Make Requests Processes and create process hierarchy. Associate OpenRepository with context. (#17125)

This PR registers requests with the process manager and manages hierarchy within the processes.

Git repos are then associated with a context, (usually the request's context) - with sub commands using this context as their base context.

Signed-off-by: Andrew Thornton <art27@cantab.net>

4 files changed, 319 insertions, 63 deletions

diff --git a/modules/process/context.go b/modules/process/context.go
new file mode 100644
index 0000000000..6df5bc1513
--- /dev/null
+++ b/modules/process/context.go
@@ -0,0 +1,69 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package process
+
+import (
+	"context"
+)
+
+// Context is a wrapper around context.Context and contains the current pid for this context
+type Context struct {
+	context.Context
+	pid IDType
+}
+
+// GetPID returns the PID for this context
+func (c *Context) GetPID() IDType {
+	return c.pid
+}
+
+// GetParent returns the parent process context (if any)
+func (c *Context) GetParent() *Context {
+	return GetContext(c.Context)
+}
+
+// Value is part of the interface for context.Context. We mostly defer to the internal context - but we return this in response to the ProcessContextKey
+func (c *Context) Value(key interface{}) interface{} {
+	if key == ProcessContextKey {
+		return c
+	}
+	return c.Context.Value(key)
+}
+
+// ProcessContextKey is the key under which process contexts are stored
+var ProcessContextKey interface{} = "process-context"
+
+// GetContext will return a process context if one exists
+func GetContext(ctx context.Context) *Context {
+	if pCtx, ok := ctx.(*Context); ok {
+		return pCtx
+	}
+	pCtxInterface := ctx.Value(ProcessContextKey)
+	if pCtxInterface == nil {
+		return nil
+	}
+	if pCtx, ok := pCtxInterface.(*Context); ok {
+		return pCtx
+	}
+	return nil
+}
+
+// GetPID returns the PID for this context
+func GetPID(ctx context.Context) IDType {
+	pCtx := GetContext(ctx)
+	if pCtx == nil {
+		return ""
+	}
+	return pCtx.GetPID()
+}
+
+// GetParentPID returns the ParentPID for this context
+func GetParentPID(ctx context.Context) IDType {
+	var parentPID IDType
+	if parentProcess := GetContext(ctx); parentProcess != nil {
+		parentPID = parentProcess.GetPID()
+	}
+	return parentPID
+}
diff --git a/modules/process/manager.go b/modules/process/manager.go
index e42e38a0f0..10a89d04dd 100644
--- a/modules/process/manager.go
+++ b/modules/process/manager.go
@@ -12,6 +12,7 @@ import (
 	"io"
 	"os/exec"
 	"sort"
+	"strconv"
 	"sync"
 	"time"
 )
@@ -28,57 +29,151 @@ var (
 	DefaultContext = context.Background()
 )
 
-// Process represents a working process inheriting from Gitea.
-type Process struct {
-	PID         int64 // Process ID, not system one.
-	Description string
-	Start       time.Time
-	Cancel      context.CancelFunc
-}
+// IDType is a pid type
+type IDType string
+
+// FinishedFunc is a function that marks that the process is finished and can be removed from the process table
+// - it is simply an alias for context.CancelFunc and is only for documentary purposes
+type FinishedFunc = context.CancelFunc
 
-// Manager knows about all processes and counts PIDs.
+// Manager manages all processes and counts PIDs.
 type Manager struct {
 	mutex sync.Mutex
 
-	counter   int64
-	processes map[int64]*Process
+	next     int64
+	lastTime int64
+
+	processes map[IDType]*Process
 }
 
 // GetManager returns a Manager and initializes one as singleton if there's none yet
 func GetManager() *Manager {
 	managerInit.Do(func() {
 		manager = &Manager{
-			processes: make(map[int64]*Process),
+			processes: make(map[IDType]*Process),
+			next:      1,
 		}
 	})
 	return manager
 }
 
-// Add a process to the ProcessManager and returns its PID.
-func (pm *Manager) Add(description string, cancel context.CancelFunc) int64 {
+// AddContext creates a new context and adds it as a process. Once the process is finished, finished must be called
+// to remove the process from the process table. It should not be called until the process is finished but must always be called.
+//
+// cancel should be used to cancel the returned context, however it will not remove the process from the process table.
+// finished will cancel the returned context and remove it from the process table.
+//
+// Most processes will not need to use the cancel function but there will be cases whereby you want to cancel the process but not immediately remove it from the
+// process table.
+func (pm *Manager) AddContext(parent context.Context, description string) (ctx context.Context, cancel context.CancelFunc, finished FinishedFunc) {
+	parentPID := GetParentPID(parent)
+
+	ctx, cancel = context.WithCancel(parent)
+
+	pid, finished := pm.Add(parentPID, description, cancel)
+
+	return &Context{
+		Context: ctx,
+		pid:     pid,
+	}, cancel, finished
+}
+
+// AddContextTimeout creates a new context and add it as a process. Once the process is finished, finished must be called
+// to remove the process from the process table. It should not be called until the process is finsihed but must always be called.
+//
+// cancel should be used to cancel the returned context, however it will not remove the process from the process table.
+// finished will cancel the returned context and remove it from the process table.
+//
+// Most processes will not need to use the cancel function but there will be cases whereby you want to cancel the process but not immediately remove it from the
+// process table.
+func (pm *Manager) AddContextTimeout(parent context.Context, timeout time.Duration, description string) (ctx context.Context, cancel context.CancelFunc, finshed FinishedFunc) {
+	parentPID := GetParentPID(parent)
+
+	ctx, cancel = context.WithTimeout(parent, timeout)
+
+	pid, finshed := pm.Add(parentPID, description, cancel)
+
+	return &Context{
+		Context: ctx,
+		pid:     pid,
+	}, cancel, finshed
+}
+
+// Add create a new process
+func (pm *Manager) Add(parentPID IDType, description string, cancel context.CancelFunc) (IDType, FinishedFunc) {
 	pm.mutex.Lock()
-	pid := pm.counter + 1
-	pm.processes[pid] = &Process{
+	start, pid := pm.nextPID()
+
+	parent := pm.processes[parentPID]
+	if parent == nil {
+		parentPID = ""
+	}
+
+	process := &Process{
 		PID:         pid,
+		ParentPID:   parentPID,
 		Description: description,
-		Start:       time.Now(),
+		Start:       start,
 		Cancel:      cancel,
 	}
-	pm.counter = pid
+
+	finished := func() {
+		cancel()
+		pm.remove(process)
+	}
+
+	if parent != nil {
+		parent.AddChild(process)
+	}
+	pm.processes[pid] = process
 	pm.mutex.Unlock()
 
-	return pid
+	return pid, finished
+}
+
+// nextPID will return the next available PID. pm.mutex should already be locked.
+func (pm *Manager) nextPID() (start time.Time, pid IDType) {
+	start = time.Now()
+	startUnix := start.Unix()
+	if pm.lastTime == startUnix {
+		pm.next++
+	} else {
+		pm.next = 1
+	}
+	pm.lastTime = startUnix
+	pid = IDType(strconv.FormatInt(start.Unix(), 16))
+
+	if pm.next == 1 {
+		return
+	}
+	pid = IDType(string(pid) + "-" + strconv.FormatInt(pm.next, 10))
+	return
 }
 
 // Remove a process from the ProcessManager.
-func (pm *Manager) Remove(pid int64) {
+func (pm *Manager) Remove(pid IDType) {
 	pm.mutex.Lock()
 	delete(pm.processes, pid)
 	pm.mutex.Unlock()
 }
 
+func (pm *Manager) remove(process *Process) {
+	pm.mutex.Lock()
+	if p := pm.processes[process.PID]; p == process {
+		delete(pm.processes, process.PID)
+	}
+	parent := pm.processes[process.ParentPID]
+	pm.mutex.Unlock()
+
+	if parent == nil {
+		return
+	}
+
+	parent.RemoveChild(process)
+}
+
 // Cancel a process in the ProcessManager.
-func (pm *Manager) Cancel(pid int64) {
+func (pm *Manager) Cancel(pid IDType) {
 	pm.mutex.Lock()
 	process, ok := pm.processes[pid]
 	pm.mutex.Unlock()
@@ -88,14 +183,28 @@ func (pm *Manager) Cancel(pid int64) {
 }
 
 // Processes gets the processes in a thread safe manner
-func (pm *Manager) Processes() []*Process {
+func (pm *Manager) Processes(onlyRoots bool) []*Process {
 	pm.mutex.Lock()
 	processes := make([]*Process, 0, len(pm.processes))
-	for _, process := range pm.processes {
-		processes = append(processes, process)
+	if onlyRoots {
+		for _, process := range pm.processes {
+			if _, has := pm.processes[process.ParentPID]; !has {
+				processes = append(processes, process)
+			}
+		}
+	} else {
+		for _, process := range pm.processes {
+			processes = append(processes, process)
+		}
 	}
 	pm.mutex.Unlock()
-	sort.Sort(processList(processes))
+
+	sort.Slice(processes, func(i, j int) bool {
+		left, right := processes[i], processes[j]
+
+		return left.Start.Before(right.Start)
+	})
+
 	return processes
 }
 
@@ -134,8 +243,8 @@ func (pm *Manager) ExecDirEnvStdIn(timeout time.Duration, dir, desc string, env
 	stdOut := new(bytes.Buffer)
 	stdErr := new(bytes.Buffer)
 
-	ctx, cancel := context.WithTimeout(DefaultContext, timeout)
-	defer cancel()
+	ctx, _, finished := pm.AddContextTimeout(DefaultContext, timeout, desc)
+	defer finished()
 
 	cmd := exec.CommandContext(ctx, cmdName, args...)
 	cmd.Dir = dir
@@ -150,13 +259,11 @@ func (pm *Manager) ExecDirEnvStdIn(timeout time.Duration, dir, desc string, env
 		return "", "", err
 	}
 
-	pid := pm.Add(desc, cancel)
 	err := cmd.Wait()
-	pm.Remove(pid)
 
 	if err != nil {
 		err = &Error{
-			PID:         pid,
+			PID:         GetPID(ctx),
 			Description: desc,
 			Err:         err,
 			CtxErr:      ctx.Err(),
@@ -168,23 +275,9 @@ func (pm *Manager) ExecDirEnvStdIn(timeout time.Duration, dir, desc string, env
 	return stdOut.String(), stdErr.String(), err
 }
 
-type processList []*Process
-
-func (l processList) Len() int {
-	return len(l)
-}
-
-func (l processList) Less(i, j int) bool {
-	return l[i].PID < l[j].PID
-}
-
-func (l processList) Swap(i, j int) {
-	l[i], l[j] = l[j], l[i]
-}
-
 // Error is a wrapped error describing the error results of Process Execution
 type Error struct {
-	PID         int64
+	PID         IDType
 	Description string
 	Err         error
 	CtxErr      error
@@ -193,7 +286,7 @@ type Error struct {
 }
 
 func (err *Error) Error() string {
-	return fmt.Sprintf("exec(%d:%s) failed: %v(%v) stdout: %s stderr: %s", err.PID, err.Description, err.Err, err.CtxErr, err.Stdout, err.Stderr)
+	return fmt.Sprintf("exec(%s:%s) failed: %v(%v) stdout: %s stderr: %s", err.PID, err.Description, err.Err, err.CtxErr, err.Stdout, err.Stderr)
 }
 
 // Unwrap implements the unwrappable implicit interface for go1.13 Unwrap()
diff --git a/modules/process/manager_test.go b/modules/process/manager_test.go
index a515fc32cd..eb4228e72c 100644
--- a/modules/process/manager_test.go
+++ b/modules/process/manager_test.go
@@ -21,44 +21,72 @@ func TestGetManager(t *testing.T) {
 	assert.NotNil(t, pm)
 }
 
-func TestManager_Add(t *testing.T) {
-	pm := Manager{processes: make(map[int64]*Process)}
+func TestManager_AddContext(t *testing.T) {
+	pm := Manager{processes: make(map[IDType]*Process), next: 1}
 
-	pid := pm.Add("foo", nil)
-	assert.Equal(t, int64(1), pid, "expected to get pid 1 got %d", pid)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	p1Ctx, _, finished := pm.AddContext(ctx, "foo")
+	defer finished()
+	assert.NotEmpty(t, GetContext(p1Ctx).GetPID(), "expected to get non-empty pid")
+
+	p2Ctx, _, finished := pm.AddContext(p1Ctx, "bar")
+	defer finished()
+
+	assert.NotEmpty(t, GetContext(p2Ctx).GetPID(), "expected to get non-empty pid")
 
-	pid = pm.Add("bar", nil)
-	assert.Equal(t, int64(2), pid, "expected to get pid 2 got %d", pid)
+	assert.NotEqual(t, GetContext(p1Ctx).GetPID(), GetContext(p2Ctx).GetPID(), "expected to get different pids %s == %s", GetContext(p2Ctx).GetPID(), GetContext(p1Ctx).GetPID())
+	assert.Equal(t, GetContext(p1Ctx).GetPID(), GetContext(p2Ctx).GetParent().GetPID(), "expected to get pid %s got %s", GetContext(p1Ctx).GetPID(), GetContext(p2Ctx).GetParent().GetPID())
 }
 
 func TestManager_Cancel(t *testing.T) {
-	pm := Manager{processes: make(map[int64]*Process)}
+	pm := Manager{processes: make(map[IDType]*Process), next: 1}
 
-	ctx, cancel := context.WithCancel(context.Background())
-	pid := pm.Add("foo", cancel)
+	ctx, _, finished := pm.AddContext(context.Background(), "foo")
+	defer finished()
+
+	pm.Cancel(GetPID(ctx))
+
+	select {
+	case <-ctx.Done():
+	default:
+		assert.Fail(t, "Cancel should cancel the provided context")
+	}
+	finished()
 
-	pm.Cancel(pid)
+	ctx, cancel, finished := pm.AddContext(context.Background(), "foo")
+	defer finished()
+
+	cancel()
 
 	select {
 	case <-ctx.Done():
 	default:
 		assert.Fail(t, "Cancel should cancel the provided context")
 	}
+	finished()
 }
 
 func TestManager_Remove(t *testing.T) {
-	pm := Manager{processes: make(map[int64]*Process)}
+	pm := Manager{processes: make(map[IDType]*Process), next: 1}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	p1Ctx, _, finished := pm.AddContext(ctx, "foo")
+	defer finished()
+	assert.NotEmpty(t, GetContext(p1Ctx).GetPID(), "expected to have non-empty PID")
 
-	pid1 := pm.Add("foo", nil)
-	assert.Equal(t, int64(1), pid1, "expected to get pid 1 got %d", pid1)
+	p2Ctx, _, finished := pm.AddContext(p1Ctx, "bar")
+	defer finished()
 
-	pid2 := pm.Add("bar", nil)
-	assert.Equal(t, int64(2), pid2, "expected to get pid 2 got %d", pid2)
+	assert.NotEqual(t, GetContext(p1Ctx).GetPID(), GetContext(p2Ctx).GetPID(), "expected to get different pids got %s == %s", GetContext(p2Ctx).GetPID(), GetContext(p1Ctx).GetPID())
 
-	pm.Remove(pid2)
+	pm.Remove(GetPID(p2Ctx))
 
-	_, exists := pm.processes[pid2]
-	assert.False(t, exists, "PID %d is in the list but shouldn't", pid2)
+	_, exists := pm.processes[GetPID(p2Ctx)]
+	assert.False(t, exists, "PID %d is in the list but shouldn't", GetPID(p2Ctx))
 }
 
 func TestExecTimeoutNever(t *testing.T) {
diff --git a/modules/process/process.go b/modules/process/process.go
new file mode 100644
index 0000000000..662f878d7f
--- /dev/null
+++ b/modules/process/process.go
@@ -0,0 +1,66 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package process
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+// Process represents a working process inheriting from Gitea.
+type Process struct {
+	PID         IDType // Process ID, not system one.
+	ParentPID   IDType
+	Description string
+	Start       time.Time
+	Cancel      context.CancelFunc
+
+	lock     sync.Mutex
+	children []*Process
+}
+
+// Children gets the children of the process
+// Note: this function will behave nicely even if p is nil
+func (p *Process) Children() (children []*Process) {
+	if p == nil {
+		return
+	}
+
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	children = make([]*Process, len(p.children))
+	copy(children, p.children)
+	return children
+}
+
+// AddChild adds a child process
+// Note: this function will behave nicely even if p is nil
+func (p *Process) AddChild(child *Process) {
+	if p == nil {
+		return
+	}
+
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	p.children = append(p.children, child)
+}
+
+// RemoveChild removes a child process
+// Note: this function will behave nicely even if p is nil
+func (p *Process) RemoveChild(process *Process) {
+	if p == nil {
+		return
+	}
+
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	for i, child := range p.children {
+		if child == process {
+			p.children = append(p.children[:i], p.children[i+1:]...)
+			return
+		}
+	}
+}