[BP 7.2.0] - XDCR - Prolonged TMPFAIL or ENOMEM could lead to memory bloat

1. XDCR receives ENOMEM and prepares the packet for resend (http://src.couchbase.org/source/xref/6.6.2/goproj/src/github.com/couchbase/goxdcr/parts/xmem_nozzle.go#2041)
2. Leading to this call to get bytes: http://src.couchbase.org/source/xref/6.6.2/goproj/src/github.com/couchbase/goxdcr/parts/xmem_nozzle.go#2426-2427
3. At first glance, the above looks to be using a slice reference, but digging into gomemcached…
4. http://src.couchbase.org/source/xref/6.6.2/godeps/src/github.com/couchbase/gomemcached/mc_req.go#104-118 <- this call actually make copies of the data

So even if the stats do not move (i.e. the analysis I’ve shown), and yet target keeps returning ENOMEM (and potentially TMPFAIL), XDCR will keep retrying to resend…. but each resend actually allocates memory instead of reusing existing ones.