CODEWITHSUNDEEP
node.jsmongodbrestifydatabase-concurrency
Ameya Savale
Ameya Savale

Reputation: 441

Creating atomic function in nodejs

The title isn't accurate because based on what I have found in my research there doesn't seem to be a way to make a function atomic in nodejs, but I will lay out my problem to see if you people can come up with something that I have not been able to think about.

I am trying to setup a scheduler where I can set my appointment time slots say 1 hr long each and when someone makes an appointment I want to make sure that the time slot is not taken before scheduling it.

So for example I decide that I will be working from 9 am to 2 pm with a time slot of one hour. Then my schedule would be 9-10, 10-11, 11-12, 12-1, 1-2.

An appointment will come in with a start time of 11 and end time of 12. I need to make sure that slot isn't already taken.

I am using mongodb with nodejs and restify.

I understand that in my appointments collection I can set an index on a combination of values like start time and end time, as discussed here Creating Multifield Indexes in Mongoose / MongoDB.

But if I decide to change my time slot from 1 hour to say 1.5 hours then I will have scheduling conflicts as the start time and end time of entries in the database will not match up with the new interval

Currently I have a function which checks to make sure that the new appointment will not conflict but I am not sure if it will work out well when I have multiple requests coming in. This is a nodejs and restify app so basically an api with a mongodb that it talks to, to handle appointments.

I am running it with multiple workers, so I am worried that at a certain point two requests will come in at the same time, handled by two different workers for the same time slot. When my conflict checking function executes it will return saying that the slot is open for both of them since no appointment has been made yet and then there will be a scheduling conflict.

Any ideas on how to combat this, or is there something in the way javascript executes so that I shouldn't have to worry about it this? All input will be appreciated

Thanks!

Upvotes: 4

Views: 1828

Answers (1)

Ameya Savale
Ameya Savale

Reputation: 441

I ended up using https://github.com/Automattic/kue, to queue my requests and added another endpoint where you can check the status of your request. So when you want to make an appointment your request ends up in the job queue, and you can then periodically check the status of your request. This way only one appointment request gets processed at a time so no concurrency issues.

Upvotes: 1

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