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process.go
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process.go
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package watcher
import (
"context"
"sync"
"time"
"github.com/mickyco94/saucisson/internal/config"
"github.com/mitchellh/go-ps"
"github.com/sirupsen/logrus"
)
type State uint32
// Op
const (
Open State = iota
Close
)
type Processes func() ([]ps.Process, error)
type Process struct {
source Processes
logger logrus.FieldLogger
runningMu sync.Mutex
done chan struct{}
close chan struct{}
running bool
entries []processEntry
watching map[string]struct{}
}
type processEntry struct {
executable string
listenFor State
isRunning bool
h func()
}
func NewProcess(logger logrus.FieldLogger) *Process {
return &Process{
source: ps.Processes, //Setting this here supports mocking
logger: logger,
runningMu: sync.Mutex{},
done: make(chan struct{}),
close: make(chan struct{}),
running: false,
entries: make([]processEntry, 0),
watching: make(map[string]struct{}),
}
}
var stateStringToEnum = map[config.State]State{
config.Close: Close,
config.Open: Open,
}
func (p *Process) HandleFunc(config *config.Process, f func()) {
entry := processEntry{
executable: config.Executable,
listenFor: stateStringToEnum[config.State],
isRunning: false,
h: f,
}
p.entries = append(p.entries, entry)
p.watching[config.Executable] = struct{}{}
}
func (entry processEntry) startJob() {
go entry.h()
}
func (p *Process) processes() ([]ps.Process, error) {
backoff := 1
for {
procs, err := p.source()
if err == nil {
return procs, nil
}
if backoff > 32 {
return nil, err
}
p.logger.
WithError(err).
Debug("Retrying fetching proccesses")
time.Sleep(time.Duration(backoff * int(time.Second)))
backoff *= 2
}
}
var pollingInterval = 100 * time.Millisecond
func (p *Process) setInitialState() error {
if len(p.entries) == 0 {
//No state to set
return nil
}
processes, err := p.processes()
if err != nil {
return err
}
runningProcs := make(map[string]struct{})
for _, process := range processes {
_, watching := p.watching[process.Executable()]
//perf: Micro-optimisation to make runningProcs small as possible
if watching {
runningProcs[process.Executable()] = struct{}{}
}
}
for i, entry := range p.entries {
_, isRunning := runningProcs[entry.executable]
p.entries[i].isRunning = isRunning
}
return nil
}
func (p *Process) Run() error {
p.runningMu.Lock()
if p.running {
p.runningMu.Unlock()
return nil
}
p.running = true
p.runningMu.Unlock()
err := p.setInitialState()
if err != nil {
return err
}
return p.run()
}
func (p *Process) run() error {
for {
select {
case <-p.close:
p.done <- struct{}{}
return nil
case <-time.After(pollingInterval):
if len(p.entries) == 0 {
continue
}
processes, err := p.processes()
if err != nil {
return err
}
runningProcs := make(map[string]struct{})
for _, process := range processes {
_, watching := p.watching[process.Executable()]
//perf: Micro-optimisation to make runningProcs small as possible
if watching {
runningProcs[process.Executable()] = struct{}{}
}
}
for i, entry := range p.entries {
_, isRunning := runningProcs[entry.executable]
if isRunning && entry.listenFor == Open && !entry.isRunning {
entry.startJob()
}
if !isRunning && entry.listenFor == Close && entry.isRunning {
entry.startJob()
}
p.entries[i].isRunning = isRunning
}
}
}
}
// Stop signals to the main goroutine to halt processing and exit
// this method also waits for the main goroutine to signal that
// it has successfully closed.
// If `Process` is already stopped then this noops
func (proc *Process) Stop(ctx context.Context) error {
if !proc.running {
return nil
}
proc.close <- struct{}{}
select {
case <-ctx.Done():
return ctx.Err()
case <-proc.done:
return nil
}
}