Flask get request call times for each api

Question

I use the uwsgi to start my flask server, which has 15 workers, and I want to get the call times for each api, and return the result like:

{
    "api/students": 10,
    "api/teachers": 20,
    ...
}

I add the before_request handle for app:

@app.before_request
def before_request_handler():
    # here to do statistics
    # count += 1

And I write an api to get the count value. However, I found that each time the values was not increment, because there're multi workers, each time I just got one worker's call times

So, my question is how to collect all the request call times from all the workers in Flask?

There is a global variable `g` for managing shared variable all over the app. you can use a default `dict` that keeps name (url) and value (how many times the URL is invoked) in `before_request` decorated function. I am not sure about thread safety yet. But please be sure about that multiple workers do not change the value of URL dict in a same time. — Saiful Azad, Sep 14 '17 at 06:38
no simple solution inside flask, but I guess you could just do logging api call time and do the stats on logs, which is much easier to me. — georgexsh, Sep 14 '17 at 06:44

score 0 · Answer 1 · answered Sep 14 '17 at 06:47

You cannot track counters like this across workers as you'll run into problems like:

Assuming workers are running in separate processes, you'll need to reconcile your counters
Assuming workers are running in threads, you'll need to make sure your counters are thread safe.

In the comment section, it is suggested to use the g object, this won't work as g is global per request only. After each request, g gets torn down.

The correct way to implement counters is to use a 3rd party data store. A database can do the job (concurrency can be handled in transactions) but it's recommended to use a caching service like Redis or Memcached.

Flask get request call times for each api

1 Answers1