Design workflows of slog handlers:
- fanout: distribute
log.Recordto multipleslog.Handlerin parallel - pipeline: rewrite
log.Recordon the fly (eg: for privacy reason) - routing: forward
log.Recordto all matchingslog.Handler - failover: forward
log.Recordto the first availableslog.Handler - load balancing: increase log bandwidth by sending
log.Recordto a pool ofslog.Handler
Here a simple workflow with both pipeline and fanout:
See also:
- slog-multi:
slog.Handlerchaining, fanout, routing, failover, load balancing... - slog-formatter:
slogattribute formatting - slog-sampling:
slogsampling policy
HTTP middlewares:
- slog-gin: Gin middleware for
sloglogger - slog-echo: Echo middleware for
sloglogger - slog-fiber: Fiber middleware for
sloglogger - slog-chi: Chi middleware for
sloglogger - slog-http:
net/httpmiddleware forsloglogger
Loggers:
- slog-zap: A
sloghandler forZap - slog-zerolog: A
sloghandler forZerolog - slog-logrus: A
sloghandler forLogrus
Log sinks:
- slog-datadog: A
sloghandler forDatadog - slog-betterstack: A
sloghandler forBetterstack - slog-rollbar: A
sloghandler forRollbar - slog-loki: A
sloghandler forLoki - slog-sentry: A
sloghandler forSentry - slog-syslog: A
sloghandler forSyslog - slog-logstash: A
sloghandler forLogstash - slog-fluentd: A
sloghandler forFluentd - slog-graylog: A
sloghandler forGraylog - slog-slack: A
sloghandler forSlack - slog-telegram: A
sloghandler forTelegram - slog-mattermost: A
sloghandler forMattermost - slog-microsoft-teams: A
sloghandler forMicrosoft Teams - slog-webhook: A
sloghandler forWebhook - slog-kafka: A
sloghandler forKafka - slog-nats: A
sloghandler forNATS - slog-parquet: A
sloghandler forParquet+Object Storage - slog-channel: A
sloghandler for Go channels
go get github.com/samber/slog-multiCompatibility: go >= 1.21
No breaking changes will be made to exported APIs before v2.0.0.
GoDoc: https://pkg.go.dev/github.com/samber/slog-multi
Distribute logs to multiple slog.Handler in parallel.
import (
slogmulti "github.com/samber/slog-multi"
"log/slog"
)
func main() {
logstash, _ := net.Dial("tcp", "logstash.acme:4242") // use github.com/netbrain/goautosocket for auto-reconnect
stderr := os.Stderr
logger := slog.New(
slogmulti.Fanout(
slog.NewJSONHandler(logstash, &slog.HandlerOptions{}), // pass to first handler: logstash over tcp
slog.NewTextHandler(stderr, &slog.HandlerOptions{}), // then to second handler: stderr
// ...
),
)
logger.
With(
slog.Group("user",
slog.String("id", "user-123"),
slog.Time("created_at", time.Now()),
),
).
With("environment", "dev").
With("error", fmt.Errorf("an error")).
Error("A message")
}Stderr output:
time=2023-04-10T14:00:0.000000+00:00 level=ERROR msg="A message" user.id=user-123 user.created_at=2023-04-10T14:00:0.000000+00:00 environment=dev error="an error"
Netcat output:
{
"time":"2023-04-10T14:00:0.000000+00:00",
"level":"ERROR",
"msg":"A message",
"user":{
"id":"user-123",
"created_at":"2023-04-10T14:00:0.000000+00:00"
},
"environment":"dev",
"error":"an error"
}Distribute logs to all matching slog.Handler in parallel.
import (
slogmulti "github.com/samber/slog-multi"
slogslack "github.com/samber/slog-slack"
"log/slog"
)
func main() {
slackChannelUS := slogslack.Option{Level: slog.LevelError, WebhookURL: "xxx", Channel: "supervision-us"}.NewSlackHandler()
slackChannelEU := slogslack.Option{Level: slog.LevelError, WebhookURL: "xxx", Channel: "supervision-eu"}.NewSlackHandler()
slackChannelAPAC := slogslack.Option{Level: slog.LevelError, WebhookURL: "xxx", Channel: "supervision-apac"}.NewSlackHandler()
logger := slog.New(
slogmulti.Router().
Add(slackChannelUS, recordMatchRegion("us")).
Add(slackChannelEU, recordMatchRegion("eu")).
Add(slackChannelAPAC, recordMatchRegion("apac")).
Handler(),
)
logger.
With("region", "us").
With("pool", "us-east-1").
Error("Server desynchronized")
}
func recordMatchRegion(region string) func(ctx context.Context, r slog.Record) bool {
return func(ctx context.Context, r slog.Record) bool {
ok := false
r.Attrs(func(attr slog.Attr) bool {
if attr.Key == "region" && attr.Value.Kind() == slog.KindString && attr.Value.String() == region {
ok = true
return false
}
return true
})
return ok
}
}List multiple targets for a slog.Record instead of retrying on the same unavailable log management system.
import (
"net"
slogmulti "github.com/samber/slog-multi"
"log/slog"
)
func main() {
// ncat -l 1000 -k
// ncat -l 1001 -k
// ncat -l 1002 -k
// list AZs
// use github.com/netbrain/goautosocket for auto-reconnect
logstash1, _ := net.Dial("tcp", "logstash.eu-west-3a.internal:1000")
logstash2, _ := net.Dial("tcp", "logstash.eu-west-3b.internal:1000")
logstash3, _ := net.Dial("tcp", "logstash.eu-west-3c.internal:1000")
logger := slog.New(
slogmulti.Failover()(
slog.HandlerOptions{}.NewJSONHandler(logstash1, nil), // send to this instance first
slog.HandlerOptions{}.NewJSONHandler(logstash2, nil), // then this instance in case of failure
slog.HandlerOptions{}.NewJSONHandler(logstash3, nil), // and finally this instance in case of double failure
),
)
logger.
With(
slog.Group("user",
slog.String("id", "user-123"),
slog.Time("created_at", time.Now()),
),
).
With("environment", "dev").
With("error", fmt.Errorf("an error")).
Error("A message")
}Increase log bandwidth by sending log.Record to a pool of slog.Handler.
import (
"net"
slogmulti "github.com/samber/slog-multi"
"log/slog"
)
func main() {
// ncat -l 1000 -k
// ncat -l 1001 -k
// ncat -l 1002 -k
// list AZs
// use github.com/netbrain/goautosocket for auto-reconnect
logstash1, _ := net.Dial("tcp", "logstash.eu-west-3a.internal:1000")
logstash2, _ := net.Dial("tcp", "logstash.eu-west-3b.internal:1000")
logstash3, _ := net.Dial("tcp", "logstash.eu-west-3c.internal:1000")
logger := slog.New(
slogmulti.Pool()(
// a random handler will be picked
slog.HandlerOptions{}.NewJSONHandler(logstash1, nil),
slog.HandlerOptions{}.NewJSONHandler(logstash2, nil),
slog.HandlerOptions{}.NewJSONHandler(logstash3, nil),
),
)
logger.
With(
slog.Group("user",
slog.String("id", "user-123"),
slog.Time("created_at", time.Now()),
),
).
With("environment", "dev").
With("error", fmt.Errorf("an error")).
Error("A message")
}Rewrite log.Record on the fly (eg: for privacy reason).
func main() {
// first middleware: format go `error` type into an object {error: "*myCustomErrorType", message: "could not reach https://a.b/c"}
errorFormattingMiddleware := slogmulti.NewHandleInlineMiddleware(errorFormattingMiddleware)
// second middleware: remove PII
gdprMiddleware := NewGDPRMiddleware()
// final handler
sink := slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{})
logger := slog.New(
slogmulti.
Pipe(errorFormattingMiddleware).
Pipe(gdprMiddleware).
// ...
Handler(sink),
)
logger.
With(
slog.Group("user",
slog.String("id", "user-123"),
slog.String("email", "user-123"),
slog.Time("created_at", time.Now()),
),
).
With("environment", "dev").
Error("A message",
slog.String("foo", "bar"),
slog.Any("error", fmt.Errorf("an error")),
)
}Stderr output:
{
"time":"2023-04-10T14:00:0.000000+00:00",
"level":"ERROR",
"msg":"A message",
"user":{
"id":"*******",
"email":"*******",
"created_at":"*******"
},
"environment":"dev",
"foo":"bar",
"error":{
"type":"*myCustomErrorType",
"message":"an error"
}
}Middleware must match the following prototype:
type Middleware func(slog.Handler) slog.HandlerThe example above uses:
Note: WithAttrs and WithGroup methods of custom middleware must return a new instance, instead of this.
An "inline middleware" (aka. lambda), is a shortcut to middleware implementation, that hooks a single method and proxies others.
// hook `logger.Enabled` method
mdw := slogmulti.NewEnabledInlineMiddleware(func(ctx context.Context, level slog.Level, next func(context.Context, slog.Level) bool) bool{
// [...]
return next(ctx, level)
})// hook `logger.Handle` method
mdw := slogmulti.NewHandleInlineMiddleware(func(ctx context.Context, record slog.Record, next func(context.Context, slog.Record) error) error {
// [...]
return next(ctx, record)
})// hook `logger.WithAttrs` method
mdw := slogmulti.NewWithAttrsInlineMiddleware(func(attrs []slog.Attr, next func([]slog.Attr) slog.Handler) slog.Handler{
// [...]
return next(attrs)
})// hook `logger.WithGroup` method
mdw := slogmulti.NewWithGroupInlineMiddleware(func(name string, next func(string) slog.Handler) slog.Handler{
// [...]
return next(name)
})A super inline middleware that hooks all methods.
Warning: you would rather implement your own middleware.
mdw := slogmulti.NewInlineMiddleware(
func(ctx context.Context, level slog.Level, next func(context.Context, slog.Level) bool) bool{
// [...]
return next(ctx, level)
},
func(ctx context.Context, record slog.Record, next func(context.Context, slog.Record) error) error{
// [...]
return next(ctx, record)
},
func(attrs []slog.Attr, next func([]slog.Attr) slog.Handler) slog.Handler{
// [...]
return next(attrs)
},
func(name string, next func(string) slog.Handler) slog.Handler{
// [...]
return next(name)
},
)- Ping me on twitter @samuelberthe (DMs, mentions, whatever :))
- Fork the project
- Fix open issues or request new features
Don't hesitate ;)
# Install some dev dependencies
make tools
# Run tests
make test
# or
make watch-testGive a ⭐️ if this project helped you!
Copyright © 2023 Samuel Berthe.
This project is MIT licensed.