syncthing/vendor/github.com/prometheus/procfs/proc.go

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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
package procfs
import (
"fmt"
"io/ioutil"
"os"
"strconv"
"strings"
)
// Proc provides information about a running process.
type Proc struct {
// The process ID.
PID int
fs FS
}
// Procs represents a list of Proc structs.
type Procs []Proc
func (p Procs) Len() int { return len(p) }
func (p Procs) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
func (p Procs) Less(i, j int) bool { return p[i].PID < p[j].PID }
// Self returns a process for the current process read via /proc/self.
func Self() (Proc, error) {
fs, err := NewFS(DefaultMountPoint)
if err != nil {
return Proc{}, err
}
return fs.Self()
}
// NewProc returns a process for the given pid under /proc.
func NewProc(pid int) (Proc, error) {
fs, err := NewFS(DefaultMountPoint)
if err != nil {
return Proc{}, err
}
return fs.NewProc(pid)
}
// AllProcs returns a list of all currently available processes under /proc.
func AllProcs() (Procs, error) {
fs, err := NewFS(DefaultMountPoint)
if err != nil {
return Procs{}, err
}
return fs.AllProcs()
}
// Self returns a process for the current process.
func (fs FS) Self() (Proc, error) {
p, err := os.Readlink(fs.Path("self"))
if err != nil {
return Proc{}, err
}
pid, err := strconv.Atoi(strings.Replace(p, string(fs), "", -1))
if err != nil {
return Proc{}, err
}
return fs.NewProc(pid)
}
// NewProc returns a process for the given pid.
func (fs FS) NewProc(pid int) (Proc, error) {
if _, err := os.Stat(fs.Path(strconv.Itoa(pid))); err != nil {
return Proc{}, err
}
return Proc{PID: pid, fs: fs}, nil
}
// AllProcs returns a list of all currently available processes.
func (fs FS) AllProcs() (Procs, error) {
d, err := os.Open(fs.Path())
if err != nil {
return Procs{}, err
}
defer d.Close()
names, err := d.Readdirnames(-1)
if err != nil {
return Procs{}, fmt.Errorf("could not read %s: %s", d.Name(), err)
}
p := Procs{}
for _, n := range names {
pid, err := strconv.ParseInt(n, 10, 64)
if err != nil {
continue
}
p = append(p, Proc{PID: int(pid), fs: fs})
}
return p, nil
}
// CmdLine returns the command line of a process.
func (p Proc) CmdLine() ([]string, error) {
f, err := os.Open(p.path("cmdline"))
if err != nil {
return nil, err
}
defer f.Close()
data, err := ioutil.ReadAll(f)
if err != nil {
return nil, err
}
if len(data) < 1 {
return []string{}, nil
}
return strings.Split(string(data[:len(data)-1]), string(byte(0))), nil
}
// Comm returns the command name of a process.
func (p Proc) Comm() (string, error) {
f, err := os.Open(p.path("comm"))
if err != nil {
return "", err
}
defer f.Close()
data, err := ioutil.ReadAll(f)
if err != nil {
return "", err
}
return strings.TrimSpace(string(data)), nil
}
// Executable returns the absolute path of the executable command of a process.
func (p Proc) Executable() (string, error) {
exe, err := os.Readlink(p.path("exe"))
if os.IsNotExist(err) {
return "", nil
}
return exe, err
}
// FileDescriptors returns the currently open file descriptors of a process.
func (p Proc) FileDescriptors() ([]uintptr, error) {
names, err := p.fileDescriptors()
if err != nil {
return nil, err
}
fds := make([]uintptr, len(names))
for i, n := range names {
fd, err := strconv.ParseInt(n, 10, 32)
if err != nil {
return nil, fmt.Errorf("could not parse fd %s: %s", n, err)
}
fds[i] = uintptr(fd)
}
return fds, nil
}
// FileDescriptorTargets returns the targets of all file descriptors of a process.
// If a file descriptor is not a symlink to a file (like a socket), that value will be the empty string.
func (p Proc) FileDescriptorTargets() ([]string, error) {
names, err := p.fileDescriptors()
if err != nil {
return nil, err
}
targets := make([]string, len(names))
for i, name := range names {
target, err := os.Readlink(p.path("fd", name))
if err == nil {
targets[i] = target
}
}
return targets, nil
}
// FileDescriptorsLen returns the number of currently open file descriptors of
// a process.
func (p Proc) FileDescriptorsLen() (int, error) {
fds, err := p.fileDescriptors()
if err != nil {
return 0, err
}
return len(fds), nil
}
// MountStats retrieves statistics and configuration for mount points in a
// process's namespace.
func (p Proc) MountStats() ([]*Mount, error) {
f, err := os.Open(p.path("mountstats"))
if err != nil {
return nil, err
}
defer f.Close()
return parseMountStats(f)
}
func (p Proc) fileDescriptors() ([]string, error) {
d, err := os.Open(p.path("fd"))
if err != nil {
return nil, err
}
defer d.Close()
names, err := d.Readdirnames(-1)
if err != nil {
return nil, fmt.Errorf("could not read %s: %s", d.Name(), err)
}
return names, nil
}
func (p Proc) path(pa ...string) string {
return p.fs.Path(append([]string{strconv.Itoa(p.PID)}, pa...)...)
}