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Service Performance Profiler


You need to install dependencies for the middleware you want to use

Introduction to Pyinstrument

Pyinstrument is a statistical python profiler which records call stack every 1 ms rather than recording the whole trace. This is done in order to avoid profiling overhead which can increase a lot if some functions are getting called many times and not taking that much time to complete.

This kind of behavior can even distort results by highlighting part of the code/function which might not be slow but getting called many times completing faster. In a way it kind of tries to avoid profiling noise by removing profiling information of faster parts of code.

This kind of behavior also has a drawback that some of the function calls which ran quite fast will not be recorded but they are already fast.

Pyinstrument uses an OS feature called signals to ask OS to send a signal and handle signals using a python signal handler (PyEval_SetProfile) for recording every 1 ms.


import random

def add(a, b):
    return a+b

def get_sum_of_list():
    final_list = []
    for i in range(1000000):
        rand1 = random.randint(1,100)
        rand2 = random.randint(1,100)
        out = add(rand1, rand2)
    return final_list

if __name__ == "__main__":
    l = get_sum_of_list()
  • Below we have profiled script using Pyinstrument without default options. Please make a note that we are using the ! symbol which lets us execute a shell command from Jupyter Notebook. This command can be run exactly the same way from a shell.

!pyinstrument profiling_examples/


  _     ._   __/__   _ _  _  _ _/_   Recorded: 16:39:21  Samples:  2192
 /_//_/// /_\ / //_// / //_'/ //     Duration: 2.199     CPU time: 2.197
/   _/                      v3.2.0

Program: profiling_examples/

2.199 <module>
└─ 2.199 get_sum_of_list
   ├─ 1.714 randint
        [6 frames hidden]  random
           1.442 randrange
           ├─ 0.734 [self]
           └─ 0.708 _randbelow
              ├─ 0.501 [self]
              ├─ 0.153 Random.getrandbits  ../<built-in>:0
              └─ 0.054 int.bit_length  ../<built-in>:0
   ├─ 0.405 [self]
   ├─ 0.050 add
   └─ 0.030 list.append  ../<built-in>:0

To view this report with different options, run:
    pyinstrument --load-prev 2020-11-12T16-39-21 [options]

Reference: pyinstrument-statistical-profiler-for-python-code

Middleware Integration

With AuthX the abstract of profiling is easy, it's just about calling the ProfilerMiddleware 's class and calling it in add_middleware(ProfilerMiddleware) func that FastAPI provides.

How to install

Make sure to have the necessary dependencies installed:

$ pip install authx_extra

---> 100%


import os
import uvicorn

from fastapi import FastAPI
from fastapi.responses import JSONResponse

from authx_extra.profiler import ProfilerMiddleware

app = FastAPI()

async def normal_request():
    return JSONResponse({"retMsg": "Hello World!"})

if __name__ == '__main__':
    app_name = os.path.basename(__file__).replace(".py", "")"{app_name}:app", host="", port=8080, workers=1)

Middleware Options

This class to have 3 functions that expose the profiling information, one is to get the profiling information, one is to get the profiling information in a JSON format and one is to get the profiling information in a HTML format.

app.add_middleware(PyInstrumentProfilerMiddleware, profiler_output_type="html", is_print_each_request=False, html_file_name="profiling.html")