func init() {
    http.HandleFunc("/", handler)
}

在处理程序函数中，有代码遍历数据列表、处理它并聚合结果。

假设对于给定的查询，有 100 个项目需要处理。对于我向 Appengine 控制台写入日志的每个项目，“Item n has been processed”。

问题是:

请求没有返回。前 40 条左右的日志消息，然后重复，再重复。它总是停止相同的项目，然后重新启动。

我最好的猜测是应用程序达到了内存限制或其他原因，而 Appengine Go 运行时只是重新启动并重新执行处理程序。

对于一小部分项目，处理按预期进行，并且日志没有显示任何循环。

请求日志中没有错误，但另一个日志显示:

panic: poll_ctl

goroutine 3 [running]:
runtime/eventloop.(*pollServer).ctlfd(0x9035f8, 0x204100000005, 0x3, 0x2041, 0x0, ...)
    go/src/pkg/runtime/eventloop/poll_linux_amd64.go:428 +0xdf
runtime/eventloop.(*pollServer).loop(0x9035f8, 0x0)
    go/src/pkg/runtime/eventloop/poll_linux_amd64.go:411 +0x4d8
created by runtime/eventloop.init·1
    go/src/pkg/runtime/eventloop/poll_linux_amd64.go:232 +0x40

goroutine 1 [select (no cases)]:
appengine_internal/fd_transport.serveHTTP(0x7fff76502f58, 0x70615f2f00000002, 0x7fff76502f5b, 0x3, 0x7fff76502f6c, ...)
    go/src/pkg/appengine_internal/fd_transport/fd_transport.go:44 +0x26b
appengine_internal.Main()
    go/src/pkg/appengine_internal/internal.go:184 +0x1a8
main.main()
    _go_main.go:16 +0x18

goroutine 2 [select]:
created by _
    _.go:568 +0xd2

goroutine 10 [chan receive]:
runtime/eventloop.(*pollServer).wait(0x9035f8, 0xf840095a60, 0xf84011ac30, 0xb, 0x1, ...)
    go/src/pkg/runtime/eventloop/poll_linux_amd64.go:472 +0x1a7
runtime/eventloop.(*FD).ReadFrom(0xf840095a50, 0xf840138000, 0x7d0000007d0, 0xf800000000, 0x0, ...)
    go/src/pkg/runtime/eventloop/fd.go:135 +0x1c2
created by _
    _.go:144 +0x7a

goroutine 5 [chan receive]:
created by _
    _.go:461 +0x3ca

goroutine 6 [semacquire]:
sync.runtime_Semacquire(0xf8408034d8, 0xf8408034d8)
    go/src/pkg/runtime/zsema_amd64.c:146 +0x25
sync.(*Cond).Wait(0xf840096bb0, 0x1)
    go/src/pkg/sync/cond.go:67 +0xaa
created by _
    _.go:462 +0x3e1

goroutine 7 [chan receive]:
runtime/eventloop.(*pollServer).wait(0x9035f8, 0xf840095c70, 0xf84011ac30, 0xb, 0x1, ...)
    go/src/pkg/runtime/eventloop/poll_linux_amd64.go:472 +0x1a7
runtime/eventloop.(*FD).Read(0xf840095c60, 0xf84113a000, 0x972a80000000c, 0x2b5800000000, 0xf84011ac30, ...)
    go/src/pkg/runtime/eventloop/fd.go:93 +0x18c
io.ReadAtLeast(0xf84012c0c0, 0xf840095c60, 0xf84113a000, 0x972a80000000c, 0x2b580000000c, ...)
    go/src/pkg/io/io.go:254 +0xc3
io.ReadFull(0xf84012c0c0, 0xf840095c60, 0xf84113a000, 0x972a80000000c, 0xf840095c60, ...)
    go/src/pkg/io/io.go:273 +0x69
created by _
    _.go:845 +0x2c6

goroutine 11 [runnable]:
runtime/eventloop.(*pollServer).wait(0x9035f8, 0xf840095b10, 0xf84011ac30, 0xb, 0x1, ...)
    go/src/pkg/runtime/eventloop/poll_linux_amd64.go:472 +0x1a7
runtime/eventloop.(*FD).Accept(0xf840095b00, 0x0, 0x0, 0xf84011ac30, 0xb, ...)
    go/src/pkg/runtime/eventloop/fd.go:72 +0x185
net/http.(*Server).Serve(0xf840129f00, 0xf8400cfa80, 0xf840095b00, 0x0, 0x0, ...)
    go/src/pkg/net/http/server.go:1012 +0x88
net/http.Serve(0xf8400cfa80, 0xf840095b00, 0xf84012c090, 0xf8400e0b10, 0xf8400e0b10, ...)
    go/src/pkg/net/http/server.go:977 +0x71
created by _
    _.go:145 +0xe9

goroutine 12 [timer goroutine (idle)]:
created by addtimer
    go/src/pkg/runtime/ztime_amd64.c:70

goroutine 13 [runnable]:
runtime/eventloop.(*pollServer).wait(0x9035f8, 0xf8400959b0, 0xf84011ac30, 0xb, 0x1, ...)
    go/src/pkg/runtime/eventloop/poll_linux_amd64.go:472 +0x1a7
runtime/eventloop.(*FD).Read(0xf8400959a0, 0xf840139000, 0x100000001000, 0x0, 0xf84011ac30, ...)
    go/src/pkg/runtime/eventloop/fd.go:93 +0x18c
io.(*LimitedReader).Read(0xf840123580, 0xf840139000, 0x100000001000, 0xf8900000000, 0x0, ...)
    go/src/pkg/io/io.go:394 +0xc1
bufio.(*Reader).fill(0xf840129f80, 0x2b5853e92000)
    go/src/pkg/bufio/bufio.go:77 +0xf0
bufio.(*Reader).Read(0xf840129f80, 0xf84013d000, 0x27100000000c, 0xc, 0x0, ...)
    go/src/pkg/bufio/bufio.go:142 +0x188
io.ReadAtLeast(0xf84012c600, 0xf84012c570, 0xf84013d000, 0x27100000000c, 0xc, ...)
    go/src/pkg/io/io.go:254 +0xc3
io.ReadFull(0xf84012c600, 0xf84012c570, 0xf84013d000, 0x27100000000c, 0xf84012c570, ...)
    go/src/pkg/io/io.go:273 +0x69
net/http.(*conn).serve(0xf8401320c0, 0x0)
    go/src/pkg/net/http/server.go:656 +0x621
created by net/http.(*Server).Serve
    go/src/pkg/net/http/server.go:1040 +0x430

goroutine 59 [sleep]:
time.Sleep(0x5dfdee1, 0xf8408034d0)
    go/src/pkg/runtime/ztime_amd64.c:22 +0x49
created by _
    _.go:791 +0xc4

goroutine 15 [chan receive]:

也许我没有记录所有错误，但即使如此，什么会导致循环？

更新 近乎无休止的循环很快耗尽了我的数据存储写入配额，现在我收到了一个无引号错误，正在记录。错误记录后，再次调用处理程序。又一次……

func handleError(w http.ResponseWriter, c appengine.Context, err error) {
    c.Infof("ERROR")
    c.Errorf("ERROR datastore: %s", err.Error())
}


...
rk, err := datastore.Put(c, rk, e)
if err != nil {
    handleError(w, c, err)
    return
}

更新 2 切换到 f4 实例后，代码按预期运行。我仍然认为 Appengine Go 运行时由于某种原因(内存)默默地失败，并重新启动处理程序执行。这是我最好的猜测，我不知道。

最佳答案

http 请求有 30 秒超时。在您转移到更快的实例之前，流程是否需要那么长时间？您可以使用后端进程进行长期处理。 https://developers.google.com/appengine/docs/go/backends/overview

关于google-app-engine - Go AppEngine 重复部分执行 http.handler，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/10165376/