[feat] Support mongodb replica set for mongo shared clusters support

[robertsLando]

Consider this question: https://developer.mongodb.com/community/forums/t/mongodb-pub-sub-using-tailable-cursors-in-nodejs-with-clusters/3027/4

This package could have some problems when using mongodb running on shared clusters.

In the question linked there are all the tips to use to make the support, maybe a new mqemitter packege could be created for that instead of making this supporting both

[mcollina]

Is this fixed?

[robertsLando]

Nope, this is an idea for a future development based on the question I linked in previous comment.

Tailable cursors may not be the best solution with MONGODB SHARED CLUSTERS

My PR has fixed mqemitter when using with NODEJS CLUSTERS.

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On 23 Apr 2020, at 19:59, Matteo Collina notifications@github.com wrote:

 Is this fixed?

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[mcollina]

I don't know if it's possible to use something else on top of mongo. Go ahead and write another package if it would be a total rewrite of this one.

[robertsLando]

@mcollina Yes, sure :+1: Keep this open in the meanwhile

[1977744311]

@mcollina @robertsLando I tried to start two node services to connect to the same mongo client. I found that the latest task will be consumed twice. Is this normal? How can I solve it?

[robertsLando]

Code snippet to reproduce the issue?

[1977744311]

You can try to pull the code to execute locally git clone git@github.com:1977744311/issue-mq.git And you can do: npm install npm run issue Then you can see two services in pm2, You can visit the address of one of the services http://127.0.0.1:3000/api/emit, you can find the result of two emits in pm2 logs How should I avoid this, or is this package not supporting different instances connecting to the same database

[robertsLando]

I found that the latest task will be consumed twice. Is this normal? How can I solve it?

What do you mean with 'consumed twice' ? Do you mean that both services receive it once or that each service receive it twice?

[1977744311]

both services receive it once

[robertsLando]

both services receive it once

That's the expected behaviour so. mqemitter is used exactly for that purpose, share messages across multiple instances. If you don't want all instances to receive a specific message you should create your own logic

[1977744311]

both services receive it once

That's the expected behaviour so. mqemitter is used exactly for that purpose, share messages across multiple instances. If you don't want all instances to receive a specific message you should create your own logic

okey，thanks for your answer