Jactl Execution Environment
This section is only relevant if using Jactl in its async non-blocking mode. If you are using synchronous execution (JactlContext.async(false)), then this section can be ignored.
In order for Jactl to support event-loop based applications with non-blocking execution of scripts, it needs to know how to schedule blocking and non-blocking operations.
An implementation of the io.jactl.JactlEnv interface must be provided that supplies a bridge from Jactl to
the execution environment in which it is running.
The interface has the following methods that need to be implemented:
public interface JactlEnv {
Object getThreadContext();
void scheduleEvent(Object threadContext, Runnable event);
void scheduleEvent(Object threadContext, Runnable event, long timeMs);
void scheduleEvent(Runnable event, long timeMs);
void scheduleBlocking(Runnable blocking);
}
There are also two other optional methods with default implementations (saveCheckpoint() and deleteCheckpoint())
that will be described in the section on Checkpoints.
getThreadContext()
In order to support event-loop based applications where resumption of a long-running operation should occur on the
original thread that spawned the long-running task, there is a method called getThreadContext() that should return
a handle that identifies the current event-loop thread, and which, when passed to scheduleEvent() will allow
the new event to be rescheduled on the same original event-loop thread.
If there is no such concept of rescheduling on the same thread then getThreadContext() is allowed to return null.
If getThreadContext() is called from a non-event-loop thread then it should return null unless it makes
sense to return a context for a specific event-loop thread (for example if there is some way for it to know
that the currently running code is somehow related to a previous event on a specific event-loop thread).
scheduleEvent()
The scheduleEvent() methods are used to schedule non-blocking events onto an event-loop thread.
If passed a thread context that was returned from getThreadContext() then the event should be scheduled onto the
same event-loop thread.
If not passed a thread context then it is free to pick an event-loop to schedule the event on.
If passed a timeMs value then the event should be scheduled to run after the specified amount of time has expired.
scheduleBlocking()
This method is used to add execution of some blocking code to a queue for execution by a blocking thread once one becomes available.
Example Implementation
As an example of how to write a JactlEnv class have a look at the
io.jactl.vertx.JactlVertxEnv
class provided in the jactl-vertx project or see the default
io.jactl.DefaultEnv implementation.
.jactlrc File
If your environment class has a no-arg constructor, and you want to be able to run your extension functions and methods
(see below) in the Jactl REPL or in command-line scripts,
then you can configure your .jactlrc file with the name of your environment class.
See .jactlrc File for more details.