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Configuring a logger for the go-sdk

· 2 min read
Skye Gill
Software Engineer at NET Reply, OpenFeature contributor

Logging is the act of keeping a log. A log (in this case) records events that occur in software.

Subject to many opinions and differing principles of best practice, the best thing we could do for the go-sdk was to create an implementation as open & configurable as possible. To achieve this, we've integrated logr, this allows the use of any logger that conforms to its API.

Applications may already have a chosen logging solution at the point of introducing openfeature. An integration with logr may already exist for their chosen solution (integrations exist for many of the popular logger packages in go). If not, they could write their own integration.


Configure the popular go logger zap with the go-sdk.


  • Golang 1.17+


  1. Go get the following dependencies

    go get
    go get
    go get
    go get # an integration of zap with logr's API
  2. Import all of the above into your main.go and create func main()

    package main

    import (

    func main() {


Integrating the logger

  1. Create the zap logger with preset development config (for the sake of this tutorial)

    func main() {
    zc := zap.NewDevelopmentConfig()
    zc.Level = zap.NewAtomicLevelAt(zapcore.Level(-1)) // the level here decides the verbosity of our logs
    z, err := zc.Build()
    if err != nil {
  2. Create the zapr logger (zap logger that conforms to logr's interface)

    l := zapr.NewLogger(z)
  3. Set the logger to the global openfeature singleton

  4. Create an openfeature client and invoke a flag evaluation

    c := openfeature.NewClient("log")

    evalCtx := openfeature.NewEvaluationContext("foo", nil)

    c.BooleanValue(context.Background(), "bar", false, evalCtx)
  5. Check the result of go run main.go

    2022-09-02T14:22:31.109+0100    INFO    openfeature/openfeature.go:76   set global logger
    2022-09-02T14:22:31.110+0100 DEBUG openfeature/client.go:230 evaluating flag {"flag": "bar", "type": "bool", "defaultValue": false, "evaluationContext": {"targetingKey":"foo","attributes":null}, "evaluationOptions": {}}
    2022-09-02T14:22:31.110+0100 DEBUG openfeature/client.go:336 executing before hooks
    2022-09-02T14:22:31.110+0100 DEBUG openfeature/client.go:349 executed before hooks
    2022-09-02T14:22:31.110+0100 DEBUG openfeature/client.go:355 executing after hooks
    2022-09-02T14:22:31.110+0100 DEBUG openfeature/client.go:364 executed after hooks
    2022-09-02T14:22:31.110+0100 DEBUG openfeature/client.go:318 evaluated flag {"flag": "bar", "details": {"FlagKey":"bar","FlagType":0,"Value":false,"ErrorCode":"","Reason":"","Variant":""}, "type": "bool"}
    2022-09-02T14:22:31.110+0100 DEBUG openfeature/client.go:377 executing finally hooks
    2022-09-02T14:22:31.110+0100 DEBUG openfeature/client.go:383 executed finally hooks
  6. (optional) Tweak the level set in step 1 to decrease the verbosity