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From: Pushkar Kulkarni <>
Date: Wed, 14 Dec 2016 16:59:47 +0530

Hi there,

I am working on the Foundation libraries of open source Swift. The
implementation of URLSession there, uses libcurl underneath.

There's an issue where we make ~180 GET calls to the *same endpoint* (the
GitHub API). Internally, for each GET call we seem to be configuring an
easy handle and then registering it with a multi handle. In one of these
iterations (randomly), I see libcurl returning CURLE_CANNOT_CONNECT.

So, I turned on the verbose mode and before each transfer I could see this:
[1] Connection #0 to host left intact

Only, before the failing connection, I see:
[1] Connection #0 to host left intact
[1] Closing connection 0`

Nothing else is logged on failure. When I try to use strace, to find the
failing system call, the failure gets masked.

I am not sure how to proceed with the analysis. Can someone please help me
take this further, please?

List admin:
Received on 2016-12-14