[zeromq-dev] will receive fail if TCP goes down in REQ socket

[Matt Connolly]

On 14 Dec 2013, at 11:46 am, Justin Karneges <justin at affinix.com> wrote:

> ZeroMQ does not resend messages, so while the reconnect/queuing logic 
> will protect you to some degree, you still need to account for message loss.
> 
> If you're using REQ then you'll need to timeout the request, otherwise 
> if a request or response message is lost then you'll never be able to 
> make a request on the socket ever again. So don't just indefinitely 
> block on a send or receive. Further, ZeroMQ historically hasn't had a 
> way to get a REQ socket out of the "waiting for response" state in the 
> event of a timeout other than by closing the socket and starting over. 
> This means the REQ type is not really usable in production. Better to 
> use DEALER and format a REQ-compatible message yourself. REP does not 
> suffer from these problems, so you can keep on using that and have 
> DEALER talk to REP.

Surely REQ is still very useful in production: simply a client making a request. Connect, send request, wait for reply (or timeout) disconnect, job done. In the same way a HTTP connection would give you a single request and response. ?

Of course the error handling on the client is to close the REQ socket and make a new one for a new request, but this is still fairly similar to a HTTP request.

-Matt