README.md
# winston-loki
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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](./examples/)
Several usage examples with a test configuration for Grafana+Loki+Promtail reside under [`examples/`](./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:
```js
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:
```js
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
```sh
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.
### Run tests
```sh
npm test
```
Write new ones under `/test`