161 lines
4.7 KiB
Go
161 lines
4.7 KiB
Go
/*
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Copyright 2014 The Kubernetes Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package runtime
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import (
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"fmt"
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"runtime"
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"sync"
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"time"
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"github.com/golang/glog"
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)
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var (
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// ReallyCrash controls the behavior of HandleCrash and now defaults
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// true. It's still exposed so components can optionally set to false
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// to restore prior behavior.
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ReallyCrash = true
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)
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// PanicHandlers is a list of functions which will be invoked when a panic happens.
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var PanicHandlers = []func(interface{}){logPanic}
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// HandleCrash simply catches a crash and logs an error. Meant to be called via
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// defer. Additional context-specific handlers can be provided, and will be
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// called in case of panic. HandleCrash actually crashes, after calling the
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// handlers and logging the panic message.
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//
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// TODO: remove this function. We are switching to a world where it's safe for
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// apiserver to panic, since it will be restarted by kubelet. At the beginning
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// of the Kubernetes project, nothing was going to restart apiserver and so
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// catching panics was important. But it's actually much simpler for montoring
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// software if we just exit when an unexpected panic happens.
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func HandleCrash(additionalHandlers ...func(interface{})) {
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if r := recover(); r != nil {
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for _, fn := range PanicHandlers {
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fn(r)
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}
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for _, fn := range additionalHandlers {
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fn(r)
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}
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if ReallyCrash {
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// Actually proceed to panic.
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panic(r)
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}
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}
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}
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// logPanic logs the caller tree when a panic occurs.
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func logPanic(r interface{}) {
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callers := getCallers(r)
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glog.Errorf("Observed a panic: %#v (%v)\n%v", r, r, callers)
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}
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func getCallers(r interface{}) string {
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callers := ""
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for i := 0; true; i++ {
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_, file, line, ok := runtime.Caller(i)
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if !ok {
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break
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}
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callers = callers + fmt.Sprintf("%v:%v\n", file, line)
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}
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return callers
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}
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// ErrorHandlers is a list of functions which will be invoked when an unreturnable
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// error occurs.
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// TODO(lavalamp): for testability, this and the below HandleError function
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// should be packaged up into a testable and reusable object.
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var ErrorHandlers = []func(error){
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logError,
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(&rudimentaryErrorBackoff{
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lastErrorTime: time.Now(),
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// 1ms was the number folks were able to stomach as a global rate limit.
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// If you need to log errors more than 1000 times a second you
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// should probably consider fixing your code instead. :)
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minPeriod: time.Millisecond,
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}).OnError,
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}
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// HandlerError is a method to invoke when a non-user facing piece of code cannot
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// return an error and needs to indicate it has been ignored. Invoking this method
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// is preferable to logging the error - the default behavior is to log but the
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// errors may be sent to a remote server for analysis.
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func HandleError(err error) {
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// this is sometimes called with a nil error. We probably shouldn't fail and should do nothing instead
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if err == nil {
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return
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}
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for _, fn := range ErrorHandlers {
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fn(err)
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}
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}
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// logError prints an error with the call stack of the location it was reported
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func logError(err error) {
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glog.ErrorDepth(2, err)
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}
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type rudimentaryErrorBackoff struct {
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minPeriod time.Duration // immutable
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// TODO(lavalamp): use the clock for testability. Need to move that
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// package for that to be accessible here.
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lastErrorTimeLock sync.Mutex
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lastErrorTime time.Time
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}
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// OnError will block if it is called more often than the embedded period time.
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// This will prevent overly tight hot error loops.
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func (r *rudimentaryErrorBackoff) OnError(error) {
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r.lastErrorTimeLock.Lock()
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defer r.lastErrorTimeLock.Unlock()
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d := time.Since(r.lastErrorTime)
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if d < r.minPeriod {
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time.Sleep(r.minPeriod - d)
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}
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r.lastErrorTime = time.Now()
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}
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// GetCaller returns the caller of the function that calls it.
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func GetCaller() string {
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var pc [1]uintptr
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runtime.Callers(3, pc[:])
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f := runtime.FuncForPC(pc[0])
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if f == nil {
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return fmt.Sprintf("Unable to find caller")
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}
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return f.Name()
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}
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// RecoverFromPanic replaces the specified error with an error containing the
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// original error, and the call tree when a panic occurs. This enables error
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// handlers to handle errors and panics the same way.
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func RecoverFromPanic(err *error) {
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if r := recover(); r != nil {
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callers := getCallers(r)
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*err = fmt.Errorf(
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"recovered from panic %q. (err=%v) Call stack:\n%v",
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r,
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*err,
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callers)
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}
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}
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