Benchmark Data

Summary Links

samber/slog-zap is a wrapper around the pre-existing uber-go/zap logging library.

samber/slog-zap
uber-go/zap

Benchmark Data

Score: 54.33

Benchmark	Runs	Ns/Op	Allocs/Op	Bytes/Op	MB/Sec	Score
Attributes	231,032	5,756.00	47	6,646	67.58	50.77
Big Group	2,034	594,119.00	8,236	440,998	43.86	15.19
Disabled	322,795,513	3.72	0	0	0.00	96.86
Key Values	200,066	5,887.00	47	6,646	66.07	50.62
Logging	10,000	101,970.00	1,020	121,340	81.32	61.36
Simple	2,544,134	467.50	2	336	156.15	86.65
Simple Source	1,673,392	714.50	5	592	149.76	90.19
With Attrs Attributes	124,971	9,936.00	69	12,454	61.19	43.58
With Attrs Key Values	122,162	9,978.00	69	12,453	60.93	43.62
With Attrs Simple	232,490	5,080.00	42	5,540	82.88	51.76
With Group Attributes	113,708	10,878.00	128	12,632	34.75	30.44
With Group Key Values	110,640	10,803.00	128	12,633	34.99	30.85

Benchmark Charts

Warnings

Score: 50.77

Required

EmptyAttributes Empty attribute(s) logged ("":null)

Handlers are supposed to avoid logging empty attributes.

"- If an Attr's key and value are both the zero value, ignore the Attr."

Verify: Attribute With Empty
	{ "": null, "first": "one", "level": "info", "msg": "This is a message", "pi": 3.141592653589793, "time": "2024-05-19T01:15:07Z" }
Verify: Attributes Empty
	{ "": null, "first": "one", "level": "info", "msg": "This is a message", "pi": 3.141592653589793, "time": "2024-05-19T01:15:07Z" }
Verify: Attributes With Empty
	{ "": null, "first": "one", "level": "info", "msg": "This is a message", "pi": 3.141592653589793, "second": 2, "time": "2024-05-19T01:15:07Z" }

GroupInline Group with empty key does not inline subfields

Handlers should expand groups named "" (the empty string) into the enclosing log record.

"- If a group's key is empty, inline the group's Attrs."

Verify: Group Inline
	{ "": { "fourth": "forth", "second": 2, "third": "3" }, "first": "one", "level": "info", "msg": "This is a message", "pi": 3.141592653589793, "time": "2024-05-19T01:15:07Z" }

Resolver LogValuer objects are not resolved

Handlers should resolve all objects implementing the LogValuer or Stringer interfaces. This is a powerful feature which can customize logging of objects and speed up logging by delaying argument resolution until logging time.

"- Attr's values should be resolved."

Verify: Resolve Group
	{ "group": { "hidden": {}, "pi": 3.141592653589793 }, "level": "info", "msg": "This is a message", "time": "2024-05-19T01:15:07Z" }
Verify: Resolve Group With
	{ "group": { "hidden": {}, "pi": 3.141592653589793 }, "level": "info", "msg": "This is a message", "time": "2024-05-19T01:15:07Z" }
Verify: Resolve Valuer
	{ "hidden": {}, "level": "info", "msg": "This is a message", "time": "2024-05-19T01:15:07Z" }
Verify: Resolve With
	{ "hidden": {}, "level": "info", "msg": "This is a message", "time": "2024-05-19T01:15:07Z" }

SlogTest Failure of embedded slog/slogtest

Documentation on building a handler suggests testing using slog/slogtest, part of the Go release since 1.21. While the verification suite includes tests patterned after those in slogtest, an additional single test invokes the slogtest testing sequence (involving multiple tests). Since this is a separate package, all error messages are returned at once. This is the only warning that affects TestSlogTest and all of its error messages.

Verify: Slog Test

unexpected key ""
a Handler should ignore an empty Attr

unexpected key "time"
a Handler should ignore a zero Record.Time

missing key "c"
a Handler should inline the Attrs of a group with an empty key

"k"
got "

"b"
got map[string]interface {}{}, want "v2": a Handler should call Resolve on attribute values in groups

"k"
got "

"b"
got map[string]interface {}{}, want "v2": a Handler should call Resolve on attribute values in groups from WithAttrs

ZeroPC SourceKey logged for zero PC

The slog.Record.PC field can be loaded with a program counter (PC). This is normally done by the slog.Logger code. If the PC is non-zero and the slog.HandlerOptions.AddSource flag is set the source field will contain a slog.Source record containing the function name, file name, and file line at which the log record was generated. If the PC is zero then this field and its associated group should not be logged.

"- If r.PC is zero, ignore it."

Verify: Zero PC		non-standard key 'caller'
	{ "caller": ":0", "level": "info", "msg": "This is a message", "time": "2024-05-19T01:15:07Z" }

ZeroTime Zero time is logged

Handlers should not log the basic time field if it is zero.

"- If r.Time is the zero time, ignore the time."

Verify: Zero Time		2024-05-19T01:15:07Z
	{ "level": "info", "msg": "This is a message", "time": "2024-05-19T01:15:07Z" }

Implied

NoReplAttrBasic HandlerOptions.ReplaceAttr not available for basic fields

Some handlers (e.g. phsym/zeroslog) support HandlerOptions.ReplaceAttr except for the four main fields time, level, msg, and source. When that is the case it is better to use this (WarnNoReplAttrBasic) warning.

Verify: Replace Attr Basic		too many attributes: 4 time field still exists msg field still exists source ==

Verify: Replace Attr Fn Level Case		level value not null

Verify: Replace Attr Fn Multi
	{ "group": { "alpha": "OMEGA", "pi": 3.141592653589793, "subGroup": { "e": 2.718281828459045, "goober": "snoofus", "la la la": "omega", "oneMore": { "alpha": "omega", "gibbering": "moontic", "phi": 1.618033988749895 } } }, "level": "info", "msg": "This is a message", "time": "2024-05-19T01:15:07Z" }
Verify: Replace Attr Fn Remove Empty Key

Verify: Replace Attr Fn Remove Time		time value not empty string

SourceCaller Source data logged as 'caller' instead of 'source'

Some handlers return source data as a single string on the caller field in the format <file>:<line> where <file> and <line> correspond to the File and Line fields of the source data group and Function is not provided.

Bench: Simple Source		tests/benchmarks.go:96
	{ "caller": "tests/benchmarks.go:96", "level": "info", "msg": "This is a message", "time": "2024-05-19T01:14:25Z" }
Verify: Source Key		reflect/value.go:596
	{ "caller": "reflect/value.go:596", "level": "info", "msg": "This is a message", "time": "2024-05-19T01:15:07Z" }

Suggested

DurationSeconds slog.Duration() logs seconds instead of nanoseconds

The slog.JSONHandler uses nanoseconds for time.Duration but some other handlers use seconds.

Go issue 59345: Nanoseconds is a recent change with Go 1.21

Verify: Log Attributes

GroupDuration

Some handlers that change the way time.Duration objects are logged (see warnings DurationMillis and DurationSeconds) only manage to make the change at the top level of the logged record, duration objects in groups are still in nanoseconds.

Verify: Group Duration		29002.000000 != 29002000000000.000000
	{ "group": { "inner": 29002000000000 }, "level": "info", "msg": "This is a message", "outer": 29002, "time": "2024-05-19T01:15:07Z" }

LevelCase Log level in lowercase

Each JSON log record contains the logging level of the log statement as a string. Different handlers provide that string in uppercase or lowercase. Documentation for slog.Level says that its String() and MarshalJSON() methods will return uppercase but UnmarshalJSON() will parse in a case-insensitive manner.

Verify: Canceled Context		'info'

Verify: Canceled Context		'info'

Verify: Canceled Context		'info'

Verify: Key Case		'error'

Verify: Key Case		'debug'

Verify: Key Case		'info'

Verify: Key Case		'warn'

Verify: Keys		'info'

Verify: Source Key		'info'

Verify: Zero PC		'info'

Verify: Zero Time		'info'

TimeMillis slog.Time() logs milliseconds instead of nanoseconds

The slog.JSONHandler uses nanoseconds for time.Time but some other handlers use milliseconds. This does not apply to the basic time field, only attribute fields. I can't find any supporting documentation or bug on this but Go issue 59345 (see previous warning) may have fixed this as well in Go 1.21.

Verify: Log Attributes		2024-05-19T01:15:07Z

Handler samber/slog-zap

Benchmark Data

Benchmark Charts

Warnings