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Re: Setting connection timeout per host?

From: Daniel Stenberg via curl-library <>
Date: Sat, 9 Jan 2021 23:45:22 +0100 (CET)

On Sun, 10 Jan 2021, Midnight Wonderer wrote:

>> - Users expect the timeout to expire after the given time, so if the host has
>> N addresses, they still don't want the timeout to be multiplied with N.
> This is true if we are talking about "timeout", which should refer to the
> timeout as a whole. But we are talking about "connection timeout" here, most
> people would assume it is per connection.

Then you know more about most curl users than I do.

> However, we are setting the connection timeout, mostly, because we don't
> want to waste more time on a hopeless connection.

Correct. You typically don't know how many addresses a host name resolves to,
and these days it isn't even unusual 20 addresses.

Users I've talked to want an option that works like this:

  - "I want to connect to the server within 10 seconds or give up"

*The server* or even "the URL". That's a single unity and there's a single
timeout value, given in a time unit.

They very rarely say:

  - "I want to attempt to connect to each address of the host name for 10
seconds each before we give up, which can take anywhere from 10 to 200 or more

>> So what does nginx do when the first IP address just silently drops all TCP
>> packets? Fail the connection after one second even if there are also 9 working
>> IP addresses?
> It will try the next one.

So a 10 second timeout can legitimately take 200 seconds before it expires.
That surely will surprise some users.

But sure, that's just a decision taken in the opposite way we did.

> So the connection timeout is per connection.

It wouldn't strictly be "per connection" though since no connection could be

It could be per *connection attempt* and it probably makes IPv4 and IPv6
connection attempts in parallel, happy eyeballs style.

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Received on 2021-01-09