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Re: Total http/2 concurrency for multiplexed multi-handle
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From: Daniel Stenberg via curl-library <curl-library_at_lists.haxx.se>
Date: Thu, 9 Feb 2023 09:31:12 +0100 (CET)
On Wed, 8 Feb 2023, Jeroen Ooms via curl-library wrote:
> HTTP/2 stream 20139 was not closed cleanly before end of the underlying stream
>
> So either they introduced a server bug, or perhaps GitHub is deliberately
> blocking abusive behavior due to high concurrency.
My guess: they probably just cut off something (like the connection) instead
of closing down the streams nicely, hence this error.
> I am using a multi handle with CURLPIPE_MULTIPLEX and otherwise default
> settings. Am I correct that this means libcurl starts 100 concurrent streams
> (CURLMOPT_MAX_CONCURRENT_STREAMS), and still make 6 concurrent connections
> (CURLMOPT_MAX_HOST_CONNECTIONS) per host, i.e. download 600 files in
> parallel? I can imagine that could be considered abusive.
If you have added >= 600 transfers to the multi handle, libcurl will attempt
to do them like that.
This said, we also have a bug in HTTP/2 that makes it not always "fill up" the
connections properly after the first one is saturated. (Fixed in master)
> Should I set CURLMOPT_MAX_HOST_CONNECTIONS to 1 in case of http/2
> multiplexing? Or is CURLMOPT_MAX_HOST_CONNECTIONS ignored in case of
> multiplexing?
It is independent of multiplexing.
> One other thing I noticed is that GitHub does not seem to set any
> MAX_CONCURRENT_STREAMS, or at least I am not seeing any. For example on
> httpbin I see this:
>
> curl -v 'https://httpbin.org/get' --http2
> * Connection state changed (MAX_CONCURRENT_STREAMS == 128)!
>
> However for GitHub I don't see such a thing:
>
> curl -v 'https://raw.githubusercontent.com/curl/curl/master/README' --http2
>
> So does this mean libcurl will assume 100 streams is OK?
Yes I believe so.
> Is there a way to debug this, and monitor how many active downloads a
> multi-handle is making in total (summed over all connections)?
I think libcurl lacks that ability. The 'running_handles' counter the
*perform() function returns include transfers that are queued up. You
basically want running_handles - num_pending.
Maybe we should provide a curl_multi_getinfo() for things like this?
Date: Thu, 9 Feb 2023 09:31:12 +0100 (CET)
On Wed, 8 Feb 2023, Jeroen Ooms via curl-library wrote:
> HTTP/2 stream 20139 was not closed cleanly before end of the underlying stream
>
> So either they introduced a server bug, or perhaps GitHub is deliberately
> blocking abusive behavior due to high concurrency.
My guess: they probably just cut off something (like the connection) instead
of closing down the streams nicely, hence this error.
> I am using a multi handle with CURLPIPE_MULTIPLEX and otherwise default
> settings. Am I correct that this means libcurl starts 100 concurrent streams
> (CURLMOPT_MAX_CONCURRENT_STREAMS), and still make 6 concurrent connections
> (CURLMOPT_MAX_HOST_CONNECTIONS) per host, i.e. download 600 files in
> parallel? I can imagine that could be considered abusive.
If you have added >= 600 transfers to the multi handle, libcurl will attempt
to do them like that.
This said, we also have a bug in HTTP/2 that makes it not always "fill up" the
connections properly after the first one is saturated. (Fixed in master)
> Should I set CURLMOPT_MAX_HOST_CONNECTIONS to 1 in case of http/2
> multiplexing? Or is CURLMOPT_MAX_HOST_CONNECTIONS ignored in case of
> multiplexing?
It is independent of multiplexing.
> One other thing I noticed is that GitHub does not seem to set any
> MAX_CONCURRENT_STREAMS, or at least I am not seeing any. For example on
> httpbin I see this:
>
> curl -v 'https://httpbin.org/get' --http2
> * Connection state changed (MAX_CONCURRENT_STREAMS == 128)!
>
> However for GitHub I don't see such a thing:
>
> curl -v 'https://raw.githubusercontent.com/curl/curl/master/README' --http2
>
> So does this mean libcurl will assume 100 streams is OK?
Yes I believe so.
> Is there a way to debug this, and monitor how many active downloads a
> multi-handle is making in total (summed over all connections)?
I think libcurl lacks that ability. The 'running_handles' counter the
*perform() function returns include transfers that are queued up. You
basically want running_handles - num_pending.
Maybe we should provide a curl_multi_getinfo() for things like this?
-- / daniel.haxx.se | Commercial curl support up to 24x7 is available! | Private help, bug fixes, support, ports, new features | https://curl.se/support.html -- Unsubscribe: https://lists.haxx.se/listinfo/curl-library Etiquette: https://curl.se/mail/etiquette.htmlReceived on 2023-02-09