Are coroutines supported? #267

aleGpereira · 2022-12-08T19:38:35Z

aleGpereira
Dec 8, 2022

Can memray be used for applications that uses asyncio? does it trace async/await functions properly?

Dec 9, 2022

Coroutines are supported, but the way they are reported may be surprising. Internally, the way that coroutines work is by yielding control back to an event loop when control is yielded from one coroutine to another, so in the implementation, coroutines are directly called by the event loop. The stacks that Memray shows for coroutines reflect that reality. Our flame graphs may not show which coroutine awaited another coroutine, and can instead show which runner ran each coroutine. This accurately reflects the reality of how coroutines get run, but the lack of context about why the runner is running a particular coroutine can make it hard to reason about the reports.

For instance, this flam…

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godlygeek · 2022-12-09T17:02:15Z

godlygeek
Dec 9, 2022
Maintainer

Coroutines are supported, but the way they are reported may be surprising. Internally, the way that coroutines work is by yielding control back to an event loop when control is yielded from one coroutine to another, so in the implementation, coroutines are directly called by the event loop. The stacks that Memray shows for coroutines reflect that reality. Our flame graphs may not show which coroutine awaited another coroutine, and can instead show which runner ran each coroutine. This accurately reflects the reality of how coroutines get run, but the lack of context about why the runner is running a particular coroutine can make it hard to reason about the reports.

For instance, this flame graph:

Is the result of running this Python program:

import
 asyncio


xs
 =
 []

async
 def
 foo
():
    
return
 await
 bar
()

async
 def
 bar
():
    
return
 await
 baz
()

async
 def
 baz
():
    
await
 asyncio
.
sleep
(
0.1
)
    
xs
.
append
(
"x"
 *
 1024
 *
 1024
)

async
 def
 main
():
    
print
(
await
 asyncio
.
gather
(
foo
(), 
bar
(), 
baz
()))

asyncio
.
run
(
main
())

We do show 3 different call stacks that all lead to baz being called, and all 3 are reported reasonably in our flame graph. But, all 3 of those are being awaited by asyncio.gather, and the frame for asyncio.gather does not itself appear in the flame graph.

3 replies

papb Jun 20, 2023

Hi @godlygeek ! I have a few follow-up questions about this:

Does with memray.Tracker("some_output_file.bin"): work when I have an await something() inside the with block)?
Are there any plans on improving the way coroutine calls are reported into a less surprising output (maybe under an option)?

Note: for 1, you can assume no other Trackers are ever active (I've read in the API docs that only one Tracker can be active at a time).

godlygeek Jun 20, 2023
Maintainer

Hi @papb !

Yes, that will work fine - tracking will start when the with block is entered, and stop when the with block is exited, just as you'd expect.
There are no plans to change the way that stacks are reported, no. I'm not sure what we could do differently. We're reporting the actual stack. The stack that we report is the same one that would be shown in a traceback printed by the interpreter itself, and the same one as you'd see from other profilers like cProfile. There's no way for the foo coroutine in my example above to know that the thing waiting for it to finish is the asyncio.gather call inside the main coroutine.

papb Jun 23, 2023

Nice, thank you!

aleGpereira · 2022-12-09T18:21:42Z

aleGpereira
Dec 9, 2022
Author

Thank you so much for the detailed response!

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Are coroutines supported? #267

aleGpereira Dec 8, 2022

Replies: 2 comments · 3 replies

godlygeek Dec 9, 2022 Maintainer

papb Jun 20, 2023

godlygeek Jun 20, 2023 Maintainer

papb Jun 23, 2023

aleGpereira Dec 9, 2022 Author

aleGpereira
Dec 8, 2022

Replies: 2 comments 3 replies

godlygeek
Dec 9, 2022
Maintainer

godlygeek Jun 20, 2023
Maintainer

aleGpereira
Dec 9, 2022
Author