topic Re: ABAP: Parallelize cl_http_client in Application Development and Automation Discussions

ABAP: Parallelize cl_http_client

TimoStark — Sat, 04 Feb 2023 09:28:43 GMT

Hi,

Is it possible in ABAP - without work process parallelization - to parallelize multiple external HTTP requests?

Example (what I would expect to work):

Instantiate 10 HTTP Requests (cl_http_request)
Call "send" 10 times --> All 10 requests are processed by the external system
Call Receive on the first Request --> Synchronously blocks the processing until first request is done
Call Receive on the second Request --> Assumption, all requests are procesed identically fast, the second/third (etc..) Request should have already received the data --> no waiting

Implementing this code naivly with cl_http_client is not working. The second, third, fourth (...) receive call is taking the same time like the first call.

Example Code how sth. like that would look like in JS / TS:

const prom1 = axios.get("....");
const prom2 = axios.get("....");

const [answer1, answer2] = Promise.all([prom1, prom2]);<br>

I can not really believe nth. for this is existing in ABAP, as this seems to be a very simple requirement.. Instantiating workers (i.E. using function modules) is a massive overhead for such a simple task. I want to avoid that, as it causes a drain of worker-processes, which i need for other activities (i.E. users).

Thanks,

Timo

Re: ABAP: Parallelize cl_http_client

Sandra_Rossi — Sat, 04 Feb 2023 10:42:38 GMT

It has always been more complex in ABAP (because ABAP is verbose). You can create your own generic parallelization framework and share with the community. That would be helpful.

Re: ABAP: Parallelize cl_http_client

TimoStark — Sat, 04 Feb 2023 15:35:41 GMT

sandra.rossi Thanks for your response. Maybe I wasn't clear enough or I misunderstand your answer.

I know that I can easily parallelize via ABAP work processes. The point is: I want to parallelize in the HTTP clients - not the full blown ABAP work processes (which would be a big overhead).

I would like to achieve multiple active HTTP requests for the same ABAP work process.

Background: I have a scalable REST service (not under my control) which provides me one information for one plant. I need to call it for 10 different plants.

Possibility 1: make 10 sequential calls (bah...)

Possibility 2: use abap parallelization (not good, as it blocks work processes.. It is highly possile that 20 users are executing the same code at the same time)

Possibility 3: use http (icm) paralleization - normal approach for any other runtime stack (browser / nodejs / java / ... ) I am aware of.

Re: ABAP: Parallelize cl_http_client

Sandra_Rossi — Sat, 04 Feb 2023 16:10:10 GMT

I always saw CL_HTTP_CLIENT as being a synchronous call, and never saw the possibility of asynchronous call. I wonder if the ABAP Channels would be the answer you are looking for. I never used them. I'm curious to see what other people can propose. Let's see.

Re: ABAP: Parallelize cl_http_client

Marian_Zeis — Sat, 04 Feb 2023 17:18:14 GMT

You could either use ZTHREAD or have a look how it is implemented:

data(myThread) = new zcl_thread(aRunnable).
new zcl_thread(anotherRunnable)->start( ).
new zcl_thread(yetAnotherRunnable)->start( ).

myThread->start( ).
myThread->join( ). "waits for this specific thread" 

zcl_thread=>join_all( ). "waits for all threads to finish"

Re: ABAP: Parallelize cl_http_client

TimoStark — Sat, 04 Feb 2023 20:52:22 GMT

Hi Marian,

Thanks for your response (and also the very nice thread impl.). After a quick check in github it is though still using starting new task (and therefore using a worker process).

I do not want work processes as these are a very limited resource..

Basically I would expect that the *send* command is sending (but not waiting) and the receive is waiting (compare it to await) - so the parallization is actually happening on the http receiver side.. On abap side there is just another open http request..

This way with an Extremely scalable micro service I could call the rest endpoint I.e. 1000 times at the same time.. Without wasting actual processes on sap side.

When you are fit with Javascript : nobody would do two service workers (=threads) to implement two parallel http requests. Or in Java Nobody would make two http requests.

Instead the http request itself is async..

Re: ABAP: Parallelize cl_http_client

ThorstenHoefer — Tue, 07 Feb 2023 16:28:28 GMT

Hi,

for asynchronous programming, you should check this resource:

https://codezentrale.de/tag/wait-for-asynchronous-tasks-until/

Re: ABAP: Parallelize cl_http_client

TimoStark — Fri, 17 Feb 2023 13:54:19 GMT

Answered myself here https://blogs.sap.com/2023/02/17/parallelize-cl_http_client/

Re: ABAP: Parallelize cl_http_client

Marian_Zeis — Fri, 17 Feb 2023 14:05:28 GMT

8ae6723ab3fa43a8980099fe48f90b04 you can accept your own answer