[zeromq-dev] Which ZMQ Messaging Pattern to use?

[codyq0987]

Hello Matteo,

First of all, the application keeps generating data stream into DB no
matter whether there are clients or not.
Second, most of time, each topic ONLY goes to one client and we can
assume each client has different interest.

For example,

The application keeps saving all stocks current prices into DB.
ClientA needs the stock price for IBM since 8:30AM.
ClientB needs the stock price for Apple since 8:30AM.
When the sever receives the request from ClientA, it only sends the
IBM stock price to ClientA and only send Apple stock price to ClientB.

A publisher has no connected subscribers, then it will simply drop all messages.
For example,
Given the above example, if we see a clientC requesting stock price for Apple.
The clientB and clientC cannot share the same pub/sub because all
previously published Apple price will be invisible to the later
jointed clientC.
So the server has to start a new session for clientC instead of asking
ClientC to subscribe the Apple topic.

I don't see how the pub/sub pattern directly fits this usage.

Thank you



On Fri, Dec 14, 2018 at 2:39 PM Matteo <matteo.brichese at gmail.com> wrote:
>
> Hi,
>
> i believe pub/sub is the best approach.
> The publisher holds all the logic on sending based on time.
>
> At the end of the pubblication the pub could send a termination message and shutdown if necessary.
>
> Does it make sense?
> What was holding you?
>
> Regards
>
>
> On Fri, Dec 14, 2018 at 14:31 codyq0987 <askmatlab at gmail.com> wrote:
>>
>> Hello all,
>>
>> I have an application that keeps computing stream data from T1(i.e 8:00 AM) to T2(i.e. 10:00 AM). I want to utilize the pyzmq to serve the data to clients by building a data service based on ZMQ.
>>
>> Here is the user cases:
>>
>> For example,
>> Case 1> if a client connects to the server @8:10 AM, the server will send all old data before 8:10 AM and all new updates to the client. The client will get data based on the submitted topic.
>>
>> Case 2> If the client connects to the server @7:00 AM, the server simply does nothing and will send updates to the client after 8:00AM and close the connection @10:00AM.
>>
>> Case 3> If the client connects to the server @11:00 AM, the server will send all available data from 8:00AM-10:00AM to the client and then close the connection.
>>
>> Note: if two clients connect to the server, each of them will get the full data starting from 8:00AM.
>>
>> Based on my understanding, I cannot find any of the standard message patter that is suitable for this purpose.
>>
>> PAIR
>> Client/Server
>> Publish/Subscribe
>> Push/Pull
>>
>> Question> In my use case, how I should implement the client/server with ZMQ and which messaging pattern I should use?
>>
>> Thank you
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>
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