| author | Alberto Bertogli
<albertito@blitiri.com.ar> 2019-10-31 01:29:05 UTC |
| committer | Alberto Bertogli
<albertito@blitiri.com.ar> 2019-10-31 02:05:55 UTC |
| .gitignore | +2 | -0 |
| LICENSE | +219 | -0 |
| README.md | +47 | -0 |
| config.toml | +32 | -0 |
| go.mod | +8 | -0 |
| go.sum | +86 | -0 |
| main.go | +174 | -0 |
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We also recommend that a + file or class name and description of purpose be included on the + same "printed page" as the copyright notice for easier + identification within third-party archives. + +Copyright [yyyy] [name of copyright owner] + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. diff --git a/README.md b/README.md new file mode 100644 index 0000000..d0520a7 --- /dev/null +++ b/README.md @@ -0,0 +1,47 @@ + +# prometheus-expvar-exporter + +[prometheus-expvar-exporter] collects [expvar] metrics from different sources, +and [exports] them for [Prometheus]. + +[prometheus-expvar-exporter]: https://blitiri.com.ar/git/r/prometheus-expvar-exporter/ +[expvar]: https://golang.org/pkg/expvar/ +[exports]: https://prometheus.io/docs/instrumenting/exporters/ +[Prometheus]: https://prometheus.io/ + + +## Install + +``` +go get blitiri.com.ar/go/prometheus-expvar-exporter +``` + + +## Configure + +The exporter is configured using a [toml](https://en.wikipedia.org/wiki/TOML) +file. + +For example: + +```toml +# Address to listen on. Prometheus should be told to scrape this. +listen_addr = ":8000" + +# Expvar target. +[server] +url = "http://localhost:2222/debug/vars" +``` + +By default, the exporter will try to auto-convert all expvars. It is only +able to auto-convert float and boolean expvars without labels. The +configuration allows for manual set up of conversion, and label support. + +See [config.toml](config.toml) for more details and an example. + + +## Run + +``` +~/go/bin/prometheus-expvar-exporter --config=config.toml +``` diff --git a/config.toml b/config.toml new file mode 100644 index 0000000..9912b10 --- /dev/null +++ b/config.toml @@ -0,0 +1,32 @@ + +# Address to listen on. Prometheus should be told to scrape this. +listen_addr = ":8080" + + +# Expvar target. +# Name is for description only. There can be multiple of these. +[myserver] + +# URL with the expvars to scrape and export. +url = "http://localhost:20099/debug/vars" + +# From here on, everything is optional. + +# List of variables to export. +# By default, the exporter will try to auto-convert all expvars. It is only +# able to auto-convert float and boolean expvars without labels. +# +# In the configuration we can manually tell the exporter how to name the +# prometheus variables, which help message to use, and support labels (single +# level). +# +# Each variable is configured the following way: +# m.<prometheus name>.expvar = "<expvar name>" +# m.<prometheus name>.help = "<prometheus help message>" +# m.<prometheus name>.label_name = "<expvar label name>" + +m.var_a.expvar = "variable-a" + +m.var_b.expvar = "variable-b" +m.var_b.help = "this is a counter of Bs, per hour of the day" +m.var_b.label_name = "hour_of_day" diff --git a/go.mod b/go.mod new file mode 100644 index 0000000..c9bf8c0 --- /dev/null +++ b/go.mod @@ -0,0 +1,8 @@ +module blitiri.com.ar/go/prometheus-expvar-exporter + +go 1.13 + +require ( + github.com/pelletier/go-toml v1.6.0 + github.com/prometheus/client_golang v1.2.1 +) diff --git a/go.sum b/go.sum new file mode 100644 index 0000000..bbb2bf0 --- /dev/null +++ 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"github.com/prometheus/client_golang/prometheus" + "github.com/prometheus/client_golang/prometheus/promhttp" +) + +var ( + configPath = flag.String("config", "config.toml", + "configuration file") +) + +func main() { + flag.Parse() + + config, err := toml.LoadFile(*configPath) + if err != nil { + log.Fatalf("error loading config file %q: %v", *configPath, err) + } + + for _, t := range config.Keys() { + if !config.Has(t + ".url") { + continue + } + + c := &Collector{ + url: config.Get(t + ".url").(string), + names: map[string]string{}, + helps: map[string]string{}, + labelName: map[string]string{}, + } + + for _, name := range config.Get(t + ".m").(*toml.Tree).Keys() { + info := config.Get(t + ".m." + name).(*toml.Tree) + expvar := info.Get("expvar").(string) + c.names[expvar] = name + if info.Has("help") { + c.helps[expvar] = info.Get("help").(string) + } + if info.Has("label_name") { + c.labelName[expvar] = info.Get("label_name").(string) + } + } + + log.Printf("Collecting %q\n", c.url) + prometheus.MustRegister(c) + } + + http.Handle("/metrics", promhttp.Handler()) + + addr := config.Get("listen_addr").(string) + log.Printf("Listening on %q", addr) + log.Fatal(http.ListenAndServe(addr, nil)) +} + +type Collector struct { + // URL to collect from. + url string + + // expvar -> prometheus name + names map[string]string + + // expvar -> prometheus help + helps map[string]string + + // expvar -> prometheus label name + labelName map[string]string +} + +func (c *Collector) Describe(ch chan<- *prometheus.Desc) { + // Not returning anything is explicitly allowed, and seems to fit our use + // case. + // From the documentation: + // Sending no descriptor at all marks the Collector as “unchecked”, i.e. + // no checks will be performed at registration time, and the Collector + // may yield any Metric it sees fit in its Collect method/ + return +} + +func (c *Collector) Collect(ch chan<- prometheus.Metric) { + resp, err := http.Get(c.url) + if err != nil { + panic(err) + } + + body, err := ioutil.ReadAll(resp.Body) + if err != nil { + panic(err) + } + + // Replace "\xNN" with "?" because the default parser doesn't handle them + // well. + re := regexp.MustCompile(`\\x..`) + body = re.ReplaceAllFunc(body, func(s []byte) []byte { + return []byte("?") + }) + + var vs map[string]interface{} + err = json.Unmarshal(body, &vs) + if err != nil { + panic(err) + } + + for k, v := range vs { + name := strings.ReplaceAll(k, "/", "_") + if n, ok := c.names[k]; ok { + name = n + } + + help := fmt.Sprintf("expvar %q", k) + if h, ok := c.helps[k]; ok { + help = h + } + + lnames := []string{} + if ln, ok := c.labelName[k]; ok { + lnames = append(lnames, ln) + } + + desc := prometheus.NewDesc(name, help, lnames, nil) + + switch v := v.(type) { + case float64: + ch <- prometheus.MustNewConstMetric(desc, prometheus.UntypedValue, v) + case bool: + ch <- prometheus.MustNewConstMetric(desc, prometheus.UntypedValue, + valToFloat(v)) + case map[string]interface{}: + // We only support explicitly written label names. + if len(lnames) != 1 { + continue + } + for lk, lv := range v { + ch <- prometheus.MustNewConstMetric(desc, prometheus.UntypedValue, + valToFloat(lv), lk) + } + case string: + // Not supported by Prometheus. + continue + case []interface{}: + // Not supported by Prometheus. + continue + default: + // TODO: support nested labels / richer structures? + fmt.Printf("XXX %q %#v\n", name, v) + continue + } + } +} + +func valToFloat(v interface{}) float64 { + switch v := v.(type) { + case float64: + return v + case bool: + if v { + return 1.0 + } + return 0.0 + } + panic(fmt.Sprintf("unexpected value type: %#v")) +}