├── go.sum ├── go.mod ├── gcp ├── basic.png ├── correlated.png ├── init │ └── init.go ├── setup_test.go ├── trace_test.go ├── setup.go ├── README.md └── trace.go ├── slogtest ├── another_test.go ├── slogtest_test.go └── slogtest.go ├── .chainguard └── source.yaml ├── examples ├── logger │ ├── main_test.go │ └── main.go └── handler │ └── main.go ├── .github ├── dependabot.yml └── workflows │ └── go.yml ├── .gitignore ├── handler_test.go ├── slag └── flag.go ├── example_test.go ├── handler.go ├── README.md ├── log.go ├── logger_test.go ├── logger.go └── LICENSE /go.sum: -------------------------------------------------------------------------------- 1 | -------------------------------------------------------------------------------- /go.mod: -------------------------------------------------------------------------------- 1 | module github.com/chainguard-dev/clog 2 | 3 | go 1.24.4 4 | -------------------------------------------------------------------------------- /gcp/basic.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/chainguard-dev/clog/HEAD/gcp/basic.png -------------------------------------------------------------------------------- /gcp/correlated.png: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/chainguard-dev/clog/HEAD/gcp/correlated.png -------------------------------------------------------------------------------- /slogtest/another_test.go: -------------------------------------------------------------------------------- 1 | package slogtest_test 2 | 3 | import ( 4 | "context" 5 | 6 | "github.com/chainguard-dev/clog" 7 | ) 8 | 9 | func fn(ctx context.Context) { clog.FromContext(ctx).With("foo", "bar").Infof("hello from fn") } 10 | -------------------------------------------------------------------------------- /.chainguard/source.yaml: -------------------------------------------------------------------------------- 1 | # Copyright 2023 Chainguard, Inc. 2 | # SPDX-License-Identifier: Apache-2.0 3 | 4 | spec: 5 | authorities: 6 | - keyless: {} 7 | - key: 8 | # Allow commits signed by GitHub. 9 | kms: https://github.com/web-flow.gpg 10 | -------------------------------------------------------------------------------- /examples/logger/main_test.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "testing" 5 | 6 | "github.com/chainguard-dev/clog" 7 | "github.com/chainguard-dev/clog/slogtest" 8 | ) 9 | 10 | func TestFoo(t *testing.T) { 11 | ctx := slogtest.TestContextWithLogger(t) 12 | 13 | for _, tc := range []string{"a", "b"} { 14 | t.Run(tc, func(t *testing.T) { 15 | clog.FromContext(ctx).Infof("hello world") 16 | }) 17 | } 18 | } 19 | -------------------------------------------------------------------------------- /.github/dependabot.yml: -------------------------------------------------------------------------------- 1 | # Copyright 2024 Chainguard, Inc. 2 | # SPDX-License-Identifier: Apache-2.0 3 | 4 | version: 2 5 | updates: 6 | - package-ecosystem: gomod 7 | directory: "/" 8 | schedule: 9 | interval: "weekly" 10 | open-pull-requests-limit: 10 11 | groups: 12 | all: 13 | update-types: 14 | - "minor" 15 | - "patch" 16 | - package-ecosystem: "github-actions" 17 | directory: "/" 18 | schedule: 19 | interval: "weekly" 20 | open-pull-requests-limit: 10 21 | -------------------------------------------------------------------------------- /gcp/init/init.go: -------------------------------------------------------------------------------- 1 | package init 2 | 3 | import ( 4 | "log/slog" 5 | "os" 6 | 7 | "github.com/chainguard-dev/clog" 8 | "github.com/chainguard-dev/clog/gcp" 9 | ) 10 | 11 | // Set up structured logging at Info+ level. 12 | func init() { 13 | level := slog.LevelInfo 14 | if e, ok := os.LookupEnv("LOG_LEVEL"); ok { 15 | if err := level.UnmarshalText([]byte(e)); err != nil { 16 | clog.Fatalf("slog: invalid log level: %v", err) 17 | } 18 | } 19 | slog.SetDefault(slog.New(gcp.NewHandler(level))) 20 | } 21 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # If you prefer the allow list template instead of the deny list, see community template: 2 | # https://github.com/github/gitignore/blob/main/community/Golang/Go.AllowList.gitignore 3 | # 4 | # Binaries for programs and plugins 5 | *.exe 6 | *.exe~ 7 | *.dll 8 | *.so 9 | *.dylib 10 | 11 | # Test binary, built with `go test -c` 12 | *.test 13 | 14 | # Output of the go coverage tool, specifically when used with LiteIDE 15 | *.out 16 | 17 | # Dependency directories (remove the comment below to include it) 18 | # vendor/ 19 | 20 | # Go workspace file 21 | go.work 22 | -------------------------------------------------------------------------------- /examples/handler/main.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "context" 5 | "log/slog" 6 | "os" 7 | 8 | "github.com/chainguard-dev/clog" 9 | ) 10 | 11 | func init() { 12 | slog.SetDefault(slog.New(clog.NewHandler(slog.NewTextHandler(os.Stdout, nil)))) 13 | } 14 | 15 | func main() { 16 | ctx := context.Background() 17 | ctx = clog.WithValues(ctx, "foo", "bar") 18 | 19 | // Use slog package directly 20 | slog.InfoContext(ctx, "hello world", slog.Bool("baz", true)) 21 | 22 | // glog / zap style (note: can't pass additional attributes) 23 | clog.Errorf("hello %s", "world") 24 | } 25 | -------------------------------------------------------------------------------- /gcp/setup_test.go: -------------------------------------------------------------------------------- 1 | package gcp 2 | 3 | import ( 4 | "context" 5 | "log/slog" 6 | "testing" 7 | ) 8 | 9 | func TestHandler(t *testing.T) { 10 | ctx := context.Background() 11 | l := slog.New(NewHandler(slog.LevelInfo)) 12 | l.With("level", "INFO").Log(ctx, slog.LevelInfo, "hello world") // okay 13 | l.With("level", "INFO").Log(ctx, slog.LevelWarn, "hello world") // weird, but okay (info) 14 | 15 | // These should not panic. 16 | l.With("level", nil).Log(ctx, slog.LevelInfo, "hello world") 17 | l.With("level", 123).Log(ctx, slog.LevelInfo, "hello world") 18 | l.With("level", map[string]string{}).Log(ctx, slog.LevelInfo, "hello world") 19 | } 20 | -------------------------------------------------------------------------------- /examples/logger/main.go: -------------------------------------------------------------------------------- 1 | package main 2 | 3 | import ( 4 | "context" 5 | "flag" 6 | "log/slog" 7 | "os" 8 | 9 | "github.com/chainguard-dev/clog" 10 | "github.com/chainguard-dev/clog/slag" 11 | ) 12 | 13 | func main() { 14 | var level slag.Level 15 | flag.Var(&level, "log-level", "log level") 16 | flag.Parse() 17 | 18 | slog.SetDefault(slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: &level}))) 19 | 20 | log := clog.NewLogger(slog.Default()).With("a", "b") 21 | ctx := clog.WithLogger(context.Background(), log) 22 | 23 | // Grab logger from context and use 24 | clog.FromContext(ctx).With("foo", "bar").Debugf("hello debug world") 25 | clog.FromContext(ctx).With("info", true).Infof("hello info world") 26 | clog.FromContext(ctx).With("warn", 42).Warnf("hello warn world") 27 | 28 | // Package level context loggers are also aware 29 | clog.ErrorContext(ctx, "hello error world") 30 | } 31 | -------------------------------------------------------------------------------- /.github/workflows/go.yml: -------------------------------------------------------------------------------- 1 | # This workflow will build a golang project 2 | # For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-go 3 | 4 | name: Go 5 | 6 | on: 7 | push: 8 | branches: [ "main" ] 9 | pull_request: 10 | branches: [ "main" ] 11 | 12 | permissions: {} 13 | 14 | jobs: 15 | 16 | build: 17 | permissions: 18 | contents: read # for actions/checkout to fetch code 19 | runs-on: ubuntu-latest 20 | steps: 21 | - name: Harden the runner (Audit all outbound calls) 22 | uses: step-security/harden-runner@df199fb7be9f65074067a9eb93f12bb4c5547cf2 # v2.13.3 23 | with: 24 | egress-policy: audit 25 | 26 | - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1 27 | 28 | - name: Set up Go 29 | uses: actions/setup-go@4dc6199c7b1a012772edbd06daecab0f50c9053c # v6.1.0 30 | with: 31 | go-version-file: './go.mod' 32 | 33 | - name: Build 34 | run: go build -v ./... 35 | 36 | - name: Test 37 | run: go test -v ./... 38 | -------------------------------------------------------------------------------- /handler_test.go: -------------------------------------------------------------------------------- 1 | package clog 2 | 3 | import ( 4 | "bytes" 5 | "context" 6 | "encoding/json" 7 | "log/slog" 8 | "reflect" 9 | "testing" 10 | ) 11 | 12 | func TestContextHandler(t *testing.T) { 13 | ctx := context.Background() 14 | ctx = WithValues(ctx, "foo", "bar") 15 | ctx2 := WithValues(ctx, 16 | "a", "b", 17 | "c", "d", 18 | ) 19 | ctx = WithValues(ctx, "b", 1) 20 | 21 | for _, tc := range []struct { 22 | ctx context.Context 23 | want map[string]any 24 | }{ 25 | {ctx, map[string]any{ 26 | "b": float64(1), 27 | "foo": "bar", 28 | }}, 29 | {ctx2, map[string]any{ 30 | "foo": "bar", 31 | "a": "b", 32 | "c": "d", 33 | }}, 34 | } { 35 | t.Run("", func(t *testing.T) { 36 | b := new(bytes.Buffer) 37 | log := slog.New(NewHandler(slog.NewJSONHandler(b, testopts))) 38 | log.InfoContext(tc.ctx, "") 39 | 40 | tc.want["level"] = "INFO" 41 | tc.want["msg"] = "" 42 | 43 | var got map[string]any 44 | if err := json.Unmarshal(b.Bytes(), &got); err != nil { 45 | t.Fatal(err) 46 | } 47 | 48 | if !reflect.DeepEqual(tc.want, got) { 49 | t.Errorf("want %v, got %v", tc.want, got) 50 | } 51 | }) 52 | } 53 | } 54 | -------------------------------------------------------------------------------- /slogtest/slogtest_test.go: -------------------------------------------------------------------------------- 1 | package slogtest_test 2 | 3 | import ( 4 | "log/slog" 5 | "testing" 6 | 7 | "github.com/chainguard-dev/clog" 8 | "github.com/chainguard-dev/clog/slogtest" 9 | ) 10 | 11 | func TestSlogTest(t *testing.T) { 12 | ctx := slogtest.Context(t) 13 | 14 | clog.FromContext(ctx).With("foo", "bar").Infof("hello world") 15 | clog.FromContext(ctx).With("bar", "baz").Infof("me again") 16 | clog.FromContext(ctx).With("baz", true).Infof("okay last one") 17 | 18 | clog.FromContext(ctx).Debug("hello debug") 19 | clog.FromContext(ctx).Info("hello info") 20 | clog.FromContext(ctx).Warn("hello warn") 21 | clog.FromContext(ctx).Error("hello error") 22 | 23 | fn(ctx) 24 | } 25 | 26 | // TestSlogTestTContext tests the use of t.Context() in Go 1.24+. 27 | func TestSlogTestTContext(t *testing.T) { 28 | ctx := t.Context() 29 | slog.SetDefault(slog.New(slogtest.TestLogger(t).Handler())) 30 | 31 | clog.FromContext(ctx).With("foo", "bar").Infof("hello world") 32 | clog.FromContext(ctx).With("bar", "baz").Infof("me again") 33 | clog.FromContext(ctx).With("baz", true).Infof("okay last one") 34 | 35 | clog.FromContext(ctx).Debug("hello debug") 36 | clog.FromContext(ctx).Info("hello info") 37 | clog.FromContext(ctx).Warn("hello warn") 38 | clog.FromContext(ctx).Error("hello error") 39 | 40 | fn(ctx) 41 | } 42 | -------------------------------------------------------------------------------- /slag/flag.go: -------------------------------------------------------------------------------- 1 | // Package slag provides a method for setting the log level from the command line. 2 | // 3 | // func main() { 4 | // var level slag.Level 5 | // flag.Var(&level, "log-level", "log level") 6 | // flag.Parse() 7 | // slog.SetDefault(slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: &level}))) 8 | // } 9 | // 10 | // See [./examples/logger](./examples/logger) for a full example. 11 | // 12 | // This allows the log level to be set from the command line: 13 | // 14 | // $ ./myprogram -log-level=debug 15 | // 16 | // The slag.Level type is a wrapper around slog.Level that implements the flag.Value interface, 17 | // as well as Cobra's pflag.Value interface. 18 | // 19 | // func main() { 20 | // var level slag.Level 21 | // cmd := &cobra.Command{ 22 | // Use: "myprogram", 23 | // ... 24 | // } 25 | // cmd.PersistentFlags().Var(&level, "log-level", "log level") 26 | // cmd.Execute() 27 | // } 28 | package slag 29 | 30 | import "log/slog" 31 | 32 | type Level slog.Level 33 | 34 | func (l *Level) Set(s string) error { 35 | var ll slog.Level 36 | if err := ll.UnmarshalText([]byte(s)); err != nil { 37 | return err 38 | } 39 | *l = Level(ll) 40 | return nil 41 | } 42 | func (l *Level) String() string { return slog.Level(*l).String() } 43 | func (l *Level) Level() slog.Level { return slog.Level(*l) } 44 | 45 | // Implements https://pkg.go.dev/github.com/spf13/pflag#Value 46 | func (l *Level) Type() string { return "string" } 47 | -------------------------------------------------------------------------------- /example_test.go: -------------------------------------------------------------------------------- 1 | package clog_test 2 | 3 | import ( 4 | "context" 5 | "log/slog" 6 | "os" 7 | 8 | "github.com/chainguard-dev/clog" 9 | "github.com/chainguard-dev/clog/slogtest" 10 | ) 11 | 12 | func ExampleHandler() { 13 | log := slog.New(clog.NewHandler(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{ 14 | // Remove time for repeatable results 15 | ReplaceAttr: slogtest.RemoveTime, 16 | }))) 17 | 18 | ctx := context.Background() 19 | ctx = clog.WithValues(ctx, "foo", "bar") 20 | log.InfoContext(ctx, "hello world", slog.Bool("baz", true)) 21 | 22 | // Output: 23 | // level=INFO msg="hello world" baz=true foo=bar 24 | } 25 | 26 | func ExampleLogger() { 27 | log := clog.NewLogger(slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{ 28 | // Remove time for repeatable results 29 | ReplaceAttr: slogtest.RemoveTime, 30 | }))) 31 | log = log.With("a", "b") 32 | ctx := clog.WithLogger(context.Background(), log) 33 | 34 | // Grab logger from context and use 35 | // Note: this is a formatter aware method, not an slog.Attr method. 36 | clog.FromContext(ctx).With("foo", "bar").Infof("hello %s", "world") 37 | 38 | // Package level context loggers are also aware 39 | clog.ErrorContext(ctx, "asdf", slog.Bool("baz", true)) 40 | 41 | // Output: 42 | // level=INFO msg="hello world" a=b foo=bar 43 | // level=ERROR msg=asdf a=b baz=true 44 | } 45 | 46 | func ExampleFromContext_preserveContext() { 47 | log := clog.NewLogger(slog.New(slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{ 48 | // Remove time for repeatable results 49 | ReplaceAttr: slogtest.RemoveTime, 50 | }))).With("foo", "bar") 51 | ctx := clog.WithLogger(context.Background(), log) 52 | 53 | // Previous context values are preserved when using FromContext 54 | clog.FromContext(ctx).Info("hello world") 55 | 56 | // Output: 57 | // level=INFO msg="hello world" foo=bar 58 | } 59 | -------------------------------------------------------------------------------- /gcp/trace_test.go: -------------------------------------------------------------------------------- 1 | package gcp 2 | 3 | import ( 4 | "log/slog" 5 | "net/http" 6 | "net/http/httptest" 7 | "testing" 8 | 9 | "github.com/chainguard-dev/clog" 10 | ) 11 | 12 | func TestTrace(t *testing.T) { 13 | // This ensures the metadata server is not called at all during tests. 14 | md := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { 15 | t.Fatalf("metadata server called") 16 | })) 17 | defer md.Close() 18 | t.Setenv("GCE_METADATA_HOST", md.URL) 19 | 20 | slog.SetDefault(slog.New(NewHandler(slog.LevelDebug))) 21 | for _, c := range []struct { 22 | name string 23 | env string 24 | wantTrace string 25 | }{ 26 | {"no env set", "", ""}, 27 | {"env set", "my-project", "projects/my-project/traces/traceid"}, 28 | } { 29 | t.Run(c.name, func(t *testing.T) { 30 | t.Setenv("GOOGLE_CLOUD_PROJECT", c.env) 31 | 32 | // Set up a server that logs a message with trace context added. 33 | slog.SetDefault(slog.New(NewHandler(slog.LevelDebug))) 34 | h := WithCloudTraceContext(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { 35 | ctx := r.Context() 36 | clog.InfoContext(ctx, "hello world") 37 | 38 | // TODO: This doesn't propagate the trace context to the logger. 39 | //clog.FromContext(ctx).Info("hello world") 40 | 41 | if r.Header.Get("traceparent") == "" { 42 | t.Error("got empty trace context header, want non-empty") 43 | } 44 | 45 | traceCtx := TraceFromContext(ctx) 46 | if traceCtx != c.wantTrace { 47 | t.Fatalf("got %s, want %s", traceCtx, c.wantTrace) 48 | } 49 | })) 50 | srv := httptest.NewServer(h) 51 | defer srv.Close() 52 | 53 | // Send a request to the server with a trace context header. 54 | req, err := http.NewRequest(http.MethodGet, srv.URL, nil) 55 | if err != nil { 56 | t.Fatal(err) 57 | } 58 | req.Header.Set("traceparent", "00-traceid-spanid-01") 59 | if _, err := http.DefaultClient.Do(req); err != nil { 60 | t.Fatal(err) 61 | } 62 | }) 63 | } 64 | } 65 | -------------------------------------------------------------------------------- /gcp/setup.go: -------------------------------------------------------------------------------- 1 | package gcp 2 | 3 | import ( 4 | "context" 5 | "io" 6 | "log/slog" 7 | "os" 8 | ) 9 | 10 | // LevelCritical is an extra log level supported by Cloud Logging. 11 | const LevelCritical = slog.Level(12) 12 | 13 | // Handler that outputs JSON understood by the structured log agent. 14 | // See https://cloud.google.com/logging/docs/agent/logging/configuration#special-fields 15 | type Handler struct { 16 | handler slog.Handler 17 | } 18 | 19 | // NewHandler returns a new Handler that writes to stderr. 20 | func NewHandler(level slog.Level) *Handler { 21 | return NewHandlerForWriter(os.Stderr, level) 22 | } 23 | 24 | // NewHandlerForWriter returns a new Handler that writes to the given writer. 25 | func NewHandlerForWriter(w io.Writer, level slog.Level) *Handler { 26 | return &Handler{handler: slog.NewJSONHandler(w, &slog.HandlerOptions{ 27 | AddSource: true, 28 | Level: level, 29 | ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr { 30 | if a.Key == slog.MessageKey { 31 | a.Key = "message" 32 | } else if a.Key == slog.SourceKey { 33 | a.Key = "logging.googleapis.com/sourceLocation" 34 | } else if a.Key == slog.LevelKey { 35 | a.Key = "severity" 36 | level, ok := a.Value.Any().(slog.Level) 37 | if ok && level == LevelCritical { 38 | a.Value = slog.StringValue("CRITICAL") 39 | } 40 | } 41 | return a 42 | }, 43 | })} 44 | } 45 | 46 | func (h *Handler) Enabled(ctx context.Context, level slog.Level) bool { 47 | return h.handler.Enabled(ctx, level) 48 | } 49 | 50 | func (h *Handler) Handle(ctx context.Context, rec slog.Record) error { 51 | if trace := TraceFromContext(ctx); trace != "" { 52 | rec = rec.Clone() 53 | // Add trace ID to the record so it is correlated with the request log 54 | // See https://cloud.google.com/trace/docs/trace-log-integration 55 | rec.Add("logging.googleapis.com/trace", slog.StringValue(trace)) 56 | } 57 | 58 | return h.handler.Handle(ctx, rec) 59 | } 60 | 61 | func (h *Handler) WithAttrs(attrs []slog.Attr) slog.Handler { 62 | return &Handler{handler: h.handler.WithAttrs(attrs)} 63 | } 64 | 65 | func (h *Handler) WithGroup(name string) slog.Handler { 66 | return &Handler{handler: h.handler.WithGroup(name)} 67 | } 68 | -------------------------------------------------------------------------------- /handler.go: -------------------------------------------------------------------------------- 1 | package clog 2 | 3 | import ( 4 | "context" 5 | "log/slog" 6 | ) 7 | 8 | var ( 9 | ctxKey = key{} 10 | ) 11 | 12 | type key struct{} 13 | type ctxVal map[string]any 14 | 15 | // With returns a new context with the given values. 16 | // Values are expected to be key-value pairs, where the key is a string. 17 | // e.g. WithValues(ctx, "foo", "bar", "baz", 1) 18 | // If a value already exists, it is overwritten. 19 | // If an odd number of arguments are provided, With panics. 20 | func WithValues(ctx context.Context, args ...any) context.Context { 21 | if len(args)%2 != 0 { 22 | panic("non-even number of arguments") 23 | } 24 | 25 | values := ctxVal{} 26 | 27 | // Copy existing values 28 | for k, v := range get(ctx) { 29 | values[k] = v 30 | } 31 | 32 | for i := 0; i < len(args); i++ { 33 | key, ok := args[i].(string) 34 | if !ok { 35 | panic("non-string key") 36 | } 37 | i++ 38 | if i >= len(args) { 39 | break 40 | } 41 | value := args[i] 42 | values[key] = value 43 | } 44 | return context.WithValue(ctx, ctxKey, values) 45 | } 46 | 47 | func get(ctx context.Context) ctxVal { 48 | if value, ok := ctx.Value(ctxKey).(ctxVal); ok { 49 | return value 50 | } 51 | return nil 52 | } 53 | 54 | // Handler is a slog.Handler that adds context values to the log record. 55 | // Values are added via [WithValues]. 56 | type Handler struct { 57 | h slog.Handler 58 | } 59 | 60 | // NewHandler configures a new context aware slog handler. 61 | // If h is nil, the default slog handler is used. 62 | func NewHandler(h slog.Handler) Handler { 63 | return Handler{h} 64 | } 65 | 66 | func (h Handler) inner() slog.Handler { 67 | if h.h == nil { 68 | return slog.Default().Handler() 69 | } 70 | return h.h 71 | } 72 | 73 | func (h Handler) Enabled(ctx context.Context, level slog.Level) bool { 74 | return h.inner().Enabled(ctx, level) 75 | } 76 | 77 | func (h Handler) Handle(ctx context.Context, r slog.Record) error { 78 | values := get(ctx) 79 | for k, v := range values { 80 | r.Add(k, v) 81 | } 82 | return h.inner().Handle(ctx, r) 83 | } 84 | 85 | func (h Handler) WithAttrs(attrs []slog.Attr) slog.Handler { 86 | return Handler{h.inner().WithAttrs(attrs)} 87 | } 88 | 89 | func (h Handler) WithGroup(name string) slog.Handler { 90 | return Handler{h.inner().WithGroup(name)} 91 | } 92 | -------------------------------------------------------------------------------- /slogtest/slogtest.go: -------------------------------------------------------------------------------- 1 | // Package slogtest provides utilities for emitting test logs using clog. 2 | // 3 | // func TestExample(t *testing.T) { 4 | // ctx := slogtest.Context(t) 5 | // clog.FromContext(ctx).With("foo", "bar").Info("hello world") 6 | // } 7 | // 8 | // This produces the following test output: 9 | // 10 | // === RUN TestExample 11 | // slogtest.go:24: level=INFO source=/path/to/example_test.go:13 msg="hello world" foo=bar 12 | // 13 | // This package is intended to be used in tests only. 14 | // 15 | // In Go 1.24, *testing.T etc added `t.Context()` methods, which return a 16 | // context.Context to be used in tests. You can use `clog.FromContext(t.Context())` 17 | // to get a logger in tests instead, and configure the default logger to get the 18 | // same logging behavior as `slogtest.Context(t)`. 19 | package slogtest 20 | 21 | import ( 22 | "context" 23 | "io" 24 | "log/slog" 25 | "strings" 26 | "testing" 27 | 28 | "github.com/chainguard-dev/clog" 29 | ) 30 | 31 | var _ io.Writer = &logAdapter{} 32 | 33 | type logAdapter struct{ l Logger } 34 | 35 | func (l *logAdapter) Write(b []byte) (int, error) { 36 | l.l.Log(strings.TrimSuffix(string(b), "\n")) 37 | return len(b), nil 38 | } 39 | 40 | var _ Logger = (*testing.T)(nil) 41 | var _ Logger = (*testing.B)(nil) 42 | var _ Logger = (*testing.F)(nil) 43 | 44 | type Logger interface { 45 | Log(args ...any) 46 | Context() context.Context 47 | } 48 | 49 | // TestLogger gets a logger to use in unit and end to end tests. 50 | // This logger is configured to log at debug level. 51 | func TestLogger(t Logger) *clog.Logger { 52 | return clog.New(slog.NewTextHandler(&logAdapter{l: t}, &slog.HandlerOptions{ 53 | Level: slog.LevelDebug, 54 | AddSource: true, 55 | ReplaceAttr: RemoveTime, 56 | })) 57 | } 58 | 59 | // TestLoggerWithOptions gets a logger to use in unit and end to end tests. 60 | func TestLoggerWithOptions(t Logger, opts *slog.HandlerOptions) *clog.Logger { 61 | return clog.New(slog.NewTextHandler(&logAdapter{l: t}, opts)) 62 | } 63 | 64 | // Context returns a context with a logger to be used in tests. 65 | func Context(t Logger) context.Context { 66 | return clog.WithLogger(t.Context(), TestLogger(t)) 67 | } 68 | 69 | // TestContextWithLogger returns a context with a logger to be used in tests 70 | // 71 | // Deprecated: Use Context instead. 72 | func TestContextWithLogger(t Logger) context.Context { return Context(t) } 73 | 74 | // RemoveTime removes the top-level time attribute. 75 | // It is intended to be used as a ReplaceAttr function, 76 | // to make example output deterministic. 77 | // 78 | // This is taken from slog/internal/slogtest.RemoveTime. 79 | func RemoveTime(groups []string, a slog.Attr) slog.Attr { 80 | if a.Key == slog.TimeKey && len(groups) == 0 { 81 | return slog.Attr{} 82 | } 83 | return a 84 | } 85 | -------------------------------------------------------------------------------- /gcp/README.md: -------------------------------------------------------------------------------- 1 | # `clog/gcp`: structured logging for Google Cloud using [`slog`](https://pkg.go.dev/log/slog) 2 | 3 | Contrary to the 4 | [documented "standard" approach for logging](https://cloud.google.com/logging/docs/setup/go), 5 | this doesn't use any third-party logging package for logging. 6 | 7 | Instead, it relies on Google Cloud's support for ingesting structured logs by 8 | simply printing JSON to stderr. 9 | 10 | This method of emitting structured logs is supported by: 11 | 12 | - [Cloud Run](https://cloud.google.com/run/docs/logging#using-json) 13 | - [Kubernetes Engine](https://cloud.google.com/logging/docs/structured-logging#special-payload-fields) 14 | - [Cloud Functions](https://cloud.google.com/functions/docs/monitoring/logging#writing_structured_logs) 15 | - [App Engine](https://cloud.google.com/logging/docs/structured-logging#special-payload-fields) 16 | (standard and flexible) 17 | - and in other products, using the 18 | [Cloud Logging agent](https://cloud.google.com/logging/docs/agent/logging) and 19 | [Ops agent](https://cloud.google.com/logging/docs/agent/ops-agent). 20 | 21 | ## Basic Usage 22 | 23 | To use this, underscore-import `gcp/init`, which will configure `slog` to use 24 | the GCP-optimized JSON handler for all log messages: 25 | 26 | Then when you use `slog`, all log messages will be output in JSON format to 27 | standard error, which is automatically ingested by Cloud Logging. 28 | 29 | ```go 30 | import _ "github.com/chainguard-dev/clog/gcp/init" 31 | 32 | ... 33 | 34 | http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { 35 | slog.InfoContext(r.Context(), "my message", 36 | "mycount", 42, 37 | "mystring", "myvalue", 38 | ) 39 | }) 40 | ``` 41 | 42 | This logs the message, with the additional structured logging fields in Cloud 43 | Logging: 44 | 45 |
46 | 47 | ## Correlating Logs with Requests 48 | 49 | You can also use this to correlate log lines with the request that generated 50 | them, by associating the log message with the request's trace context header. 51 | 52 | ```go 53 | import "github.com/chainguard-dev/clog/gcp" 54 | 55 | ... 56 | 57 | http.Handle("/", gcp.WithCloudTraceContext(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { 58 | slog.InfoContext(r.Context(), "my message", 59 | "mycount", 42, 60 | "mystring", "myvalue", 61 | ) 62 | }))) 63 | ``` 64 | 65 | This logs the message, associated with the request's trace, in Cloud Logging: 66 | 67 |
68 | 69 | Other logs with the same `trace` attribute are generated by the same incoming 70 | request. 71 | 72 | See https://cloud.google.com/trace/docs/trace-log-integration for more 73 | information. 74 | 75 | ## Critical Logging 76 | 77 | Cloud Logging supports a **CRITICAL** logging level, which doesn't map cleanly 78 | to `slog`'s built-in levels. 79 | 80 | To log at this level: 81 | 82 | ```go 83 | slog.Log(ctx, gcp.LevelCritical, "I have a bad feeling about this...") 84 | ``` 85 | 86 | See `./cmd/example` for a deployable example. 87 | 88 | --- 89 | 90 | This repo is forked from https://github.com/remko/cloudrun-slog, which 91 | originated this idea and implementation. 92 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # 👞 clog 2 | 3 | [![Go Reference](https://pkg.go.dev/badge/github.com/chainguard-dev/clog.svg)](https://pkg.go.dev/github.com/chainguard-dev/clog) 4 | 5 | Context-aware [`slog`](https://pkg.go.dev/log/slog) 6 | 7 | `slog` was added in Go 1.21, so using this requires Go 1.21 or later. 8 | 9 | ## Usage 10 | 11 | ### Context Logger 12 | 13 | The context Logger can be used to use Loggers from the context. This is 14 | sometimes preferred over the [Context Handler](#context-handler), since this can 15 | make it easier to use different loggers in different contexts (e.g. testing). 16 | 17 | This approach is heavily inspired by 18 | [`knative.dev/pkg/logging`](https://pkg.go.dev/knative.dev/pkg/logging), but with [zero dependencies outside the standard library](https://github.com/chainguard-dev/clog/blob/main/go.mod) (compare with [`pkg/logging`'s deps](https://pkg.go.dev/knative.dev/pkg/logging?tab=imports)). 19 | 20 | ```go 21 | package main 22 | 23 | import ( 24 | "context" 25 | "log/slog" 26 | 27 | "github.com/chainguard-dev/clog" 28 | ) 29 | 30 | func main() { 31 | // One-time setup 32 | log := clog.New(slog.Default().Handler()).With("a", "b") 33 | ctx := clog.WithLogger(context.Background(), log) 34 | 35 | f(ctx) 36 | } 37 | 38 | func f(ctx context.Context) { 39 | // Grab logger from context and use. 40 | log := clog.FromContext(ctx) 41 | log.Info("in f") 42 | 43 | // Add logging context and pass on. 44 | ctx = clog.WithLogger(ctx, log.With("f", "hello")) 45 | g(ctx) 46 | } 47 | 48 | func g(ctx context.Context) { 49 | // Grab logger from context and use. 50 | log := clog.FromContext(ctx) 51 | log.Info("in g") 52 | 53 | // Package level context loggers are also aware 54 | clog.ErrorContext(ctx, "asdf") 55 | } 56 | 57 | ``` 58 | 59 | ```sh 60 | $ go run . 61 | 2009/11/10 23:00:00 INFO in f a=b 62 | 2009/11/10 23:00:00 INFO in g a=b f=hello 63 | 2009/11/10 23:00:00 ERROR asdf a=b f=hello 64 | ``` 65 | 66 | #### Testing 67 | 68 | The `slogtest` package provides utilities to make it easy to create loggers that 69 | will use the native testing logging. 70 | 71 | ```go 72 | func TestFoo(t *testing.T) { 73 | ctx := slogtest.TestContextWithLogger(t) 74 | 75 | for _, tc := range []string{"a", "b"} { 76 | t.Run(tc, func(t *testing.T) { 77 | clog.FromContext(ctx).Infof("hello world") 78 | }) 79 | } 80 | } 81 | ``` 82 | 83 | ```sh 84 | $ go test -v ./examples/logger 85 | === RUN TestLog 86 | === RUN TestLog/a 87 | === NAME TestLog 88 | slogtest.go:20: time=2023-12-12T18:42:53.020-05:00 level=INFO msg="hello world" 89 | 90 | === RUN TestLog/b 91 | === NAME TestLog 92 | slogtest.go:20: time=2023-12-12T18:42:53.020-05:00 level=INFO msg="hello world" 93 | 94 | --- PASS: TestLog (0.00s) 95 | --- PASS: TestLog/a (0.00s) 96 | --- PASS: TestLog/b (0.00s) 97 | PASS 98 | ok github.com/chainguard-dev/clog/examples/logger 99 | ``` 100 | 101 | ### Context Handler 102 | 103 | The context Handler can be used to insert values from the context. 104 | 105 | ```go 106 | func init() { 107 | slog.SetDefault(slog.New(clog.NewHandler(slog.NewTextHandler(os.Stdout, nil)))) 108 | } 109 | 110 | func main() { 111 | ctx := context.Background() 112 | ctx = clog.WithValues(ctx, "foo", "bar") 113 | 114 | // Use slog package directly 115 | slog.InfoContext(ctx, "hello world", slog.Bool("baz", true)) 116 | 117 | // glog / zap style (note: can't pass additional attributes) 118 | clog.ErrorContextf(ctx, "hello %s", "world") 119 | } 120 | ``` 121 | 122 | ```sh 123 | $ go run . 124 | time=2009-11-10T23:00:00.000Z level=INFO msg="hello world" baz=true foo=bar 125 | time=2009-11-10T23:00:00.000Z level=ERROR msg="hello world" foo=bar 126 | ``` 127 | 128 | ### Google Cloud Platform support 129 | 130 | This package also provides a GCP-optimized JSON handler for structured logging and trace attribution. 131 | 132 | See [`./gcp/README.md`](./gcp/README.md) for details. 133 | -------------------------------------------------------------------------------- /gcp/trace.go: -------------------------------------------------------------------------------- 1 | package gcp 2 | 3 | import ( 4 | "context" 5 | "fmt" 6 | "io" 7 | "log/slog" 8 | "net" 9 | "net/http" 10 | "os" 11 | "runtime" 12 | "strings" 13 | "sync" 14 | "time" 15 | ) 16 | 17 | func insideTest() bool { 18 | // Ask runtime.Callers for up to 10 PCs, including runtime.Callers itself. 19 | pc := make([]uintptr, 10) 20 | n := runtime.Callers(0, pc) 21 | if n == 0 { 22 | slog.Debug("WithCloudTraceContext: no PCs available") 23 | return true 24 | } 25 | frames := runtime.CallersFrames(pc[:n]) 26 | for { 27 | frame, more := frames.Next() 28 | if !more { 29 | break 30 | } 31 | if strings.HasPrefix(frame.Function, "testing.") && 32 | strings.HasSuffix(frame.File, "src/testing/testing.go") { 33 | slog.Debug("WithCloudTraceContext: inside test", "function", frame.Function, "file", frame.File, "line", frame.Line) 34 | return true 35 | } 36 | } 37 | return false 38 | } 39 | 40 | var ( 41 | projectID string 42 | lookupOnce sync.Once 43 | ) 44 | 45 | // WithCloudTraceContext returns an http.handler that adds the GCP Cloud Trace 46 | // ID to the context. This is used to correlate the structured logs with the 47 | // request log. 48 | func WithCloudTraceContext(h http.Handler) http.Handler { 49 | // Get the project ID from the environment if specified 50 | fromEnv := os.Getenv("GOOGLE_CLOUD_PROJECT") 51 | if fromEnv != "" { 52 | projectID = fromEnv 53 | } else { 54 | lookupOnce.Do(func() { 55 | if insideTest() { 56 | slog.Debug("WithCloudTraceContext: inside test, not looking up project ID") 57 | return 58 | } 59 | 60 | // By default use the metadata IP; otherwise use the environment variable 61 | // for consistency with https://pkg.go.dev/cloud.google.com/go/compute/metadata#Client.Get 62 | host := "169.254.169.254" 63 | if h := os.Getenv("GCE_METADATA_HOST"); h != "" { 64 | host = h 65 | } 66 | req, err := http.NewRequest(http.MethodGet, fmt.Sprintf("http://%s/computeMetadata/v1/project/project-id", host), nil) 67 | if err != nil { 68 | slog.Debug("WithCloudTraceContext: could not get GCP project ID from metadata server", "err", err) 69 | return 70 | } 71 | req.Header.Set("Metadata-Flavor", "Google") 72 | resp, err := (&http.Client{ // Timeouts copied from https://pkg.go.dev/cloud.google.com/go/compute/metadata#Get 73 | Transport: &http.Transport{ 74 | Dial: (&net.Dialer{Timeout: 2 * time.Second}).Dial, 75 | }, 76 | Timeout: 5 * time.Second, 77 | }).Do(req) 78 | if err != nil { 79 | slog.Debug("WithCloudTraceContext: could not get GCP project ID from metadata server", "err", err) 80 | return 81 | } 82 | if resp.StatusCode != http.StatusOK { 83 | slog.Debug("WithCloudTraceContext: could not get GCP project ID from metadata server", "code", resp.StatusCode, "status", resp.Status) 84 | return 85 | } 86 | defer resp.Body.Close() 87 | all, err := io.ReadAll(resp.Body) 88 | if err != nil { 89 | slog.Debug("WithCloudTraceContext: could not get GCP project ID from metadata server", "err", err) 90 | return 91 | } 92 | projectID = string(all) 93 | }) 94 | } 95 | 96 | return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { 97 | if projectID != "" { 98 | var trace string 99 | traceHeader := r.Header.Get("traceparent") 100 | traceID := parseTraceFromW3CHeader(traceHeader) 101 | if traceID != "" { 102 | trace = fmt.Sprintf("projects/%s/traces/%s", projectID, traceID) 103 | } 104 | r = r.WithContext(WithTrace(r.Context(), trace)) 105 | } 106 | h.ServeHTTP(w, r) 107 | }) 108 | } 109 | 110 | type traceKey struct{} 111 | 112 | // WithTrace adds a trace information to the context. 113 | func WithTrace(ctx context.Context, trace string) context.Context { 114 | if trace == "" { 115 | return ctx 116 | } 117 | return context.WithValue(ctx, traceKey{}, trace) 118 | } 119 | 120 | // TraceFromContext retrieves the trace information from the context. 121 | func TraceFromContext(ctx context.Context) string { 122 | trace := ctx.Value(traceKey{}) 123 | if trace == nil { 124 | return "" 125 | } 126 | return trace.(string) 127 | } 128 | 129 | func parseTraceFromW3CHeader(traceparent string) string { 130 | traceParts := strings.Split(traceparent, "-") 131 | if len(traceParts) > 1 { 132 | return traceParts[1] 133 | } 134 | return "" 135 | } 136 | -------------------------------------------------------------------------------- /log.go: -------------------------------------------------------------------------------- 1 | package clog 2 | 3 | import ( 4 | "context" 5 | "log/slog" 6 | "os" 7 | ) 8 | 9 | // Info calls Info on the default logger. 10 | func Info(msg string, args ...any) { 11 | wrap(context.Background(), DefaultLogger(), slog.LevelInfo, msg, args...) 12 | } 13 | 14 | // InfoContext calls InfoContext on the context logger. 15 | // If a Logger is found in the context, it will be used. 16 | func InfoContext(ctx context.Context, msg string, args ...any) { 17 | wrap(ctx, FromContext(ctx), slog.LevelInfo, msg, args...) 18 | } 19 | 20 | // Infof calls Infof on the default logger. 21 | func Infof(format string, args ...any) { 22 | wrapf(context.Background(), DefaultLogger(), slog.LevelInfo, format, args...) 23 | } 24 | 25 | // InfoContextf calls InfoContextf on the context logger. 26 | // If a Logger is found in the context, it will be used. 27 | func InfoContextf(ctx context.Context, format string, args ...any) { 28 | wrapf(ctx, FromContext(ctx), slog.LevelInfo, format, args...) 29 | } 30 | 31 | // Warn calls Warn on the default logger. 32 | func Warn(msg string, args ...any) { 33 | wrap(context.Background(), DefaultLogger(), slog.LevelWarn, msg, args...) 34 | } 35 | 36 | // WarnContext calls WarnContext on the context logger. 37 | // If a Logger is found in the context, it will be used. 38 | func WarnContext(ctx context.Context, msg string, args ...any) { 39 | wrap(ctx, FromContext(ctx), slog.LevelWarn, msg, args...) 40 | } 41 | 42 | // Warnf calls Warnf on the default logger. 43 | func Warnf(format string, args ...any) { 44 | wrapf(context.Background(), DefaultLogger(), slog.LevelWarn, format, args...) 45 | } 46 | 47 | // WarnContextf calls WarnContextf on the context logger. 48 | // If a Logger is found in the context, it will be used. 49 | func WarnContextf(ctx context.Context, format string, args ...any) { 50 | wrapf(ctx, FromContext(ctx), slog.LevelWarn, format, args...) 51 | } 52 | 53 | // Error calls Error on the default logger. 54 | func Error(msg string, args ...any) { 55 | wrap(context.Background(), DefaultLogger(), slog.LevelError, msg, args...) 56 | } 57 | 58 | // ErrorContext calls ErrorContext on the context logger. 59 | func ErrorContext(ctx context.Context, msg string, args ...any) { 60 | wrap(ctx, FromContext(ctx), slog.LevelError, msg, args...) 61 | } 62 | 63 | // Errorf calls Errorf on the default logger. 64 | func Errorf(format string, args ...any) { 65 | wrapf(context.Background(), DefaultLogger(), slog.LevelError, format, args...) 66 | } 67 | 68 | // ErrorContextf calls ErrorContextf on the context logger. 69 | func ErrorContextf(ctx context.Context, format string, args ...any) { 70 | wrapf(ctx, FromContext(ctx), slog.LevelError, format, args...) 71 | } 72 | 73 | // Debug calls Debug on the default logger. 74 | func Debug(msg string, args ...any) { 75 | wrap(context.Background(), DefaultLogger(), slog.LevelDebug, msg, args...) 76 | } 77 | 78 | // DebugContext calls DebugContext on the context logger. 79 | func DebugContext(ctx context.Context, msg string, args ...any) { 80 | wrap(ctx, FromContext(ctx), slog.LevelDebug, msg, args...) 81 | } 82 | 83 | // Debugf calls Debugf on the default logger. 84 | func Debugf(format string, args ...any) { 85 | wrapf(context.Background(), DefaultLogger(), slog.LevelDebug, format, args...) 86 | } 87 | 88 | // DebugContextf calls DebugContextf on the context logger. 89 | // If a Logger is found in the context, it will be used. 90 | func DebugContextf(ctx context.Context, format string, args ...any) { 91 | wrapf(ctx, FromContext(ctx), slog.LevelDebug, format, args...) 92 | } 93 | 94 | // Fatal calls Error on the default logger, then exits. 95 | func Fatal(msg string, args ...any) { 96 | wrap(context.Background(), DefaultLogger(), slog.LevelError, msg, args...) 97 | os.Exit(1) 98 | } 99 | 100 | // FatalContext calls ErrorContext on the context logger, then exits. 101 | func FatalContext(ctx context.Context, msg string, args ...any) { 102 | wrap(ctx, FromContext(ctx), slog.LevelError, msg, args...) 103 | os.Exit(1) 104 | } 105 | 106 | // Fatalf calls Errorf on the default logger, then exits. 107 | func Fatalf(format string, args ...any) { 108 | wrapf(context.Background(), DefaultLogger(), slog.LevelError, format, args...) 109 | os.Exit(1) 110 | } 111 | 112 | // FatalContextf calls ErrorContextf on the context logger, then exits. 113 | func FatalContextf(ctx context.Context, format string, args ...any) { 114 | wrapf(ctx, FromContext(ctx), slog.LevelError, format, args...) 115 | os.Exit(1) 116 | } 117 | -------------------------------------------------------------------------------- /logger_test.go: -------------------------------------------------------------------------------- 1 | package clog 2 | 3 | import ( 4 | "bytes" 5 | "context" 6 | "encoding/json" 7 | "fmt" 8 | "log/slog" 9 | "reflect" 10 | "testing" 11 | ) 12 | 13 | var ( 14 | testopts = &slog.HandlerOptions{ 15 | ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr { 16 | // Ignore time to make testing easier. 17 | if a.Key == "time" { 18 | return slog.Attr{} 19 | } 20 | return a 21 | }, 22 | } 23 | ) 24 | 25 | func TestLogger(t *testing.T) { 26 | ctx := context.Background() 27 | b := new(bytes.Buffer) 28 | base := slog.New(NewHandler(slog.NewJSONHandler(b, testopts))) 29 | log := NewLogger(base).With("a", "b") 30 | log.InfoContext(ctx, "") 31 | t.Log(b.String()) 32 | 33 | want := map[string]any{ 34 | "level": "INFO", 35 | "msg": "", 36 | "a": "b", 37 | } 38 | 39 | var got map[string]any 40 | if err := json.Unmarshal(b.Bytes(), &got); err != nil { 41 | t.Fatal(err) 42 | } 43 | if !reflect.DeepEqual(want, got) { 44 | t.Errorf("want %v, got %v", want, got) 45 | } 46 | } 47 | 48 | func TestLoggerNilBase(t *testing.T) { 49 | log := NewLogger(nil) 50 | log.Info("") 51 | } 52 | 53 | func TestLoggerFromContext(t *testing.T) { 54 | b := new(bytes.Buffer) 55 | base := slog.New(NewHandler(slog.NewJSONHandler(b, testopts))) 56 | log := NewLogger(base).With("a", "b") 57 | 58 | ctx := WithLogger(context.Background(), log) 59 | FromContext(ctx).Info("") 60 | 61 | want := map[string]any{ 62 | "level": "INFO", 63 | "msg": "", 64 | "a": "b", 65 | } 66 | 67 | t.Run("FromContext.Info", func(t *testing.T) { 68 | var got map[string]any 69 | if err := json.Unmarshal(b.Bytes(), &got); err != nil { 70 | t.Fatal(err) 71 | } 72 | if !reflect.DeepEqual(want, got) { 73 | t.Errorf("want %v, got %v", want, got) 74 | } 75 | }) 76 | 77 | b.Reset() 78 | 79 | t.Run("clog.Info", func(t *testing.T) { 80 | InfoContext(ctx, "") 81 | var got map[string]any 82 | if err := json.Unmarshal(b.Bytes(), &got); err != nil { 83 | t.Fatal(err) 84 | } 85 | if !reflect.DeepEqual(want, got) { 86 | t.Errorf("want %v, got %v", want, got) 87 | } 88 | }) 89 | } 90 | 91 | func TestLoggerPC(t *testing.T) { 92 | b := new(bytes.Buffer) 93 | log := NewLogger(slog.New(NewHandler(slog.NewJSONHandler(b, &slog.HandlerOptions{ 94 | AddSource: true, 95 | ReplaceAttr: testopts.ReplaceAttr, 96 | })))) 97 | 98 | log.Info("") 99 | t.Log(b.String()) 100 | 101 | var got struct { 102 | Source struct { 103 | File string `json:"file"` 104 | Function string `json:"function"` 105 | } `json:"source"` 106 | } 107 | if err := json.Unmarshal(b.Bytes(), &got); err != nil { 108 | t.Fatal(err) 109 | } 110 | // Knowing that the PC is from this test is good enough. 111 | want := fmt.Sprintf("github.com/chainguard-dev/clog.%s", t.Name()) 112 | if got.Source.Function != want { 113 | t.Errorf("want %v, got %v", want, got) 114 | } 115 | } 116 | 117 | func TestWith(t *testing.T) { 118 | ctx := context.WithValue(context.Background(), "test", "test") 119 | log := NewLoggerWithContext(ctx, nil) 120 | withed := log.With("a", "b") 121 | if want := withed.ctx; want != ctx { 122 | t.Errorf("want %v, got %v", want, ctx) 123 | } 124 | withed = log.WithGroup("a") 125 | if want := withed.ctx; want != ctx { 126 | t.Errorf("want %v, got %v", want, ctx) 127 | } 128 | } 129 | 130 | func TestDefaultHandler(t *testing.T) { 131 | old := slog.Default() 132 | defer func() { 133 | slog.SetDefault(old) 134 | }() 135 | 136 | b := new(bytes.Buffer) 137 | slog.SetDefault(slog.New(slog.NewJSONHandler(b, testopts))) 138 | 139 | t.Run("Info", func(t *testing.T) { 140 | FromContext(WithValues(context.Background(), "a", "b")).Info("") 141 | want := map[string]any{ 142 | "level": "INFO", 143 | "msg": "", 144 | "a": "b", 145 | } 146 | var got map[string]any 147 | if err := json.Unmarshal(b.Bytes(), &got); err != nil { 148 | t.Fatal(err) 149 | } 150 | if !reflect.DeepEqual(want, got) { 151 | t.Errorf("want %v, got %v", want, got) 152 | } 153 | }) 154 | 155 | b.Reset() 156 | 157 | t.Run("InfoContext", func(t *testing.T) { 158 | // Set logger with original value 159 | ctx := WithValues(context.Background(), "a", "b") 160 | logger := FromContext(ctx) 161 | 162 | // Override value in request context - we expect this to overwrite the original value set in the logger 163 | logger.InfoContext(WithValues(ctx, "a", "c"), "") 164 | 165 | want := map[string]any{ 166 | "level": "INFO", 167 | "msg": "", 168 | "a": "c", 169 | } 170 | var got map[string]any 171 | if err := json.Unmarshal(b.Bytes(), &got); err != nil { 172 | t.Fatal(err) 173 | } 174 | if !reflect.DeepEqual(want, got) { 175 | t.Errorf("want %v, got %v", want, got) 176 | } 177 | }) 178 | 179 | b.Reset() 180 | 181 | t.Run("Debug - no log", func(t *testing.T) { 182 | logger := FromContext(context.Background()) 183 | logger.Debug("asdf") 184 | 185 | if b.Len() != 0 { 186 | t.Errorf("want empty, got %q", b.String()) 187 | } 188 | }) 189 | } 190 | 191 | func TestContext(t *testing.T) { 192 | old := slog.Default() 193 | t.Cleanup(func() { 194 | slog.SetDefault(old) 195 | }) 196 | 197 | b := new(bytes.Buffer) 198 | slog.SetDefault(slog.New(slog.NewJSONHandler(b, testopts))) 199 | 200 | msg := "hello world" 201 | want := map[string]any{ 202 | "level": "INFO", 203 | "msg": msg, 204 | "a": "b", 205 | } 206 | 207 | ctx := WithValues(context.Background(), "a", "b") 208 | // These should all give the same output and be functionally equivalent. 209 | for _, tc := range []struct { 210 | name string 211 | fn func() 212 | }{ 213 | { 214 | name: "clog.InfoContext", 215 | fn: func() { 216 | InfoContext(ctx, msg) 217 | }, 218 | }, 219 | { 220 | name: "clog.FromContext.Info", 221 | fn: func() { 222 | FromContext(ctx).Info(msg) 223 | }, 224 | }, 225 | { 226 | name: "clog.FromContext.InfoContext", 227 | fn: func() { 228 | FromContext(ctx).InfoContext(ctx, msg) 229 | }, 230 | }, 231 | } { 232 | t.Run(tc.name, func(t *testing.T) { 233 | b.Reset() 234 | tc.fn() 235 | 236 | var got map[string]any 237 | if err := json.Unmarshal(b.Bytes(), &got); err != nil { 238 | t.Fatal(err) 239 | } 240 | if !reflect.DeepEqual(want, got) { 241 | t.Errorf("want %v, got %v", want, got) 242 | } 243 | }) 244 | } 245 | } 246 | -------------------------------------------------------------------------------- /logger.go: -------------------------------------------------------------------------------- 1 | package clog 2 | 3 | import ( 4 | "context" 5 | "fmt" 6 | "log/slog" 7 | "os" 8 | "runtime" 9 | "time" 10 | ) 11 | 12 | // Logger implements a wrapper around [slog.Logger] that adds formatter functions (e.g. Infof, Errorf) 13 | type Logger struct { 14 | ctx context.Context 15 | slog.Logger 16 | } 17 | 18 | // DefaultLogger returns a new logger that uses the default [slog.Logger]. 19 | func DefaultLogger() *Logger { 20 | return NewLogger(nil) 21 | } 22 | 23 | // NewLogger returns a new logger that wraps the given [slog.Logger] with the default context. 24 | func NewLogger(l *slog.Logger) *Logger { 25 | return NewLoggerWithContext(context.Background(), l) 26 | } 27 | 28 | // NewLoggerWithContext returns a new logger that wraps the given [slog.Logger]. 29 | func NewLoggerWithContext(ctx context.Context, l *slog.Logger) *Logger { 30 | if l == nil { 31 | l = slog.New(NewHandler(slog.Default().Handler())) 32 | } 33 | return &Logger{ 34 | ctx: ctx, 35 | Logger: *l, 36 | } 37 | } 38 | 39 | // New returns a new logger that wraps the given [slog.Handler]. 40 | func New(h slog.Handler) *Logger { 41 | return NewWithContext(context.Background(), h) 42 | } 43 | 44 | // NewWithContext returns a new logger that wraps the given [slog.Handler] using the given context. 45 | func NewWithContext(ctx context.Context, h slog.Handler) *Logger { 46 | return NewLoggerWithContext(ctx, slog.New(NewHandler(h))) 47 | } 48 | 49 | // With calls [Logger.With] on the default logger. 50 | func With(args ...any) *Logger { 51 | return DefaultLogger().With(args...) 52 | } 53 | 54 | // With calls [Logger.With] on the logger. 55 | func (l *Logger) With(args ...any) *Logger { 56 | return NewLoggerWithContext(l.context(), l.Logger.With(args...)) 57 | } 58 | 59 | // WithGroup calls [Logger.WithGroup] on the default logger. 60 | func (l *Logger) WithGroup(name string) *Logger { 61 | return NewLoggerWithContext(l.context(), l.Logger.WithGroup(name)) 62 | } 63 | 64 | func (l *Logger) context() context.Context { 65 | if l.ctx == nil { 66 | return context.Background() 67 | } 68 | return l.ctx 69 | } 70 | 71 | // Info logs at LevelInfo with the given message and treats the args as key/value pairs to form log message attributes. 72 | func (l *Logger) Info(msg string, args ...any) { 73 | wrap(l.context(), l, slog.LevelInfo, msg, args...) 74 | } 75 | 76 | // Infof logs at LevelInfo with the given format and arguments. 77 | func (l *Logger) Infof(format string, args ...any) { 78 | wrapf(l.context(), l, slog.LevelInfo, format, args...) 79 | } 80 | 81 | // InfoContextf logs at LevelInfo with the given context, format, and arguments. 82 | func (l *Logger) InfoContextf(ctx context.Context, format string, args ...any) { 83 | wrapf(ctx, l, slog.LevelInfo, format, args...) 84 | } 85 | 86 | // Warn logs at LevelWarn with the given message and treats the args as key/value pairs to form log message attributes. 87 | func (l *Logger) Warn(msg string, args ...any) { 88 | wrap(l.context(), l, slog.LevelWarn, msg, args...) 89 | } 90 | 91 | // Warnf logs at LevelWarn with the given format and arguments. 92 | func (l *Logger) Warnf(format string, args ...any) { 93 | wrapf(l.context(), l, slog.LevelWarn, format, args...) 94 | } 95 | 96 | // WarnContextf logs at LevelWarn with the given context, format and arguments. 97 | func (l *Logger) WarnContextf(ctx context.Context, format string, args ...any) { 98 | wrapf(ctx, l, slog.LevelWarn, format, args...) 99 | } 100 | 101 | // Error logs at LevelError with the given message and treats the args as key/value pairs to form log message attributes. 102 | func (l *Logger) Error(msg string, args ...any) { 103 | wrap(l.context(), l, slog.LevelError, msg, args...) 104 | } 105 | 106 | // Errorf logs at LevelError with the given format and arguments. 107 | func (l *Logger) Errorf(format string, args ...any) { 108 | wrapf(l.context(), l, slog.LevelError, format, args...) 109 | } 110 | 111 | // ErrorContextf logs at LevelError with the given context, format and arguments. 112 | func (l *Logger) ErrorContextf(ctx context.Context, format string, args ...any) { 113 | wrapf(ctx, l, slog.LevelError, format, args...) 114 | } 115 | 116 | // Debug logs at LevelDebug with the given message and treats the args as key/value pairs to form log message attributes. 117 | func (l *Logger) Debug(msg string, args ...any) { 118 | wrap(l.context(), l, slog.LevelDebug, msg, args...) 119 | } 120 | 121 | // Debugf logs at LevelDebug with the given format and arguments. 122 | func (l *Logger) Debugf(format string, args ...any) { 123 | wrapf(l.context(), l, slog.LevelDebug, format, args...) 124 | } 125 | 126 | // DebugContextf logs at LevelDebug with the given context, format and arguments. 127 | func (l *Logger) DebugContextf(ctx context.Context, format string, args ...any) { 128 | wrapf(ctx, l, slog.LevelDebug, format, args...) 129 | } 130 | 131 | // Fatal logs at LevelError with the given message, then exits. 132 | func (l *Logger) Fatal(msg string, args ...any) { 133 | wrap(l.context(), l, slog.LevelError, msg, args...) 134 | os.Exit(1) 135 | } 136 | 137 | // Fatalf logs at LevelError with the given format and arguments, then exits. 138 | func (l *Logger) Fatalf(format string, args ...any) { 139 | wrapf(l.context(), l, slog.LevelError, format, args...) 140 | os.Exit(1) 141 | } 142 | 143 | // FatalContextf logs at LevelError with the given context, format and arguments, then exits. 144 | func (l *Logger) FatalContextf(ctx context.Context, format string, args ...any) { 145 | wrapf(ctx, l, slog.LevelError, format, args...) 146 | os.Exit(1) 147 | } 148 | 149 | // FatalContext logs at LevelError with the given context and message, then exits. 150 | func (l *Logger) FatalContext(ctx context.Context, msg string, args ...any) { 151 | wrap(ctx, l, slog.LevelError, msg, args...) 152 | os.Exit(1) 153 | } 154 | 155 | // Base returns the underlying [slog.Logger]. 156 | func (l *Logger) Base() *slog.Logger { 157 | return &l.Logger 158 | } 159 | 160 | // Handler returns the underlying [slog.Handler]. 161 | func (l *Logger) Handler() slog.Handler { 162 | return l.Logger.Handler() 163 | } 164 | 165 | func wrap(ctx context.Context, logger *Logger, level slog.Level, msg string, args ...any) { 166 | if !logger.Handler().Enabled(ctx, level) { 167 | return 168 | } 169 | 170 | var pcs [1]uintptr 171 | runtime.Callers(3, pcs[:]) // skip [Callers, Infof, wrapf] 172 | r := slog.NewRecord(time.Now(), level, msg, pcs[0]) 173 | r.Add(args...) 174 | _ = logger.Handler().Handle(ctx, r) 175 | } 176 | 177 | // wrapf is like wrap, but uses fmt.Sprintf to format the message. 178 | // NOTE: args are passed to fmt.Sprintf, not as [slog.Attr]. 179 | func wrapf(ctx context.Context, logger *Logger, level slog.Level, format string, args ...any) { 180 | if !logger.Handler().Enabled(ctx, level) { 181 | return 182 | } 183 | 184 | var pcs [1]uintptr 185 | runtime.Callers(3, pcs[:]) // skip [Callers, Infof, wrapf] 186 | r := slog.NewRecord(time.Now(), level, fmt.Sprintf(format, args...), pcs[0]) 187 | _ = logger.Handler().Handle(ctx, r) 188 | } 189 | 190 | type loggerKey struct{} 191 | 192 | func WithLogger(ctx context.Context, logger *Logger) context.Context { 193 | return context.WithValue(ctx, loggerKey{}, logger.Logger) 194 | } 195 | 196 | func FromContext(ctx context.Context) *Logger { 197 | if logger, ok := ctx.Value(loggerKey{}).(slog.Logger); ok { 198 | return &Logger{ 199 | ctx: ctx, 200 | Logger: logger, 201 | } 202 | } 203 | return NewLoggerWithContext(ctx, nil) 204 | } 205 | 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