// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
+// Note: run 'go generate' (which will run 'go test -generate') to update the "Supported metrics" list.
+//go:generate go test -run=Docs -generate
+
/*
Package metrics provides a stable interface to access implementation-defined
metrics exported by the Go runtime. This package is similar to existing functions
-like runtime.ReadMemStats and debug.ReadGCStats, but significantly more general.
+like [runtime.ReadMemStats] and [debug.ReadGCStats], but significantly more general.
The set of metrics defined by this package may evolve as the runtime itself
evolves, and also enables variation across Go implementations, whose relevant
metric sets may not intersect.
-Interface
+# Interface
Metrics are designated by a string key, rather than, for example, a field name in
a struct. The full list of supported metrics is always available in the slice of
-Descriptions returned by All. Each Description also includes useful information
-about the metric, such as how to display it (for example, gauge vs. counter)
-and how difficult or disruptive it is to obtain it (for example, do you need to
-stop the world?).
+Descriptions returned by [All]. Each [Description] also includes useful information
+about the metric.
Thus, users of this API are encouraged to sample supported metrics defined by the
slice returned by All to remain compatible across Go versions. Of course, situations
is guaranteed not to change. If it must change, then a new metric will be introduced
with a new key and a new "kind."
-Metric key format
+# Metric key format
As mentioned earlier, metric keys are strings. Their format is simple and well-defined,
designed to be both human and machine readable. It is split into two components,
For more details on the precise definition of the metric key's path and unit formats, see
the documentation of the Name field of the Description struct.
-A note about floats
+# A note about floats
This package supports metrics whose values have a floating-point representation. In
order to improve ease-of-use, this package promises to never produce the following
classes of floating-point values: NaN, infinity.
-Supported metrics
+# Supported metrics
Below is the full list of supported metrics, ordered lexicographically.
+ /cgo/go-to-c-calls:calls
+ Count of calls made from Go to C by the current process.
+
+ /cpu/classes/gc/mark/assist:cpu-seconds
+ Estimated total CPU time goroutines spent performing GC
+ tasks to assist the GC and prevent it from falling behind the
+ application. This metric is an overestimate, and not directly
+ comparable to system CPU time measurements. Compare only with
+ other /cpu/classes metrics.
+
+ /cpu/classes/gc/mark/dedicated:cpu-seconds
+ Estimated total CPU time spent performing GC tasks on processors
+ (as defined by GOMAXPROCS) dedicated to those tasks. This metric
+ is an overestimate, and not directly comparable to system CPU
+ time measurements. Compare only with other /cpu/classes metrics.
+
+ /cpu/classes/gc/mark/idle:cpu-seconds
+ Estimated total CPU time spent performing GC tasks on spare CPU
+ resources that the Go scheduler could not otherwise find a use
+ for. This should be subtracted from the total GC CPU time to
+ obtain a measure of compulsory GC CPU time. This metric is an
+ overestimate, and not directly comparable to system CPU time
+ measurements. Compare only with other /cpu/classes metrics.
+
+ /cpu/classes/gc/pause:cpu-seconds
+ Estimated total CPU time spent with the application paused by
+ the GC. Even if only one thread is running during the pause,
+ this is computed as GOMAXPROCS times the pause latency because
+ nothing else can be executing. This is the exact sum of samples
+ in /gc/pause:seconds if each sample is multiplied by GOMAXPROCS
+ at the time it is taken. This metric is an overestimate,
+ and not directly comparable to system CPU time measurements.
+ Compare only with other /cpu/classes metrics.
+
+ /cpu/classes/gc/total:cpu-seconds
+ Estimated total CPU time spent performing GC tasks. This metric
+ is an overestimate, and not directly comparable to system CPU
+ time measurements. Compare only with other /cpu/classes metrics.
+ Sum of all metrics in /cpu/classes/gc.
+
+ /cpu/classes/idle:cpu-seconds
+ Estimated total available CPU time not spent executing
+ any Go or Go runtime code. In other words, the part of
+ /cpu/classes/total:cpu-seconds that was unused. This metric is
+ an overestimate, and not directly comparable to system CPU time
+ measurements. Compare only with other /cpu/classes metrics.
+
+ /cpu/classes/scavenge/assist:cpu-seconds
+ Estimated total CPU time spent returning unused memory to the
+ underlying platform in response eagerly in response to memory
+ pressure. This metric is an overestimate, and not directly
+ comparable to system CPU time measurements. Compare only with
+ other /cpu/classes metrics.
+
+ /cpu/classes/scavenge/background:cpu-seconds
+ Estimated total CPU time spent performing background tasks to
+ return unused memory to the underlying platform. This metric is
+ an overestimate, and not directly comparable to system CPU time
+ measurements. Compare only with other /cpu/classes metrics.
+
+ /cpu/classes/scavenge/total:cpu-seconds
+ Estimated total CPU time spent performing tasks that return
+ unused memory to the underlying platform. This metric is an
+ overestimate, and not directly comparable to system CPU time
+ measurements. Compare only with other /cpu/classes metrics.
+ Sum of all metrics in /cpu/classes/scavenge.
+
+ /cpu/classes/total:cpu-seconds
+ Estimated total available CPU time for user Go code or the Go
+ runtime, as defined by GOMAXPROCS. In other words, GOMAXPROCS
+ integrated over the wall-clock duration this process has been
+ executing for. This metric is an overestimate, and not directly
+ comparable to system CPU time measurements. Compare only with
+ other /cpu/classes metrics. Sum of all metrics in /cpu/classes.
+
+ /cpu/classes/user:cpu-seconds
+ Estimated total CPU time spent running user Go code. This may
+ also include some small amount of time spent in the Go runtime.
+ This metric is an overestimate, and not directly comparable
+ to system CPU time measurements. Compare only with other
+ /cpu/classes metrics.
+
/gc/cycles/automatic:gc-cycles
Count of completed GC cycles generated by the Go runtime.
/gc/cycles/total:gc-cycles
Count of all completed GC cycles.
+ /gc/gogc:percent
+ Heap size target percentage configured by the user, otherwise
+ 100. This value is set by the GOGC environment variable, and the
+ runtime/debug.SetGCPercent function.
+
+ /gc/gomemlimit:bytes
+ Go runtime memory limit configured by the user, otherwise
+ math.MaxInt64. This value is set by the GOMEMLIMIT environment
+ variable, and the runtime/debug.SetMemoryLimit function.
+
/gc/heap/allocs-by-size:bytes
- Distribution of all objects allocated by approximate size.
+ Distribution of heap allocations by approximate size.
+ Bucket counts increase monotonically. Note that this does not
+ include tiny objects as defined by /gc/heap/tiny/allocs:objects,
+ only tiny blocks.
+
+ /gc/heap/allocs:bytes
+ Cumulative sum of memory allocated to the heap by the
+ application.
+
+ /gc/heap/allocs:objects
+ Cumulative count of heap allocations triggered by the
+ application. Note that this does not include tiny objects as
+ defined by /gc/heap/tiny/allocs:objects, only tiny blocks.
/gc/heap/frees-by-size:bytes
- Distribution of all objects freed by approximate size.
+ Distribution of freed heap allocations by approximate size.
+ Bucket counts increase monotonically. Note that this does not
+ include tiny objects as defined by /gc/heap/tiny/allocs:objects,
+ only tiny blocks.
+
+ /gc/heap/frees:bytes
+ Cumulative sum of heap memory freed by the garbage collector.
+
+ /gc/heap/frees:objects
+ Cumulative count of heap allocations whose storage was freed
+ by the garbage collector. Note that this does not include tiny
+ objects as defined by /gc/heap/tiny/allocs:objects, only tiny
+ blocks.
/gc/heap/goal:bytes
Heap size target for the end of the GC cycle.
+ /gc/heap/live:bytes
+ Heap memory occupied by live objects that were marked by the
+ previous GC.
+
/gc/heap/objects:objects
Number of objects, live or unswept, occupying heap memory.
+ /gc/heap/tiny/allocs:objects
+ Count of small allocations that are packed together into blocks.
+ These allocations are counted separately from other allocations
+ because each individual allocation is not tracked by the
+ runtime, only their block. Each block is already accounted for
+ in allocs-by-size and frees-by-size.
+
+ /gc/limiter/last-enabled:gc-cycle
+ GC cycle the last time the GC CPU limiter was enabled.
+ This metric is useful for diagnosing the root cause of an
+ out-of-memory error, because the limiter trades memory for CPU
+ time when the GC's CPU time gets too high. This is most likely
+ to occur with use of SetMemoryLimit. The first GC cycle is cycle
+ 1, so a value of 0 indicates that it was never enabled.
+
/gc/pauses:seconds
- Distribution individual GC-related stop-the-world pause latencies.
+ Distribution of individual GC-related stop-the-world pause
+ latencies. Bucket counts increase monotonically.
+
+ /gc/scan/globals:bytes
+ The total amount of global variable space that is scannable.
+
+ /gc/scan/heap:bytes
+ The total amount of heap space that is scannable.
+
+ /gc/scan/stack:bytes
+ The number of bytes of stack that were scanned last GC cycle.
+
+ /gc/scan/total:bytes
+ The total amount space that is scannable. Sum of all metrics in
+ /gc/scan.
+
+ /gc/stack/starting-size:bytes
+ The stack size of new goroutines.
+
+ /godebug/non-default-behavior/execerrdot:events
+ The number of non-default behaviors executed by the os/exec
+ package due to a non-default GODEBUG=execerrdot=... setting.
+
+ /godebug/non-default-behavior/gocachehash:events
+ The number of non-default behaviors executed by the cmd/go
+ package due to a non-default GODEBUG=gocachehash=... setting.
+
+ /godebug/non-default-behavior/gocachetest:events
+ The number of non-default behaviors executed by the cmd/go
+ package due to a non-default GODEBUG=gocachetest=... setting.
+
+ /godebug/non-default-behavior/gocacheverify:events
+ The number of non-default behaviors executed by the cmd/go
+ package due to a non-default GODEBUG=gocacheverify=... setting.
+
+ /godebug/non-default-behavior/gotypesalias:events
+ The number of non-default behaviors executed by the go/types
+ package due to a non-default GODEBUG=gotypesalias=... setting.
+
+ /godebug/non-default-behavior/http2client:events
+ The number of non-default behaviors executed by the net/http
+ package due to a non-default GODEBUG=http2client=... setting.
+
+ /godebug/non-default-behavior/http2server:events
+ The number of non-default behaviors executed by the net/http
+ package due to a non-default GODEBUG=http2server=... setting.
+
+ /godebug/non-default-behavior/httplaxcontentlength:events
+ The number of non-default behaviors executed by the net/http
+ package due to a non-default GODEBUG=httplaxcontentlength=...
+ setting.
+
+ /godebug/non-default-behavior/httpmuxgo121:events
+ The number of non-default behaviors executed by the net/http
+ package due to a non-default GODEBUG=httpmuxgo121=... setting.
+
+ /godebug/non-default-behavior/installgoroot:events
+ The number of non-default behaviors executed by the go/build
+ package due to a non-default GODEBUG=installgoroot=... setting.
+
+ /godebug/non-default-behavior/jstmpllitinterp:events
+ The number of non-default behaviors executed by
+ the html/template package due to a non-default
+ GODEBUG=jstmpllitinterp=... setting.
+
+ /godebug/non-default-behavior/multipartmaxheaders:events
+ The number of non-default behaviors executed by
+ the mime/multipart package due to a non-default
+ GODEBUG=multipartmaxheaders=... setting.
+
+ /godebug/non-default-behavior/multipartmaxparts:events
+ The number of non-default behaviors executed by
+ the mime/multipart package due to a non-default
+ GODEBUG=multipartmaxparts=... setting.
+
+ /godebug/non-default-behavior/multipathtcp:events
+ The number of non-default behaviors executed by the net package
+ due to a non-default GODEBUG=multipathtcp=... setting.
+
+ /godebug/non-default-behavior/panicnil:events
+ The number of non-default behaviors executed by the runtime
+ package due to a non-default GODEBUG=panicnil=... setting.
+
+ /godebug/non-default-behavior/randautoseed:events
+ The number of non-default behaviors executed by the math/rand
+ package due to a non-default GODEBUG=randautoseed=... setting.
+
+ /godebug/non-default-behavior/tarinsecurepath:events
+ The number of non-default behaviors executed by the archive/tar
+ package due to a non-default GODEBUG=tarinsecurepath=...
+ setting.
+
+ /godebug/non-default-behavior/tls10server:events
+ The number of non-default behaviors executed by the crypto/tls
+ package due to a non-default GODEBUG=tls10server=... setting.
+
+ /godebug/non-default-behavior/tlsmaxrsasize:events
+ The number of non-default behaviors executed by the crypto/tls
+ package due to a non-default GODEBUG=tlsmaxrsasize=... setting.
+
+ /godebug/non-default-behavior/x509sha1:events
+ The number of non-default behaviors executed by the crypto/x509
+ package due to a non-default GODEBUG=x509sha1=... setting.
+
+ /godebug/non-default-behavior/x509usefallbackroots:events
+ The number of non-default behaviors executed by the crypto/x509
+ package due to a non-default GODEBUG=x509usefallbackroots=...
+ setting.
+
+ /godebug/non-default-behavior/zipinsecurepath:events
+ The number of non-default behaviors executed by the archive/zip
+ package due to a non-default GODEBUG=zipinsecurepath=...
+ setting.
/memory/classes/heap/free:bytes
Memory that is completely free and eligible to be returned to
physical memory.
/memory/classes/heap/objects:bytes
- Memory occupied by live objects and dead objects that have
- not yet been marked free by the garbage collector.
+ Memory occupied by live objects and dead objects that have not
+ yet been marked free by the garbage collector.
/memory/classes/heap/released:bytes
- Memory that is completely free and has been returned to
- the underlying system. This metric is the runtime's estimate of
- free address space that is still mapped into the process, but
- is not backed by physical memory.
+ Memory that is completely free and has been returned to the
+ underlying system. This metric is the runtime's estimate of free
+ address space that is still mapped into the process, but is not
+ backed by physical memory.
/memory/classes/heap/stacks:bytes
- Memory allocated from the heap that is reserved for stack
- space, whether or not it is currently in-use.
+ Memory allocated from the heap that is reserved for stack space,
+ whether or not it is currently in-use. Currently, this
+ represents all stack memory for goroutines. It also includes all
+ OS thread stacks in non-cgo programs. Note that stacks may be
+ allocated differently in the future, and this may change.
/memory/classes/heap/unused:bytes
Memory that is reserved for heap objects but is not currently
used to hold heap objects.
/memory/classes/metadata/mcache/free:bytes
- Memory that is reserved for runtime mcache structures, but
- not in-use.
+ Memory that is reserved for runtime mcache structures, but not
+ in-use.
/memory/classes/metadata/mcache/inuse:bytes
- Memory that is occupied by runtime mcache structures that
- are currently being used.
+ Memory that is occupied by runtime mcache structures that are
+ currently being used.
/memory/classes/metadata/mspan/free:bytes
- Memory that is reserved for runtime mspan structures, but
- not in-use.
+ Memory that is reserved for runtime mspan structures, but not
+ in-use.
/memory/classes/metadata/mspan/inuse:bytes
Memory that is occupied by runtime mspan structures that are
currently being used.
/memory/classes/metadata/other:bytes
- Memory that is reserved for or used to hold runtime
- metadata.
+ Memory that is reserved for or used to hold runtime metadata.
/memory/classes/os-stacks:bytes
Stack memory allocated by the underlying operating system.
+ In non-cgo programs this metric is currently zero. This may
+ change in the future.In cgo programs this metric includes
+ OS thread stacks allocated directly from the OS. Currently,
+ this only accounts for one stack in c-shared and c-archive build
+ modes, and other sources of stacks from the OS are not measured.
+ This too may change in the future.
/memory/classes/other:bytes
- Memory used by execution trace buffers, structures for
- debugging the runtime, finalizer and profiler specials, and
- more.
+ Memory used by execution trace buffers, structures for debugging
+ the runtime, finalizer and profiler specials, and more.
/memory/classes/profiling/buckets:bytes
Memory that is used by the stack trace hash map used for
/memory/classes/total:bytes
All memory mapped by the Go runtime into the current process
as read-write. Note that this does not include memory mapped
- by code called via cgo or via the syscall package.
- Sum of all metrics in /memory/classes.
+ by code called via cgo or via the syscall package. Sum of all
+ metrics in /memory/classes.
+
+ /sched/gomaxprocs:threads
+ The current runtime.GOMAXPROCS setting, or the number of
+ operating system threads that can execute user-level Go code
+ simultaneously.
/sched/goroutines:goroutines
Count of live goroutines.
+
+ /sched/latencies:seconds
+ Distribution of the time goroutines have spent in the scheduler
+ in a runnable state before actually running. Bucket counts
+ increase monotonically.
+
+ /sync/mutex/wait/total:seconds
+ Approximate cumulative time goroutines have spent blocked
+ on a sync.Mutex or sync.RWMutex. This metric is useful for
+ identifying global changes in lock contention. Collect a mutex
+ or block profile using the runtime/pprof package for more
+ detailed contention data.
*/
package metrics