Config property: retry logic customization

[ayush3797]

This is something we might consider as a follow up for this issue: #618,
whether we want to provide the developers with the option to configure the retry count via the config file and maybe the retry strategy (e.g. exponential backoff) and the base (2,3,4,...) to be used.

[ayush3797]

@yorek @Aniruddh25 , do we want to add this functionality?

[Aniruddh25]

Since we should be minimizing adding new configurations (add them only when absolutely essential), perhaps, we can reuse the retry logic configuration set in the app.config for e.g. by following this:
https://devblogs.microsoft.com/azure-sql/configurable-retry-logic-for-microsoft-data-sqlclient/

@ayush3797, could you please try the suggestions mentioned in the blog post and see if our dab engine customers can use the same?

[yorek]

Is that is definitely a nice to have. I don't think it is super urgent, but it will be something I'm sure it will be appreciated.

What library we have been using for implementing the retry logic? Polly.NET, is that right?

In general I don't think we need to complexity of the SqlClient configuration. The complexity in that case is there as the goal was to allow to configure retry logic without changing existing code. Since we're building something we from scratch I'll prefer to have something much simpler (for example, just allow to configure how many times one has to retry, and just go with an exponential backoff to start with, allowing to add/change/remove handled error code would be nice too)

[ayush3797]

@yorek, correct we are using Polly right now.
@Aniruddh25, I agree with Davide here that we don't need the complexity of SqlClient configuration here since we are developing from scratch. Also, instead of having the developer to set the configuration in two different places/files, won't it make sense to have it done in one single place i.e. the dab-config file? (Although it means adding new properties to the config file)

[ayush3797]

@yorek , need your inputs on this. There are some things I wanted to get clear with:

1. I am of the opinion that we should not have the config spread across multiple files. I think we should go ahead with adding the properties within our dab-config file. What is your opinion on this?
2. Is this something we should target for a nearby milestone, maybe not for Oct2022 but Nov2022 maybe? I think it is a good to have flexibility for the developers because depending on their use case, they might want less/more number of retries and time interval between successive retries.

[yorek]

@ayush3797 I agree with you on 1. Let's just keep everything in one place. Let's discuss prioritization in the next meeting, but I would say that this is really a P2 (since we already have a retry-logic in place, we just have to make it configurable). Can you please tell me what is the retry logic we use now, so that I can document it? Thanks!

[ayush3797]

@yorek, The retry logic that we use now is:
Exponential Backoff strategy for retries with the maximum number of retries set to 5. Between every subsequent retry we backoff by a timespan of power(2,retryAttempt). For 1st retry, it is performed after a gap of 2 seconds, 2nd retry after a timespan of 4 seconds, 3rd after 8,......, 5th after 32 seconds.

Relevant link: https://docs.microsoft.com/en-us/azure/architecture/best-practices/retry-service-specific#sql-database-using-adonet

[ayush3797]

@Aniruddh25 , @yorek do we want to include this in the Nov22 milestone?

[Aniruddh25]

I dont think this is necessary for Nov22 - let us gather feedback from what we have and then decide on how to expose configuring it.

[ayush3797]

@Aniruddh25 @yorek, do we have any feedback yet on whether we need to support configurable retry logic?