README.md

Logz - yet another logger library for go

The logz is logger library for grouping application logs related a access log. The logz uses OpenTelemetry(https://opentelemetry.io) to generate the trace id.
This is for Google Cloud Logging (formerly known as Stackdriver Logging).

Features

• Writes access log each http requests
• Writes application log
• Grouping application logs related a access log.
  • The parent entry will inherit the severity of its children
• Supports to App Engine 2nd and Cloud Run and GKE.

Use go111 package if your project is App Engine 1st generation.

Contribution Packages

The logz contribution packages that provides middlewares for 3rd-party Go packages.

• gin
• echo
• gRPC

For more details: https://github.com/glassonion1/logz/tree/main/contrib

Install

$ go get github.com/glassonion1/logz

Usage

Google App Engine Standard

func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        ctx := r.Context()

        // Writes info log
        logz.Infof(ctx, "writes %s log", "info")
    })

    logz.SetConfig(logz.Config{
        NeedsAccessLog: true, // Writes the access log
    })
    logz.InitTracer()
    // Sets the middleware
    h := middleware.NetHTTP("tracer name")(mux)

    log.Fatal(http.ListenAndServe(":8080", h))
}

Cloud Run

func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        ctx := r.Context()

        // Writes info log
        logz.Infof(ctx, "writes %s log", "info")
    })

    logz.SetConfig(logz.Config{
        ProjectID:       "your gcp project id",
        NeedsAccessLog: false, // Writes no access log
    })
    logz.InitTracer()
    // Sets the middleware
    h := middleware.NetHTTP("tracer name")(mux)

    log.Fatal(http.ListenAndServe(":8080", h))
}

GKE

func main() {
    mux := http.NewServeMux()
    mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        ctx := r.Context()

        // Writes info log
        logz.Infof(ctx, "writes %s log", "info")
    })

    logz.SetConfig(logz.Config{
        ProjectID:       "your gcp project id",
        NeedsAccessLog: true, // Writes the access log
    })
    logz.InitTracer()
    // Sets the middleware
    h := middleware.NetHTTP("tracer name")(mux)

    log.Fatal(http.ListenAndServe(":8080", h))
}

Examples

See this sample projects for logz detailed usage
https://github.com/glassonion1/logz/tree/main/example

How logs are grouped

The logz leverages the grouping feature of GCP Cloud Logging. See following references for more details.

• https://godoc.org/cloud.google.com/go/logging#hdr-Grouping_Logs_by_Request

Log format

The log format is based on LogEntry's structured payload

Application log format

{
  "severity":"INFO",
  "message":"writes info log",
  "time":"2020-12-31T23:59:59.999999999Z",
  "logging.googleapis.com/sourceLocation":{
    "file":"logger_test.go",
    "line":"57",
    "function":"github.com/glassonion1/logz/internal/logger_test.TestLoggerWriteApplicationLog.func3"
  },
  "logging.googleapis.com/trace":"projects/test/traces/00000000000000000000000000000000",
  "logging.googleapis.com/spanId":"0000000000000000",
  "logging.googleapis.com/trace_sampled":false
}

Access log format

{
  "severity":"DEFAULT",
  "time":"2020-12-31T23:59:59.999999999Z",
  "logging.googleapis.com/trace":"projects/test/traces/a0d3eee13de6a4bbcf291eb444b94f28",
  "httpRequest":{
    "requestMethod":"GET",
    "requestUrl":"/test1",
    "requestSize":"0",
    "status":200,
    "responseSize":"333",
    "remoteIp":"192.0.2.1",
    "serverIp":"192.168.100.115",
    "latencyy":{
      "nanos":100,
      "seconds":0
    },
    "protocol":"HTTP/1.1"
  }
}