Since backups may now taken on arbitrary hosts, we need a blackbox
monitor that _some_ backup was produced.
Add a Prometheus exporter which calls `wal-g backup-list` and reports
statistics about the backups.
This could be extended to include `wal-g wal-verify`, but that
requires a connection to the PostgreSQL server.
Taking backups on the database primary adds additional disk load,
which can impact the performance of the application.
Switch to taking backups on replicas, if they exist. Some deployments
may have multiple replicas, and taking backups on all of them is
wasteful and potentially confusing; add a flag to inhibit taking
nightly snapshots on the host.
If the deployment is a single instance of PostgreSQL, with no
replicas, it takes backups as before, modulo the extra flag to allow
skipping taking them.
7c023042cf moved the logrotate configuration to being a templated
file, from a static file, but missed that the static file was still
referenced from `zulip_ops::app_frontend`; it only updated
`zulip::profile::app_frontend`. This caused errors in applying puppet
on any `zulip_ops::app_frontend` host.
Prior to 7c023042cf, the Puppet role was identical between those two
classes; deduplicate the rule by moving the updated template
definition into `zulip::app_frontend_base` which is common to those
two classes and not used in any other classes.
Since logrotate runs in a daily cron, this practically means "daily,
but only if it's larger than 500M." For large installs with large
traffic, this is effectively daily for 10 days; for small installs, it
is an unknown amount of time.
Switch to daily logfiles, defaulting to 14 days to match nginx; this
can be overridden using a zulip.conf setting. This makes it easier to
ensure that access logs are only kept for a bounded period of time.
Following zulip/python-zulip-api/pull/758/, we're no longer using
python-zephyr, and don't need to build it from source. Additionally,
we no longer need to build a forked Zephyr package, since ZLoadSession
and ZDumpSession were merged in
e6a545e759.
To not change the `supervisor.conf` file, which requires a restart of
supervisor (and thus all services running under it, which is extremely
disruptive) we carefully leave the contents unchanged for most
installs, and append a new piece to the file, only for the zmirror
configuration, using `concat`.
We see connection timeouts and other access issues when run exactly on
the hour, either due to load on their servers from similar cron jobs,
or from operational processes of theirs.
Move to on the :17s to avoid these access issues.
Increasing worker_connections has a memory cost, unlike the rest of
the changes in 1c76036c61d8; setting it to 1 million caused nginx to
consume several GB of memory.
Reduce the default down to 10k, and allow deploys to configure it up
if necessary. `worker_rlimit_nofile` is left at 1M, since it has no
impact on memory consumption.
There is no reason that the base node access method should be run
under supervisor, which exists primarily to give access to the `zulip`
user to restart its managed services. This access is unnecessary for
Teleport, and also causes unwanted restarts of Teleport services when
the `supervisor` base configuration changes. Additionally,
supervisor does not support the in-place upgrade process that Teleport
uses, as it replaces its core process with a new one.
Switch to installing a systemd configuration file (as generated by
`teleport install systemd`) for each part of Teleport, customized to
pass a `--config` path. As such, we explicitly disable the `teleport`
service provided by the package.
The supervisor process is shut down by dint of no longer installing
the file, which purges it from the managed directory, and reloads
Supervisor to pick up the removed service.
Zulip already has integrations for server-side Sentry integration;
however, it has historically used the Zulip-specific `blueslip`
library for monitoring browser-side errors. However, the latter sends
errors to email, as well optionally to an internal `#errors` stream.
While this is sufficient for low volumes of users, and useful in that
it does not rely on outside services, at higher volumes it is very
difficult to do any analysis or filtering of the errors. Client-side
errors are exceptionally noisy, with many false positives due to
browser extensions or similar, so determining real real errors from a
stream of un-grouped emails or messages in a stream is quite
difficult.
Add a client-side Javascript sentry integration. To provide useful
backtraces, this requires extending the pre-deploy hooks to upload the
source-maps to Sentry. Additional keys are added to the non-public
API of `page_params` to control the DSN, realm identifier, and sample
rates.
The current threshold of 40k descriptors was set in 2016, chosen to be
"at least 40x our current scale." At present, that only provides a
50% safety margin. Increase to 1 million to provide the same 40x
buffer as previously.
The highest value currently allowed by the kernels in
production (linux 5.3.0) is 1048576. This is set as the hard limit.
The 1 million limit is likely far above what the system can handle for
other reasons (memory, cpu, etc). While this removes a potential
safeguard on overload due to too many connections, due to the longpoll
architecture we would generally prefer to service more connections at
lower quality (due to CPU limitations) rather than randomly reject
additional connections.
Relevant prior commits:
- 836f313e69
- f2f97dd335
- ec23996538
- 8806ec698a
- e4fce10f46
After reflecting a bit on the last commit, I think it's substantially
easier to understand what's happening for these two tasks to be
defined in the same file, because we want the timing to be different
to avoid potential races.
5db55c38dc switched from `ensure => present` to the more specific
`ensure => directory` on the premise that tarballs would result in
more than one file being copied out of them. However, we only extract
a single file from the wal-g tarball, and install it at the output
path. The new rule attempts to replace it with an empty directory
after extraction.
Switch back to `ensure => present` for the tarball codepath.
These hooks are run immediately around the critical section of the
upgrade. If the upgrade fails for preparatory reasons, the pre-deploy
hook may not be run; if it fails during the upgrade, the post-deploy
hook will not be run. Hooks are called from the CWD of the new
deploy, with arguments of the old version and the new version. If
they exit with non-0 exit code, the deploy aborts.
Similar to the previous commit, Django was responsible for setting the
Content-Disposition based on the filename, whereas the Content-Type
was set by nginx based on the filename. This difference is not
exploitable, as even if they somehow disagreed with Django's expected
Content-Type, nginx will only ever respond with Content-Types found in
`uploads.types` -- none of which are unsafe for user-supplied content.
However, for consistency, have Django provide both Content-Type and
Content-Disposition headers.
The Content-Type of user-provided uploads was provided by the browser
at initial upload time, and stored in S3; however, 04cf68b45e
switched to determining the Content-Disposition merely from the
filename. This makes uploads vulnerable to a stored XSS, wherein a
file uploaded with a content-type of `text/html` and an extension of
`.png` would be served to browsers as `Content-Disposition: inline`,
which is unsafe.
The `Content-Security-Policy` headers in the previous commit mitigate
this, but only for browsers which support them.
Revert parts of 04cf68b45e, specifically by allowing S3 to provide
the Content-Disposition header, and using the
`ResponseContentDisposition` argument when necessary to override it to
`attachment`. Because we expect S3 responses to vary based on this
argument, we include it in the cache key; since the query parameter
has dashes in it, we can't use use the helper `$arg_` variables, and
must parse it from the query parameters manually.
Adding the disposition may decrease the cache hit rate somewhat, but
downloads are infrequent enough that it is unlikely to have a
noticeable effect. We take care to not adjust the cache key for
requests which do not specify the disposition.
This was missed in 04cf68b45ebb5c03247a0d6453e35ffc175d55da; as this
content is fundamentally untrusted, it must be served with
`Content-Security-Policy` headers in order to be safe. These headers
were not provided previously for S3 content because it was served from
the S3 domain.
This mitigates content served from Zulip which could be a stored XSS,
but only in browsers which support Content-Security-Policy headers;
see subsequent commit for the complete solution.
In nginx, `location` blocks operate on the _decoded_ URI[^1]:
> The matching is performed against a normalized URI, after decoding
> the text encoded in the “%XX” form
This means that if a user-uploaded file contains characters that are
not URI-safe, the browser encodes them in UTF-8 and then URI-encodes
them -- and nginx decodes them and reassembles the original character
before running the `location ~ ^/...` match. This means that the `$2`
_is not URI-encoded_ and _may contain non-ASCII characters.
When `proxy_pass` is passed a value containing one or more variables,
it does no encoding on that expanded value, assuming that the bytes
are exactly as they should be passed to the upstream. This means that
directly calling `proxy_pass https://$1/$2` would result in sending
high-bit characters to the S3 upstream, which would rightly balk.
However, a longstanding bug in nginx's `set` directive[^2] means that
the following line:
```nginx
set $download_url https://$1/$2;
```
...results in nginx accidentally URI-encoding $1 and $2 when they are
inserted, resulting in a `$download_url` which is suitable to pass to
`proxy_pass`. This bug is only present with numeric capture
variables, not named captures; this is particularly relevant because
numeric captures are easily overridden by additional regexes
elsewhere, as subsequent commits will add.
Fixing this is complicated; nginx does not supply any way to escape
values[^3], besides a third-party module[^4] which is an undue
complication to begin using. The only variable which nginx exposes
which is _not_ un-escaped already is `$request_uri`, which contains
the very original URL sent by the browser -- and thus can't respect
any work done in Django to generate the `X-Accel-Redirect` (e.g., for
`/user_uploads/temporary/` URLs). We also cannot pass these URLs to
nginx via query-parameters, since `$arg_foo` values are not
URI-decoded by nginx, there is no function to do so[^3], and the
values must be URI-encoded because they themselves are URLs with query
parameters.
Extra-URI-encode the path that we pass to the `X-Accel-Redirect`
location, for S3 redirects. We rely on the `location` block
un-escaping that layer, leaving `$s3_hostname` and `$s3_path` as they
were intended in Django.
This works around the nginx bug, with no behaviour change.
[^1]: http://nginx.org/en/docs/http/ngx_http_core_module.html#location
[^2]: https://trac.nginx.org/nginx/ticket/348
[^3]: https://trac.nginx.org/nginx/ticket/52
[^4]: https://github.com/openresty/set-misc-nginx-module#set_escape_uri
Alex Vandiver
Tim Abbott
Anders Kaseorg
Mateusz Mandera