# Go GELF Logging Library

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Minimal helper package to send application logs to Graylog via GELF
while still writing to the standard Go logger.

## Overview

This module wraps [gopkg.in/aphistic/golf.v0][golf] and exposes a
small API for common log levels.

Behavior summary:

- If GELF is configured with `SetDefaultConfig`, messages are sent to
  Graylog over UDP.
- Messages are also written to the standard Go logger (`log` package).
- If GELF is not configured, logging still works locally via the
  standard logger.

## Installation

```bash
go get scm.yoorie.de/go-lib/gelf
```

## Quick Start

```go
package main

import (
  "scm.yoorie.de/go-lib/gelf"
)

func main() {
  gelf.SetDefaultConfig("graylog.example.local", 12201,
    map[string]interface{}{
      "service": "billing-api",
      "env":     "prod",
    },
  )

  gelf.Info("service started")
  gelf.Infof("listening on %s", ":8080")
  gelf.Alert("database latency is high")
}
```

## API

### Configuration

- `SetDefaultConfig(host string, port int, attrs map[string]interface{})`

Creates and configures the default GELF logger. Attributes in
`attrs` are attached as default fields to all GELF messages.

### Logging Functions

- `Debug(msg string)`
- `Debugf(format string, va ...interface{})`
- `Info(msg string)`
- `Infof(format string, va ...interface{})`
- `Alert(msg string)`
- `Alertf(format string, va ...interface{})`
- `Fatal(msg string)`
- `Fatalf(format string, va ...interface{})`

## Notes

- `Fatal` and `Fatalf` terminate the program by calling `log.Fatalf`.
- Graylog delivery uses UDP (`udp://host:port`).
- Calling `SetDefaultConfig` again replaces the previous client.

## Development

Run tests:

```bash
go test ./...
```

Module information is defined in [go.mod](go.mod).

## Additional Documentation

- [Definition of Done](docs/DEFINITION_OF_DONE.md)
- [Releasing](docs/RELEASING.md)

## License

See [LICENSE](LICENSE).

---
Copyright © 2023 yoorie.de

[build-badge]: https://drone.yoorie.de/api/badges/go-lib/gelf/status.svg
[build-link]: https://drone.yoorie.de/go-lib/gelf
[golf]: https://gopkg.in/aphistic/golf.v0