr:@logtape/syslog

npm

npm add @logtape/syslog

pnpm

pnpm add @logtape/syslog

Yarn

yarn add @logtape/syslog

Bun

bun add @logtape/syslog

The quickest way to get started is to use the getSyslogSink() function without any arguments:

import { configure } from "@logtape/logtape";
import { getSyslogSink } from "@logtape/syslog";

await configure({
  sinks: {
    syslog: getSyslogSink(),
  },
  loggers: [
    { category: [], sinks: ["syslog"], lowestLevel: "debug" },
  ],
});

This will send log messages to a syslog server running on localhost:514 using UDP protocol with the default facility local0 and application name derived from the process.

You can customize the syslog configuration by passing options to the getSyslogSink() function:

import { configure } from "@logtape/logtape";
import { getSyslogSink } from "@logtape/syslog";

await configure({
  sinks: {
    syslog: getSyslogSink({
      hostname: "syslog.example.com",
      port: 1514,
      protocol: "tcp",
      facility: "mail",
      appName: "my-application",
      timeout: 5000,
    }),
  },
  loggers: [
    { category: [], sinks: ["syslog"], lowestLevel: "info" },
  ],
});

Structured data

RFC 5424 syslog supports structured data, which allows you to include key–value pairs in log messages. LogTape automatically includes log record properties as structured data when the includeStructuredData option is enabled:

import { configure } from "@logtape/logtape";
import { getSyslogSink } from "@logtape/syslog";

await configure({
  sinks: {
    syslog: getSyslogSink({
      includeStructuredData: true,
      structuredDataId: "myapp@12345",
    }),
  },
  loggers: [
    { category: [], sinks: ["syslog"], lowestLevel: "debug" },
  ],
});

With this configuration, log records with properties will include them as structured data in the syslog message:

import { configure, getLogger } from "@logtape/logtape";
import { getSyslogSink } from "@logtape/syslog";

await configure({
  sinks: {
    syslog: getSyslogSink({
      includeStructuredData: true,
      structuredDataId: "myapp@12345",
    }),
  },
  loggers: [
    { category: [], sinks: ["syslog"], lowestLevel: "debug" },
  ],
});

const logger = getLogger();
logger.info("User login successful", { userId: 12345, method: "oauth" });

This will generate a syslog message like:

<134>1 2024-01-01T12:00:00.000Z hostname myapp 1234 - [myapp@12345 userId="12345" method="oauth"] User login successful

Supported facilities

The syslog sink supports all standard RFC 5424 facilities:

• kern, user, mail, daemon, auth, syslog, lpr, news
• uucp, cron, authpriv, ftp
• local0, local1, local2, local3, local4, local5, local6, local7

Protocol support

The syslog sink supports both UDP and TCP protocols:

UDP (default)

Fire-and-forget delivery, suitable for high-throughput logging where occasional message loss is acceptable.

TCP

Reliable delivery with connection management, suitable for critical log messages that must not be lost.

For more details, see the getSyslogSink() function and SyslogSinkOptions interface in the API reference.