On Wed, 11 Jun 2025 21:16:40 GMT, Mark Sheppard <[email protected]> wrote:
>>> Alan @AlanBateman, do you suggest we continue with this text or would any
>>> update be necessary?
>>
>> I think it's helpful here to give some indication in this API note as what
>> the timeout might be. It doesn't really matter if it says 60s or 75s, the
>> point is that establishing a TCP connection is subject to a timeout imposed
>> by the operating system. It helps for cases where someone calls connect with
>> a timeout of say 300_000 (5 minutes) and is surprised to get
>> ConnectException "Operation timed out" after a minute or so. This is exactly
>> what prompted JDK-7116990, someone called connect with a timeout that is
>> larger than the OS configured timeout.
>
> Looking at this on the 3 main OS platforms (Windows, OL and macOS) and
> running a simple test to trigger a connect timeout then finding are
>
> macOS the connect timeout is 75 seconds as this is derived from 4.3 BSD
>
> If OL linux has a syn retries set to 6 and an RTO == 1 sec then it’s connect
> timeout is 130 seconds approx
> That’s initial syn timeout of 1 seconds and then 6 retries totalling 127
> seconds
>
> Windows by default connect timeout is 21 seconds
> RTT == 3 seconds and two connect retries
> Initial syn timeout 3 seconds + 2 retries at 6 and 12 seconds == 21 seconds
FWIW an possible alternative wording
Establishing a TCP/IP connection is subject to a connect timeout, determined by
configuration settings
of the operating system, for example the number of connect retries together
with an implementation’s back off strategy. Thus, TCP/IP Connect timeout values
can vary across operating system, for example 75 seconds on macOS, with a
default value of 21 seconds on Windows system. As such, the operating system
TCP/IP Connect timeout may expire before that specified to the connect method.
If the operating system Connect timeout expires
before the {@code timeout} specified to this method then an {@code IOException}
is thrown. The {@code timeout}
specified to this method is typically a timeout value that is shorter than the
operating system timeout.
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PR Review Comment: https://git.openjdk.org/jdk/pull/25690#discussion_r2142282586
