Python initialization and runtime sequence for http communication

This article explains the initialization and runtime sequence of Python http modules.

Overview

The initialization and runtime sequence of Python scripts follows two general phases:

• The initialization phase: this phase takes place during the module initialization
• The runtime phase: this phase takes place after the module start

Note that if the initialization phase does not end correctly^[1]

It can be the case if the Python script takes too much time to start-up, or if there is an exception during the initialization of the script

, then the Python http module initialization will be aborted. Else the runtime phase will be started.

Initialization phase

The initialization phase follows the following steps:

• The Python script is started using the specified Python executable in a separate process
• The pythonHttpModule.py script sets the pythonHttpUtils field to the Python script
• The Python script start(self) method is called if the method exists

If all went well, at this point the Python module is initialized, and the runtime phase is started. Note that the Python module initialization will be aborted if:

• The Python script start-up and instantiation took longer than the expected waitAtStart parameter^[2]
  If not specified, the value is set to 200 ms
  . See also Waiting for Python runtime initialization

Runtime phase

The runtime phase follows the following steps:

• To get the content of a service, the notify(self, serviceName, instanceId=0) method of the pythonHttpUtils.py can be called. It will send a GET request for the associated route to the server
• To invoke a service, the invoke(self, serviceName) method of the pythonHttpUtils.py can be called. It will send a POST request for the associated route to the server

Using lengthy methods for the Python scripts

If you have some code for initializing your Python script which takes a lot of time to complete, you can:

• Put this code in the def __init__(self)( method, and make sure that the waitAtStart value if sufficient