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.
Even if Django and PostgreSQL are on the same host, the `nagios` user
may lack permissions to read accessory configuration files needed to
load the Django configuration (e.g. authentication keys).
Catch those failures, and switch to loading the required settings from
`/etc/zulip/zulip.conf`.
Without this, uwsgi does not release the GIL before going back into
`epoll_wait` to wait for the next request. This results in any
background threads languishing, unserviced.[1]
Practically, this results in Sentry background reporter threads timing
out when attempting to post results -- but only in situations with low
traffic, as in those significant time is spent in `epoll_wait`. This
is seen in logs as:
WARN [urllib3.connectionpool] Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError(SSLEOFError(8, 'EOF occurred in violation of protocol (_ssl.c:1131)'))': /api/123456789/envelope/
Or:
WARN [urllib3.connectionpool] Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'ProxyError('Cannot connect to proxy.', RemoteDisconnected('Remote end closed connection without response'))': /api/123456789/envelope/
Sentry attempts to detect this and warn, but due to startup ordering,
the warning is not printed without lazy-loading.
Enable threads, at a miniscule performance cost, in order to support
background workers like Sentry[2].
[1] https://github.com/unbit/uwsgi/issues/1141#issuecomment-169042767
[2] https://docs.sentry.io/clients/python/advanced/#a-note-on-uwsgi
This is a reprise of c97162e485, but for the case where certbot
certs are no longer in use by way of enabling `http_only` and letting
another server handle TLS termination.
Fixes: #22034.
This allows system-level configuration to be done by `apt-get install`
of nginx modules, which place their load statements in this directory.
The initial import in ed0cb0a5f8 of the stock nginx config omitted
this include -- one potential explanation was in an effort to reduce
the memory footprint of the server.
The default nginx install enables:
50-mod-http-auth-pam.conf
50-mod-http-dav-ext.conf
50-mod-http-echo.conf
50-mod-http-geoip2.conf
50-mod-http-geoip.conf
50-mod-http-image-filter.conf
50-mod-http-subs-filter.conf
50-mod-http-upstream-fair.conf
50-mod-http-xslt-filter.conf
50-mod-mail.conf
50-mod-stream.conf
While Zulip doesn't actively use any of these, they likely don't do
any harm to simply be loaded -- they are loaded into every nginx by
default.
Having the `modules-enabled` include allows easier extension of the
server, as neither of the existing wildcard
includes (`/etc/nginx/conf.d/*.conf` and
`/etc/nginx/zulip-include/app.d/*.conf`) are in the top context, and
thus able to load modules.
54b6a83412 fixed the typo introduced in 49ad188449, but that does
not clean up existing installs which had the file with the wrong name
already.
Remove the file with the typo'd name, so two jobs do not race, and fix
the typo in the comment.
The top-level `chdir` setting only does the chdir once, at initial
`uwsgi` startup time. Rolling restarts, however, however, require
that `uwsgi` pick up the _new_ value of the `current` directory, and
start new workers in that directory -- as currently implemented,
rolling restarts cannot restart into newer versions of the code, only
the same one in which they were started.
Use [configurable hooks][1] to execute the `chdir` after every fork.
This causes the following behaviour:
```
Thu May 12 18:56:55 2022 - chain reload starting...
Thu May 12 18:56:55 2022 - chain next victim is worker 1
Gracefully killing worker 1 (pid: 1757689)...
worker 1 killed successfully (pid: 1757689)
Respawned uWSGI worker 1 (new pid: 1757969)
Thu May 12 18:56:56 2022 - chain is still waiting for worker 1...
running "chdir:/home/zulip/deployments/current" (post-fork)...
Thu May 12 18:56:57 2022 - chain is still waiting for worker 1...
Thu May 12 18:56:58 2022 - chain is still waiting for worker 1...
Thu May 12 18:56:59 2022 - chain is still waiting for worker 1...
WSGI app 0 (mountpoint='') ready in 3 seconds on interpreter 0x55dfca409170 pid: 1757969 (default app)
Thu May 12 18:57:00 2022 - chain next victim is worker 2
[...]
```
..and so forth down the line of processes. Each process is correctly
started in the _current_ value of `current`, and thus picks up the
correct code.
[1]: https://uwsgi-docs.readthedocs.io/en/latest/Hooks.html
Our current EC2 systems don’t have an interface named ‘eth0’, and if
they did, this script would do nothing but crash with ImportError
because we have never installed boto.utils for Python 3.
(The message of commit 2a4d851a7c made
an effort to document for future researchers why this script should
not have been blindly converted to Python 3. However, commit
2dc6d09c2a (#14278) was evidently
unresearched and untested.)
Signed-off-by: Anders Kaseorg <anders@zulip.com>
6f5ae8d13d removed the `$replication` variable from the
configurations of PostgreSQL 12 and higher, but left it in the
templates for PostgreSQL 10 and 11. Because `undef != ''`,
deployments on PostgreSQL 10 and 11 started trying to push to S3
backups, regardless of if they were configured, leaving frequent log
messages like:
```
2022-04-30 12:45:47.805 UTC [626d24ec.1f8db0]: [107-1] LOG: archiver process (PID 2086106) exited with exit code 1
2022-04-30 12:45:49.680 UTC [626d24ee.1f8dc3]: [18-1] LOG: checkpoint complete: wrote 19 buffers (0.0%); 0 WAL file(s) added, 0 removed, 0 recycled; write=1.910 s, sync=0.022 s, total=1.950 s; sync files=16, longest=0.018 s, average=0.002 s; distance=49 kB, estimate=373 kB
/usr/bin/timeout: failed to run command "/usr/local/bin/env-wal-g": No such file or directory
2022-04-30 12:46:17.852 UTC [626d2f99.1fd4e9]: [1-1] FATAL: archive command failed with exit code 127
2022-04-30 12:46:17.852 UTC [626d2f99.1fd4e9]: [2-1] DETAIL: The failed archive command was: /usr/bin/timeout 10m /usr/local/bin/env-wal-g wal-push pg_wal/000000010000000300000080
```
Switch the PostgreSQL 10 and 11 configuration to check
`s3_backups_bucket`, like the other versions.
It is possible to have previously installed certbot, but switched back
to using self-signed certificates -- in which case renewing them using
certbot may fail.
Verify that the certificate is a symlink into certbot's output
directory before running `fix-standalone-certbot`.
Commit f6d27562fa (#21564) tried to
ensure Chrony is running, which fails in containers where Chrony
doesn’t have permission to update the host clock.
The Debian package should still attempt to start it, and Puppet should
still restart it when chrony.conf is modified.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
Since wal-g does not provide binaries for aarch64, build them from
source. While building them from source for arm64 would better ensure
that build process is tested, the build process takes 7min and 700M of
temp files, which is an unacceptable cost; we thus only build on
aarch64.
Since the wal-g build process uses submodules, which are not in the
Github export, we clone the full wal-g repository. Because the
repository is relatively small, we clone it anew on each new version,
rather than attempt to manage the remotes.
Fixes#21070.
The default timeout for `exec` commands in Puppet is 5 minutes[1]. On
slow connections, this may not be sufficient to download larger
downloads, such as the ~135MB golang tarball.
Increase the timeout to 10 minutes; this is a minimum download speed
of is ~225kB/s.
Fixes#21449.
[1]: https://puppet.com/docs/puppet/5.5/types/exec.html#exec-attribute-timeout
This commit adds a cron job which runs every hour to add the users to
full members system group if user is promoted to a full member.
This should ensure that full member status is available no more than
an hour after configuration suggests it should be.
Previously, it was possible to configure `wal-g` backups without
replication enabled; this resulted in only daily backups, not
streaming backups. It was also possible to enable replication without
configuring the `wal-g` backups bucket; this simply failed to work.
Make `wal-g` backups always streaming, and warn loudly if replication
is enabled but `wal-g` is not configured.
It would confuse a future Debian 15.10 release with Ubuntu 15.10, it
relies on the legacy fact $::operatingsystemrelease, the modern fact
$::os provides this information without extra logic, and it’s unused
as of commit 03bffd3938.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
Zulip writes a `rabbitmq.config` configuration file which locks down
RabbitMQ to listen only on localhost:5672, as well as the RabbitMQ
distribution port, on localhost:25672.
The "distribution port" is part of Erlang's clustering configuration;
while it is documented that the protocol is fundamentally
insecure ([1], [2]) and can result in remote arbitrary execution of
code, by default the RabbitMQ configuration on Debian and Ubuntu
leaves it publicly accessible, with weak credentials.
The configuration file that Zulip writes, while effective, is only
written _after_ the package has been installed and the service
started, which leaves the port exposed until RabbitMQ or system
restart.
Ensure that rabbitmq's `/etc/rabbitmq/rabbitmq.config` is written
before rabbitmq is installed or starts, and that changes to that file
trigger a restart of the service, such that the ports are only ever
bound to localhost. This does not mitigate existing installs, since
it does not force a rabbitmq restart.
[1] https://www.erlang.org/doc/apps/erts/erl_dist_protocol.html
[2] https://www.erlang.org/doc/reference_manual/distributed.html#distributed-erlang-system
This is required in order to lock down the RabbitMQ port to only
listen on localhost. If the nodename is `rabbit@hostname`, in most
circumstances the hostname will resolve to an external IP, which the
rabbitmq port will not be bound to.
Installs which used `rabbit@hostname`, due to RabbitMQ having been
installed before Zulip, would not have functioned if the host or
RabbitMQ service was restarted, as the localhost restrictions in the
RabbitMQ configuration would have made rabbitmqctl (and Zulip cron
jobs that call it) unable to find the rabbitmq server.
The previous commit ensures that configure-rabbitmq is re-run after
the nodename has changed. However, rabbitmq needs to be stopped
before `rabbitmq-env.conf` is changed; we use an `onlyif` on an `exec`
to print the warning about the node change, and let the subsequent
config change and notify of the service and configure-rabbitmq to
complete the re-configuration.
`/etc/rabbitmq/rabbitmq-env.conf` sets the nodename; anytime the
nodename changes, the backing database changes, and this requires
re-creating the rabbitmq users and permissions.
Trigger this in puppet by running configure-rabbitmq after the file
changes.
The Erlang `epmd` daemon listens on port 4369, and provides
information (without authentication) about which Erlang processes are
listening on what ports. This information is not itself a
vulnerability, but may provide information for remote attackers about
what local Erlang services (such as `rabbitmq-server`) are running,
and where.
`epmd` supports an `ERL_EPMD_ADDRESS` environment variable to limit
which interfaces it binds on. While this environment variable is set
in `/etc/default/rabbitmq-server`, Zulip unfortunately attempts to
start `epmd` using an explicit `exec` block, which ignores those
settings.
Regardless, this lack of `ERL_EPMD_ADDRESS` variable only controls
`epmd`'s startup upon first installation. Upon reboot, there are two
ways in which `epmd` might be started, neither of which respect
`ERL_EPMD_ADDRESS`:
- On Focal, an `epmd` service exists and is activated, which uses
systemd's configuration to choose which interfaces to bind on, and
thus `ERL_EPMD_ADDRESS` is irrelevant.
- On Bionic (and Focal, due to a broken dependency from
`rabbitmq-server` to `epmd@` instead of `epmd`, which may lead to
the explicit `epmd` service losing a race), `epmd` is started by
`rabbitmq-server` when it does not detect a running instance.
Unfortunately, only `/etc/init.d/rabbitmq-server` would respects
`/etc/default/rabbitmq-server` -- and it defers the actual startup
to using systemd, which does not pass the environment variable
down. Thus, `ERL_EPMD_ADDRESS` is also irrelevant here.
We unfortunately cannot limit `epmd` to only listening on localhost,
due to a number of overlapping bugs and limitations:
- Manually starting `epmd` with `-address 127.0.0.1` silently fails
to start on hosts with IPv6 disabled, due to an Erlang bug ([1],
[2]).
- The dependencies of the systemd `rabbitmq-server` service can be
fixed to include the `epmd` service, and systemd can be made to
bind to `127.0.0.1:4369` and pass that socket to `epmd`, bypassing
the above bug. However, the startup of this service is not
guaranteed, because it races with other sources of `epmd` (see
below).
- Any process that runs `rabbitmqctl` results in `epmd` being started
if one is not currently running; these instances do not respect any
environment variables as to which addresses to bind on. This is
also triggered by `service rabbitmq-server status`, as well as
various Zulip cron jobs which inspect the rabbitmq queues. As
such, it is difficult-to-impossible to ensure that some other
`epmd` process will not win the race and open the port on all
interfaces.
Since the only known exposure from leaving port 4369 open is
information that rabbitmq is running on the host, and the complexity
of adjusting this to only bind on localhost is high, we remove the
setting which does not address the problem, and document that the port
is left open, and should be protected via system-level or
network-level firewalls.
[1]: https://bugs.launchpad.net/ubuntu/+source/erlang/+bug/1374109
[2]: https://github.com/erlang/otp/issues/4820
mochiweb was renamed to web_dispatch in RabbitMQ 3.8.0, and the plugin
is not enabled. Nor does this control the management interface, which
would listen on port 15672.
This addresses the problems mentioned in the previous commit, but for
existing installations which have `authenticator = standalone` in
their configurations.
This reconfigures all hostnames in certbot to use the webroot
authenticator, and attempts to force-renew their certificates.
Force-renewal is necessary because certbot contains no way to merely
update the configuration. Let's Encrypt allows for multiple extra
renewals per week, so this is a reasonable cost.
Because the certbot configuration is `configobj`, and not
`configparser`, we have no way to easily parse to determine if webroot
is in use; additionally, `certbot certificates` does not provide this
information. We use `grep`, on the assumption that this will catch
nearly all cases.
It is possible that this will find `authenticator = standalone`
certificates which are managed by Certbot, but not Zulip certificates.
These certificates would also fail to renew while Zulip is running, so
switching them to use the Zulip webroot would still be an improvement.
Fixes#20593.
As a consequence:
• Bump minimum supported Python version to 3.7.
• Move Vagrant environment to Debian 10, which has Python 3.7.
• Move CI frontend tests to Debian 10.
• Move production build test to Debian 10.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
Doing so requires protecting /metrics from direct access when proxied
through nginx. If camo is placed on a separate host, the equivalent
/metrics URL may need to be protected.
See https://github.com/cactus/go-camo#metrics for details on the
statistics so reported. Note that 5xx responses are _expected_ from
go-camo's statistics, as it returns 502 status code when the remote
server responds with 500/502/503/504, or 504 when the remote host
times out.
Because Camo includes logic to deny access to private subnets, routing
its requests through Smokescreen is generally not necessary. However,
it may be necessary if Zulip has configured a non-Smokescreen exit
proxy.
Default Camo to using the proxy only if it is not Smokescreen, with a
new `proxy.enable_for_camo` setting to override this behaviour if need
be. Note that that setting is in `zulip.conf` on the host with Camo
installed -- not the Zulip frontend host, if they are different.
Fixes: #20550.
For `no_serve_uploads`, `http_only`, which previously specified
"non-empty" to enable, this tightens what values are true. For
`pgroonga` and `queue_workers_multiprocess`, this broadens the
possible values from `enabled`, and `true` respectively.
Restarting the uwsgi processes by way of supervisor opens a window
during which nginx 502's all responses. uwsgi has a configuration
called "chain reloading" which allows for rolling restart of the uwsgi
processes, such that only one process at once in unavailable; see
uwsgi documentation ([1]).
The tradeoff is that this requires that the uwsgi processes load the
libraries after forking, rather than before ("lazy apps"); in theory
this can lead to larger memory footprints, since they are not shared.
In practice, as Django defers much of the loading, this is not as much
of an issue. In a very basic test of memory consumption (measured by
total memory - free - caches - buffers; 6 uwsgi workers), both
immediately after restarting Django, and after requesting `/` 60 times
with 6 concurrent requests:
| Non-lazy | Lazy app | Difference
------------------+------------+------------+-------------
Fresh | 2,827,216 | 2,870,480 | +43,264
After 60 requests | 3,332,284 | 3,409,608 | +77,324
..................|............|............|.............
Difference | +505,068 | +539,128 | +34,060
That is, "lazy app" loading increased the footprint pre-requests by
43MB, and after 60 requests grew the memory footprint by 539MB, as
opposed to non-lazy loading, which grew it by 505MB. Using wsgi "lazy
app" loading does increase the memory footprint, but not by a large
percentage.
The other effect is that processes may be served by either old or new
code during the restart window. This may cause transient failures
when new frontend code talks to old backend code.
Enable chain-reloading during graceful, puppetless restarts, but only
if enabled via a zulip.conf configuration flag.
Fixes#2559.
[1]: https://uwsgi-docs.readthedocs.io/en/latest/articles/TheArtOfGracefulReloading.html#chain-reloading-lazy-apps
Fix another tidy error caused by 1e4e6a09af23; as also noted in
f9a39b6703, these resources are necessary such that tidy does not
cleanup of smokescreen, and then force a recompilation of it again.
1e4e6a09af removed the resources for the unpacked directory, on the
argument that they were unnecessary. However, the directory (or file,
see below) that is unpacked must be managed, or it will be tidied on
the next puppet apply.
Add back the resource for `$dir`, but mark it `ensure => present`, to
support tarballs which only unpack to a single file (e.g. wal-g).
The homedir of a user cannot be changed if any processes are running
as them, so having it change over time as upgrades happen will break
puppet application, as the old grafana process under supervisor will
effectively lock changes to the user's homedir.
Unfortunately, that means that this change will thus fail to
puppet-apply unless `supervisorctl stop grafana` is run first, but
there's no way around that.
In the event that extracting doesn't produce the binary we expected it
to, all this will do is create an _empty_ file where we expect the
binary to be. This will likely muddle debugging.
Since the only reason the resourfce was made in the first place was to
make dependencies clear, switch to depending on the External_Dep
itself, when such a dependency is needed.
ab130ceb35 added a dependency on scripts.lib.zulip_tools; however,
check_postgresql_replication_lag is run on hosts which do not have a
zulip tree installed.
Inline the simple functions that were imported.
It should not use the configured zulip username, but should instead
pull from the login user (likely `nagios`), or an explicit alternate
provided PostgreSQL username. Failure to do so results in Nagios
failures because the `nagios` login does not have permissions to
authenticated the `zulip` PostgreSQL user.
This requires CI changes, as the install tests install as the `zulip`
login username, which allowed Nagios tests to pass previously; with
the custom database and username, however, they must be passed to
process_fts_updates explicitly when validating the install.
The Redis configuration, and the systemd file for it, assumes there
will be a pid file written to `/var/run/redis/redis.pid`, but
`/var/run/redis` is not created during installation.
Create `/run/redis`; as `/var/run` is a symlink to `/run` on systemd
systems, this is equivalent to `/var/run/redis`.
The systemd config file installed by the `memcached` package assumes
there will be a PID written to `/run/memcached/memcached.pid`. Since we
override `memcached.conf`, we have omitted the line that writes out the
PID to this file.
Systemd is smart enough to not _need_ the PID file to start up the
service correctly, but match the configuration. We create the
directory since the package does not do so. It is created as
`/run/memcached` and not `/var/run/memcached` because `/var/run` is a
symlink to `/run`.
The certbot package installs its own systemd timer (and cron job,
which disabled itself if systemd is enabled) which updates
certificates. This process races with the cron job which Zulip
installs -- the only difference being that Zulip respects the
`certbot.auto_renew` setting, and that it passes the deploy hook.
This means that occasionally nginx would not be reloaded, when the
systemd timer caught the expiration first.
Remove the custom cron job and `certbot-maybe-renew` script, and
reconfigure certbot to always reload nginx after deploying, using
certbot directory hooks.
Since `certbot.auto_renew` can't have an effect, remove the setting.
In turn, this removes the need for `--no-zulip-conf` to
`setup-certbot`. `--deploy-hook` is similarly removed, as running
deploy hooks to restart nginx is now the default; pass
`--no-directory-hooks` in standalone mode to not attempt to reload
nginx. The other property of `--deploy-hook`, of skipping symlinking
into place, is given its own flog.
PostgreSQL 11 and below used a configuration file names
`recovery.conf` to manage replicas and standbys; support for this was
removed in PostgreSQL 12[1], and the configuration parameters were
moved into the main `postgresql.conf`.
Add `zulip.conf` settings for the primary server hostname and
replication username, so that the complete `postgresql.conf`
configuration on PostgreSQL 14 can continue to be managed, even when
replication is enabled. For consistency, also begin writing out the
`recovery.conf` for PostgreSQL 11 and below.
In PostgreSQL 12 configuration and later, the `wal_level =
hot_standby` setting is removed, as `hot_standby` is equivalent to
`replica`, which is the default value[2]. Similarly, the
`hot_standby = on` setting is also the default[3].
Documentation is added for these features, and the commentary on the
"Export and Import" page referencing files under `puppet/zulip_ops/`
is removed, as those files no longer have any replication-specific
configuration.
[1]: https://www.postgresql.org/docs/current/recovery-config.html
[2]: https://www.postgresql.org/docs/12/runtime-config-wal.html#GUC-WAL-LEVEL
[3]: https://www.postgresql.org/docs/12/runtime-config-replication.html#GUC-HOT-STANDBY
These are both unsupported by PostgreSQL itself, as well as by Zulip;
the removal of Ubuntu Xenial and Debian Stretch support in Zulip 3.0
removed the requirement for PostgreSQL 9.6, and the previous versions
date back yet farther.
Writing the secret to the supervisor configuration file makes changes
to the secret requires a zulip-puppet-apply to take hold. The Docker
image is constructed to avoid having to run zulip-puppet-apply on
startup, and indeed cannot run zulip-puppet-apply after having
configured secrets, as it has replaced the zulip.conf file with a
symlink, for example. This means that camo gets the static secret
that was built into the image, and not the one regenerated on first
startup.
Read the camo secret at process startup time. Because this pattern is
likely common with "12-factor" applications which can read from
environment variables, write a generic tool to map secrets to
environment variables before exec'ing a binary, and use that for Camo.
The default in the previous commit, inherited from camo, was to bind
to 0.0.0.0:9292. In standalone deployments, camo is deployed on the
same host as the nginx reverse proxy, and as such there is no need to
open it up to other IPs.
Make `zulip::camo` take an optional parameter, which allows overriding
it in puppet, but skips a `zulip.conf` setting for it, since it is
unlikely to be adjust by most users.
The upstream of the `camo` repository[1] has been unmaintained for
several years, and is now archived by the owner. Additionally, it has
a number of limitations:
- It is installed as a sysinit service, which does not run under
Docker
- It does not prevent access to internal IPs, like 127.0.0.1
- It does not respect standard `HTTP_proxy` environment variables,
making it unable to use Smokescreen to prevent the prior flaw
- It occasionally just crashes, and thus must have a cron job to
restart it.
Swap camo out for the drop-in replacement go-camo[2], which has the
same external API, requiring not changes to Django code, but is more
maintained. Additionally, it resolves all of the above complaints.
go-camo is not configured to use Smokescreen as a proxy, because its
own private-IP filtering prevents using a proxy which lies within that
IP space. It is also unclear if the addition of Smokescreen would
provide any additional protection over the existing IP address
restrictions in go-camo.
go-camo has a subset of the security headers that our nginx reverse
proxy sets, and which camo set; provide the missing headers with `-H`
to ensure that go-camo, if exposed from behind some other non-nginx
load-balancer, still provides the necessary security headers.
Fixes#18351 by moving to supervisor.
Fixeszulip/docker-zulip#298 also by moving to supervisor.
[1] https://github.com/atmos/camo
[2] https://github.com/cactus/go-camo
This is an additional security hardening step, to make Zulip default
to preventing SSRF attacks. The overhead of running Smokescreen is
minimal, and there is no reason to force deployments to take
additional steps in order to secure themselves against SSRF attacks.
Deployments which already have a different external proxy configured
will not gain a local Smokescreen installation, and running without
Smokescreen is supported by explicitly unsetting the `host` or `port`
values in `/etc/zulip/zulip.conf`.
In a subsequent commit, we intend to include it from
`zulip::app_frontend_base`, which is a layering violation if it only
exists in the form of a profile.
This will cause the output binary path to be sensitive to golang
version, causing it to be rebuilt on new golang, and an updated
supervisor config file written out, and thus supervisor also
restarted.
As with the previous commit for `/srv/golang`, we have the custom of
namespacing things under `/srv` with `zulip-` to help ensure that we
play nice with anything else that happens to be on the host.
We have the custom of namespacing things under `/srv` with `zulip-`
to help ensure that we play nice with anything else that happens
to be on the host.
Alex Vandiver
Anders Kaseorg
Sahil Batra