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panichandler.go
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panichandler.go
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package panichandler
import (
"runtime/debug"
"sync"
"time"
"go.uber.org/fx"
)
var globalPanicHandlerRegistry *PanicHandlerRegistry
func init() {
globalPanicHandlerRegistry = getPanicHandlerRegistry()
}
// PanicHandlerRegistry defines a list of panic handlers.
type PanicHandlerRegistry struct {
mutex sync.RWMutex
Handlers []PanicHandler
}
// PanicHandlerRegistryIn holds parameters, list of panic handlers, for RegisterPanicHandlers.
type PanicHandlerRegistryIn struct {
fx.In
Handlers []PanicHandler `group:"panic-handlers"`
}
// RegisterPanicHandlers register panic handlers to panic handler registry.
func RegisterPanicHandlers(in PanicHandlerRegistryIn) {
// loop the handlers
for _, handler := range in.Handlers {
RegisterPanicHandler(handler)
}
}
// PanicHandler is a panic handling function that is called when a panic occurs with full stacktrace.
type PanicHandler func(interface{}, Callstack)
// getPanicHandlerRegistry returns the global panic handler registry.
func getPanicHandlerRegistry() *PanicHandlerRegistry {
if globalPanicHandlerRegistry == nil {
globalPanicHandlerRegistry = &PanicHandlerRegistry{
Handlers: make([]PanicHandler, 0),
}
}
return globalPanicHandlerRegistry
}
// Go calls registry's internal Go function to start f on a new go routine.
func Go(f func()) {
getPanicHandlerRegistry().Go(f)
}
// Crash calls registry's internal Crash function to invoke registered panic handler.
func Crash(v interface{}) {
getPanicHandlerRegistry().Crash(v)
}
// RegisterPanicHandler calls global registry's internal register panic handler function to panic handler registry.
func RegisterPanicHandler(ph PanicHandler) {
getPanicHandlerRegistry().RegisterPanicHandler(ph)
}
// crashOnce prevents multiple panics to interfere each other, process single panic.
var crashOnce = sync.Once{}
// RegisterPanicHandler appends panic handler to list of global registry's panic handler.
func (r *PanicHandlerRegistry) RegisterPanicHandler(ph PanicHandler) {
r.mutex.Lock()
defer r.mutex.Unlock()
if r.Handlers == nil {
r.Handlers = make([]PanicHandler, 0)
}
r.Handlers = append(r.Handlers, ph)
}
// Crash invokes each of the registered panic handler and then rethrows panic - shutting down the app.
func (r *PanicHandlerRegistry) Crash(v interface{}) {
stackTrace := Capture()
waitCh := make(chan struct{})
go crashOnce.Do(func() {
r.mutex.RLock()
defer r.mutex.RUnlock()
wg := sync.WaitGroup{}
wg.Add(len(r.Handlers))
for _, handler := range r.Handlers {
h := handler
go func() {
defer wg.Done()
h(v, stackTrace)
}()
}
wg.Wait()
close(waitCh)
})
select {
case <-waitCh:
case <-time.After(5 * time.Second):
}
panic(v)
}
// Go calls f on a new go-routine, reporting panics to the registered handlers.
func (r *PanicHandlerRegistry) Go(f func()) {
go func() {
// SetPanicOnFault allows the runtime trigger only a panic.
debug.SetPanicOnFault(true)
defer func() {
if v := recover(); v != nil {
r.Crash(v)
}
}()
f()
}()
}
// PanicHandlerOut enables registering panic handlers via Fx.
type PanicHandlerOut struct {
fx.Out
PanicHandler PanicHandler `group:"panic-handlers"`
}