Remove proxy settings detection behavior in "default proxy mode." #1188
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This commit partially reverts microsoft@eb108ad in order to work around a reliability problem with WinHttpGetProxyForUrl. That function hangs unless there is an available thread pool thread to complete the WPAD request. As a result, if a customer issued ~512 concurrent HTTP requests, or otherwise needed that many thread pool threads, there would not be a thread available for WinHTTP to complete the operation, and the program would deadlock. Moreover this call to WinHttpGetDefaultProxyConfiguration is extremely expensive, taking ~20% of overall CPU for the entire program for some Azure Storage SDK customers. The function WinHttpGetProxyForUrlEx is supposed to help with this problem by being asynchronous, but that function was added in Windows 8, so we can't use it unconditionally. And on Windows 8.1 we already are using WINHTTP_ACCESS_TYPE_AUTOMATIC_PROXY instead of trying to do proxy autodetect ourselves.
Member
Author
|
@vadz Any comments? |
Member
Author
|
Ivan Pashov of the WinHTTP team confirms that WINHTTP_ACCESS_TYPE_AUTOMATIC_PROXY completely obsoletes WinHttpGetProxyForUrl. |
Contributor
|
@BillyONeal sorry for the delay with reply. In any case, I don't have much to say: I didn't notice any performance problems, but that's because I use the library from interactive application doing just a few requests. For me the important thing is that it works out of the box even in restricted corporate environments, but I think this should still be the case with your changes. TL;DR: no real comments. |
Member
Author
|
@vadz In that case you will need to pass in a proxy config set to auto_discovery to request WPAD after this change.. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This commit partially reverts eb108ad in order to work around a reliability problem with WinHttpGetProxyForUrl. That function hangs unless there is an available thread pool thread to complete the WPAD request. As a result, if a customer issued ~512 concurrent HTTP requests, or otherwise needed that many thread pool threads, there would not be a thread available for WinHTTP to complete the operation, and the program would deadlock.
Moreover this call to WinHttpGetDefaultProxyConfiguration is extremely expensive, taking ~20% of overall CPU for the entire program for some Azure Storage SDK customers.
The function WinHttpGetProxyForUrlEx is supposed to help with this problem by being asynchronous, but that function was added in Windows 8, so we can't use it unconditionally. And on Windows 8.1 we already are using WINHTTP_ACCESS_TYPE_AUTOMATIC_PROXY instead of trying to do proxy autodetect ourselves.