Add service for single point of interaction with database

[YashKumarVerma]

Summary

There are three issues linked with the project, here's a summary of what this PR accomplishes.

• a central point of database interaction, provides a thin abstraction over mongdb driver. Takes care of points raised in #88.
• A tiny utility function to kill the process if database connections have failed after multiple tries. As discussed in #82
• Rewrite of functions using the async-await syntax (replacing callbacks, fallbacks explained in #89 )

Details

• util.js for commonly used utility functions that are consumed by database services, like data transformers.
• exhaustive JSDocs for each member function, with due references to MongoDB documentation.
• All functions which were previously scattered across the application (and also duplicated) combined into one class, eliminating redundancy in code.
• Single point to change the behavior of database connections
• single point connector that provides connection instances to other modules
• kills the process if the connection repeatedly fails.
• all the places which were initially interacting with the database have been refactored to use to database service along with the async-await syntax.

Motivation

• Fixes #82
• Fixes #88
• Fixes #89

Testing

• service tested by running along with the system, unit tests are in process of being written
• Screencast showing termination of process with NZEC as the connection was not successful.

Questions

• Suggestions are welcomed.
• please suggest a suitable name for the PR.

[birm]

Have you done any other configuration changes compared to the defaults in develop.yml? I can't get it to read from mongo at all.

[YashKumarVerma]

just checked, the problem was that the connector function was appending mongodb:// in the passed connection string from process.env, fixing it

[YashKumarVerma]

Hello there, is there something that I can improve in the PR ??

[birm]

I'm still not getting any results from any of the find endpoints despite data being in the database. Similarly, posting slide metadata doesn't update the mongo collections or the backend's slide/find route's results. If you've done the usual test (add slide, view slide, delete slide) successfully, then perhaps there's something more deeply different than expected about our environments or something of the sort.

[YashKumarVerma]

Changelog:

• add unit tests for components of database service
• log errors of db service components
• handle cases of invalid objectID

@birm could you please try the changes and see what tests fail on your end. I'm afraid there might be some particulars that are different on my local setup.

As of now, I'm facing issues in getting a smooth running distro instance on my machine, therefore cannot test the service with /caracal codebase.

[YashKumarVerma]

So I tried debugging the issue, isolated the service, and tested it, but couldn't find the area of the problem.

Then I did the following, based on routes.json, created a postman collection of the endpoints that operate on database actions.

The endpoints were behaving as expected, but there was one patten: the listing route was not working.

The problem was a simple typo in dataHandler that was calling mongo.add in place of mongo.find

The tests I wrote were testing the service, but the handler, therefore it was not detected in the tests.

[YashKumarVerma]

I've deployed my fork at:http://yashkumarverma-workbench.uaenorth.cloudapp.azure.com:4010/apps/table.html

[YashKumarVerma]

@birm ping :)

[YashKumarVerma]

Thanks! meanwhile got to learn a lot about the project ⭐