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
70 includes time spent with the world stopped due to the GC. This
71 metric is an overestimate, and not directly comparable to system
72 CPU time measurements. Compare only with other /cpu/classes
75 /cpu/classes/gc/mark/idle:cpu-seconds
76 Estimated total CPU time spent performing GC tasks on spare CPU
77 resources that the Go scheduler could not otherwise find a use
78 for. This should be subtracted from the total GC CPU time to
79 obtain a measure of compulsory GC CPU time. This metric is an
80 overestimate, and not directly comparable to system CPU time
81 measurements. Compare only with other /cpu/classes metrics.
83 /cpu/classes/gc/pause:cpu-seconds
84 Estimated total CPU time spent with the application paused by
85 the GC. Even if only one thread is running during the pause,
86 this is computed as GOMAXPROCS times the pause latency because
87 nothing else can be executing. This is the exact sum of samples
88 in /gc/pause:seconds if each sample is multiplied by GOMAXPROCS
89 at the time it is taken. This metric is an overestimate,
90 and not directly comparable to system CPU time measurements.
91 Compare only with other /cpu/classes metrics.
93 /cpu/classes/gc/total:cpu-seconds
94 Estimated total CPU time spent performing GC tasks. This metric
95 is an overestimate, and not directly comparable to system CPU
96 time measurements. Compare only with other /cpu/classes metrics.
97 Sum of all metrics in /cpu/classes/gc.
99 /cpu/classes/idle:cpu-seconds
100 Estimated total available CPU time not spent executing
101 any Go or Go runtime code. In other words, the part of
102 /cpu/classes/total:cpu-seconds that was unused. This metric is
103 an overestimate, and not directly comparable to system CPU time
104 measurements. Compare only with other /cpu/classes metrics.
106 /cpu/classes/scavenge/assist:cpu-seconds
107 Estimated total CPU time spent returning unused memory to the
108 underlying platform in response eagerly in response to memory
109 pressure. This metric is an overestimate, and not directly
110 comparable to system CPU time measurements. Compare only with
111 other /cpu/classes metrics.
113 /cpu/classes/scavenge/background:cpu-seconds
114 Estimated total CPU time spent performing background tasks to
115 return unused memory to the underlying platform. This metric is
116 an overestimate, and not directly comparable to system CPU time
117 measurements. Compare only with other /cpu/classes metrics.
119 /cpu/classes/scavenge/total:cpu-seconds
120 Estimated total CPU time spent performing tasks that return
121 unused memory to the underlying platform. This metric is an
122 overestimate, and not directly comparable to system CPU time
123 measurements. Compare only with other /cpu/classes metrics.
124 Sum of all metrics in /cpu/classes/scavenge.
126 /cpu/classes/total:cpu-seconds
127 Estimated total available CPU time for user Go code or the Go
128 runtime, as defined by GOMAXPROCS. In other words, GOMAXPROCS
129 integrated over the wall-clock duration this process has been
130 executing for. This metric is an overestimate, and not directly
131 comparable to system CPU time measurements. Compare only with
132 other /cpu/classes metrics. Sum of all metrics in /cpu/classes.
134 /cpu/classes/user:cpu-seconds
135 Estimated total CPU time spent running user Go code. This may
136 also include some small amount of time spent in the Go runtime.
137 This metric is an overestimate, and not directly comparable
138 to system CPU time measurements. Compare only with other
139 /cpu/classes metrics.
141 /gc/cycles/automatic:gc-cycles
142 Count of completed GC cycles generated by the Go runtime.
144 /gc/cycles/forced:gc-cycles
145 Count of completed GC cycles forced by the application.
147 /gc/cycles/total:gc-cycles
148 Count of all completed GC cycles.
150 /gc/heap/allocs-by-size:bytes
151 Distribution of heap allocations by approximate size.
152 Bucket counts increase monotonically. Note that this does not
153 include tiny objects as defined by /gc/heap/tiny/allocs:objects,
156 /gc/heap/allocs:bytes
157 Cumulative sum of memory allocated to the heap by the
160 /gc/heap/allocs:objects
161 Cumulative count of heap allocations triggered by the
162 application. Note that this does not include tiny objects as
163 defined by /gc/heap/tiny/allocs:objects, only tiny blocks.
165 /gc/heap/frees-by-size:bytes
166 Distribution of freed heap allocations by approximate size.
167 Bucket counts increase monotonically. Note that this does not
168 include tiny objects as defined by /gc/heap/tiny/allocs:objects,
172 Cumulative sum of heap memory freed by the garbage collector.
174 /gc/heap/frees:objects
175 Cumulative count of heap allocations whose storage was freed
176 by the garbage collector. Note that this does not include tiny
177 objects as defined by /gc/heap/tiny/allocs:objects, only tiny
181 Heap size target for the end of the GC cycle.
183 /gc/heap/objects:objects
184 Number of objects, live or unswept, occupying heap memory.
186 /gc/heap/tiny/allocs:objects
187 Count of small allocations that are packed together into blocks.
188 These allocations are counted separately from other allocations
189 because each individual allocation is not tracked by the
190 runtime, only their block. Each block is already accounted for
191 in allocs-by-size and frees-by-size.
193 /gc/limiter/last-enabled:gc-cycle
194 GC cycle the last time the GC CPU limiter was enabled.
195 This metric is useful for diagnosing the root cause of an
196 out-of-memory error, because the limiter trades memory for CPU
197 time when the GC's CPU time gets too high. This is most likely
198 to occur with use of SetMemoryLimit. The first GC cycle is cycle
199 1, so a value of 0 indicates that it was never enabled.
202 Distribution of individual GC-related stop-the-world pause
203 latencies. Bucket counts increase monotonically.
205 /gc/stack/starting-size:bytes
206 The stack size of new goroutines.
208 /godebug/non-default-behavior/execerrdot:events
209 The number of non-default behaviors executed by the os/exec
210 package due to a non-default GODEBUG=execerrdot=... setting.
212 /godebug/non-default-behavior/http2client:events
213 The number of non-default behaviors executed by the net/http
214 package due to a non-default GODEBUG=http2client=... setting.
216 /godebug/non-default-behavior/http2server:events
217 The number of non-default behaviors executed by the net/http
218 package due to a non-default GODEBUG=http2server=... setting.
220 /godebug/non-default-behavior/installgoroot:events
221 The number of non-default behaviors executed by the go/build
222 package due to a non-default GODEBUG=installgoroot=... setting.
224 /godebug/non-default-behavior/jstmpllitinterp:events
225 The number of non-default behaviors executed by
226 the html/template package due to a non-default
227 GODEBUG=jstmpllitinterp=... setting.
229 /godebug/non-default-behavior/multipartmaxheaders:events
230 The number of non-default behaviors executed by
231 the mime/multipart package due to a non-default
232 GODEBUG=multipartmaxheaders=... setting.
234 /godebug/non-default-behavior/multipartmaxparts:events
235 The number of non-default behaviors executed by
236 the mime/multipart package due to a non-default
237 GODEBUG=multipartmaxparts=... setting.
239 /godebug/non-default-behavior/panicnil:events
240 The number of non-default behaviors executed by the runtime
241 package due to a non-default GODEBUG=panicnil=... setting.
243 /godebug/non-default-behavior/randautoseed:events
244 The number of non-default behaviors executed by the math/rand
245 package due to a non-default GODEBUG=randautoseed=... setting.
247 /godebug/non-default-behavior/tarinsecurepath:events
248 The number of non-default behaviors executed by the archive/tar
249 package due to a non-default GODEBUG=tarinsecurepath=...
252 /godebug/non-default-behavior/x509sha1:events
253 The number of non-default behaviors executed by the crypto/x509
254 package due to a non-default GODEBUG=x509sha1=... setting.
256 /godebug/non-default-behavior/x509usefallbackroots:events
257 The number of non-default behaviors executed by the crypto/x509
258 package due to a non-default GODEBUG=x509usefallbackroots=...
261 /godebug/non-default-behavior/zipinsecurepath:events
262 The number of non-default behaviors executed by the archive/zip
263 package due to a non-default GODEBUG=zipinsecurepath=...
266 /memory/classes/heap/free:bytes
267 Memory that is completely free and eligible to be returned to
268 the underlying system, but has not been. This metric is the
269 runtime's estimate of free address space that is backed by
272 /memory/classes/heap/objects:bytes
273 Memory occupied by live objects and dead objects that have not
274 yet been marked free by the garbage collector.
276 /memory/classes/heap/released:bytes
277 Memory that is completely free and has been returned to the
278 underlying system. This metric is the runtime's estimate of free
279 address space that is still mapped into the process, but is not
280 backed by physical memory.
282 /memory/classes/heap/stacks:bytes
283 Memory allocated from the heap that is reserved for stack space,
284 whether or not it is currently in-use.
286 /memory/classes/heap/unused:bytes
287 Memory that is reserved for heap objects but is not currently
288 used to hold heap objects.
290 /memory/classes/metadata/mcache/free:bytes
291 Memory that is reserved for runtime mcache structures, but not
294 /memory/classes/metadata/mcache/inuse:bytes
295 Memory that is occupied by runtime mcache structures that are
296 currently being used.
298 /memory/classes/metadata/mspan/free:bytes
299 Memory that is reserved for runtime mspan structures, but not
302 /memory/classes/metadata/mspan/inuse:bytes
303 Memory that is occupied by runtime mspan structures that are
304 currently being used.
306 /memory/classes/metadata/other:bytes
307 Memory that is reserved for or used to hold runtime metadata.
309 /memory/classes/os-stacks:bytes
310 Stack memory allocated by the underlying operating system.
312 /memory/classes/other:bytes
313 Memory used by execution trace buffers, structures for debugging
314 the runtime, finalizer and profiler specials, and more.
316 /memory/classes/profiling/buckets:bytes
317 Memory that is used by the stack trace hash map used for
320 /memory/classes/total:bytes
321 All memory mapped by the Go runtime into the current process
322 as read-write. Note that this does not include memory mapped
323 by code called via cgo or via the syscall package. Sum of all
324 metrics in /memory/classes.
326 /sched/gomaxprocs:threads
327 The current runtime.GOMAXPROCS setting, or the number of
328 operating system threads that can execute user-level Go code
331 /sched/goroutines:goroutines
332 Count of live goroutines.
334 /sched/latencies:seconds
335 Distribution of the time goroutines have spent in the scheduler
336 in a runnable state before actually running. Bucket counts
337 increase monotonically.
339 /sync/mutex/wait/total:seconds
340 Approximate cumulative time goroutines have spent blocked
341 on a sync.Mutex or sync.RWMutex. This metric is useful for
342 identifying global changes in lock contention. Collect a mutex
343 or block profile using the runtime/pprof package for more
344 detailed contention data.