AppMap Agent for Python

About

appmap is a Python package for recording AppMaps of your code.

The AppMap data format includes code structure (packages, modules, classes, and methods), trace events (function calls, web services, RPC calls, SQL, parameters, return values, exceptions, etc), and code metadata (repo URL, commit SHA, etc). It’s more granular than a performance profile, but it’s less granular than a full debug trace. It’s designed to be optimal for understanding the design intent and structure of code and key data flows.

Supported versions

Support for new versions is added frequently, please check back regularly for updates.

Installation

If your project uses pip for dependency management, add the appmap package to the requirements file or install it directly with

pip install appmap

For projects that use poetry , add the appmap package to pyproject.toml.

poetry add --group=dev appmap

pipenv is also supported:

pipenv install --dev appmap

To use AppMaps in your code editor, you’ll also want to install the corresponding AppMap extension:

Configuration

Add your modules as path entries in appmap.yml, and external packages (distributions) as dist:

  name: my_python_app
  packages:
  - path: app.mod1
    shallow: true
  - path: app.mod2
    exclude:
    - MyClass
    - MyOtherClass.my_instance_method
    - MyOtherClass.my_class_method
  # You can record dependency packages, such as Django.
  # We don't recommend recording Django by default though, your AppMaps will be quite large
  # and mostly about Django itself, not your own code.
  #- dist: Django
  #  exclude:
  #  - django.db

Note that an exclude is resolved relative to the associated path. So, for example, this configuration excludes app.mod2.MyClass.

For external distribution packages use the dist specifier; the names are looked up in the database of installed Python distributions. This is generally the same package name as you’d give to pip install or put in pyproject.toml. You can additionally use path and exclude on dist entries to limit the capture to specific patterns.

By default, shallow capture is enabled on dist packages, supressing tracking of most internal execution flow. This allows you to capture the interaction without getting bogged down with detail. To see these details, set shallow: false. You can also use shallow: true on path entries.

Tests recording

appmap supports recording pytest and unittest test cases.

pytest

appmap is a pytest plugin. When it’s installed in a project that uses pytest, it will be available to generate AppMaps.

root@e9987eaa93c8:/src/appmap/test/data/pytest# pip show appmap
Name: appmap
Version: 0.0.0
Summary: Create AppMap files by recording a Python application.
Home-page: None
Author: Alan Potter
Author-email: alan@app.land
License: None
Location: /usr/local/lib/python3.9/site-packages
Requires: orjson, PyYAML, inflection
Required-by:
root@e9987eaa93c8:/src/appmap/test/data/pytest# APPMAP_LOG_LEVEL=info pytest -svv
[2021-02-10 11:37:59,345] INFO root: appmap enabled: True
[2021-02-10 11:37:59,350] INFO appmap._implementation.configuration: ConfigFilter, includes {'simple'}
[2021-02-10 11:37:59,350] INFO appmap._implementation.configuration: ConfigFilter, excludes set()
===================================================================== test session starts =====================================================================
platform linux -- Python 3.9.1, pytest-6.2.2, py-1.10.0, pluggy-0.13.1 -- /usr/local/bin/python
cachedir: .pytest_cache
rootdir: /src, configfile: pytest.ini
plugins: appmap-0.0.0
collected 1 item

test_simple.py::test_hello_world [2021-02-10 11:37:59,482] INFO appmap.pytest: starting recording /tmp/pytest/test_hello_world.appmap.json
[2021-02-10 11:37:59,484] INFO appmap._implementation.configuration: included class simple.Simple
[2021-02-10 11:37:59,484] INFO appmap._implementation.configuration: included function simple.Simple.hello
[2021-02-10 11:37:59,489] INFO appmap._implementation.configuration: included function simple.Simple.hello_world
[2021-02-10 11:37:59,490] INFO appmap._implementation.configuration: included function simple.Simple.world
[2021-02-10 11:37:59,828] INFO appmap.pytest: wrote recording /tmp/pytest/test_hello_world.appmap.json
PASSED

====================================================================== 1 passed in 0.45s ======================================================================

unittest

A subclass of unittest.TestCase is instrumented automatically, and an AppMap is recorded for each test_* function in the subclass.

Requests recording

appmap-python can automatically record and save an AppMap for each HTTP server request. To do this, the AppMap agent hooks into the web server request processing framework. It starts a recording when each new request is received, records the execution thread into an AppMap, and saves in when the request is completed.

Note Your application must be running in a supported web framework (Django, Flask) for requests recording to work.

Remote recording

The AppMap agent supports remote recording of Django and Flask web applications during development. When your application is run with debugging support, remote recording will be enabled automatically.

To enable debugging support, ensure:

  • Django DEBUG = True in settings.py
  • Flask run with the --debug option

Note Your application must be running in a supported web framework (Django, Flask) for remote recording to work.

Code Block Recording

You can use appmap.record as a context manager to record a specific span of code. With this method, you can control exactly what code is recorded, and where the recording is saved.

Given a source file record_sample.py:

import os
import sys

import appmap

r = appmap.Recording()
with r:
    import sample
    print(sample.C().hello_world(), file=sys.stderr)

with os.fdopen(sys.stdout.fileno(), "w", closefd=False) as stdout:
    stdout.write(appmap.generation.dump(r))
    stdout.flush()

and a source file sample.py:

class C:
    def make_str(self, s):
        return s;

    def hello_world(self):
        return f'{self.make_str("Hello")} {self.make_str("world!")}'

as well as appmap.yml:

name: sample
packages:
- path: sample
language: python
appmap_dir: tmp/appmap

you can generate a recording of the code

% python record_sample.py > record_sample.appmap.json
% jq '.events | length' record_sample.appmap.json
6
% jq < record_sample.appmap.json | head -10
{
  "version": "1.4",
  "metadata": {
    "language": {
      "name": "python",
      "engine": "CPython",
      "version": "3.9.1"
    },
    "client": {
      "name": "appmap",

Web framework support

appmap-python integrates with both the Django and Flask web frameworks. When an application is started in a development environment, it inserts itself into the application’s request processing stack. This enables recording of requests, as well as support for the AppMap remote recording API.

Django

To start a Django app with AppMap integration enabled, add

DEBUG = True

to your application’s settings.py.

Flask

When flask is invoked with the --debug switch, debugging is enabled, as well as AppMap integration.

Decorators

@appmap.labels

The AppMap data format provides for class and function labels, which can be used to enhance the AppMap visualizations, and to programatically analyze the data.

You can apply function labels using the appmap.labels decorator in your Python code. To apply a label to a function, decorate the function with @appmap.labels.

For example, to label a function as an authentication provider:

import appmap

class ApiKey
  @appmap.labels('provider.authentication', 'security')
  def authenticate(self, key):
      # logic to verify the key here...

Then the AppMap metadata section for this function will include:

  {
    "name": "authenticate",
    "type": "function",
    "labels": [ "provider.authentication", "security" ]
  }

@appmap.noappmap

The @appmap.noappmap decorator can be used to disable recording of pytest and unittest tests. If applied to a specific function, that function will not generate an AppMap. Alternatively, it can be applied to a test class to disable generation of AppMaps for all tests in the class.

For example:

import appmap

def test_test1():
    ...

@appmap.noappmap
def test_test2():
    ....

When the tests above are executed, test_test1 will generate an AppMap, but test_test2 will not.

For example, to decorate a test class:

import unitest

import appmap

@appmap.noappmap
class TestNoAppMaps(unittest.TestCase):
    def test_test1(self):
        ...

    def test_test2(self):
        ...

When functions within TestNoAppMaps are executed, no AppMaps will be generated.

Environment variables

General configuration

These environment variables can be used to control various aspects of the AppMap agent.

  • APPMAP_CONFIG specifies the configuration file to use. Defaults to appmap.yml in the current directory.

  • APPMAP_LOG_LEVEL specifies log level to use, from the set CRITICAL, ERROR, WARNING, INFO, DEBUG. Not case-sensitive, defaults to INFO.

  • APPMAP_DISPLAY_PARAMS enables rendering of parameters as strings. If true (the default, not case-sensitive), parameters are rendered using repr. If false, a generic string is used instead.

Controlling recording

These variables control the types of recordings generated by the agent.

Disabling recording methods

Some recording types are enabled by default. These variables allow you to disable them.

  • APPMAP_RECORD_<PYTEST|UNITTEST> disables recording for individual test frameworks when set to false. For example, to disable recording when using pytest, use the variable APPMAP_RECORD_PYTEST.

  • APPMAP_RECORD_REQUESTS disables recording of HTTP requests when set to false.

  • APPMAP_RECORD_REMOTE disables remote recording when set to false.

  • APPMAP controls all instrumentation and recording. When set to false, application code will run as if the AppMap agent was not installed.

Enabling recording methods

Some recording types are not enabled by default. These variables allow you to enable them

  • APPMAP_RECORD_PROCESS controls recording of the entire python process that loads the agent. When true, recording starts when the agent is loaded. When the process exits, an AppMap will be created.

GitHub repository

https://github.com/getappmap/appmap-python


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