Created
February 14, 2020 22:07
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| func GetFriends(ctx context.Context, user int64) (map[string]*User, error) { | |
| friendIds := make(chan int64) | |
| // Produce | |
| go func() { | |
| defer close(friendIds) | |
| for it := GetFriendIds(user); ; { | |
| if id, err := it.Next(ctx); err != nil { | |
| if err == io.EOF { | |
| break | |
| } | |
| // What to do here? | |
| log.Fatalf("GetFriendIds %d: %s", user, err) | |
| } else { | |
| friendIds <- id | |
| } | |
| } | |
| }() | |
| friends := make(chan *User) | |
| // Map | |
| workers := int32(nWorkers) | |
| for i := 0; i < nWorkers; i++ { | |
| go func() { | |
| defer func() { | |
| // Last one out closes shop | |
| if atomic.AddInt32(&workers, -1) == 0 { | |
| close(friends) | |
| } | |
| }() | |
| for id := range friendIds { | |
| if friend, err := GetUserProfile(ctx, id); err != nil { | |
| // What to do here? | |
| log.Fatalf("GetUserProfile %d: %s", user, err) | |
| } else { | |
| friends <- friend | |
| } | |
| } | |
| }() | |
| } | |
| // Reduce | |
| ret := map[string]*User{} | |
| for friend := range friends { | |
| ret[friend.Name] = friend | |
| } | |
| return ret, nil | |
| } |
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