Use contexts with SNMP. (#481)

When Prometheus times out the scrape and closes the http connection,
this will now make the snmp walk stop.

Fixes #17

Signed-off-by: Brian Brazil <[email protected]>

collector.go

@@ -14,6 +14,7 @@
 package main
 
 import (
+	"context"
 	"encoding/binary"
 	"fmt"
 	"net"
@@ -82,9 +83,10 @@ func listToOid(l []int) string {
 	return strings.Join(result, ".")
 }
 
-func ScrapeTarget(target string, config *config.Module, logger log.Logger) ([]gosnmp.SnmpPDU, error) {
+func ScrapeTarget(ctx context.Context, target string, config *config.Module, logger log.Logger) ([]gosnmp.SnmpPDU, error) {
 	// Set the options.
 	snmp := gosnmp.GoSNMP{}
+	snmp.Context = ctx
 	snmp.MaxRepetitions = config.WalkParams.MaxRepetitions
 	// User specifies timeout of each retry attempt but GoSNMP expects total timeout for all attempts.
 	snmp.Retries = config.WalkParams.Retries
@@ -195,6 +197,7 @@ func buildMetricTree(metrics []*config.Metric) *MetricNode {
 }
 
 type collector struct {
+	ctx    context.Context
 	target string
 	module *config.Module
 	logger log.Logger
@@ -208,7 +211,7 @@ func (c collector) Describe(ch chan<- *prometheus.Desc) {
 // Collect implements Prometheus.Collector.
 func (c collector) Collect(ch chan<- prometheus.Metric) {
 	start := time.Now()
-	pdus, err := ScrapeTarget(c.target, c.module, c.logger)
+	pdus, err := ScrapeTarget(c.ctx, c.target, c.module, c.logger)
 	if err != nil {
 		level.Info(c.logger).Log("msg", "Error scraping target", "err", err)
 		ch <- prometheus.NewInvalidMetric(prometheus.NewDesc("snmp_error", "Error scraping target", nil, nil), err)

go.mod

@@ -3,12 +3,11 @@ module github.com/prometheus/snmp_exporter
 require (
 	github.com/alecthomas/units v0.0.0-20190924025748-f65c72e2690d // indirect
 	github.com/go-kit/kit v0.9.0
-	github.com/golang/mock v1.3.1 // indirect
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/prometheus/client_golang v1.2.1
 	github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4
 	github.com/prometheus/common v0.7.0
-	github.com/soniah/gosnmp v1.22.0
+	github.com/soniah/gosnmp v1.23.1-0.20200214014533-6d3944030084
 	golang.org/x/sys v0.0.0-20191022100944-742c48ecaeb7 // indirect
 	gopkg.in/alecthomas/kingpin.v2 v2.2.6
 	gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127 // indirect

go.sum

@@ -31,8 +31,6 @@ github.com/go-stack/stack v1.8.0/go.mod h1:v0f6uXyyMGvRgIKkXu+yp6POWl0qKG85gN/me
 github.com/gogo/protobuf v1.1.1/go.mod h1:r8qH/GZQm5c6nD/R0oafs1akxWv10x8SbQlK7atdtwQ=
 github.com/golang/mock v1.2.0 h1:28o5sBqPkBsMGnC6b4MvE2TzSr5/AT4c/1fLqVGIwlk=
 github.com/golang/mock v1.2.0/go.mod h1:oTYuIxOrZwtPieC+H1uAHpcLFnEyAGVDL/k47Jfbm0A=
-github.com/golang/mock v1.3.1 h1:qGJ6qTW+x6xX/my+8YUVl4WNpX9B7+/l2tRsHGZ7f2s=
-github.com/golang/mock v1.3.1/go.mod h1:sBzyDLLjw3U8JLTeZvSv8jJB+tU5PVekmnlKIyFUx0Y=
 github.com/golang/protobuf v1.2.0 h1:P3YflyNX/ehuJFLhxviNdFxQPkGK5cDcApsge1SqnvM=
 github.com/golang/protobuf v1.2.0/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
 github.com/golang/protobuf v1.3.1 h1:YF8+flBXS5eO826T4nzqPrxfhQThhXl0YzfuUPu4SBg=
@@ -89,8 +87,8 @@ github.com/prometheus/procfs v0.0.5 h1:3+auTFlqw+ZaQYJARz6ArODtkaIwtvBTx3N2NehQl
 github.com/prometheus/procfs v0.0.5/go.mod h1:4A/X28fw3Fc593LaREMrKMqOKvUAntwMDaekg4FpcdQ=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
-github.com/soniah/gosnmp v1.22.0 h1:jVJi8+OGvR+JHIaZKMmnyNP0akJd2vEgNatybwhZvxg=
-github.com/soniah/gosnmp v1.22.0/go.mod h1:DuEpAS0az51+DyVBQwITDsoq4++e3LTNckp2GoasF2I=
+github.com/soniah/gosnmp v1.23.1-0.20200214014533-6d3944030084 h1:ZIBlrzG+IO20XFoyi3UlmJ6n58OEiosnALRevXkdIGM=
+github.com/soniah/gosnmp v1.23.1-0.20200214014533-6d3944030084/go.mod h1:DuEpAS0az51+DyVBQwITDsoq4++e3LTNckp2GoasF2I=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.2.2 h1:bSDNvY7ZPG5RlJ8otE/7V6gMiyenm9RtJ7IUVIAoJ1w=
@@ -102,12 +100,10 @@ github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81P
 golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/net v0.0.0-20181114220301-adae6a3d119a/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
-golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190613194153-d28f0bde5980/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
 golang.org/x/sync v0.0.0-20181108010431-42b317875d0f/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4 h1:YUO/7uOKsKeq9UokNS62b8FYywz3ker1l1vDZRCRefw=
 golang.org/x/sync v0.0.0-20181221193216-37e7f081c4d4/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.0.0-20180905080454-ebe1bf3edb33/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -116,7 +112,6 @@ golang.org/x/sys v0.0.0-20191010194322-b09406accb47/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20191022100944-742c48ecaeb7 h1:HmbHVPwrPEKPGLAcHSrMe6+hqSUlvZU0rab6x5EXfGU=
 golang.org/x/sys v0.0.0-20191022100944-742c48ecaeb7/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/tools v0.0.0-20190425150028-36563e24a262/go.mod h1:RgjU9mgBXZiqYHBnxXauZ1Gv1EHHAz9KjViQ78xBX0Q=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6 h1:jMFz6MfLP0/4fUyZle81rXUoxOBFi19VUFKVDOQfozc=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=

main.go

@@ -100,7 +100,7 @@ func handler(w http.ResponseWriter, r *http.Request, logger log.Logger) {
 
 	start := time.Now()
 	registry := prometheus.NewRegistry()
-	collector := collector{target: target, module: module, logger: logger}
+	collector := collector{ctx: r.Context(), target: target, module: module, logger: logger}
 	registry.MustRegister(collector)
 	// Delegate http serving to Prometheus client library, which will call collector.Collect.
 	h := promhttp.HandlerFor(registry, promhttp.HandlerOpts{})