In-Memory Cache

[seantleonard]

Why make this change?

• Second set of work attributed to Caching - REST #1618 Caching - GraphQL #1617

What is this change?

• Implements the design in REST and GraphQL Query Caching Design Doc #1801. The one behavior which isn't in this PR is caching GraphQL "list" queries. That will come in a separate commit once i resolve the errors that arise with generics and the DataReaderHandler delegates.
• Creates a DabCacheService which is used in database queries (REST/GraphQL) such that requests and responses are cached in memory.
• This PR is not dependent on Add Cache properties to runtime config file with JSON Serialize/Deserialize #1865. However, once that PR and this PR are merged, a third follow-up PR will make a small adjustment in SqlQueryEngine.ExecuteAsync(...) such that the cacheEntryTtl and cacheEnabled values are resolved from runtime config and used determine whether to use the cache and how to use the cache.

How was this tested?

• Integration Tests -> integration tests included which mock the QueryExecutor and test how the DabCacheService handles request metadata and caching method execution. The integration tests aim to test the behavior of the DabCacheService and intentionally do not make private methods public or break out key generation and entry size calculation into separate classes. Additionally, the integration tests are not meant to test the functionality of FusionCache. That library has its own tests which validate functionality.

Sample Request(s)

Until all related PRs are merged, this feature is gated by a feature flag. To add the feature flag, add the following snippet to the AppConfig.json:

// Define feature flags in config file
    "FeatureManagement": {
        "CachingPreview": true, // Turn-On feature
    }

Point requests will be cached with a default 10 second ttl. You can try out whether response times are quicker for your use case.

[Aniruddh25]

Looks good, posting comments so far, tests remaining..

[Aniruddh25]

Very Comprehensive tests, left some questions.

[seantleonard]

/azp run

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[severussundar]

Neat. Good usage of mocks for writing the integration tests.

Few nits, otherwise, LGTM!

[seantleonard]

/azp run

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[seantleonard]

/azp run

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[seantleonard]

/azp run

Addressed comments and received additional reviews.

[azure-pipelines]

Azure Pipelines successfully started running 6 pipeline(s).