is no sane way to refcount (dynamic) backends in relation to VCL
use at this point in the 4.1 release cycle.

Solve the problem, for now, by cooling dynamic backends off for a
minute before actually removing them.

Varnish 5 will have to look at proper refcounting of (all) VCL objects.

we need.

Send warm dynamic backends "COLD" event before deleting them.

with EINTR.

I suspect the underlying issue is that SIGCHLD is being sent
to a random thread and that happens to be the s1 thread on some
platforms.

Partially from minusf via github

Spotted by:	Dridi

previous commit.

Fixes: #1755

connection count.

Instead we mark the dynamic backends unhealthy with the status "deleted",
hide it from CLI displays, prevent new connections from being opened
and clean the backend up when the connection count goes to zero.

Radically different from patch from: Dridi

conversions between enum and text.

Based on patch from:  Dridi

There is potential for improvement in this whole
documentation build business of ours.

The amount of output does (did) not correspond with the importance of
this task. Now at least we'll see the warnings clearly.

I think it makes sense to ship a built HTML copy in
the tarball, as well as the RST sources.

The old cleanup code was a tad eager and made phk miss
his svg. Hopefully this way is a bit more future proof.

automake is our friend.

We might have to update some packaging files later on.
(and perhaps the git push hook.)

Partially from minusf via github

I have not added any other lock-order reversals.

Give the backend tcp-pools their own lock class instead of mixing
them up with the backend lock class.

held over Wait_Enter() processing, and that makes it impossible
for the code using the waiter to avoid one deadlock or another.

Depending on what the call-back code does, this may increase or
decrease contests for the waiters mutex.

This output was very wide and hard to get any sense out of without
actually reading it closely.

The things you are interested in, typically counter name, description
and value, are now on separate lines.

In addition the output should now fit nicely on any VT100 terminals in
80 character mode, I'm sure there are some still in use somewhere.

JSON document layout (key names, hierarchy) is the same as before.