Promtail Client

A native Golang client for Grafana's Loki logging server (written with love and tests).

Description

It's a lightweight client for pushing logs with Loki server written in pure Go with zero external dependencies.

Current implementation contains:

• REST client with batching that supports 6 levels of logs: Debug, Info, Warning, Error, Fatal, Panic
• Pluggable logs exchange mechanism (see StreamExchanger interface) and it's Loki JSON v1 API implementation
• Embedded label logLevel for easier log grepping
• TODO: add proto logs format for Loki API

How to use

The easiest way is to initialize a predefined JSON v1 API client via:

package mypackage

import "github.com/ic2hrmk/promtail"

func foo() error {
    // List of default labels which would be attached to every log message
    identifiers := map[string]string {
        "instanceId": "myAwesomeApp-1",
    }

    promtailClient, err := promtail.NewJSONv1Client("loki:3100", identifiers)
    if err != nil {
       return err
    }
    defer promtailClient.Close()

    promtailClient.Infof("I am here for ya %s", "buddy")

    // Some staff...

    promtailClient.Logf(promtail.Info, "Still here")

    promtailClient.Debugf("I am here for ya %s", "buddy")    
    promtailClient.Infof("I am here for ya %s", "buddy")    
    promtailClient.Warnf("I am here for ya %s", "buddy")    
    promtailClient.Errorf("I am here for ya %s", "buddy")    
    promtailClient.Fatalf("I am here for ya %s", "buddy")    
    promtailClient.Panicf("I am here for ya %s", "buddy")    
    
    customLabels := map[string]string {
        "somethingSpecial": "right-here",
    }
    promtailClient.LogfWithLabels(promtail.Info, customLabels, "Still here")

    return nil
}

How to tune

[Q]: How can I use another version/protocol of Loki API's implementation? [A]: You can implement StreamExchanger and pass it to constructor NewClient() or make an issue :)

[Q]: How can I get errors from exchanging process instead reading logs? [A]: Initialize a client with option WithErrorCallback(errorHandler func(err error)):

allertHandler := func(err error) {
   slack.NotifyError("loki logging is unavailable due to: %s", err)
}

promtailClient, err := NewJSONv1Client("loki:3100",  nil, 
    WithErrorCallback(allertHandler)
)

Also, take a look at WithSendBatchSize() (max messages number to send at one time) and WithSendBatchTimeout() (max timeout of messages if not messages number isn't reaching send batch size).

Issues / Contributing

Feel free to post a Github Issue, I will respond ASAP