Know Your Execution Context

Lorenzo Barasti

15MWE December 2016

Table de Matières

What's an execution context?
CPU bound and IO bound operations
Which execution context should I use?
Conclusions

def executionContext

An Execution Context is an abstraction that lets us schedule and run tasks in a predictable way

(Some) Types of

Execution Context

```
FixedThreadPool
```
```
SingleThreadExecutor 
```
```
WorkStealingPool
```
```
ExecutionContext.global 
```

FixedThreadPool

reuses a fixed number of threads operating off a shared unbounded queue

WorkStealingPool - fork/join

Dynamic number of threads up to a custom level
Multi-Queue
No guarantees on the order in which tasks will be executed

CachedThreadPool

creates new threads as needed, but will reuse previously constructed threads when they are available

CPU/IO Bound Operations

CPU bound operations characterise tasks where we focus on computations - e.g. processing data

IO bound operations characterise tasks where we are waiting for data to be sent in or out of our process - e.g. http communication, DB reading/writing

Which EC should I use?

Let's settle it with some very unscientific...

Demo Time!

Conclusions

Look for the right EC for your use case
Avoid using the same execution context for different types of operations
Mind that in this context implementation matters
Tell your friends!

References

Docs for Java's Executor
Introducing thread pools
Executor's factory methods
Scala docs for the Global Execution Context
The Fork/Join framework and a general definition of work stealing