Detect cancelled allocation more cleanly

to avoid the weave script trying to parse an error message as a CIDR

ipam/allocate.go

@@ -59,7 +59,7 @@ func (g *allocate) Try(alloc *Allocator) bool {
 }
 
 func (g *allocate) Cancel() {
-	g.resultChan <- allocateResult{0, fmt.Errorf("Allocate request for %s cancelled", g.ident)}
+	g.resultChan <- allocateResult{0, &errorCancelled{"Allocate", g.ident}}
 }
 
 func (g *allocate) ForContainer(ident string) bool {

ipam/allocator.go

@@ -184,6 +184,15 @@ func hasBeenCancelled(cancelChan <-chan bool) func() bool {
 	}
 }
 
+type errorCancelled struct {
+	kind  string
+	ident string
+}
+
+func (e *errorCancelled) Error() string {
+	return fmt.Sprintf("%s request for %s cancelled", e.kind, e.ident)
+}
+
 // Actor client API
 
 // Allocate (Sync) - get new IP address for container with given name in range

ipam/claim.go

@@ -95,7 +95,7 @@ func (c *claim) deniedBy(alloc *Allocator, owner router.PeerName) {
 }
 
 func (c *claim) Cancel() {
-	c.sendResult(fmt.Errorf("Operation cancelled."))
+	c.sendResult(&errorCancelled{"Claim", c.ident})
 }
 
 func (c *claim) ForContainer(ident string) bool {

ipam/http.go

@@ -35,12 +35,18 @@ func doAllocate(alloc *Allocator, dockerCli *docker.Client, w http.ResponseWrite
 	ident := vars["id"]
 	addr, err := alloc.Allocate(ident, subnet.HostRange(), closedChan)
 	if err != nil {
+		if _, ok := err.(*errorCancelled); ok { // cancellation is not really an error
+			common.Log.Infoln("[allocator]:", err.Error())
+			fmt.Fprint(w, "cancelled")
+			return
+		}
 		badRequest(w, err)
 		return
 	}
 	if r.FormValue("check-alive") == "true" && dockerCli != nil && dockerCli.IsContainerNotRunning(ident) {
 		common.Log.Infof("[allocator] '%s' is not running: freeing %s", ident, addr)
 		alloc.Free(ident, addr)
+		fmt.Fprint(w, "cancelled")
 		return
 	}
 

weave

@@ -919,6 +919,8 @@ ipam_cidrs() {
         if [ "$IPAM_CIDRS" = "404 page not found" ] ; then
             echo "No IP address supplied (use the -iprange option on 'weave launch' to enable IP address allocation)" >&2
             return 1
+        elif [ "$IPAM_CIDRS" = "cancelled" ] ; then
+            return 1
         fi
         ALL_CIDRS="$IPAM_CIDRS"
     fi
@@ -933,6 +935,8 @@ ipam_cidrs() {
             if [ "$CIDR" = "404 page not found" ] ; then
                 echo "IP address allocation must be enabled to use 'net:'" >&2
                 return 1
+            elif [ "$IPAM_CIDRS" = "cancelled" ] ; then
+                return 1
             fi
             if ! is_cidr "$CIDR" ; then
                 echo "$CIDR" >&2