Occasional truncated responses with nginx+passenger

[Jonathan del Strother]

Heya,
I'm having problems with our nginx setup (nginx 0.7.67 -> passenger
2.2.15 -> rails 2.3.6, all running on Solaris 5.11).  Most requests
are fine, but occasionally - maybe every 1 in 50 - I get a truncated
response.

I set up a test script that repeatedly requests a page that's 22kb
long.  Every so often I get a truncated response body, truncated to a
multiple of 5KB - usually 15kb.  The header content length still
indicates 22kb, but only 15kb are transferred according to the
access.log.

I wrote some Rack middleware to at least check that the responses
coming out of Rails were sane, which leaves nginx and/or passenger.
Any suggestions on tracing it further?

-Jonathan