1 // Copyright 2020 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // Note: run 'go generate' (which will run 'go test -generate') to update the "Supported metrics" list.
6 //go:generate go test -run=Docs -generate
9 Package metrics provides a stable interface to access implementation-defined
10 metrics exported by the Go runtime. This package is similar to existing functions
11 like [runtime.ReadMemStats] and [debug.ReadGCStats], but significantly more general.
13 The set of metrics defined by this package may evolve as the runtime itself
14 evolves, and also enables variation across Go implementations, whose relevant
15 metric sets may not intersect.
19 Metrics are designated by a string key, rather than, for example, a field name in
20 a struct. The full list of supported metrics is always available in the slice of
21 Descriptions returned by [All]. Each [Description] also includes useful information
24 Thus, users of this API are encouraged to sample supported metrics defined by the
25 slice returned by All to remain compatible across Go versions. Of course, situations
26 arise where reading specific metrics is critical. For these cases, users are
27 encouraged to use build tags, and although metrics may be deprecated and removed,
28 users should consider this to be an exceptional and rare event, coinciding with a
29 very large change in a particular Go implementation.
31 Each metric key also has a "kind" that describes the format of the metric's value.
32 In the interest of not breaking users of this package, the "kind" for a given metric
33 is guaranteed not to change. If it must change, then a new metric will be introduced
34 with a new key and a new "kind."
38 As mentioned earlier, metric keys are strings. Their format is simple and well-defined,
39 designed to be both human and machine readable. It is split into two components,
40 separated by a colon: a rooted path and a unit. The choice to include the unit in
41 the key is motivated by compatibility: if a metric's unit changes, its semantics likely
42 did also, and a new key should be introduced.
44 For more details on the precise definition of the metric key's path and unit formats, see
45 the documentation of the Name field of the Description struct.
49 This package supports metrics whose values have a floating-point representation. In
50 order to improve ease-of-use, this package promises to never produce the following
51 classes of floating-point values: NaN, infinity.
55 Below is the full list of supported metrics, ordered lexicographically.
57 /cgo/go-to-c-calls:calls
58 Count of calls made from Go to C by the current process.
60 /cpu/classes/gc/mark/assist:cpu-seconds
61 Estimated total CPU time goroutines spent performing GC
62 tasks to assist the GC and prevent it from falling behind the
63 application. This metric is an overestimate, and not directly
64 comparable to system CPU time measurements. Compare only with
65 other /cpu/classes metrics.
67 /cpu/classes/gc/mark/dedicated:cpu-seconds
68 Estimated total CPU time spent performing GC tasks on processors
69 (as defined by GOMAXPROCS) dedicated to those tasks. This metric
70 is an overestimate, and not directly comparable to system CPU
71 time measurements. Compare only with other /cpu/classes metrics.
73 /cpu/classes/gc/mark/idle:cpu-seconds
74 Estimated total CPU time spent performing GC tasks on spare CPU
75 resources that the Go scheduler could not otherwise find a use
76 for. This should be subtracted from the total GC CPU time to
77 obtain a measure of compulsory GC CPU time. This metric is an
78 overestimate, and not directly comparable to system CPU time
79 measurements. Compare only with other /cpu/classes metrics.
81 /cpu/classes/gc/pause:cpu-seconds
82 Estimated total CPU time spent with the application paused by
83 the GC. Even if only one thread is running during the pause,
84 this is computed as GOMAXPROCS times the pause latency because
85 nothing else can be executing. This is the exact sum of samples
86 in /gc/pause:seconds if each sample is multiplied by GOMAXPROCS
87 at the time it is taken. This metric is an overestimate,
88 and not directly comparable to system CPU time measurements.
89 Compare only with other /cpu/classes metrics.
91 /cpu/classes/gc/total:cpu-seconds
92 Estimated total CPU time spent performing GC tasks. This metric
93 is an overestimate, and not directly comparable to system CPU
94 time measurements. Compare only with other /cpu/classes metrics.
95 Sum of all metrics in /cpu/classes/gc.
97 /cpu/classes/idle:cpu-seconds
98 Estimated total available CPU time not spent executing
99 any Go or Go runtime code. In other words, the part of
100 /cpu/classes/total:cpu-seconds that was unused. This metric is
101 an overestimate, and not directly comparable to system CPU time
102 measurements. Compare only with other /cpu/classes metrics.
104 /cpu/classes/scavenge/assist:cpu-seconds
105 Estimated total CPU time spent returning unused memory to the
106 underlying platform in response eagerly in response to memory
107 pressure. This metric is an overestimate, and not directly
108 comparable to system CPU time measurements. Compare only with
109 other /cpu/classes metrics.
111 /cpu/classes/scavenge/background:cpu-seconds
112 Estimated total CPU time spent performing background tasks to
113 return unused memory to the underlying platform. This metric is
114 an overestimate, and not directly comparable to system CPU time
115 measurements. Compare only with other /cpu/classes metrics.
117 /cpu/classes/scavenge/total:cpu-seconds
118 Estimated total CPU time spent performing tasks that return
119 unused memory to the underlying platform. This metric is an
120 overestimate, and not directly comparable to system CPU time
121 measurements. Compare only with other /cpu/classes metrics.
122 Sum of all metrics in /cpu/classes/scavenge.
124 /cpu/classes/total:cpu-seconds
125 Estimated total available CPU time for user Go code or the Go
126 runtime, as defined by GOMAXPROCS. In other words, GOMAXPROCS
127 integrated over the wall-clock duration this process has been
128 executing for. This metric is an overestimate, and not directly
129 comparable to system CPU time measurements. Compare only with
130 other /cpu/classes metrics. Sum of all metrics in /cpu/classes.
132 /cpu/classes/user:cpu-seconds
133 Estimated total CPU time spent running user Go code. This may
134 also include some small amount of time spent in the Go runtime.
135 This metric is an overestimate, and not directly comparable
136 to system CPU time measurements. Compare only with other
137 /cpu/classes metrics.
139 /gc/cycles/automatic:gc-cycles
140 Count of completed GC cycles generated by the Go runtime.
142 /gc/cycles/forced:gc-cycles
143 Count of completed GC cycles forced by the application.
145 /gc/cycles/total:gc-cycles
146 Count of all completed GC cycles.
149 Heap size target percentage configured by the user, otherwise
150 100. This value is set by the GOGC environment variable, and the
151 runtime/debug.SetGCPercent function.
154 Go runtime memory limit configured by the user, otherwise
155 math.MaxInt64. This value is set by the GOMEMLIMIT environment
156 variable, and the runtime/debug.SetMemoryLimit function.
158 /gc/heap/allocs-by-size:bytes
159 Distribution of heap allocations by approximate size.
160 Bucket counts increase monotonically. Note that this does not
161 include tiny objects as defined by /gc/heap/tiny/allocs:objects,
164 /gc/heap/allocs:bytes
165 Cumulative sum of memory allocated to the heap by the
168 /gc/heap/allocs:objects
169 Cumulative count of heap allocations triggered by the
170 application. Note that this does not include tiny objects as
171 defined by /gc/heap/tiny/allocs:objects, only tiny blocks.
173 /gc/heap/frees-by-size:bytes
174 Distribution of freed heap allocations by approximate size.
175 Bucket counts increase monotonically. Note that this does not
176 include tiny objects as defined by /gc/heap/tiny/allocs:objects,
180 Cumulative sum of heap memory freed by the garbage collector.
182 /gc/heap/frees:objects
183 Cumulative count of heap allocations whose storage was freed
184 by the garbage collector. Note that this does not include tiny
185 objects as defined by /gc/heap/tiny/allocs:objects, only tiny
189 Heap size target for the end of the GC cycle.
192 Heap memory occupied by live objects that were marked by the
195 /gc/heap/objects:objects
196 Number of objects, live or unswept, occupying heap memory.
198 /gc/heap/tiny/allocs:objects
199 Count of small allocations that are packed together into blocks.
200 These allocations are counted separately from other allocations
201 because each individual allocation is not tracked by the
202 runtime, only their block. Each block is already accounted for
203 in allocs-by-size and frees-by-size.
205 /gc/limiter/last-enabled:gc-cycle
206 GC cycle the last time the GC CPU limiter was enabled.
207 This metric is useful for diagnosing the root cause of an
208 out-of-memory error, because the limiter trades memory for CPU
209 time when the GC's CPU time gets too high. This is most likely
210 to occur with use of SetMemoryLimit. The first GC cycle is cycle
211 1, so a value of 0 indicates that it was never enabled.
214 Distribution of individual GC-related stop-the-world pause
215 latencies. Bucket counts increase monotonically.
217 /gc/scan/globals:bytes
218 The total amount of global variable space that is scannable.
221 The total amount of heap space that is scannable.
224 The number of bytes of stack that were scanned last GC cycle.
227 The total amount space that is scannable. Sum of all metrics in
230 /gc/stack/starting-size:bytes
231 The stack size of new goroutines.
233 /godebug/non-default-behavior/execerrdot:events
234 The number of non-default behaviors executed by the os/exec
235 package due to a non-default GODEBUG=execerrdot=... setting.
237 /godebug/non-default-behavior/gocachehash:events
238 The number of non-default behaviors executed by the cmd/go
239 package due to a non-default GODEBUG=gocachehash=... setting.
241 /godebug/non-default-behavior/gocachetest:events
242 The number of non-default behaviors executed by the cmd/go
243 package due to a non-default GODEBUG=gocachetest=... setting.
245 /godebug/non-default-behavior/gocacheverify:events
246 The number of non-default behaviors executed by the cmd/go
247 package due to a non-default GODEBUG=gocacheverify=... setting.
249 /godebug/non-default-behavior/gotypesalias:events
250 The number of non-default behaviors executed by the go/types
251 package due to a non-default GODEBUG=gotypesalias=... setting.
253 /godebug/non-default-behavior/http2client:events
254 The number of non-default behaviors executed by the net/http
255 package due to a non-default GODEBUG=http2client=... setting.
257 /godebug/non-default-behavior/http2server:events
258 The number of non-default behaviors executed by the net/http
259 package due to a non-default GODEBUG=http2server=... setting.
261 /godebug/non-default-behavior/httplaxcontentlength:events
262 The number of non-default behaviors executed by the net/http
263 package due to a non-default GODEBUG=httplaxcontentlength=...
266 /godebug/non-default-behavior/httpmuxgo121:events
267 The number of non-default behaviors executed by the net/http
268 package due to a non-default GODEBUG=httpmuxgo121=... setting.
270 /godebug/non-default-behavior/installgoroot:events
271 The number of non-default behaviors executed by the go/build
272 package due to a non-default GODEBUG=installgoroot=... setting.
274 /godebug/non-default-behavior/jstmpllitinterp:events
275 The number of non-default behaviors executed by
276 the html/template package due to a non-default
277 GODEBUG=jstmpllitinterp=... setting.
279 /godebug/non-default-behavior/multipartmaxheaders:events
280 The number of non-default behaviors executed by
281 the mime/multipart package due to a non-default
282 GODEBUG=multipartmaxheaders=... setting.
284 /godebug/non-default-behavior/multipartmaxparts:events
285 The number of non-default behaviors executed by
286 the mime/multipart package due to a non-default
287 GODEBUG=multipartmaxparts=... setting.
289 /godebug/non-default-behavior/multipathtcp:events
290 The number of non-default behaviors executed by the net package
291 due to a non-default GODEBUG=multipathtcp=... setting.
293 /godebug/non-default-behavior/panicnil:events
294 The number of non-default behaviors executed by the runtime
295 package due to a non-default GODEBUG=panicnil=... setting.
297 /godebug/non-default-behavior/randautoseed:events
298 The number of non-default behaviors executed by the math/rand
299 package due to a non-default GODEBUG=randautoseed=... setting.
301 /godebug/non-default-behavior/tarinsecurepath:events
302 The number of non-default behaviors executed by the archive/tar
303 package due to a non-default GODEBUG=tarinsecurepath=...
306 /godebug/non-default-behavior/tls10server:events
307 The number of non-default behaviors executed by the crypto/tls
308 package due to a non-default GODEBUG=tls10server=... setting.
310 /godebug/non-default-behavior/tlsmaxrsasize:events
311 The number of non-default behaviors executed by the crypto/tls
312 package due to a non-default GODEBUG=tlsmaxrsasize=... setting.
314 /godebug/non-default-behavior/x509sha1:events
315 The number of non-default behaviors executed by the crypto/x509
316 package due to a non-default GODEBUG=x509sha1=... setting.
318 /godebug/non-default-behavior/x509usefallbackroots:events
319 The number of non-default behaviors executed by the crypto/x509
320 package due to a non-default GODEBUG=x509usefallbackroots=...
323 /godebug/non-default-behavior/zipinsecurepath:events
324 The number of non-default behaviors executed by the archive/zip
325 package due to a non-default GODEBUG=zipinsecurepath=...
328 /memory/classes/heap/free:bytes
329 Memory that is completely free and eligible to be returned to
330 the underlying system, but has not been. This metric is the
331 runtime's estimate of free address space that is backed by
334 /memory/classes/heap/objects:bytes
335 Memory occupied by live objects and dead objects that have not
336 yet been marked free by the garbage collector.
338 /memory/classes/heap/released:bytes
339 Memory that is completely free and has been returned to the
340 underlying system. This metric is the runtime's estimate of free
341 address space that is still mapped into the process, but is not
342 backed by physical memory.
344 /memory/classes/heap/stacks:bytes
345 Memory allocated from the heap that is reserved for stack space,
346 whether or not it is currently in-use. Currently, this
347 represents all stack memory for goroutines. It also includes all
348 OS thread stacks in non-cgo programs. Note that stacks may be
349 allocated differently in the future, and this may change.
351 /memory/classes/heap/unused:bytes
352 Memory that is reserved for heap objects but is not currently
353 used to hold heap objects.
355 /memory/classes/metadata/mcache/free:bytes
356 Memory that is reserved for runtime mcache structures, but not
359 /memory/classes/metadata/mcache/inuse:bytes
360 Memory that is occupied by runtime mcache structures that are
361 currently being used.
363 /memory/classes/metadata/mspan/free:bytes
364 Memory that is reserved for runtime mspan structures, but not
367 /memory/classes/metadata/mspan/inuse:bytes
368 Memory that is occupied by runtime mspan structures that are
369 currently being used.
371 /memory/classes/metadata/other:bytes
372 Memory that is reserved for or used to hold runtime metadata.
374 /memory/classes/os-stacks:bytes
375 Stack memory allocated by the underlying operating system.
376 In non-cgo programs this metric is currently zero. This may
377 change in the future.In cgo programs this metric includes
378 OS thread stacks allocated directly from the OS. Currently,
379 this only accounts for one stack in c-shared and c-archive build
380 modes, and other sources of stacks from the OS are not measured.
381 This too may change in the future.
383 /memory/classes/other:bytes
384 Memory used by execution trace buffers, structures for debugging
385 the runtime, finalizer and profiler specials, and more.
387 /memory/classes/profiling/buckets:bytes
388 Memory that is used by the stack trace hash map used for
391 /memory/classes/total:bytes
392 All memory mapped by the Go runtime into the current process
393 as read-write. Note that this does not include memory mapped
394 by code called via cgo or via the syscall package. Sum of all
395 metrics in /memory/classes.
397 /sched/gomaxprocs:threads
398 The current runtime.GOMAXPROCS setting, or the number of
399 operating system threads that can execute user-level Go code
402 /sched/goroutines:goroutines
403 Count of live goroutines.
405 /sched/latencies:seconds
406 Distribution of the time goroutines have spent in the scheduler
407 in a runnable state before actually running. Bucket counts
408 increase monotonically.
410 /sync/mutex/wait/total:seconds
411 Approximate cumulative time goroutines have spent blocked
412 on a sync.Mutex or sync.RWMutex. This metric is useful for
413 identifying global changes in lock contention. Collect a mutex
414 or block profile using the runtime/pprof package for more
415 detailed contention data.