Migrating to new host#

Prepare salt configuration for migration#

  1. Ensure that salt-master, loadbalancer, and host in question can be brought up with vagrant locally, and that their health check for the relevant service is failing in haproxy after the host is fully up

  • laptop:psf-salt user$ vagrant up salt-master

  • laptop:psf-salt user$ vagrant up loadbalancer

  • laptop:psf-salt user$ vagrant up host

To view haproxy status:

  • vagrant up the salt-master, loadbalancer, and host in question (vagrant up)

  • Prepare an ssh configuration file to access the host with native ssh commands: vagrant ssh-config salt-master loadbalancer >> vagrant-ssh

  • Open an ssh session with port forwarding to the haproxy status page: ssh -L 4646: -F vagrant-ssh loadbalancer

  • view the haproxy status page in your browser http://localhost:4646/haproxy?stats

  1. Edit pillar data for roles.sls to include both old and new hostnames (ex. hostname*)

diff --git a/pillar/prod/roles.sls b/pillar/prod/roles.sls
index 68387c9..7a8ace1 100644
--- a/pillar/prod/roles.sls
+++ b/pillar/prod/roles.sls
@@ -35,7 +35,7 @@ roles:
     purpose:  "Builds and serves CPython's documentation"
     contact:  "mdk"
-    pattern:  "downloads.nyc1.psf.io"
+    pattern:  "downloads*.nyc1.psf.io"
     purpose:  "Serves python.org downloads"
     contact:  "CPython Release Managers"

Migrate the host#

Update Salt Master with latest config including prep from above#

  1. ssh into the salt-master server ssh salt.nyc1.psf.io

  2. Navigate to srv/psf-salt user@salt:~$ cd /srv/psf-salt

  3. Run user@salt:/srv/psf-salt$ sudo git pull

  4. Run highstate to update the roles settings to reflect the new matchng pattern, as well as additional changes to support migration: user@salt:/srv/psf-salt$ sudo salt-call state.highstate

Ensure new configuration doesn’t impact host being migrated#

  1. ssh into the old-host laptop:psf-salt user$ ssh old-host

  2. Run user@old-host:~$ sudo salt-call state.highstate

Create new host#

  1. Start a new droplet  in digital ocean, and check resources being used on old host to see if we are over or under spending on resources

  2. Create a new droplet with new version of ubuntu, appropriate resources,  and name it according to hostname + 2004

Provision new host for migration#

  1. ssh into new-host via the IP address provided by DigitalOceanssh root@NNN.NNN.NNN.NNN

  2. Add Salt repositories for our current target version (add the apt-repo and install salt-minion package)

  • user@new-host:~$ wget --quiet -O /usr/share/keyrings/salt-archive-keyring.gpg https://repo.saltproject.io/py3/ubuntu/20.04/$(dpkg --print-architecture)/3004/salt-archive-keyring.gpg

  • user@new-host:~$ echo "deb [signed-by=/usr/share/keyrings/salt-archive-keyring.gpg arch=$(dpkg --print-architecture)] https://repo.saltproject.io/py3/ubuntu/20.04/$(dpkg --print-architecture)/3004 focal main" > /etc/apt/sources.list.d/salt.list

  1. Install and configure the salt-minion. On new-host, run the command

  • user@new-host:~$ apt-get update -y && apt-get install -y --no-install-recommends salt-minion

  • On the old-host, look through /etc/salt/minion.d* to set up salt-minion configuration files to match on new-host:

    • run user@old-host:~$ for file in /etc/salt/minion.d/*; do echo -e "cat > $file <<EOF"; sudo cat $file; echo "EOF"; done to generate bash that will create these files

  1. Restart the salt-minion service on the new host to pickup the configuration and register with salt-master: user@new-host:~$ sudo salt-call service.restart

  2. On salt-master, accept the key for the new-host: user@new-host:~$ sudo salt-key -a new-host

  3. On the new-host, run highstate sudo salt-call sate.highstate

  4. Log out of root session

  5. Ensure that the new host is not passing health checks in the loadbalancer: ssh -L 4646: lb-a.nyc1.psf.io then open http://localhost:4646/haproxy?stats in your browser.

  6. Run hightstate on the salt-master to create a public dns record for the new-host user@salt:/srv/psf-salt$ sudo salt-call state.highstate

Begin data migration#

  1. laptop:psf-salt user$ ssh -A new-host into new host to enable forwarding of ssh-agent

  2. Stop cron jobs user@new-host:~$ sudo service cron stop

  3. Stop public-facing services, like nginx, or the service the health check is looking for. Use this command as an example:  user@new-host:~$ sudo service nginx stop

  4. Ensure that any additional volumes are mounted and in the correct location:

  • Check what disks are currently mounted and where: df

  • Determine where any additional disks should be mounted (based on salt configuration of services, for example docs and downloads roles need a big /srv for their data storage

  • Ensure mounting of any external disks are in the right location using mount command with appropriate arguments

  • Ensure that the volumes will be remounted on startup by configuring them in /etc/fstab

  1. Run rsync once to move bulk of data and as necessary to watch for changes user@new-host:~$ sudo -E -s rsync -av --rsync-path="sudo rsync" username@old-host:/pathname/ /pathname/

  • The /pathname/ can be determined by looking at the pillar data for backups, pillar/prod/backup using the source_directory path for the given host (example: the downloads host uses /srv/)

Stop services on old host#

  1. ssh into old-host ( laptop:psf-salt user$ ssh old-host )

  2. Stop cron jobs user@old-host:~$ sudo service cron stop

  3. Stop public-facing services, like nginx, or the service the health check is looking for ex)  user@old-host:~$ sudo service nginx stop

Finish data migration and restart cron/public-facing services#

  1. Run rsync once more to finalize data migration user@new-host:~$ sudo -E -s rsync -av --rsync-path="sudo rsync" username@hostname: /pathname/ /pathname/

  2. Start cron jobs user@new-host:~$ sudo service cron start

  3. Start public-facing services involved with healthcheck, like nginx, user@new-host:~$ sudo service nginx start

  4. Ensure that the new-host is live and serving traffic by viewing loadbalancer page:

  • view the haproxy status page in your browser http://localhost:4646/haproxy?stats

  1. Check if users have any files on old-host and transfer accordingly:

  • user@new-host:~$ for user in /home/psf-users/*; do sudo -E -s rsync --delete -av --progress --rsync-path="sudo rsync" user@old-host:$user/ $user/migrated-from-ubuntu-1804-lts-host/; done

Shutdown and reclaim hostname#

  1. On old-host, stop the old-host by running, user@old-host:~$ sudo shutdown -h now

  2. Destroy the old-host in DigitalOcean

  3. Change the new-host name in DigitalOcean by removing the suffix or similar that was used to differentiate it from the old-host.

  4. Run user@salt:~$ sudo salt-key -L to list out and user@salt:~$ sudo salt-key -d old-host to remove old keys

  5. On new-host, run user@new-host:~$ sudo hostname new-host to rename

  6. Update new-host name in /etc/hostname, /etc/salt/minion_id, and /etc/hosts

  7. Restart the salt minion user@new-host:~$ sudo salt-call service.restart

  8. Restart datadog user@new-host:~$ sudo service datadog-agent restart

  9. Run user@salt:~$ sudo salt-key -a new-host to accept new keys

  10. Run highstate user@salt:~$ sudo salt-call state.highstate on salt-master to update domain name as well as known_hosts file