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zulip/docs/production/maintain-secure-upgrade.md

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Secure, maintain, and upgrade

This page covers topics that will help you maintain a healthy, up-to-date, and secure Zulip installation, including:

You may also want to read this related content:

Upgrading

We recommend reading this entire section before doing your first upgrade.

To upgrade to a new version of the zulip server, download the appropriate release tarball from https://www.zulip.org/dist/releases/.

You also have the option of creating your own release tarballs from a copy of the zulip.git repository using tools/build-release-tarball or upgrade Zulip to a version in a Git repository directly.

Next, run as root:

/home/zulip/deployments/current/scripts/upgrade-zulip zulip-server-VERSION.tar.gz

The upgrade process will shut down the Zulip service and then run apt-get upgrade, a puppet apply, any database migrations, and then bring the Zulip service back up. Upgrading will result in some brief downtime for the service, which should be under 30 seconds unless there is an expensive transition involved. Unless you have tested the upgrade in advance, we recommend doing upgrades at off hours.

Note that upgrading an existing Zulip production server from Ubuntu 14.04 Trusty to Ubuntu 16.04 Xenial will require significant manual intervention on your part to migrate the data in the database from Postgres 9.3 to Postgres 9.5. Contributions on testing and documenting this process are welcome!

Preserving local changes to configuration files

Warning: If you have modified configuration files installed by Zulip (e.g. the nginx configuration), the Zulip upgrade process will overwrite your configuration when it does the puppet apply.

You can test whether this will happen assuming no upstream changes to the configuration using scripts/zulip-puppet-apply (without the -f option), which will do a test puppet run and output and changes it would make. Using this list, you can save a copy of any files that you've modified, do the upgrade, and then restore your configuration.

If you need to do this, please report the issue so that we can make the Zulip puppet configuration flexible enough to handle your setup.

Troubleshooting with the upgrade log

The Zulip upgrade script automatically logs output to /var/log/zulip/upgrade.log. Please use those logs to include output that shows all errors in any bug reports.

After the upgrade, we recommend checking /var/log/zulip/errors.log to confirm that your users are not experiencing errors after the upgrade.

Rolling back to a prior version

The Zulip upgrade process works by creating a new deployment under /home/zulip/deployments/ containing a complete copy of the Zulip server code, and then moving the symlinks at /home/zulip/deployments/{current,last,next} as part of the upgrade process.

This means that if the new version isn't working, you can quickly downgrade to the old version by running /home/zulip/deployments/last/scripts/restart-server, or to an earlier previous version by running /home/zulip/deployments/DATE/scripts/restart-server. The restart-server script stops any running Zulip server, and starts the version corresponding to the restart-server path you call.

Updating settings

If required, you can update your settings by editing /etc/zulip/settings.py and then run /home/zulip/deployments/current/scripts/restart-server to restart the server.

Applying Ubuntu system updates

The Zulip upgrade script will automatically run apt-get update and then apt-get upgrade, to make sure you have any new versions of dependencies (this will also update system packages). We assume that you will install Ubuntu security updates regularly, according to your usual security practices for an Ubuntu server.

If you'd like to minimize downtime when installing a Zulip server upgrade, you may want to do an apt-get upgrade (and then restart the server and check everything is working) before running the Zulip upgrade script.

There's one apt package to be careful about: upgrading postgresql while the server is running may result in an outage (basically, postgresql might stop accepting new queries but refuse to shut down while waiting for connections from the Zulip server to shut down). While this only happens sometimes, it can be hard to fix for someone who isn't comfortable managing a postgresql database [1]. You can avoid that possibility with the following procedure (run as root):

apt-get update
supervisorctl stop all
apt-get upgrade -y
supervisorctl start all

[1] If this happens to you, just stop the Zulip server, restart postgres, and then start the Zulip server again, and you'll be back in business.

API and your Zulip URL

To use the Zulip API with your Zulip server, you will need to use the API endpoint of e.g. https://zulip.example.com/api. Our Python API example scripts support this via the --site=https://zulip.example.com argument. The API bindings support it via putting site=https://zulip.example.com in your .zuliprc.

Every Zulip integration supports this sort of argument (or e.g. a ZULIP_SITE variable in a zuliprc file or the environment), but this is not yet documented for some of the integrations (the included integration documentation on /integrations will properly document how to do this for most integrations). We welcome pull requests for integrations that don't discuss this!

Similarly, you will need to instruct your users to specify the URL for your Zulip server when using the Zulip desktop and mobile apps.

Memory leak mitigation

As a measure to mitigate the impact of potential memory leaks in one of the Zulip daemons, the service automatically restarts itself every Sunday early morning. See /etc/cron.d/restart-zulip for the precise configuration.

Upgrading from a git repository

Starting with version 1.4, the Zulip server supports upgrading to a commit in Git. You can configure the git repository that you'd like to use by adding a section like this to /etc/zulip/zulip.conf; by default it uses the main zulip repository (shown below).

[deployment]
git_repo_url = https://github.com/zulip/zulip.git

Once that is done (and assuming the currently installed version of Zulip is 1.7 or newer), you can do deployments by running as root:

/home/zulip/deployments/current/scripts/upgrade-zulip-from-git <branch>

and Zulip will automatically fetch the relevant branch from the specified repository to a directory under /home/zulip/deployments (where release tarball are unpacked), build the compiled static assets from source, and switches to the new version.

Upgrading using Git from Zulip 1.6 and older

If you're are upgrading from a Git repository, and you currently have Zulip 1.6 or older installed, you will need to install the dependencies for building Zulip's static assets. To do this, add zulip::static_asset_compiler to your /etc/zulip/zulip.conf file's puppet_classes entry, like this:

puppet_classes = zulip::voyager, zulip::static_asset_compiler

and run scripts/zulip-puppet-apply. After approving the changes, you'll be able to use upgrade-zulip-from-git.

After you've upgraded to Zulip 1.7 or above, you can safely remove zulip::static_asset_compiler from puppet_classes; in Zulip 1.7 and above, it is a dependency of zulip::voyager and thus these dependencies are installed by default.

Backups

There are several pieces of data that you might want to back up:

  • The postgres database. That you can back up like any postgres database; we have some example tooling for doing that incrementally into S3 using wal-e in puppet/zulip_internal/manifests/postgres_common.pp (that's what we use for zulip.com's database backups). Note that this module isn't part of the Zulip server releases since it's part of the zulip.com configuration (see https://github.com/zulip/zulip/issues/293 for a ticket about fixing this to make life easier for running backups).

  • Any user-uploaded files. If you're using S3 as storage for file uploads, this is backed up in S3, but if you have instead set LOCAL_UPLOADS_DIR, any files uploaded by users (including avatars) will be stored in that directory and you'll want to back it up.

  • Your Zulip configuration including secrets from /etc/zulip/. E.g. if you lose the value of secret_key, all users will need to login again when you setup a replacement server since you won't be able to verify their cookies; if you lose avatar_salt, any user-uploaded avatars will need to be re-uploaded (since avatar filenames are computed using a hash of avatar_salt and user's email), etc.

  • The logs under /var/log/zulip can be handy to have backed up, but they do get large on a busy server, and it's definitely lower-priority.

If you are interested in backups because you are moving from one Zulip server to another server and can't transfer a full postgres dump (which is definitely the simplest approach), our draft conversion and export design document may help. The tool is well designed, and was tested carefully with dozens of realms in mid-2016; but it's not integrated into Zulip's regular testing process, and thus it is worth asking on the Zulip developers mailing list whether it needs any minor updates to do things like export newly added tables.

Restore from backups

To restore from backups, the process is basically the reverse of the above:

  • Install new server as normal by downloading a Zulip release tarball and then using scripts/setup/install, you don't need to run the initialize-database second stage which puts default data into the database.

  • Unpack to /etc/zulip the settings.py and zulip-secrets.conf files from your backups.

  • Restore your database from the backup using wal-e; if you ran initialize-database anyway above, you'll want to first scripts/setup/postgres-init-db to drop the initial database first.

  • Reconfigure rabbitmq to use the password from secrets.conf by running, as root, scripts/setup/configure-rabbitmq.

  • If you're using local file uploads, restore those files to the path specified by settings.LOCAL_UPLOADS_DIR and (if appropriate) any logs.

  • Start the server using scripts/restart-server.

This restoration process can also be used to migrate a Zulip installation from one server to another.

We recommend running a disaster recovery after you setup backups to confirm that your backups are working; you may also want to monitor that they are up to date using the Nagios plugin at: puppet/zulip_internal/files/nagios_plugins/check_postgres_backup.

Contributions to more fully automate this process or make this section of the guide much more explicit and detailed are very welcome!

Postgres streaming replication

Zulip has database configuration for using Postgres streaming replication; you can see the configuration in these files:

  • puppet/zulip_internal/manifests/postgres_slave.pp
  • puppet/zulip_internal/manifests/postgres_master.pp
  • puppet/zulip_internal/files/postgresql/*

Contribution of a step-by-step guide for setting this up (and moving this configuration to be available in the main puppet/zulip/ tree) would be very welcome!

Monitoring

The complete Nagios configuration (sans secret keys) used to monitor zulip.com is available under puppet/zulip_internal in the Zulip Git repository (those files are not installed in the release tarballs).

The Nagios plugins used by that configuration are installed automatically by the Zulip installation process in subdirectories under /usr/lib/nagios/plugins/. The following is a summary of the various Nagios plugins included with Zulip and what they check:

Application server and queue worker monitoring:

  • check_send_receive_time (sends a test message through the system between two bot users to check that end-to-end message sending works)

  • check_rabbitmq_consumers and check_rabbitmq_queues (checks for rabbitmq being down or the queue workers being behind)

  • check_queue_worker_errors (checks for errors reported by the queue workers)

  • check_worker_memory (monitors for memory leaks in queue workers)

  • check_email_deliverer_backlog and check_email_deliverer_process (monitors for whether outgoing emails are being sent)

Database monitoring:

  • check_postgres_replication_lag (checks streaming replication is up to date).

  • check_postgres (checks the health of the postgres database)

  • check_postgres_backup (checks backups are up to date; see above)

  • check_fts_update_log (monitors for whether full-text search updates are being processed)

Standard server monitoring:

  • check_website_response.sh (standard HTTP check)

  • check_debian_packages (checks apt repository is up to date)

If you're using these plugins, bug reports and pull requests to make it easier to monitor Zulip and maintain it in production are encouraged!

Scalability

This section attempts to address the considerations involved with running Zulip with larger teams (especially >1000 users).

  • For an organization with 100+ users, it's important to have more than 4GB of RAM on the system. Zulip will install on a system with 2GB of RAM, but with less than 3.5GB of RAM, it will run its queue processors multithreaded to conserve memory; this creates a significant performance bottleneck.

  • chat.zulip.org, with thousands of user accounts and thousands of messages sent every week, has 8GB of RAM, 4 cores, and 80GB of disk. The CPUs are essentially always idle, but the 8GB of RAM is important.

  • We recommend using a remote postgres database for isolation, though it is not required. In the following, we discuss a relatively simple configuration with two types of servers: application servers (running Django, Tornado, RabbitMQ, Redis, Memcached, etc.) and database servers.

  • You can scale to a pretty large installation (O(~1000) concurrently active users using it to chat all day) with just a single reasonably large application server (e.g. AWS c3.2xlarge with 8 cores and 16GB of RAM) sitting mostly idle (<10% CPU used and only 4GB of the 16GB RAM actively in use). You can probably get away with half that (e.g. c3.xlarge), but ~8GB of RAM is highly recommended at scale. Beyond a 1000 active users, you will eventually want to increase the memory cap in memcached.conf from the default 512MB to avoid high rates of memcached misses.

  • For the database server, we highly recommend SSD disks, and RAM is the primary resource limitation. We have not aggressively tested for the minimum resources required, but 8 cores with 30GB of RAM (e.g. AWS's m3.2xlarge) should suffice; you may be able to get away with less especially on the CPU side. The database load per user is pretty optimized as long as memcached is working correctly. This has not been tested, but from extrapolating the load profile, it should be possible to scale a Zulip installation to 10,000s of active users using a single large database server without doing anything complicated like sharding the database.

  • For reasonably high availability, it's easy to run a hot spare application server and a hot spare database (using Postgres streaming replication; see the section on configuring this). Be sure to check out the section on backups if you're hoping to run a spare application server; in particular you probably want to use the S3 backend for storing user-uploaded files and avatars and will want to make sure secrets are available on the hot spare.

  • Zulip does not support dividing traffic for a given Zulip realm between multiple application servers. There are two issues: you need to share the memcached/Redis/RabbitMQ instance (these should can be moved to a network service shared by multiple servers with a bit of configuration) and the Tornado event system for pushing to browsers currently has no mechanism for multiple frontend servers (or event processes) talking to each other. One can probably get a factor of 10 in a single server's scalability by supporting multiple tornado processes on a single server, which is also likely the first part of any project to support exchanging events amongst multiple servers.

Questions, concerns, and bug reports about this area of Zulip are very welcome! This is an area we are hoping to improve.

Securing your Zulip server

Zulip's security model is discussed in a separate document.

Management commands

Zulip has a large library of Django management commands. To use them, you will want to be logged in as the zulip user and for the purposes of this documentation, we assume the current working directory is /home/zulip/deployments/current.

Below, we show several useful examples, but there are more than 100 in total. We recommend skimming the usage docs (or if there are none, the code) of a management command before using it, since they are generally less polished and more designed for expert use than the rest of the Zulip system.

manage.py shell

You can get an iPython shell with full access to code within the Zulip project using manage.py shell, e.g., you can do the following to change an email address:

$ /home/zulip/deployments/current/manage.py shell
In [1]: user_profile = get_user_profile_by_email("email@example.com")
In [2]: do_change_user_email(user_profile, "new_email@example.com")

manage.py dbshell

This will start a postgres shell connected to the Zulip database.

Grant administrator access

You can make any user a realm administrator on the command line with the knight management command:

./manage.py knight username@example.com -f

Creating API super users with manage.py

If you need to manage the IRC, Jabber, or Zephyr mirrors, you will need to create API super users. To do this, use ./manage.py knight with the --permission=api_super_user argument. See the respective integration scripts for these mirrors (under zulip/integrations/ in the Zulip Python API repo) for further detail on these.

Exporting users and realms with manage.py export

If you need to do an export of a single user or of an entire realm, we have tools in management/ that essentially export Zulip data to the file system.

export_single_user.py exports the message history and realm-public metadata for a single Zulip user (including that user's received messages as well as their sent messages).

A good overview of the process for exporting a single realm when moving a realm to a new server (without moving a full database dump) is in management/export.py. We recommend you read the comment there for words of wisdom on speed, what is and is not exported, what will break upon a move to a new server, and suggested procedure.

Other useful manage.py commands

There are a large number of useful management commands under zerver/management/commands/; you can also see them listed using ./manage.py with no arguments.

Hosting multiple Zulip organizations

This is explained in detail on its own page.