// exportPtr returns *permPtrMsg if importer is nil, and *ptrMsg otherwise.
func (r *Runtime) exportPtr(v interface{}, importer circuit.Addr) interface{} {
// Add exported value to export table
exph := r.exp.Add(v, importer)
if importer == nil {
return &permPtrMsg{ID: exph.ID, TypeID: exph.Type.ID}
}
// Monitor the importer for liveness.
// DropPtr the handles upon importer death.
r.lk.Lock()
defer r.lk.Unlock()
_, ok := r.live[importer]
if !ok {
r.live[importer] = struct{}{}
// The anonymous function creates a "lifeline" connection to the worker importing v.
// When this conncetion is broken, v is released.
go func() {
// Defer removal of v's handle from the export table to the end of this function
defer func() {
r.lk.Lock()
delete(r.live, importer)
r.lk.Unlock()
// DropPtr/forget all exported handles
r.exp.RemoveImporter(importer)
}()
conn, err := r.dialer.Dial(importer)
if err != nil {
println("problem dialing lifeline to", importer.String(), err.Error())
return
}
defer conn.Close()
if conn.Write(&dontReplyMsg{}) != nil {
println("problem writing on lifeline to", importer.String(), err.Error())
return
}
// Read returns when the remote dies and
// runs the conn into an error
conn.Read()
}()
}
return &ptrMsg{ID: exph.ID, TypeID: exph.Type.ID}
}
func getReducerTop(addr circuit.Addr, lk *sync.Mutex, top *SortablePosts) {
// Obtain cross-runtime pointer to reducer service on the worker owning file f
x, err := circuit.TryDial(addr, "reducer-service")
if err != nil {
println("dial", addr.String(), "error", err.Error())
// Skip reducers that seem to be dead
return
}
// Catch panics due to dead worker and return empty list of top ten posts in this case
defer func() {
if p := recover(); p != nil {
fmt.Fprintf(os.Stderr, "%s.Top panic: %#v\n", x.String(), p)
}
}()
// Fetch top ten posts
rtop := x.Call("Top")[0].([]*Post)
lk.Lock()
defer lk.Unlock()
println("Reducer", addr.String(), "contributed", len(rtop), "posts")
(*top) = append(*top, rtop...)
}