Increase Varnish's shm_reclen from 1024 to 2048
The 1024 byte limit is a tad too short for some EventLogging URLs.
Internet Explorer up to and including version 10 limits URLs to 2083
characters, so the 2048 limit would not only be sufficient for now, but
for the foreseeable future as well.
This also increases shm_workspace from the default of 8192 to
- varnishstat on various clusters indicates we were already
having to flush this fairly regularly (in some cases, up to ~4x
per second), so it probably deserves an increase anyways. Because
not all URLs are of (either) maximum size, doubling the workspace
should more than make up for any shm flush impact from the
shm_reclen increase, and flush rate should still drop after this
Note that we should apply these parameters via varnish daemon
restarts slowly across the clusters, rather than at runtime, as
the timing and sanity of increasing these at runtime via
varnishadm is questionable.