This takes roughly 2,7 seconds to complete, fairly a latency to gather some information. On this instance, each RestTemplate name blocks the thread it’s working on till the decision returns some information after which fingers over the thread to the following RestTemplate name. It really works like this as a result of RestTemplate, by nature, is a synchronous, blocking operation. If you wish to know the way blocking and non-blocking operations work, there’s a detailed clarification right here.
After studying this, Tracey decides that she will make use of a number of the idle threads on her system to make a number of blocking calls on the similar time. It’s good to filter a false impression right here: that is referred to as parallelism, not concurrency.
GOTCHA: Parallelism and concurrency will not be the identical factor
Even when this isn’t a coroutine particular matter, there’s a frequent false impression concerning parallelism and concurrency. These phrases are sometimes used interchangeably, however they signify distinct ideas.
Let’s take a short journey into the realms of sequential blocking, concurrency, and parallelism by imagining a bustling workplace state of affairs, the place a diligent clerk is actively helping purchasers.
Sequential/Blocking (No Concurrency or Parallelism):
In our imaginary workplace, this habits can be seen because the clerk serving to one shopper at a time. Whereas the primary shopper fills within the type, the clerk waits and would not serve some 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 entails 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 job, 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 may be made on the similar time, however they are going to use and block completely different threads, not sharing their sources.
