DOC-4802 fix string example concurrency

[andy-stark-redis]

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[ggivo]

LGTM

Curious, what was the driver for replacing CompletableFuture.allOf() with individual joins.

[andy-stark-redis]

LGTM

Curious, what was the driver for replacing CompletableFuture.allOf() with individual joins.

@ggivo Thanks for approving!

The issue with allOf() is that it executes the CompletableFuture instances concurrently, which was making the tests flaky. In the examples, we sometimes reuse keys between the individual code snippets and so a snippet running in parallel can sometimes change the value stored in the Redis DB before the assertion is called (so it gets the value from the wrong snippet and fails).

I consulted Tisho about this and we decided that using join() after each snippet is acceptable for now, but we'll wait to see what feedback we get from users. If they want to see more realistic examples of the async features in use then we might try another approach in the future.

[ggivo]

@andy-stark-redis
Make sense. Thanks for getting back with the explanation.

[tishun]

LGTM!