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Configuring a logger for the go-sdk

· 3 min read
Skye Gill
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.

Objective​

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

Prerequisites​

  • Golang 1.17+

Scaffolding​

  1. Go get the following dependencies

    go get github.com/open-feature/go-sdk
    go get go.uber.org/zap
    go get github.com/go-logr/logr
    go get github.com/go-logr/zapr # 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 (
        "github.com/go-logr/logr"
        "github.com/go-logr/zapr"
        "github.com/open-feature/go-sdk/pkg/openfeature"
        "go.uber.org/zap"
        "go.uber.org/zap/zapcore"
        "context"
        "log"
    )

    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 {
            log.Fatal(err)
        }
    }

  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

    openfeature.SetLogger(l)

  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