- exponentially back off auto-sync'ing instead disabling it in case of failure

R=rsc
DELTA=48  (35 added, 3 deleted, 10 changed)
OCL=34030
CL=34034

diff --git a/src/cmd/godoc/godoc.go b/src/cmd/godoc/godoc.go
index 5c01f55fbacd6a1768f96ad928d09309450d702f..c8d4941f71f3412a68b3f3534bebb38fb3c49503 100644 (file)
--- a/src/cmd/godoc/godoc.go
+++ b/src/cmd/godoc/godoc.go
@@ -55,6 +55,36 @@ import (
 const Pkg = "/pkg/"    // name for auto-generated package documentation tree
 
 
+type delayTime struct {
+       mutex sync.RWMutex;
+       minutes int;
+}
+
+
+func (dt *delayTime) set(minutes int) {
+       dt.mutex.Lock();
+       dt.minutes = minutes;
+       dt.mutex.Unlock();
+}
+
+
+func (dt *delayTime) backoff(max int) {
+       dt.mutex.Lock();
+       dt.minutes *= 2;
+       if dt.minutes > max {
+               dt.minutes = max
+       }
+       dt.mutex.Unlock();
+}
+
+
+func (dt *delayTime) get() int {
+       dt.mutex.RLock();
+       defer dt.mutex.RUnlock();
+       return dt.minutes;
+}
+
+
 type timeStamp struct {
        mutex sync.RWMutex;
        seconds int64;
@@ -86,6 +116,7 @@ var (
        // periodic sync
        syncCmd = flag.String("sync", "", "sync command; disabled if empty");
        syncMin = flag.Int("sync_minutes", 0, "sync interval in minutes; disabled if <= 0");
+       syncDelay delayTime;  // actual sync delay in minutes; usually syncDelay == syncMin, but delay may back off exponentially
        syncTime timeStamp;  // time of last p4 sync
 
        // layout control
@@ -569,11 +600,14 @@ func exec(c *http.Conn, args []string) bool {
 
 func dosync(c *http.Conn, r *http.Request) {
        args := []string{"/bin/sh", "-c", *syncCmd};
-       if !exec(c, args) {
-               *syncMin = 0;  // disable sync
-               return;
+       if exec(c, args) {
+               // sync succeeded
+               syncTime.set();
+               syncDelay.set(*syncMin);  //  revert to regular sync schedule
+       } else {
+               // sync failed - back off exponentially, but try at least once a day
+               syncDelay.backoff(24*60);
        }
-       syncTime.set();
 }
 
 
@@ -633,16 +667,14 @@ func main() {
 
                // Start sync goroutine, if enabled.
                if *syncCmd != "" && *syncMin > 0 {
+                       syncDelay.set(*syncMin);  // initial sync delay
                        go func() {
-                               if *verbose {
-                                       log.Stderrf("sync every %dmin", *syncMin);
-                               }
-                               for *syncMin > 0 {
+                               for {
                                        dosync(nil, nil);
-                                       time.Sleep(int64(*syncMin) * (60 * 1e9));
-                               }
-                               if *verbose {
-                                       log.Stderrf("periodic sync stopped");
+                                       if *verbose {
+                                               log.Stderrf("next sync in %dmin", syncDelay.get());
+                                       }
+                                       time.Sleep(int64(syncDelay.get()) * (60 * 1e9));
                                }
                        }();
                }