DynamoDB transaction log

[jsteinich]

Ported Azure transaction log to dynamodb.
Made a small api change to DynamoDBStorage in order to get continuation information from queries.

[ReubenBond]

@galvesribeiro please take a look

[galvesribeiro]

Thanks @jsteinich. I'll have a look later tonight when I got home.

However, before we merge it, perhaps would be good to wait for #4042 to get merged as there are changes on how the provider subsystem works and some refactory I did on the AWS providers so you can rebase this provider on top of master.

[jason-bragg]

I definitely don't want to discourage extending the range of platforms supported by transactions, but the transaction log storage abstractions are quite immature at this time, and have known issues. If users are actively working with transactions in services using DynamoDb, then we should vet and support this addition, but if this is being ported to DynamoDb simply to have coverage, I'd advocate holding off until the abstractions are more mature.

[jsteinich]

I did need to do a small amount of legacy config in the tests, so waiting for #4042 would allow for cleaning that up.

So far the project I'm working on has been local to my computer so I've just been using the in memory transaction log. I'm planning on getting an environment set up in AWS in the next couple of weeks that I would like to closely match the eventual production setup. The transaction log was just something on the list to meeting that goal. It isn't crucial for us to have this right away, but we are planning to make heavy use of transactions and expect to go through some of the growing pains.

[jason-bragg]

@jsteinich, Thanks for the contribution, and if you're planning on using this, then we'll definitely accept the PR (once reviewed) and maintain it, including updating it as the abstractions change. Just wanted to make sure the extra work equated to real value in the world, especially given the beta state of the feature.

[jason-bragg]

I'm not qualified to vet the DynamoDB specific logic, but the pattern looks consistent with the existing transaction logging and extension library patterns.

It also includes some basic testing which I presume the author has run. It's important for maintainers to exercise this because we don't have DynamoDb testing as part of our automated (CI, or nightly) test runs.

The PR needs rebased. It would be good for others in the community with DynamoDB experience to vet this, but as it does not introduce much risk to the existing transaction work, I advocate we merge this PR after the rebase, barring others finding issues in it.

[galvesribeiro]

LGTM

[galvesribeiro]

@jason-bragg

It also includes some basic testing which I presume the author has run. It's important for maintainers to exercise this because we don't have DynamoDb testing as part of our automated (CI, or nightly) test runs.

Once we have the testhost xplat, that will not be an issue. I'll do myself the port of the tests to grab the dependencies required for those providers so you would be safe to enable then in the functional run.

[jsteinich]

Looks like the test failed for something unrelated.

[galvesribeiro]

@dotnet-bot test functional please

[sergeybykov]

Thank you, @jsteinich!

[sergeybykov]

@jsteinich I opened #4906 for migration of the provider against the new interface.