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Default GOMAXPROCS to 1 (#2530)

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Avoid running on all CPUs by limiting the Go runtime to one CPU by
default. Avoids having Go routines schedule on every CPU, driving up the
visible run queue length on high CPU count systems.

This also helps workaround a kernel deadlock issue with reading from
sysfs concurrently.

See:
* https://github.com/prometheus/node_exporter/issues/1880
* https://github.com/prometheus/node_exporter/issues/2500

Signed-off-by: Ben Kochie <superq@gmail.com>
This commit is contained in:
Ben Kochie 2022-11-29 03:01:58 -08:00 committed by GitHub
parent 13a5cc1f74
commit fb26b9fc72
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2 changed files with 13 additions and 0 deletions
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7
CHANGELOG.md
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@ -5,6 +5,13 @@
* [ENHANCEMENT] * [ENHANCEMENT]
* [BUGFIX] * [BUGFIX]
NOTE: This changes the Go runtime "GOMAXPROCS" to 1. This is done to limit the
concurrency of the exporter to 1 CPU thread at a time in order to avoid a
race condition problem in the Linux kernel (#2500) and parallel IO issues
on nodes with high numbers of CPUs/CPU threads (#1880).
* [CHANGE] Default GOMAXPROCS to 1
## 1.4.0 / 2022-09-24 ## 1.4.0 / 2022-09-24
* [CHANGE] Merge metrics descriptions in textfile collector #2475 * [CHANGE] Merge metrics descriptions in textfile collector #2475

6
node_exporter.go
View file

@ -20,6 +20,7 @@ import (
_ "net/http/pprof" _ "net/http/pprof"
"os" "os"
"os/user" "os/user"
"runtime"
"sort" "sort"
"github.com/prometheus/common/promlog" "github.com/prometheus/common/promlog"
@ -159,6 +160,9 @@ func main() {
"collector.disable-defaults", "collector.disable-defaults",
"Set all collectors to disabled by default.", "Set all collectors to disabled by default.",
).Default("false").Bool() ).Default("false").Bool()
maxProcs = kingpin.Flag(
"runtime.gomaxprocs", "The target number of CPUs Go will run on (GOMAXPROCS)",
).Envar("GOMAXPROCS").Default("1").Int()
toolkitFlags = kingpinflag.AddFlags(kingpin.CommandLine, ":9100") toolkitFlags = kingpinflag.AddFlags(kingpin.CommandLine, ":9100")
) )
@ -178,6 +182,8 @@ func main() {
if user, err := user.Current(); err == nil && user.Uid == "0" { if user, err := user.Current(); err == nil && user.Uid == "0" {
level.Warn(logger).Log("msg", "Node Exporter is running as root user. This exporter is designed to run as unprivileged user, root is not required.") level.Warn(logger).Log("msg", "Node Exporter is running as root user. This exporter is designed to run as unprivileged user, root is not required.")
} }
runtime.GOMAXPROCS(*maxProcs)
level.Debug(logger).Log("msg", "Go MAXPROCS", "procs", *maxProcs)
http.Handle(*metricsPath, newHandler(!*disableExporterMetrics, *maxRequests, logger)) http.Handle(*metricsPath, newHandler(!*disableExporterMetrics, *maxRequests, logger))
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) { http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {