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dragonsinth/getfriends_parallel.go

Created February 14, 2020 22:07
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Revisions

  1. dragonsinth created this gist Feb 14, 2020.
    51 changes: 51 additions & 0 deletions getfriends_parallel.go
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,51 @@
    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
    }