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// Copyright 2011 Google Inc. All rights reserved.
// Use of this source code is governed by the Apache 2.0
// license that can be found in the LICENSE file.
/*
Package runtime exposes information about the resource usage of the application.
It also provides a way to run code in a new background context of a module.
This package does not work on App Engine "flexible environment".
*/
package runtime // import "google.golang.org/appengine/runtime"
import (
"net/http"
"golang.org/x/net/context"
"google.golang.org/appengine"
"google.golang.org/appengine/internal"
pb "google.golang.org/appengine/internal/system"
)
// Statistics represents the system's statistics.
type Statistics struct {
// CPU records the CPU consumed by this instance, in megacycles.
CPU struct {
Total float64
Rate1M float64 // consumption rate over one minute
Rate10M float64 // consumption rate over ten minutes
}
// RAM records the memory used by the instance, in megabytes.
RAM struct {
Current float64
Average1M float64 // average usage over one minute
Average10M float64 // average usage over ten minutes
}
}
func Stats(c context.Context) (*Statistics, error) {
req := &pb.GetSystemStatsRequest{}
res := &pb.GetSystemStatsResponse{}
if err := internal.Call(c, "system", "GetSystemStats", req, res); err != nil {
return nil, err
}
s := &Statistics{}
if res.Cpu != nil {
s.CPU.Total = res.Cpu.GetTotal()
s.CPU.Rate1M = res.Cpu.GetRate1M()
s.CPU.Rate10M = res.Cpu.GetRate10M()
}
if res.Memory != nil {
s.RAM.Current = res.Memory.GetCurrent()
s.RAM.Average1M = res.Memory.GetAverage1M()
s.RAM.Average10M = res.Memory.GetAverage10M()
}
return s, nil
}
/*
RunInBackground makes an API call that triggers an /_ah/background request.
There are two independent code paths that need to make contact:
the RunInBackground code, and the /_ah/background handler. The matchmaker
loop arranges for the two paths to meet. The RunInBackground code passes
a send to the matchmaker, the /_ah/background passes a recv to the matchmaker,
and the matchmaker hooks them up.
*/
func init() {
http.HandleFunc("/_ah/background", handleBackground)
sc := make(chan send)
rc := make(chan recv)
sendc, recvc = sc, rc
go matchmaker(sc, rc)
}
var (
sendc chan<- send // RunInBackground sends to this
recvc chan<- recv // handleBackground sends to this
)
type send struct {
id string
f func(context.Context)
}
type recv struct {
id string
ch chan<- func(context.Context)
}
func matchmaker(sendc <-chan send, recvc <-chan recv) {
// When one side of the match arrives before the other
// it is inserted in the corresponding map.
waitSend := make(map[string]send)
waitRecv := make(map[string]recv)
for {
select {
case s := <-sendc:
if r, ok := waitRecv[s.id]; ok {
// meet!
delete(waitRecv, s.id)
r.ch <- s.f
} else {
// waiting for r
waitSend[s.id] = s
}
case r := <-recvc:
if s, ok := waitSend[r.id]; ok {
// meet!
delete(waitSend, r.id)
r.ch <- s.f
} else {
// waiting for s
waitRecv[r.id] = r
}
}
}
}
var newContext = appengine.NewContext // for testing
func handleBackground(w http.ResponseWriter, req *http.Request) {
id := req.Header.Get("X-AppEngine-BackgroundRequest")
ch := make(chan func(context.Context))
recvc <- recv{id, ch}
(<-ch)(newContext(req))
}
// RunInBackground runs f in a background goroutine in this process.
// f is provided a context that may outlast the context provided to RunInBackground.
// This is only valid to invoke from a service set to basic or manual scaling.
func RunInBackground(c context.Context, f func(c context.Context)) error {
req := &pb.StartBackgroundRequestRequest{}
res := &pb.StartBackgroundRequestResponse{}
if err := internal.Call(c, "system", "StartBackgroundRequest", req, res); err != nil {
return err
}
sendc <- send{res.GetRequestId(), f}
return nil
}
func init() {
internal.RegisterErrorCodeMap("system", pb.SystemServiceError_ErrorCode_name)
}
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