A number of autossh connections are already left open for
port-forwarding Munin ports; autossh starts the connections and
ensures that they are automatically restarted if they are severed.
However, this represents a missed opportunity. Nagios's monitoring
uses a large number of SSH connections to the remote hosts to run
commands on them; each of these connections requires doing a complete
SSH handshake and authentication, which can have non-trivial network
latency, particularly for hosts which may be located far away, in a
network topology sense (up to 1s for a no-op command!).
Use OpenSSH's ability to multiplex multiple connections over a single
socket, to reuse the already-established connection. We leave an
explicit `ControlMaster no` in the general configuration, and not
`auto`, as we do not wish any of the short-lived Nagios connections to
get promoted to being a control socket if the autossh is not running
for some reason.
We enable protocol-level keepalives, to give a better chance of the
socket being kept open.
Replication checks should only run on primary and replicas, not
standalone hosts; while `autovac_freeze` currently only runs on
primary hosts, it functions identically on replicas, and is fine to
run there.
Make `autovac_freeze` run on all `postgresql` hosts, and make
standalone hosts no longer `postgres_primary`, so they do not fail the
replication tests.
`zmirror` itself was `zmirror_main` + `zmirrorp` but was unused; we
consistently just use the term `zmirror` for the non-personals server,
so use it as the hostgroup name.
5abf4dee92 made this distinction, then multitornado_frontends was
never used; the singletornado_frontends alerting worked even for the
multiple-Tornado instances.
Remove the useless and misleading distinction.
Failure to do this results in:
```
psql: error: failed to connect to `host=localhost user=zulip database=zulip`: failed to write startup message (x509: certificate is valid for [redacted], not localhost)
```
Host-based md5 auth for 127.0.0.1 must be removed from `pg_hba.conf`,
otherwise password authentication is preferred over certificate-based
authentication for localhost.
Nagios refuses to allow any modifications with use_authentication off;
re-enabled "authentication" but set a default user, which (by way of
the `*` permissions in 359f37389a) is allowed to take all actions.
This means that services will only open their ports if they are
actually run, without having to clutter rules.v4 with a log of `if`
statements.
This does not go as far as using `puppetlabs/firewall`[1] because that
would represent an additional DSL to learn; raw IPtables sections can
easily be inserted into the generated iptables file via
`concat::fragment` (either inline, or as a separate file), but config
can be centralized next to the appropriate service.
[1] https://forge.puppet.com/modules/puppetlabs/firewall
This verifies that the proxy is working by accessing a
highly-available website through it. Since failure of this equates to
failures of Sentry notifications and Android mobile push
notifications, this is a paging service.
Redis is not nagios, and this only leads to confusion as to why there
is a nagios domain setting on frontend servers; it also leaves the
`redis0` part of the name buried in the template.
Switch to an explicit variable for the redis hostname.
This is more broadly useful than for just Kandra; provide
documentation and means to install Smokescreen for stand-alone
servers, and motivate its use somewhat more.
The style guide for Zulip is to always use "primary" and "replica"
when describing database replication. Adjust a few comments under
`puppet/` that do not adhere to this.
Unfortunately, some references still remain to the insensitive and
inaccurate "master" / "slave" terminology. However, these are only in
files which we are attempting to preserve as close to the upstream
versions they are derived from (e.g. postgresql.conf,
postfix/master.cf).
Instead of SSH'ing around to them, run directly on the database hosts.
This means that the replicas do not know how many bytes behind they
are in _receiving_ the wall logs; thus, the monitoring also extends to
the primary database, which knows that information for each replica.
This also allows for detecting when there are too few active replicas.
This is vestigial.
It requires manually altering the `htdigest` file (not stored in this
repo) to change the digest realm from `wiki` to `monitoring`, and will
re-prompt users for their passwords if the browsers currently store
them.
Alex Vandiver
Anders Kaseorg
Alex Vandiver