Improve response time `//moto-api/reset`

Hi everyone,

I am using moto 2.2.0 on Python 3.8. I am testing code which uses s3fs, and testing it using moto_server s3. This is necessary as moto seems to have problems working with async file systems unless it runs as a standalone server.

There seems to be a large (5-6 second) overhead when calling reset the first time in my fixture, even after not having touched the emulated S3 at all. Subsequent calls return very quickly. Here is an example from a test run:

.2021-07-26 16:19:39,453 WARNING Returning from s3 base...
127.0.0.1 - - [26/Jul/2021 16:19:46] "POST //moto-api/reset HTTP/1.1" 200 -

I can’t paste the exact setup since a lot of the code is internal, but the problematic fixture is the following:

@pytest.fixture(name="s3_base")
def _s3_base(monkeypatch, s3_session_base, mocked_s3_uri):
    try:
        with monkeypatch.context() as m:
            # This ensures we always fail if we accidentally bypass moto in tests which should mock AWS, while the
            # monkeypatch context also prevents interference with (exceptional) tests that actually need to touch the
            # real S3, e.g., to check whether a bucket exists.
            m.setenv("AWS_SECRET_ACCESS_KEY", "fake_secret_access_key")
            m.setenv("AWS_ACCESS_KEY_ID", "fake_access_key_id")
            yield
    finally:
        logging.warning("Returning from s3 base...")
        requests.post(mocked_s3_uri + "/moto-api/reset")
        logging.warning("Server reset OK")

s3_session_base basically provides the moto server wrapped in a fixture, similar to the code in the s3fs code base.

The gap between making the POST request in the finally block and the moto server actually acknowledging it is ~7 seconds. Everything else, including moto server setup, is fast, less than 100ms or so.

My original goal was to allow the moto server to be reused throughout a module, and just reset it for every test, but right now it seems like just re-creating the server for every single test is faster, which seems odd.

Any pointers as to what could be causing the moto server to respond so slowly? Maybe something I could have misconfigured?

[AndreiBarsan]

This is fantastic @bblommers! Works like a charm with the new update. The teardowns now take negligible amounts of time. Thank you!

Before:

====================================================================== test session starts ======================================================================
platform linux -- Python 3.8.7, pytest-6.2.2, py-1.10.0, pluggy-0.13.1
rootdir: /home/andrei/... configfile: setup.cfg
plugins: ...
gw0 [143] / gw1 [143] / gw2 [143] / gw3 [143]
.........................................................................................................................s.....................           [100%]
============================================================= slowest 10 durations ==============================================================
5.23s teardown <moto test>
5.20s teardown <moto_test>
5.16s teardown <moto test>
5.08s teardown <moto test>
0.92s setup    <moto test>
0.83s setup    <moto test>
0.81s setup    <moto test>
...
========================================================= 142 passed, 1 skipped in 18.17s ========================================================

After:

python -m pytest ... --maxfail=4 --durations=10 -n 4
====================================================================== test session starts ======================================================================platform linux -- Python 3.8.7, pytest-6.2.2, py-1.10.0, pluggy-0.13.1
rootdir: /home/andrei/..., configfile: setup.cfg
plugins: ...
gw0 [143] / gw1 [143] / gw2 [143] / gw3 [143]
.....................................................................................................................s.........................           [100%]
===================================================================== slowest 10 durations ======================================================================
0.78s setup    <moto test>
0.67s setup    <moto test> 
0.66s setup    <moto test>
0.65s setup    <moto test>
0.51s call     <unrelated test>
...
================================================================ 142 passed, 1 skipped in 12.71s ===============================================================

[bblommers]

Yeah, that makes sense @AndreiBarsan. Either that, or simply add a specific endpoint to reset only a single service (requests.post("http://localhost:5000/moto-api/resetservice/s3")). I’ll mark this issue as an enhancement, if anyone wants to pick this up.