winston-loki/index.js

A Winston transport for Grafana Loki

const Transport = require("winston-transport");
const Batcher = require("./batcher");

module.exports = class LokiTransport extends Transport {
  constructor(options) {
    super(options);
    this.batcher = new Batcher({
      host: options.host,
      interval: options.interval
    });
    this.batcher.run();
  }

  log(info, callback) {
    setImmediate(() => {
      this.emit("logged", info);
    });

    const { label, timestamp, level, message, ...rest } = info;
    const logEntry = {
      labels: `{job="${label}", level="${level}"}`,
      entries: [
        {
          ts: timestamp,
          line: `${message} ${(rest &&
            Object.keys(rest) &&
            JSON.stringify(rest)) ||
            ""}`
        }
      ]
    };

    this.batcher.pushLogEntry(logEntry);

    callback();
  }
};