Coroutine Gotchas – Dispatchers | Weblog | bol.com

This takes roughly 2,7 seconds to complete, fairly a latency to gather some knowledge. On this instance, each RestTemplate name blocks the thread it’s working on till the decision returns some knowledge after which palms over the thread to the subsequent RestTemplate name. It really works like this as a result of RestTemplate, by nature, is a synchronous, blocking operation. If you wish to understand how blocking and non-blocking operations work, there’s a detailed clarification right here.

After studying this, Tracey decides that she will make use of among the idle threads on her system to make a number of blocking calls on the identical time. It’s good to filter out a false impression right here: that is referred to as parallelism, not concurrency.

GOTCHA: Parallelism and concurrency should not the identical factor

Even when this isn’t a coroutine particular matter, there’s a widespread false impression relating to parallelism and concurrency. These phrases are sometimes used interchangeably, however they signify distinct ideas.

Let’s take a quick journey into the realms of sequential blocking, concurrency, and parallelism by imagining a bustling workplace situation, the place a diligent clerk is actively helping purchasers.

Sequential/Blocking (No Concurrency or Parallelism):

In our imaginary workplace, this habits could be seen because the clerk serving to one shopper at a time. Whereas the primary shopper fills within the type, the clerk waits and does not serve every other shopper.

A single-threaded program works in a sequential/blocking method, the place duties are executed one after one other with none concurrent or parallel execution.

Parallelism:

This includes the clerk calling in a colleague to assist. Now, each purchasers are being served concurrently by completely different clerks. Every clerk works independently on their assigned activity, resulting in true parallel execution.

In a multi-process or multi-threaded program, duties are genuinely executed concurrently on a number of processors or cores. For instance, two RestTemplate calls will be made on the identical time, however they are going to use and block completely different threads, not sharing their assets.