Winston-loki NPM

winston-loki

A Grafana Loki transport for the nodejs logging library Winston.

Usage

This Winston transport is used similarly to other Winston transports. Require winston and define a new LokiTransport() inside its options when creating it.

Examples

Several usage examples with a test configuration for Grafana+Loki+Promtail reside under examples/. If you want the simplest possible configuration, that's probably the place to check out. By defining json: true and giving winston-loki the correct host address for Loki is enough for most.

Options

LokiTransport() takes a Javascript object as an input. These are the options that are available, required in bold:

Parameter	Description	Example	Default
`host`	URL for Grafana Loki	http://127.0.0.1:3100	null
`interval`	The interval at which batched logs are sent in seconds	30	5
`json`	Use JSON instead of Protobuf for transport	true	false
`batching`	If batching is not used, the logs are sent as they come	true	true
`clearOnError`	Discard any logs that result in an error during transport	true	false
`replaceTimestamp`	Replace any log timestamps with Date.now(). Warning: Disabling `replaceTimestamp` may result in logs failing to upload due to recent changes in the upstream Loki project. It is recommended to leave this option enabled unless you have a specific reason to disable it.	true	true
`labels`	custom labels, key-value pairs	{ module: 'http' }	undefined
`format`	winston format (https://github.com/winstonjs/winston#formats)	simple()	undefined
`gracefulShutdown`	Enable/disable graceful shutdown (wait for any unsent batches)	false	true
`timeout`	timeout for requests to grafana loki in ms	30000	undefined
`basicAuth`	basic authentication credentials to access Loki over HTTP	username:password	undefined
`onConnectionError`	Loki error connection handler	(err) => console.error(err)	undefined
`useWinstonMetaAsLabels`	Use Winston's "meta" (such as defaultMeta values) as Loki labels	true	false
`ignoredMeta`	When useWinstonMetaAsLabels is enabled, a list of meta values to ignore	"error_description"	undefined

Example

With default formatting:

const { createLogger, transports } = require("winston");
const LokiTransport = require("winston-loki");
const options = {
  ...,
  transports: [
    new LokiTransport({
      host: "http://127.0.0.1:3100"
    })
  ]
  ...
};
const logger = createLogger(options);

You can set custom labels in every log as well like this:

logger.debug({ message: 'test', labels: { 'key': 'value' } })

TODO: Add custom formatting example

Developing

Requirements

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.

Example

npm install
npm link
cd ~/your_project
npm link winston-loki
npm install

And you should have a working, requirable winston-loki package under your project's node_modules. After the link has been established, any changes to winston-loki should show on rerun of the software that uses it.