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process.go
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process.go
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// +build linux
package hcsv2
import (
"context"
"fmt"
"os/exec"
"sync"
"syscall"
"github.com/Microsoft/opengcs/internal/log"
"github.com/Microsoft/opengcs/service/gcs/gcserr"
"github.com/Microsoft/opengcs/service/gcs/runtime"
"github.com/Microsoft/opengcs/service/gcs/stdio"
oci "github.com/opencontainers/runtime-spec/specs-go"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
"go.opencensus.io/trace"
)
type Process interface {
// Kill sends `signal` to the process.
//
// If the process has already exited returns `gcserr.HrErrNotFound` by contract.
Kill(ctx context.Context, signal syscall.Signal) error
// Pid returns the process id of the process.
Pid() int
// ResizeConsole resizes the tty to `height`x`width` for the process.
ResizeConsole(ctx context.Context, height, width uint16) error
// Wait returns a channel that can be used to wait for the process to exit
// and gather the exit code. The second channel must be signaled from the
// caller when the caller has completed its use of this call to Wait.
Wait() (<-chan int, chan<- bool)
}
// Process is a struct that defines the lifetime and operations associated with
// an oci.Process.
type containerProcess struct {
// c is the owning container
c *Container
spec *oci.Process
// cid is the container id that owns this process.
cid string
process runtime.Process
pid uint32
// init is `true` if this is the container process itself
init bool
// This is only valid post the exitWg
exitCode int
// exitWg is marked as done as soon as the underlying
// (runtime.Process).Wait() call returns, and exitCode has been updated.
exitWg sync.WaitGroup
// Used to allow addtion/removal to the writersWg after an initial wait has
// already been issued. It is not safe to call Add/Done without holding this
// lock.
writersSyncRoot sync.Mutex
// Used to track the number of writers that need to finish
// before the process can be marked for cleanup.
writersWg sync.WaitGroup
// Used to track the 1st caller to the writersWg that successfully
// acknowledges it wrote the exit response.
writersCalled bool
}
// newProcess returns a containerProcess struct that has been initialized with
// an outstanding wait for process exit, and post exit an outstanding wait for
// process cleanup to release all resources once at least 1 waiter has
// successfully written the exit response.
func newProcess(c *Container, spec *oci.Process, process runtime.Process, pid uint32, init bool) *containerProcess {
p := &containerProcess{
c: c,
spec: spec,
process: process,
init: init,
cid: c.id,
pid: pid,
}
p.exitWg.Add(1)
p.writersWg.Add(1)
go func() {
ctx, span := trace.StartSpan(context.Background(), "newProcess::waitBackground")
defer span.End()
span.AddAttributes(
trace.StringAttribute("cid", p.cid),
trace.Int64Attribute("pid", int64(p.pid)))
// Wait for the process to exit
exitCode, err := p.process.Wait()
if err != nil {
log.G(ctx).WithError(err).Error("failed to wait for runc process")
}
p.exitCode = exitCode
log.G(ctx).WithField("exitCode", p.exitCode).Debug("process exited")
// Free any process waiters
p.exitWg.Done()
// Schedule the removal of this process object from the map once at
// least one waiter has read the result
go func() {
p.writersWg.Wait()
// cleanup the process state
if derr := p.process.Delete(); derr != nil {
log.G(ctx).WithFields(logrus.Fields{
"cid": p.cid,
"pid": p.pid,
}).Debugf("process cleanup error: %s", derr)
}
c.processesMutex.Lock()
_, span := trace.StartSpan(context.Background(), "newProcess::waitBackground::waitAllWaiters")
defer span.End()
span.AddAttributes(
trace.StringAttribute("cid", p.cid),
trace.Int64Attribute("pid", int64(p.pid)))
delete(c.processes, p.pid)
c.processesMutex.Unlock()
}()
}()
return p
}
// Kill sends 'signal' to the process.
//
// If the process has already exited returns `gcserr.HrErrNotFound` by contract.
func (p *containerProcess) Kill(ctx context.Context, signal syscall.Signal) error {
if err := syscall.Kill(int(p.pid), signal); err != nil {
if err == syscall.ESRCH {
return gcserr.NewHresultError(gcserr.HrErrNotFound)
}
return err
}
if p.init {
p.c.setExitType(signal)
}
return nil
}
func (p *containerProcess) Pid() int {
return int(p.pid)
}
// ResizeConsole resizes the tty to `height`x`width` for the process.
func (p *containerProcess) ResizeConsole(ctx context.Context, height, width uint16) error {
tty := p.process.Tty()
if tty == nil {
return fmt.Errorf("pid: %d, is not a tty and cannot be resized", p.pid)
}
return tty.ResizeConsole(height, width)
}
// Wait returns a channel that can be used to wait for the process to exit and
// gather the exit code. The second channel must be signaled from the caller
// when the caller has completed its use of this call to Wait.
func (p *containerProcess) Wait() (<-chan int, chan<- bool) {
ctx, span := trace.StartSpan(context.Background(), "opengcs::containerProcess::Wait")
span.AddAttributes(
trace.StringAttribute("cid", p.cid),
trace.Int64Attribute("pid", int64(p.pid)))
exitCodeChan := make(chan int, 1)
doneChan := make(chan bool)
// Increment our waiters for this waiter
p.writersSyncRoot.Lock()
p.writersWg.Add(1)
p.writersSyncRoot.Unlock()
go func() {
bgExitCodeChan := make(chan int, 1)
go func() {
p.exitWg.Wait()
bgExitCodeChan <- p.exitCode
}()
// Wait for the exit code or the caller to stop waiting.
select {
case exitCode := <-bgExitCodeChan:
exitCodeChan <- exitCode
// The caller got the exit code. Wait for them to tell us they have
// issued the write
select {
case <-doneChan:
p.writersSyncRoot.Lock()
// Decrement this waiter
log.G(ctx).Debug("wait completed, releasing wait count")
p.writersWg.Done()
if !p.writersCalled {
// We have at least 1 response for the exit code for this
// process. Decrement the release waiter that will free the
// process resources when the writersWg hits 0
log.G(ctx).Debug("first wait completed, releasing first wait count")
p.writersCalled = true
p.writersWg.Done()
}
p.writersSyncRoot.Unlock()
span.End()
}
case <-doneChan:
// In this case the caller timed out before the process exited. Just
// decrement the waiter but since no exit code we just deal with our
// waiter.
p.writersSyncRoot.Lock()
log.G(ctx).Debug("wait canceled before exit, releasing wait count")
p.writersWg.Done()
p.writersSyncRoot.Unlock()
span.End()
}
}()
return exitCodeChan, doneChan
}
func newExternalProcess(ctx context.Context, cmd *exec.Cmd, tty *stdio.TtyRelay, onRemove func(pid int)) (*externalProcess, error) {
ep := &externalProcess{
cmd: cmd,
tty: tty,
waitBlock: make(chan struct{}),
remove: onRemove,
}
if err := cmd.Start(); err != nil {
return nil, errors.Wrap(err, "failed to call Start for external process")
}
if tty != nil {
tty.Start()
}
go func() {
cmd.Wait()
ep.exitCode = cmd.ProcessState.ExitCode()
log.G(ctx).WithFields(logrus.Fields{
"pid": cmd.Process.Pid,
"exitCode": ep.exitCode,
}).Debug("external process exited")
if ep.tty != nil {
ep.tty.Wait()
}
close(ep.waitBlock)
}()
return ep, nil
}
type externalProcess struct {
cmd *exec.Cmd
tty *stdio.TtyRelay
waitBlock chan struct{}
exitCode int
removeOnce sync.Once
remove func(pid int)
}
func (ep *externalProcess) Kill(ctx context.Context, signal syscall.Signal) error {
if err := syscall.Kill(int(ep.cmd.Process.Pid), signal); err != nil {
if err == syscall.ESRCH {
return gcserr.NewHresultError(gcserr.HrErrNotFound)
}
return err
}
return nil
}
func (ep *externalProcess) Pid() int {
return ep.cmd.Process.Pid
}
func (ep *externalProcess) ResizeConsole(ctx context.Context, height, width uint16) error {
if ep.tty == nil {
return fmt.Errorf("pid: %d, is not a tty and cannot be resized", ep.cmd.Process.Pid)
}
return ep.tty.ResizeConsole(height, width)
}
func (ep *externalProcess) Wait() (<-chan int, chan<- bool) {
_, span := trace.StartSpan(context.Background(), "opengcs::externalProcess::Wait")
span.AddAttributes(trace.Int64Attribute("pid", int64(ep.cmd.Process.Pid)))
exitCodeChan := make(chan int, 1)
doneChan := make(chan bool)
go func() {
defer close(exitCodeChan)
// Wait for the exit code or the caller to stop waiting.
select {
case <-ep.waitBlock:
// Process exited send the exit code and wait for caller to close.
exitCodeChan <- ep.exitCode
<-doneChan
// At least one waiter was successful, remove this external process.
ep.removeOnce.Do(func() {
ep.remove(ep.cmd.Process.Pid)
})
case <-doneChan:
// Caller closed early, do nothing.
}
}()
return exitCodeChan, doneChan
}