Upgrading backend services¶
As time passes and new versions of our backend services are released, we may find it necessary to upgrade the version of a given service that we use (e.g. for new functionality or to patch security issues).
Our Nginx service (the
router app) is run in a Docker container and deployed as a PaaS app, in the same way as our
Flask apps (see deploying a new dockerised app).
The version of Nginx itself is set in the router app’s Dockerfile.
We successfully upgraded the Nginx version to 1.14.1 in November 2018 (to fix a security vulnerability) without any issues.
Our PostgreSQL database is a managed PaaS service.
Creating an upgraded (empty) service instance is straightforward enough, using the PaaS command
cf create-service postgres <PLAN> <SERVICE_NAME>.
However any upgrades must be managed carefully with a migration plan (TBC!), potentially with scheduled downtime to minimise any transactional data loss during the migration.
Deploying a new Elasticsearch backend requires spinning up a separate ES backend and compatible search-api alongside the existing infrastructure. The existing indices can be re-indexed into the new backend and then, once ready, the new search-api can be deployed through the standard pipeline and will automatically connect to the new ES backend. The old ES backend can then be retired after the transition.
This is less complicated due to our fairly small and relatively non-volatile indices. If we hold multiple indices that change often and must remain up-to-date, more complex setup will be required to replicate changes to both ES backends during the transition. As it is, we indexed into the new ES backend and then kicked off a re-index immediately after deploying the new search-api (connected to the new ES instance) to catch any possible service changes that may have happened between the initial index and the release.
These steps are for the Preview environment - repeat for staging and production as appropriate.
Make sure the current release of the Search API is up to date with master (and pause further releases on the app until the migration is complete).
Create a new Elasticsearch service in the preview PaaS space, with a unique name: *
cf create-service elasticsearch small-ha-5.x search_api_elasticsearch_new
In digitalmarketplace-aws, generate a manifest file for the new search API instance: *
APPLICATION_NAME=search-api STAGE=preview make generate-manifest
Edit the manifest manually, setting the following values: *
route: dm-elasticsearch-migration-preview.cloudapps.digital(a temporary route) *
services: search_api_elasticsearch_new* Add a new
Use the manifest to create a new PaaS app, based on the latest released image: *
cf push -f new-search-api-manifest.yml -o digitalmarketplace/search-api:release-1234
You now have two versions of the search-api running; the live version and your new version with an upgraded ES backend.
Re-create all required indices and settings in the new ES backend. Don’t forget to set up any required aliases for the indices (.e.g.
g-cloud-9-yyyy-mm-ddindex you’ve created). In digitalmarketplace-scripts: 1. Create G10 index:
scripts/index-to-search-service.py services preview --frameworks=g-cloud-10 --index=g-cloud-10-2018-10-18 --search-api-url=https://dm-elasticsearch-migration-preview.cloudapps.digital --create-with-mapping=services-g-cloud-102. Create G10 alias:
scripts/update-index-alias.py --stage=preview g-cloud-10 g-cloud-10-2018-10-18 https://dm-elasticsearch-migration-preview.cloudapps.digital3. Create DOS index:
scripts/index-to-search-service.py briefs preview --frameworks=digital-outcomes-and-specialists-3 --index=briefs-digital-outcomes-and-specialists-3-2018-10-18 --search-api-url=https://dm-elasticsearch-migration-preview.cloudapps.digital --create-with-mapping=briefs-digital-outcomes-and-specialists-24. Create DOS alias:
scripts/update-index-alias.py --stage=preview briefs-digital-outcomes-and-specialists briefs-digital-outcomes-and-specialists-3-2018-10-18 https://dm-elasticsearch-migration-preview.cloudapps.digital
Check that all documents have been indexed correctly (with the right mappings) for both DOS and G-Cloud, by checking the new Search API app’s
Map the new Search API app instances to the ‘live’ route. *
cf map-route elasticsearch-migration cloudapps.digital --hostname dm-search-api-preview
Both apps should now be serving requests from their respective ES services (which should be identical! You just indexed the new one, right?). Check the logs for each app to make sure they are both receiving traffic.
Remove the old Search API app instances from the route *
cf unmap-route search-api cloudapps.digital --hostname dm-search-api-preview
Remove the new Search API app instances from the temporary route. *
cf unmap-route elasticsearch-migration cloudapps.digital --hostname dm-elasticsearch-migration-preview
Rename the old ES service to
cf rename-service search_api_elasticsearch search_api_elasticsearch_old
Rename the new ES service to
cf rename-service search_api_elasticsearch_new search_api_elasticsearch
Rename the old Search API app *
cf rename search-api search-api-old
Rename the new Search API app *
cf rename elasticsearch-migration search-api
Remove the old Search API app *
cf delete search-api-old
Re-release the Search API via the pipeline to pick up the new service/name changes
Reindex everything using Jenkins, to make sure anything added to the database during the migration period is indexed. For preview/staging, waiting for the overnight job to run is fine.
Remove the old ES service. *
cf delete-service search_api_elasticsearch_old