syncthing/vendor/github.com/prometheus/procfs/proc_stat.go
Jakob Borg 916ec63af6 cmd/stdiscosrv: New discovery server (fixes #4618)
This is a new revision of the discovery server. Relevant changes and
non-changes:

- Protocol towards clients is unchanged.

- Recommended large scale design is still to be deployed nehind nginx (I
  tested, and it's still a lot faster at terminating TLS).

- Database backend is leveldb again, only. It scales enough, is easy to
  setup, and we don't need any backend to take care of.

- Server supports replication. This is a simple TCP channel - protect it
  with a firewall when deploying over the internet. (We deploy this within
  the same datacenter, and with firewall.) Any incoming client announces
  are sent over the replication channel(s) to other peer discosrvs.
  Incoming replication changes are applied to the database as if they came
  from clients, but without the TLS/certificate overhead.

- Metrics are exposed using the prometheus library, when enabled.

- The database values and replication protocol is protobuf, because JSON
  was quite CPU intensive when I tried that and benchmarked it.

- The "Retry-After" value for failed lookups gets slowly increased from
  a default of 120 seconds, by 5 seconds for each failed lookup,
  independently by each discosrv. This lowers the query load over time for
  clients that are never seen. The Retry-After maxes out at 3600 after a
  couple of weeks of this increase. The number of failed lookups is
  stored in the database, now and then (avoiding making each lookup a
  database put).

All in all this means clients can be pointed towards a cluster using
just multiple A / AAAA records to gain both load sharing and redundancy
(if one is down, clients will talk to the remaining ones).

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4648
2018-01-14 08:52:31 +00:00

176 lines
4.6 KiB
Go

package procfs
import (
"bytes"
"fmt"
"io/ioutil"
"os"
)
// Originally, this USER_HZ value was dynamically retrieved via a sysconf call
// which required cgo. However, that caused a lot of problems regarding
// cross-compilation. Alternatives such as running a binary to determine the
// value, or trying to derive it in some other way were all problematic. After
// much research it was determined that USER_HZ is actually hardcoded to 100 on
// all Go-supported platforms as of the time of this writing. This is why we
// decided to hardcode it here as well. It is not impossible that there could
// be systems with exceptions, but they should be very exotic edge cases, and
// in that case, the worst outcome will be two misreported metrics.
//
// See also the following discussions:
//
// - https://github.com/prometheus/node_exporter/issues/52
// - https://github.com/prometheus/procfs/pull/2
// - http://stackoverflow.com/questions/17410841/how-does-user-hz-solve-the-jiffy-scaling-issue
const userHZ = 100
// ProcStat provides status information about the process,
// read from /proc/[pid]/stat.
type ProcStat struct {
// The process ID.
PID int
// The filename of the executable.
Comm string
// The process state.
State string
// The PID of the parent of this process.
PPID int
// The process group ID of the process.
PGRP int
// The session ID of the process.
Session int
// The controlling terminal of the process.
TTY int
// The ID of the foreground process group of the controlling terminal of
// the process.
TPGID int
// The kernel flags word of the process.
Flags uint
// The number of minor faults the process has made which have not required
// loading a memory page from disk.
MinFlt uint
// The number of minor faults that the process's waited-for children have
// made.
CMinFlt uint
// The number of major faults the process has made which have required
// loading a memory page from disk.
MajFlt uint
// The number of major faults that the process's waited-for children have
// made.
CMajFlt uint
// Amount of time that this process has been scheduled in user mode,
// measured in clock ticks.
UTime uint
// Amount of time that this process has been scheduled in kernel mode,
// measured in clock ticks.
STime uint
// Amount of time that this process's waited-for children have been
// scheduled in user mode, measured in clock ticks.
CUTime uint
// Amount of time that this process's waited-for children have been
// scheduled in kernel mode, measured in clock ticks.
CSTime uint
// For processes running a real-time scheduling policy, this is the negated
// scheduling priority, minus one.
Priority int
// The nice value, a value in the range 19 (low priority) to -20 (high
// priority).
Nice int
// Number of threads in this process.
NumThreads int
// The time the process started after system boot, the value is expressed
// in clock ticks.
Starttime uint64
// Virtual memory size in bytes.
VSize int
// Resident set size in pages.
RSS int
fs FS
}
// NewStat returns the current status information of the process.
func (p Proc) NewStat() (ProcStat, error) {
f, err := os.Open(p.path("stat"))
if err != nil {
return ProcStat{}, err
}
defer f.Close()
data, err := ioutil.ReadAll(f)
if err != nil {
return ProcStat{}, err
}
var (
ignore int
s = ProcStat{PID: p.PID, fs: p.fs}
l = bytes.Index(data, []byte("("))
r = bytes.LastIndex(data, []byte(")"))
)
if l < 0 || r < 0 {
return ProcStat{}, fmt.Errorf(
"unexpected format, couldn't extract comm: %s",
data,
)
}
s.Comm = string(data[l+1 : r])
_, err = fmt.Fscan(
bytes.NewBuffer(data[r+2:]),
&s.State,
&s.PPID,
&s.PGRP,
&s.Session,
&s.TTY,
&s.TPGID,
&s.Flags,
&s.MinFlt,
&s.CMinFlt,
&s.MajFlt,
&s.CMajFlt,
&s.UTime,
&s.STime,
&s.CUTime,
&s.CSTime,
&s.Priority,
&s.Nice,
&s.NumThreads,
&ignore,
&s.Starttime,
&s.VSize,
&s.RSS,
)
if err != nil {
return ProcStat{}, err
}
return s, nil
}
// VirtualMemory returns the virtual memory size in bytes.
func (s ProcStat) VirtualMemory() int {
return s.VSize
}
// ResidentMemory returns the resident memory size in bytes.
func (s ProcStat) ResidentMemory() int {
return s.RSS * os.Getpagesize()
}
// StartTime returns the unix timestamp of the process in seconds.
func (s ProcStat) StartTime() (float64, error) {
stat, err := s.fs.NewStat()
if err != nil {
return 0, err
}
return float64(stat.BootTime) + (float64(s.Starttime) / userHZ), nil
}
// CPUTime returns the total CPU user and system time in seconds.
func (s ProcStat) CPUTime() float64 {
return float64(s.UTime+s.STime) / userHZ
}