This module provides a transport for pino that forwards messages to a Loki instance.

Pino-loki is based upon the highly performant logging library pino. Loki usually gets the logs through Promtail which reads system logs from files. This setup may not always be possible or require additional infrastructure, especially in situations where logs are gathered application code deployed as a SaaS in the cloud. Pino-loki sends the pino logs directly to Loki.

npm install -g pino-loki
node foo | pino-loki --hostname=http://hostname:3100

$ pino-loki -h
Options:
  -V, --version              output the version number
  -u, --user <user>          Loki username
  -p, --password <password>  Loki password
  --hostname <hostname>      URL for Loki
  -b, --batch                Should logs be sent in batch mode
  -i, --interval <interval>  The interval at which batched logs are sent in seconds
  -t, --timeout <timeout>    Timeout for request to Loki
  -s, --silenceErrors        If false, errors will be displayed in the console
  -r, --replaceTimestamp     Replace pino logs timestamps with Date.now()
  -l, --labels <label>       Additional labels to be added to all Loki logs
  --no-stdout                Disable output to stdout
  -h, --help                 display help for command

import pino from 'pino'

const transport = pino.transport({
  target: "pino-loki",
  options: {
    batching: true,
    interval: 5,
    basicAuth: {
      username: "username",
      password: "password",
    },
  },
});

const logger = pino(transport);

logger.error({ foo: 'bar' })

import pino from 'pino'

const transport = pino.transport({
  targets: [
    { target: "pino-loki" },
    { target: 'pino-pretty' }
  ],
});

const logger = pino(transport);

logger.error({ foo: 'bar' })

Out-of-order Loki errors can occur due to the asynchronous nature of Pino. The fix to this is to allow for out-of-order logs in the Loki configuration. The reason why Loki doesn't have this enabled by default is because Promtail accounts for ordering constraints, however the same issue can also happen with promtail in high-load or when working with distributed networks.

If any network issues occur, the logs can be dropped. The recommendation is therefore to implement a failover solution, this will vary greatly from system to system.

Running a local Loki for testing is probably required, and the easiest way to do that is to follow this guide: https://github.com/grafana/loki/tree/master/production#run-locally-using-docker. After that, Grafana Loki instance is available at http://localhost:3100, with a Grafana instance running at http://localhost:3000. Username admin, password admin. Add the Loki source with the URL http://loki:3100, and the explorer should work.

Refer to https://grafana.com/docs/loki/latest/api/ for documentation about the available endpoints, data formats etc.

MIT License © 2022 Julien Ripouteau