Re: max length with Dropped log message: message too long (>64K ...)


Erik Jasiak
 

Hi James / cf-dev

There are tests, but the corner case fell through the cracks -
bug[1] and additional test request[2] added. For everyone else, most of
the discussion appeared to happen in Slack. Summary is that we're
investigating a corner case where a message passes our test for
acceptable size, but then exceeds the 64K limit once it gets wrapped in
an envelope. We then send off the message but ignore any response from
sending[3].

Special thanks to Johannes Tuchscherer for first-pass analysis of this.

Thanks,
Erik


[1] https://www.pivotaltracker.com/story/show/101894886
[2] https://www.pivotaltracker.com/story/show/101897146
[3]
https://github.com/cloudfoundry/dropsonde/blob/master/log_sender/log_sender.go#L131


James Bayer wrote:

erik,

is there a set of tests for log message length?

---------- Forwarded message ----------
From: *Koper, Dies* <diesk(a)fast.au.fujitsu.com
<mailto:diesk(a)fast.au.fujitsu.com>>
Date: Thu, Aug 20, 2015 at 1:17 PM
Subject: [cf-dev] max length with Dropped log message: message too
long (>64K ...)
To: "cf-dev(a)lists.cloudfoundry.org
<mailto:cf-dev(a)lists.cloudfoundry.org>" <cf-dev(a)lists.cloudfoundry.org
<mailto:cf-dev(a)lists.cloudfoundry.org>>


Hi,

When my app outputs more than 64K of text, I get a message “Dropped
/log/message: message too long (>/64K/without a newline).

When my app outputs much less than 64K of text, I get the app’s output.

When my app outputs just under 64K of text, nothing is output: neither
the error message, nor the app’s output.

What is exactly the limit under which output is still guaranteed, and
can we update the error message accordingly?

I tried to read the source code. Not sure if the limit is because
messages are sent over UDP (UDP max data length is 65,507), or due to
other data that is included in the transmission of messages
(timestamp, app id, etc.).

Cheers,

Dies Koper




--
Thank you,

James Bayer

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