LogM is a Go log management package providing facilities to deal with logs and trace context.
- Provides simple methods to expose a slog.Logger using
logfmt
as format:DefaultLogger
: A logger ready for production.DebugLogger
: A logger exposing debug record for development.DiscardLogger
: Another to discard any logs (test purposes or no space left on disk).
- Provides a
File
with automatic rotating, maximum file size, zip archives, etc. Thanks to lumberjack. - Provides a
Trace
structure to uniquely identified actions, like an HTTP request. SeeNewTraceFromContext
to easily propagate or retrieve trace context. - Exposes HTTP middlewares to handle log and tracing:to create a trace context on each request.
LogHandler
: a logging middleware to log detail about the request and the response.RecoverHandler
: a middleware to recover on panic, log the message as ERROR and the stack trace as DEBUG.TraceHandler
: a middleware to retrieve request headerX-Trace-Id
(seeNewTraceFromHTTPRequest
) and propagate its value through the request context.
- Provides
TimeElapsed
to log in defer the time elapsed of a function. - Offers a testing sub-package named
logmtest
to verify the data logged.
$ go get -u github.com/rvflash/logm
logm
uses the Go modules, debug.BuildSetting
and the slog
package that required Go 1.18 or later.
Create a logger for an application named app
that store records in a file named app.log
, ignoring DEBUG ones.
By default, the NewFile
function returns a self rolling file as soon as it reaches the size of 100 Mo.
The rotated log files is compressed using gzip and retained forever. Each log is prefixed by the local time.
Customization is available by using File
directly.
By default, each record has the name and the current version of the application as attributes.
The version is provided on build by the
debug.ReadBuildInfo
package. It's the revision identifier for the current commit or checkout.
log := logm.DefaultLogger("app", logm.NewFile("app.log"))
log.Info("hello")
$ cat app.log
time=2023-03-25T00:04:35.287+01:00 level=INFO msg=hello app=app version=d1da844711730f2f5cbd08be93e62e71475f7d4e
log := logm.DebugLogger("app", os.Stdout)
log.Debug("hello")
time=2023-03-25T10:57:51.772+01:00 level=DEBUG msg=hello app=app version=d1da844711730f2f5cbd08be93e62e71475f7d4e
NewTrace
can create a new trace context with an UUID v4 as identifier.
It's also possible to create a custom one by directly using Trace
and propagate it through a context.Context
.
var (
t = logm.Trace{ID: "myID"}
ctx = t.NewContext(context.Background())
)
var (
l = logm.DefaultLogger("app", os.Stdout)
t = logm.NewTrace()
)
log := l.With(t.LogAttr())
log.Info("hello")
log.Warn("world")
time=2023-03-25T13:06:37.322+01:00 level=INFO msg=hello app=app version=d1da844711730f2f5cbd08be93e62e71475f7d4e trace.id=0a02e16c-7418-4558-9dcc-718c007162b6
time=2023-03-25T13:06:37.322+01:00 level=WARN msg=world app=app version=d1da844711730f2f5cbd08be93e62e71475f7d4e trace.id=0a02e16c-7418-4558-9dcc-718c007162b6
var (
log = logm.DefaultLogger("app", os.Stdout)
ctx = context.Background()
)
func(ctx context.Context, log *slog.Logger) {
defer logm.TimeElapsed(ctx, log, slog.LevelInfo, "example")()
time.Sleep(time.Millisecond)
}(ctx, log)
time=2023-03-25T12:06:17.605+01:00 level=INFO msg=example app=app version=d1da844711730f2f5cbd08be93e62e71475f7d4e trace.id=ccc05db1-68d2-4442-9353-0789e0b8ca55 trace.time_elapsed_ms=1
Testing the logged data sometimes seems useless, but it can be reassuring to quickly check a stream to preserve.
The logmtest.NewRecorder
provides an in-memory log writer useful for that,
with a method Expect
to check each Record
.
Two options to adjust the verification:
ExpectAnyOrder
to match all expectations in the order they were set or not. By default, it expects in order.ExpectUnexpected
to ignore not matching records. By default, if a record is not expected, an error will be triggered.
var (
rec = logmtest.NewRecorder()
log = logm.DefaultLogger("testing", rec)
)
log.Info("hello")
log.Warn("beautiful")
log.Error("world")
err := rec.Expect(
logmtest.Record{Contains: "hello"},
logmtest.Record{Contains: "beau"},
logmtest.Record{Contains: "world"},
)
// Will return no error.