scala.concurrent

# ExecutionContext

#### trait ExecutionContext extends AnyRef

An `ExecutionContext` can execute program logic asynchronously, typically but not necessarily on a thread pool.

A general purpose `ExecutionContext` must be asynchronous in executing any `Runnable` that is passed into its `execute`-method. A special purpose `ExecutionContext` may be synchronous but must only be passed to code that is explicitly safe to be run using a synchronously executing `ExecutionContext`.

APIs such as `Future.onComplete` require you to provide a callback and an implicit `ExecutionContext`. The implicit `ExecutionContext` will be used to execute the callback.

It is possible to simply import `scala.concurrent.ExecutionContext.Implicits.global` to obtain an implicit `ExecutionContext`. This global context is a reasonable default thread pool.

However, application developers should carefully consider where they want to set policy; ideally, one place per application (or per logically-related section of code) will make a decision about which `ExecutionContext` to use. That is, you might want to avoid hardcoding `scala.concurrent.ExecutionContext.Implicits.global` all over the place in your code. One approach is to add `(implicit ec: ExecutionContext)` to methods which need an `ExecutionContext`. Then import a specific context in one place for the entire application or module, passing it implicitly to individual methods.

A custom `ExecutionContext` may be appropriate to execute code which blocks on IO or performs long-running computations. `ExecutionContext.fromExecutorService` and `ExecutionContext.fromExecutor` are good ways to create a custom `ExecutionContext`.

The intent of `ExecutionContext` is to lexically scope code execution. That is, each method, class, file, package, or application determines how to run its own code. This avoids issues such as running application callbacks on a thread pool belonging to a networking library. The size of a networking library's thread pool can be safely configured, knowing that only that library's network operations will be affected. Application callback execution can be configured separately.

Annotations
  @implicitNotFound( msg = ... )
Source
  ExecutionContext.scala

Linear Supertypes
AnyRef, Any
Known Subclasses
ExecutionContextExecutor, ExecutionContextExecutorService
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Inherited

1. ExecutionContext
2. AnyRef
3. Any

Implicitly

1. by any2stringadd
2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

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### Abstract Value Members

1. #### abstract def execute(runnable: Runnable): Unit

   Runs a block of code on this execution context.

   Runs a block of code on this execution context.

   runnable

     the task to execute

2. #### abstract def reportFailure(cause: Throwable): Unit

   Reports that an asynchronous computation failed.

   Reports that an asynchronous computation failed.

   cause

     the cause of the failure

### Concrete Value Members

1. #### final def !=(arg0: Any): Boolean

   Definition Classes
     AnyRef → Any

2. #### final def ##(): Int

   Definition Classes
     AnyRef → Any

3. #### def +(other: String): String

   Implicit information
     This member is added by an implicit conversion from ExecutionContext to any2stringadd[ExecutionContext] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd

4. #### def ->[B](y: B): (ExecutionContext, B)

   Implicit information
     This member is added by an implicit conversion from ExecutionContext to ArrowAssoc[ExecutionContext] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()

5. #### final def ==(arg0: Any): Boolean

   Definition Classes
     AnyRef → Any

6. #### final def asInstanceOf[T0]: T0

   Definition Classes
     Any

7. #### def clone(): AnyRef

   Attributes
     protected[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )

8. #### def ensuring(cond: (ExecutionContext) ⇒ Boolean, msg: ⇒ Any): ExecutionContext

   Implicit information
     This member is added by an implicit conversion from ExecutionContext to Ensuring[ExecutionContext] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

9. #### def ensuring(cond: (ExecutionContext) ⇒ Boolean): ExecutionContext

   Implicit information
     This member is added by an implicit conversion from ExecutionContext to Ensuring[ExecutionContext] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

10. #### def ensuring(cond: Boolean, msg: ⇒ Any): ExecutionContext

    Implicit information
      This member is added by an implicit conversion from ExecutionContext to Ensuring[ExecutionContext] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

11. #### def ensuring(cond: Boolean): ExecutionContext

    Implicit information
      This member is added by an implicit conversion from ExecutionContext to Ensuring[ExecutionContext] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

12. #### final def eq(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

13. #### def equals(arg0: Any): Boolean

    Definition Classes
      AnyRef → Any

14. #### def finalize(): Unit

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )

15. #### def formatted(fmtstr: String): String

    Returns string formatted according to given `format` string.

    Returns string formatted according to given `format` string. Format strings are as for `String.format` (@see java.lang.String.format).

    Implicit information
      This member is added by an implicit conversion from ExecutionContext to StringFormat[ExecutionContext] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

16. #### final def getClass(): Class[_]

    Definition Classes
      AnyRef → Any

17. #### def hashCode(): Int

    Definition Classes
      AnyRef → Any

18. #### final def isInstanceOf[T0]: Boolean

    Definition Classes
      Any

19. #### final def ne(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

20. #### final def notify(): Unit

    Definition Classes
      AnyRef

21. #### final def notifyAll(): Unit

    Definition Classes
      AnyRef

22. #### def prepare(): ExecutionContext

    Prepares for the execution of a task.

    Prepares for the execution of a task. Returns the prepared execution context.

    `prepare` should be called at the site where an `ExecutionContext` is received (for example, through an implicit method parameter). The returned execution context may then be used to execute tasks. The role of `prepare` is to save any context relevant to an execution's call site, so that this context may be restored at the execution site. (These are often different: for example, execution may be suspended through a `Promise`'s future until the `Promise` is completed, which may be done in another thread, on another stack.)

    Note: a valid implementation of `prepare` is one that simply returns `this`.

    returns

      the prepared execution context

23. #### final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
      AnyRef

24. #### def toString(): String

    Definition Classes
      AnyRef → Any

25. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

26. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

27. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

28. #### def →[B](y: B): (ExecutionContext, B)

    Implicit information
      This member is added by an implicit conversion from ExecutionContext to ArrowAssoc[ExecutionContext] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from ExecutionContext to any2stringadd[ExecutionContext]

### Inherited by implicit conversion StringFormat from ExecutionContext to StringFormat[ExecutionContext]

### Inherited by implicit conversion Ensuring from ExecutionContext to Ensuring[ExecutionContext]

### Inherited by implicit conversion ArrowAssoc from ExecutionContext to ArrowAssoc[ExecutionContext]

### Ungrouped