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Add new FatalFunc method to logger to override behavior for Fatal-lev…
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…el logging
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@autarch
autarch committed Jan 25, 2024
1 parent 22af876 commit 70fabaf
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159 changes: 85 additions & 74 deletions log.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,106 +2,105 @@
//
// A global Logger can be use for simple logging:
//
// import "github.com/rs/zerolog/log"
// import "github.com/rs/zerolog/log"
//
// log.Info().Msg("hello world")
// // Output: {"time":1494567715,"level":"info","message":"hello world"}
// log.Info().Msg("hello world")
// // Output: {"time":1494567715,"level":"info","message":"hello world"}
//
// NOTE: To import the global logger, import the "log" subpackage "github.com/rs/zerolog/log".
//
// Fields can be added to log messages:
//
// log.Info().Str("foo", "bar").Msg("hello world")
// // Output: {"time":1494567715,"level":"info","message":"hello world","foo":"bar"}
// log.Info().Str("foo", "bar").Msg("hello world")
// // Output: {"time":1494567715,"level":"info","message":"hello world","foo":"bar"}
//
// Create logger instance to manage different outputs:
//
// logger := zerolog.New(os.Stderr).With().Timestamp().Logger()
// logger.Info().
// Str("foo", "bar").
// Msg("hello world")
// // Output: {"time":1494567715,"level":"info","message":"hello world","foo":"bar"}
// logger := zerolog.New(os.Stderr).With().Timestamp().Logger()
// logger.Info().
// Str("foo", "bar").
// Msg("hello world")
// // Output: {"time":1494567715,"level":"info","message":"hello world","foo":"bar"}
//
// Sub-loggers let you chain loggers with additional context:
//
// sublogger := log.With().Str("component": "foo").Logger()
// sublogger.Info().Msg("hello world")
// // Output: {"time":1494567715,"level":"info","message":"hello world","component":"foo"}
// sublogger := log.With().Str("component": "foo").Logger()
// sublogger.Info().Msg("hello world")
// // Output: {"time":1494567715,"level":"info","message":"hello world","component":"foo"}
//
// Level logging
//
// zerolog.SetGlobalLevel(zerolog.InfoLevel)
// zerolog.SetGlobalLevel(zerolog.InfoLevel)
//
// log.Debug().Msg("filtered out message")
// log.Info().Msg("routed message")
// log.Debug().Msg("filtered out message")
// log.Info().Msg("routed message")
//
// if e := log.Debug(); e.Enabled() {
// // Compute log output only if enabled.
// value := compute()
// e.Str("foo": value).Msg("some debug message")
// }
// // Output: {"level":"info","time":1494567715,"routed message"}
// if e := log.Debug(); e.Enabled() {
// // Compute log output only if enabled.
// value := compute()
// e.Str("foo": value).Msg("some debug message")
// }
// // Output: {"level":"info","time":1494567715,"routed message"}
//
// Customize automatic field names:
//
// log.TimestampFieldName = "t"
// log.LevelFieldName = "p"
// log.MessageFieldName = "m"
// log.TimestampFieldName = "t"
// log.LevelFieldName = "p"
// log.MessageFieldName = "m"
//
// log.Info().Msg("hello world")
// // Output: {"t":1494567715,"p":"info","m":"hello world"}
// log.Info().Msg("hello world")
// // Output: {"t":1494567715,"p":"info","m":"hello world"}
//
// Log with no level and message:
//
// log.Log().Str("foo","bar").Msg("")
// // Output: {"time":1494567715,"foo":"bar"}
// log.Log().Str("foo","bar").Msg("")
// // Output: {"time":1494567715,"foo":"bar"}
//
// Add contextual fields to global Logger:
//
// log.Logger = log.With().Str("foo", "bar").Logger()
// log.Logger = log.With().Str("foo", "bar").Logger()
//
// Sample logs:
//
// sampled := log.Sample(&zerolog.BasicSampler{N: 10})
// sampled.Info().Msg("will be logged every 10 messages")
// sampled := log.Sample(&zerolog.BasicSampler{N: 10})
// sampled.Info().Msg("will be logged every 10 messages")
//
// Log with contextual hooks:
//
// // Create the hook:
// type SeverityHook struct{}
// // Create the hook:
// type SeverityHook struct{}
//
// func (h SeverityHook) Run(e *zerolog.Event, level zerolog.Level, msg string) {
// if level != zerolog.NoLevel {
// e.Str("severity", level.String())
// }
// }
// func (h SeverityHook) Run(e *zerolog.Event, level zerolog.Level, msg string) {
// if level != zerolog.NoLevel {
// e.Str("severity", level.String())
// }
// }
//
// // And use it:
// var h SeverityHook
// log := zerolog.New(os.Stdout).Hook(h)
// log.Warn().Msg("")
// // Output: {"level":"warn","severity":"warn"}
// // And use it:
// var h SeverityHook
// log := zerolog.New(os.Stdout).Hook(h)
// log.Warn().Msg("")
// // Output: {"level":"warn","severity":"warn"}
//
// Prehooks are also available. It's called just before "level" is added to a log.
// `msg` always gets empty in `Run()`:
//
// // Use as prehook:
// var h SeverityHook
// log := zerolog.New(os.Stdout).Prehook(h)
// log.Warn().Msg("")
// // Output: {"severity":"warn", "level":"warn"}
// // Use as prehook:
// var h SeverityHook
// log := zerolog.New(os.Stdout).Prehook(h)
// log.Warn().Msg("")
// // Output: {"severity":"warn", "level":"warn"}
//
//
// Caveats
// # Caveats
//
// There is no fields deduplication out-of-the-box.
// Using the same key multiple times creates new key in final JSON each time.
//
// logger := zerolog.New(os.Stderr).With().Timestamp().Logger()
// logger.Info().
// Timestamp().
// Msg("dup")
// // Output: {"level":"info","time":1494567715,"time":1494567715,"message":"dup"}
// logger := zerolog.New(os.Stderr).With().Timestamp().Logger()
// logger.Info().
// Timestamp().
// Msg("dup")
// // Output: {"level":"info","time":1494567715,"time":1494567715,"message":"dup"}
//
// In this case, many consumers will take the last value,
// but this is not guaranteed; check yours if in doubt.
Expand All @@ -110,15 +109,15 @@
//
// Be careful when calling UpdateContext. It is not concurrency safe. Use the With method to create a child logger:
//
// func handler(w http.ResponseWriter, r *http.Request) {
// // Create a child logger for concurrency safety
// logger := log.Logger.With().Logger()
// func handler(w http.ResponseWriter, r *http.Request) {
// // Create a child logger for concurrency safety
// logger := log.Logger.With().Logger()
//
// // Add context fields, for example User-Agent from HTTP headers
// logger.UpdateContext(func(c zerolog.Context) zerolog.Context {
// ...
// })
// }
// // Add context fields, for example User-Agent from HTTP headers
// logger.UpdateContext(func(c zerolog.Context) zerolog.Context {
// ...
// })
// }
package zerolog

import (
Expand Down Expand Up @@ -236,16 +235,19 @@ func (l Level) MarshalText() ([]byte, error) {
// serialization to the Writer. If your Writer is not thread safe,
// you may consider a sync wrapper.
type Logger struct {
w LevelWriter
level Level
sampler Sampler
context []byte
hooks []Hook
prehooks []Hook
stack bool
ctx context.Context
w LevelWriter
level Level
sampler Sampler
context []byte
hooks []Hook
prehooks []Hook
stack bool
fatalFunc func(string)
ctx context.Context
}

var defaultFatalFunc = func(msg string) { os.Exit(1) }

// New creates a root logger with given output writer. If the output writer implements
// the LevelWriter interface, the WriteLevel method will be called instead of the Write
// one.
Expand All @@ -261,7 +263,7 @@ func New(w io.Writer) Logger {
if !ok {
lw = LevelWriterAdapter{w}
}
return Logger{w: lw, level: TraceLevel}
return Logger{w: lw, level: TraceLevel, fatalFunc: defaultFatalFunc}
}

// Nop returns a disabled logger for which all operation are no-op.
Expand Down Expand Up @@ -352,6 +354,15 @@ func (l Logger) Prehook(h Hook) Logger {
return l
}

// FatalFunc returns a logger with the f FatalFunc. This func will be called
// when a message is logged at the fatal level. By default, this calls
// `os.Exit(1)`, but you can override this to do something else, particularly
// for testing.
func (l Logger) FatalFunc(f func(string)) Logger {
l.fatalFunc = f
return l
}

// Trace starts a new message with trace level.
//
// You must call Msg on the returned event in order to send the event.
Expand Down Expand Up @@ -404,7 +415,7 @@ func (l *Logger) Err(err error) *Event {
//
// You must call Msg on the returned event in order to send the event.
func (l *Logger) Fatal() *Event {
return l.newEvent(FatalLevel, func(msg string) { os.Exit(1) })
return l.newEvent(FatalLevel, l.fatalFunc)
}

// Panic starts a new message with panic level. The panic() function
Expand Down
19 changes: 19 additions & 0 deletions log_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1039,3 +1039,22 @@ func TestUnmarshalTextLevel(t *testing.T) {
})
}
}

func TestFatalFunc(t *testing.T) {
out := &bytes.Buffer{}

var fatalCalled string
f := func(msg string) {
fatalCalled = msg
}
log := New(out).FatalFunc(f)
log.Fatal().Msg("foo")

if got, want := decodeIfBinaryToString(out.Bytes()), `{"level":"fatal","message":"foo"}`+"\n"; got != want {
t.Errorf("invalid log output:\ngot: %v\nwant: %v", got, want)
}

if fatalCalled != "foo" {
t.Error("fatal func was not called as expected")
}
}

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