/
diagnostics.go
88 lines (72 loc) · 2.36 KB
/
diagnostics.go
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package appinsights
import (
"fmt"
"sync"
)
type diagnosticsMessageWriter struct {
listeners []*diagnosticsMessageListener
lock sync.Mutex
}
// Handler function for receiving diagnostics messages. If this returns an
// error, then the listener will be removed.
type DiagnosticsMessageHandler func(string) error
// Listener type returned by NewDiagnosticsMessageListener.
type DiagnosticsMessageListener interface {
// Stop receiving diagnostics messages from this listener.
Remove()
}
type diagnosticsMessageListener struct {
handler DiagnosticsMessageHandler
writer *diagnosticsMessageWriter
}
func (listener *diagnosticsMessageListener) Remove() {
listener.writer.removeListener(listener)
}
// The one and only diagnostics writer.
var diagnosticsWriter = &diagnosticsMessageWriter{}
// Subscribes the specified handler to diagnostics messages from the SDK. The
// returned interface can be used to unsubscribe.
func NewDiagnosticsMessageListener(handler DiagnosticsMessageHandler) DiagnosticsMessageListener {
listener := &diagnosticsMessageListener{
handler: handler,
writer: diagnosticsWriter,
}
diagnosticsWriter.appendListener(listener)
return listener
}
func (writer *diagnosticsMessageWriter) appendListener(listener *diagnosticsMessageListener) {
writer.lock.Lock()
defer writer.lock.Unlock()
writer.listeners = append(writer.listeners, listener)
}
func (writer *diagnosticsMessageWriter) removeListener(listener *diagnosticsMessageListener) {
writer.lock.Lock()
defer writer.lock.Unlock()
for i := 0; i < len(writer.listeners); i++ {
if writer.listeners[i] == listener {
writer.listeners[i] = writer.listeners[len(writer.listeners)-1]
writer.listeners = writer.listeners[:len(writer.listeners)-1]
return
}
}
}
func (writer *diagnosticsMessageWriter) Write(message string) {
var toRemove []*diagnosticsMessageListener
for _, listener := range writer.listeners {
if err := listener.handler(message); err != nil {
toRemove = append(toRemove, listener)
}
}
for _, listener := range toRemove {
listener.Remove()
}
}
func (writer *diagnosticsMessageWriter) Printf(message string, args ...interface{}) {
// Don't bother with Sprintf if nobody is listening
if writer.hasListeners() {
writer.Write(fmt.Sprintf(message, args...))
}
}
func (writer *diagnosticsMessageWriter) hasListeners() bool {
return len(writer.listeners) > 0
}