advanced.rdoc

Advanced Techniques: Serving multiple services from the same process¶ ↑

This technique is called shared process, where multiple services coded inside the same executable work and share the process space, reducing that way the memory footprint of serving several process (all of the same kind of complementary).

This is similar on how svchost manage Windows System Services.

How To Use¶ ↑

In general lines, the creation of each service is based in the same steps as described
on the README file -- Getting Started section.
The main change is that you'll not execute each service indiviaully, but will require a 
ServiceHost object.
ServiceHost will perform the needed steps to announce the services against SCM. You first
need define your ServiceHost:
  dim MyHost as ServiceHost
Now, after you have created and assigning the name and actions for each of your services, 
add each one to the ServiceHost table:
  MyHost.Add(Service1)
  MyHost.Add(Service2)
  ...
  MyHost.Add(ServiceN)
Be aware that each service name must be unique so the Service Control Manager (SCM) could
communicate correctly with each one.
Now, you're ready to start, simply call
  MyHost.Run()
Which will perform the required actions and negotations with the SCM based on your services.

Advices¶ ↑

Sharing the same process sounds cool, but is dangerous. All the services share the same memory 
space, that means some locking must be applied when working with shared/global data.
Conceptually, if I crash a thread inside my shared process, the whole process could crash.
So far, based only on testing, couldn't recreate that scenario, but be careful.
If you defined your events (onInit, onStart, on*) globaly, they cannot be shared across services
safely unless you code some magic tricks and locking mechanisms around them. Please refer to the
Reusability Techniques section in this document for a workaround this problem.

Reusability techniques¶ ↑

With simplification in mind, ServiceFB offer you way to structure your services in the way that
isolate service internals and let you focus on your code.
TODO: describe example on setting instances of the same service code but serving / responding
each one to different service names.