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From Nick Dunkin <Nick.Dun...@vecima.com>
Subject Trying to understand no-activity timeouts
Date Tue, 23 Jun 2020 17:33:12 GMT
Hi,

We are still dealing with a particular kind of no-activity time out issue.

We are dealing with an Origin that will occasionally take 20 seconds to return a HTTP 500
(annoying, right).  We took a tcpdump and captured this occurring.  In the trace we can see
the /GET and the ACK, and then a full 20 seconds (approx) before the HTTP 500 comes back.
 Please see the below picture.

[A screenshot of a cell phone  Description automatically generated]

To be clear, apart from accepting the connection, the Origin Server sends NOTHING over the
connection during the 20 seconds.

Without Parent Routing

This looks very much like something the Origin side “no-activity” timeouts should cater
for, so we set both of the following (for good measure) to 2 seconds, but we still see exactly
the same thing occurring.

CONFIG proxy.config.http.transaction_active_timeout_out INT 2
CONFIG proxy.config.http.transaction_no_activity_timeout_out INT 2

We managed to resolve this particular issue by using adding the following configuration, which
is a “timeout to first byte”.  Is this the correct configuration solution for dealing
with this issue?

CONFIG proxy.config.http.connect_attempts_timeout INT 2

This all seems to make sense based on the available documentation.  So far so good.

With Parent Routing

However, when we enable parent routing, and put the same single Origin Server in parent.config,
we DO NOT see the “timeout to first byte” being applied.  What are we missing about these
timeouts and how they interact with parent routing?

This all seems to hinge on the fact that the Origin server does not send a single byte for
multiple seconds.    We see more predictable behavior if the Origin Server serves any data
before the 20 seconds hang.

Very grateful for any insight.

Regards,

Nick Dunkin

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