CODEWITHSUNDEEP
node.jsasynchronousrabbitmqqueuemessage-queue
Bruno Lira
Bruno Lira

Reputation: 307

How to use synchronous messages on rabbit queue?

I have a node.js function that needs to be executed for each order on my application. In this function my app gets an order number from a oracle database, process the order and then adds + 1 to that number on the database (needs to be the last thing on the function because order can fail and therefore the number will not be used).

If all recieved orders at time T are processed at the same time (asynchronously) then the same order number will be used for multiple orders and I don't want that.

So I used rabbit to try to remedy this situation since it was a queue. It seems that the processes finishes in the order they should, but a second process does NOT wait for the first one to finish (ack) to begin, so in the end I'm having the same problem of using the same order number multiple times.

Is there anyway I can configure my queue to process one message at a time? To only start process n+1 when process n has been acknowledged?

This would be a life saver to me!

Upvotes: 0

Views: 317

Answers (1)

Christopher Jones
Christopher Jones

Reputation: 10691

If the problem is to avoid duplicate order numbers, then use an Oracle sequence, or use an identity column when you insert into a table to generate the order number:

CREATE TABLE mytab (
       id NUMBER GENERATED BY DEFAULT ON NULL AS IDENTITY(START WITH 1),
       data VARCHAR2(20));
INSERT INTO mytab (data) VALUES ('abc');
INSERT INTO mytab (data) VALUES ('def');
SELECT * FROM mytab;

This will give:

        ID DATA
---------- --------------------
         1 abc
         2 def

If the problem is that you want orders to be processed sequentially, then don't pull an order from the queue until the previous one is finished. This will limit your throughput, so you need to understand your requirements and make some architectural decisions.

Overall, it sounds Oracle Advanced Queuing would be a good fit. See the node-oracledb documentation on AQ.

Upvotes: 1

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