Callflow Logging

Function calling sequence as a plantuml sequence diagram.

Experimental Feature

Callflow logging was transferred from another project and the code base contains some legacy. The feature is useable but in a beta state.

Mechanics

1. The feature works via the sys.set_trace hook, being invoked at function entry and exit, a feature which also the coverage package uses in order to record code coverage.

2. This feature here allows to specify which functions should be traced, so that the call flow charts only contain interesting stuff.

3. We record input and exit data plus invokation and exit times.

4. Then we draw plantuml files, incl. links to statically deliverable json files, with more information.

5. Once we have the plantuml files, we create svgs using the kroki plugin.

6. The svg is embedded into the html, in order to get javascript click handlers working.

7. A javascript part takes care for proper formatting within mkdocs and fetching the details on mouse over and click events.

See the example.

Syntax

• Add cfl as header parameter, in order to get the LP block written into standalone importable module, created in your build directory.

• In the show('callflow', call=..., trace=[<list of traced object>]) function call supply the entry function to be wrapped and a number of objects to be traced. These may be modules, classes and functions.

• You may supply kroki header parameters like server and puml for style, since we call this module to render the created plantuml into an svg.

Important

• Every change of the lp code body will result in new flow charts being created, together with all in and out parameters. That might pile up, so please clear your build dir from time to time and git-ignore it.
• The docs dir gets a symlink over to the build dir: docs/autodocs.

Example

We trace the standard lib's json module while calling dumps:

LP Source:

 ```python lp:python cfl addsrc
 
 import json
 def say_hello(n):
     print(n)
     return json.dumps({'name': n})
 
 def test_flow():
     say_hello('joe')
 
 show('call_flow', call=test_flow, trace=json)
 
 ```

Result:

joe

Move the mouse over the arrows and click to see the full data recorded.

Call Flow Details

You should get details infos like these

Ctrl+R (reload) to get back.

Questions and Comments?