[zeromq-dev] Why 0mq doesn't define TTL for message (for in-mem queue)?

[artemv zmq]

hi Pieter,

> You're still not explaining what problem this solves

Ok. Here's the problem which I faced recently. Here's appl. architecture
(to keep discussion focused):

iOS/Android (game ui)  <----ssl----> Tomcat <-------->  bet_service  .

There are three layers (from left to right):  game UI (0),  java webserver
(1) and concrete service layer (2).
Layer#0:
  - doesn't host 0mq library.
  - talks to L1 via ssl.
  - blocking(with timeout) on every call to L1.
Layer#1:
  - does host 0mq library.
  - it's a gateway for game ui. It's an async layer between ui and world of
services.
  - it's _asynchronous_. It's a sort of "delegator/router/etc" for a call
from L0  to  L2.
  - on every call from L0 this layer doesn't wait for response from L2.
Layer#2:
  - does host 0mq library.
  -  a concrete business service layer.
  - L0 and L1 _don't care_ will this layer produce response or not.  If not
-- L0 will hit call-timeout, L1 -- simply don't care et al.

The problem is.
When L2 goes down (whatever reason), then L1 will queue messages, and, by
turn, L0 will hit call-timeout. After certain amount of time (usually up to
1hr) L2 will be restarted. And messages,
which have been queued on L1, will be flying to L2.  In my case, I don't
want getting those messages on L2, because they are "out-of-date" for
bet_service.

The solution is -- TTL for a message.
I can implement TTL myself, making it being as a part of message, _but_  I
don't want to do that, because, TTL is low level thing, so fixing it at
higher level would bring more problems, I suppose.






2013/12/29 Pieter Hintjens <ph at imatix.com>

> On Sat, Dec 28, 2013 at 9:52 PM, artemv zmq <artemv.zmq at gmail.com> wrote:
> > That's what I'm talking about ). Why this can't/shouldn't  be done on
> 0mq?
> > The thing is -- 0mq is queueing solution (after all) and TTL is part of
> any
> > queueing. TTL is not concrete business feature, it's very common and
> > ubiquitous thing.
>
> You're still not explaining what problem this solves. Most "queuing
> solutions" offer priorities, acks, persistence, two-phase commits,
> etc. ZeroMQ does not.
>
> If you want to contribute to ZeroMQ, I'd advise you to use ZeroMQ to
> do do real work, then find areas where you need to make improvements,
> then make those improvements carefully and minimally.
>
> -Pieter
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