Export cache stats as Prometheus metrics (#75)

* Merge commits from github.com/udhos/groupcache-exporter

* Set Golang 1.22 and remove non-Mailgun groupcache references.

* Add golangci-lint GHA.

* Remove abstraction layer for multiple groupcache implementations.

* Update README.md.

* Remove unnecessary stuff.

* Update linter config.

* Tests for exporter.

* Tidy code.

* Update README.md.

* Metric `groupcache_get_from_peers_latency_slowest` returns seconds instead of ms.

* Update README.md.

* Revise metric docs.

* Restructure module as a package to be merged into the groupcache module.

* Set Golang to 1.22 and update go.mod.

* Tidy code.

* Update GHA test Golang targets.

* Simplify example in README.

* Support groups created after calling `GetMetrics()`.

* Change `NewExporter()` to option variadic arguments.

* Tests.

* Revise WithGroups() to use interface instead of callback.

* Revise README.md.

---------

Co-authored-by: Oleg Ozimok <ozimokoleg@gmail.com>
Co-authored-by: Danny Kopping <danny.kopping@grafana.com>
Co-authored-by: udhos <udhos>

Author: 3 people

.github/workflows/on-pull-request.yaml

@@ -2,37 +2,33 @@ name: CI
 
 on:
   push:
-    branches:
-      - master
-      - main
+    branches: [ master, main ]
   pull_request:
-    branches:
-      - master
-      - main
+    branches: [ master, main ]
 
 jobs:
   on-pull-request:
     name: test
     strategy:
       matrix:
         go-version:
-          - 1.18.x
-          - 1.19.x
+          - 1.22.x
+          - 1.23.x
         os: [ ubuntu-latest ]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Checkout
-        uses: actions/checkout@master
+        uses: actions/checkout@v4
 
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@v5
         with:
           go-version: ${{ matrix.go-version }}
 
       - run: go env
 
       - name: Cache deps
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: ~/go/pkg/mod
           key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
@@ -43,4 +39,4 @@ jobs:
         run: go mod download
 
       - name: Test
-        run: go test ./...
+        run: go test ./...

example_test.go

@@ -9,7 +9,7 @@ import (
 	"github.com/mailgun/groupcache/v2"
 )
 
-func ExampleUsage() {
+func ExampleGroup() {
 	/*
 		// Keep track of peers in our cluster and add our instance to the pool `http://localhost:8080`
 		pool := groupcache.NewHTTPPoolOpts("http://localhost:8080", &groupcache.HTTPPoolOptions{})

go.mod

@@ -1,19 +1,29 @@
 module github.com/mailgun/groupcache/v2
 
-go 1.19
+go 1.22
 
 require (
-	github.com/golang/protobuf v1.5.2
+	github.com/golang/protobuf v1.5.4
+	github.com/mailgun/holster/v4 v4.20.3
+	github.com/prometheus/client_golang v1.20.5
+	github.com/prometheus/client_model v0.6.1
+	github.com/prometheus/common v0.61.0
 	github.com/segmentio/fasthash v1.0.3
-	github.com/sirupsen/logrus v1.9.0
-	github.com/stretchr/testify v1.8.1
+	github.com/sirupsen/logrus v1.9.2
+	github.com/stretchr/testify v1.10.0
 )
 
 require (
+	github.com/beorn7/perks v1.0.1 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/klauspost/compress v1.17.9 // indirect
+	github.com/kr/text v0.2.0 // indirect
+	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	golang.org/x/sys v0.0.0-20220919091848-fb04ddd9f9c8 // indirect
-	golang.org/x/xerrors v0.0.0-20220609144429-65e65417b02f // indirect
-	google.golang.org/protobuf v1.28.1 // indirect
+	github.com/prometheus/procfs v0.15.1 // indirect
+	golang.org/x/sys v0.28.0 // indirect
+	google.golang.org/protobuf v1.35.2 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -1,37 +1,59 @@
+github.com/ahmetb/go-linq v3.0.0+incompatible h1:qQkjjOXKrKOTy83X8OpRmnKflXKQIL/mC/gMVVDMhOA=
+github.com/ahmetb/go-linq v3.0.0+incompatible/go.mod h1:PFffvbdbtw+QTB0WKRP0cNht7vnCfnGlEpak/DVg5cY=
+github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
+github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
+github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
+github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
-github.com/golang/protobuf v1.5.2 h1:ROPKBNFfQgOUMifHyP+KYbvpjbdoFNs+aK7DXlji0Tw=
-github.com/golang/protobuf v1.5.2/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
-github.com/google/go-cmp v0.5.5 h1:Khx7svrCpmxxtHBq5j2mp/xVjsi8hQMfNLvJFAlrGgU=
-github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/golang/protobuf v1.5.4 h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=
+github.com/golang/protobuf v1.5.4/go.mod h1:lnTiLA8Wa4RWRcIUkrtSVa5nRhsEGBg48fD6rSs7xps=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/klauspost/compress v1.17.9 h1:6KIumPrER1LHsvBVuDa0r5xaG0Es51mhhB9BQB2qeMA=
+github.com/klauspost/compress v1.17.9/go.mod h1:Di0epgTjJY877eYKx5yC51cX2A2Vl2ibi7bDH9ttBbw=
+github.com/kr/pretty v0.3.1 h1:flRD4NNwYAUpkphVc1HcthR4KEIFJ65n8Mw5qdRn3LE=
+github.com/kr/pretty v0.3.1/go.mod h1:hoEshYVHaxMs3cyo3Yncou5ZscifuDolrwPKZanG3xk=
+github.com/kr/text v0.2.0 h1:5Nx0Ya0ZqY2ygV366QzturHI13Jq95ApcVaJBhpS+AY=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
+github.com/kylelemons/godebug v1.1.0 h1:RPNrshWIDI6G2gRW9EHilWtl7Z6Sb1BR0xunSBf0SNc=
+github.com/kylelemons/godebug v1.1.0/go.mod h1:9/0rRGxNHcop5bhtWyNeEfOS8JIWk580+fNqagV/RAw=
+github.com/mailgun/holster/v4 v4.20.3 h1:FwHxBvuoWEqEpZGeNCLuk/oAHyNs3+ksGoCW0qbiHyo=
+github.com/mailgun/holster/v4 v4.20.3/go.mod h1:HuFVoS8qOhceEBL4czXnVzp0bQrrIkLeX30IAll5hQ0=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 h1:C3w9PqII01/Oq1c1nUAm88MOHcQC9l5mIlSMApZMrHA=
+github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822/go.mod h1:+n7T8mK8HuQTcFwEeznm/DIxMOiR9yIdICNftLE1DvQ=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/prometheus/client_golang v1.20.5 h1:cxppBPuYhUnsO6yo/aoRol4L7q7UFfdm+bR9r+8l63Y=
+github.com/prometheus/client_golang v1.20.5/go.mod h1:PIEt8X02hGcP8JWbeHyeZ53Y/jReSnHgO035n//V5WE=
+github.com/prometheus/client_model v0.6.1 h1:ZKSh/rekM+n3CeS952MLRAdFwIKqeY8b62p8ais2e9E=
+github.com/prometheus/client_model v0.6.1/go.mod h1:OrxVMOVHjw3lKMa8+x6HeMGkHMQyHDk9E3jmP2AmGiY=
+github.com/prometheus/common v0.61.0 h1:3gv/GThfX0cV2lpO7gkTUwZru38mxevy90Bj8YFSRQQ=
+github.com/prometheus/common v0.61.0/go.mod h1:zr29OCN/2BsJRaFwG8QOBr41D6kkchKbpeNH7pAjb/s=
+github.com/prometheus/procfs v0.15.1 h1:YagwOFzUgYfKKHX6Dr+sHT7km/hxC76UB0learggepc=
+github.com/prometheus/procfs v0.15.1/go.mod h1:fB45yRUv8NstnjriLhBQLuOUt+WW4BsoGhij/e3PBqk=
+github.com/rogpeppe/go-internal v1.10.0 h1:TMyTOH3F/DB16zRVcYyreMH6GnZZrwQVAoYjRBZyWFQ=
+github.com/rogpeppe/go-internal v1.10.0/go.mod h1:UQnix2H7Ngw/k4C5ijL5+65zddjncjaFoBhdsK/akog=
 github.com/segmentio/fasthash v1.0.3 h1:EI9+KE1EwvMLBWwjpRDc+fEM+prwxDYbslddQGtrmhM=
 github.com/segmentio/fasthash v1.0.3/go.mod h1:waKX8l2N8yckOgmSsXJi7x1ZfdKZ4x7KRMzBtS3oedY=
-github.com/sirupsen/logrus v1.9.0 h1:trlNQbNUG3OdDrDil03MCb1H2o9nJ1x4/5LYw7byDE0=
-github.com/sirupsen/logrus v1.9.0/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
+github.com/sirupsen/logrus v1.9.2 h1:oxx1eChJGI6Uks2ZC4W1zpLlVgqB8ner4EuQwV4Ik1Y=
+github.com/sirupsen/logrus v1.9.2/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
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 golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.0.0-20220919091848-fb04ddd9f9c8 h1:h+EGohizhe9XlX18rfpa8k8RAc5XyaeamM+0VHRd4lc=
-golang.org/x/sys v0.0.0-20220919091848-fb04ddd9f9c8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20220609144429-65e65417b02f h1:uF6paiQQebLeSXkrTqHqz0MXhXXS1KgF41eUdBNvxK0=
-golang.org/x/xerrors v0.0.0-20220609144429-65e65417b02f/go.mod h1:K8+ghG5WaK9qNqU5K3HdILfMLy1f3aNYFI/wnl100a8=
-google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
-google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
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-google.golang.org/protobuf v1.28.1/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=
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+golang.org/x/sys v0.28.0 h1:Fksou7UEQUWlKvIdsqzJmUmCX3cZuD2+P3XyyzwMhlA=
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 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
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+gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c/go.mod h1:JHkPIbrfpd72SG/EVd6muEfDQjcINNoR0C8j2r3qZ4Q=
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 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

groupcache.go

@@ -76,7 +76,7 @@ var (
 	initPeerServer     func()
 )
 
-// GetGroup returns the named group previously created with NewGroup, or
+// GetGroup returns the named group previously created with NewGroup or
 // nil if there's no such group.
 func GetGroup(name string) *Group {
 	mu.RLock()
@@ -85,6 +85,18 @@ func GetGroup(name string) *Group {
 	return g
 }
 
+// GetGroups returns all groups previously created with NewGroup or nil if no
+// groups.
+func GetGroups() []*Group {
+	list := make([]*Group, 0, len(groups))
+	mu.RLock()
+	for _, group := range groups {
+		list = append(list, group)
+	}
+	mu.RUnlock()
+	return list
+}
+
 // NewGroup creates a coordinated group-aware Getter from a Getter.
 //
 // The returned Getter tries (but does not guarantee) to run only one

promexporter/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2022 Grafana Labs
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

promexporter/README.md

@@ -0,0 +1,47 @@
+# Prometheus Groupcache Exporter
+
+This exporter extracts statistics from group instances and exports as Prometheus metrics.
+
+## Example
+
+```go
+import (
+	"github.com/mailgun/groupcache/v2"
+	"github.com/mailgun/groupcache/v2/promexporter"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+// ...
+
+collector := promexporter.NewExporter()
+prometheus.MustRegister(collector)
+
+// Collector will discover newly created group.
+group := groupcache.NewGroup("mygroup", cacheSize, getter)
+```
+
+## Metrics
+
+### Exported from groupcache's `CacheStats()`
+- `groupcache_cache_bytes{group,type="main|hot"}`: Gauge of current bytes in use
+- `groupcache_cache_evictions_nonexpired_total{group,type="main|hot"}`: Count of cache evictions for non-expired keys due to memory full
+- `groupcache_cache_evictions_total{group,type="main|hot"}`: Count of cache evictions
+- `groupcache_cache_gets_total{group,type="main|hot"}`: Count of cache gets
+- `groupcache_cache_hits_total{group,type="main|hot"}`: Count of cache hits
+- `groupcache_cache_items{group,type="main|hot"}`: Gauge of current items in use
+
+### Exported from groupcache's `Stats()`
+- `groupcache_get_from_peers_latency_lower{group}`: Represent slowest duration to request value from peers
+- `groupcache_gets_total{group}`: Count of cache gets (including from peers, from either main or hot caches)
+- `groupcache_hits_total{group}`: Count of cache hits (from either main or hot caches)
+- `groupcache_loads_deduped_total{group}`: Count of loads after singleflight
+- `groupcache_loads_total{group}`: Count of (gets - hits)
+- `groupcache_local_load_errs_total{group}`: Count of load errors from local cache
+- `groupcache_local_loads_total{group}`: Count of loads from local cache
+- `groupcache_peer_errors_total{group}`: Count of errors from peers
+- `groupcache_peer_loads_total{group}`: Count of loads or cache hits from peers
+- `groupcache_server_requests_total{group}`: Count of gets received from peers
+
+## Attribution
+
+This package source originated from https://github.com/udhos/groupcache_exporter.  See LICENSE for MIT license details impacting the contents of this package directory in addition to the LICENSE at the root of this repo for co-existing Apache license details.