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Use Capistrano's HOSTFILTER feature instead of rolling our own. #10146
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issyl0
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We stopped using TARGET_MACHINES in alphagov/govuk-puppet#10146.
sengi
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Fixes bug introduced in #10146 which broke all-nodes deployments.
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Fixes bug introduced in #10146 which broke all-nodes deployments.
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Feb 14, 2020
Fixes bug introduced in #10146 which broke all-nodes deployments.
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It turns out that Capistrano 2's
HOSTFILTERfeature does exactly what we've been trying to implement ourselves in ourTARGET_MACHINESchange. Specifically, it deploy to just the machines specified inHOSTFILTERand ignores any tasks for roles which the machine doesn't have.The motivation for this is to fix deployments of Whitehall to single nodes, which happens when an EC2 instance goes away and when we scale up. This has been broken since Sep 2019 (alphagov/govuk-app-deployment#325). My previous attempt, alphagov/govuk-app-deployment#358, didn't solve the problem because Cap fails when a task has no applicable machines (for example
restart_backendhas no applicable machines when deploying to awhitehall_frontendmachine).There is a caveat to this, which is that
HOSTFILTERappears to have been removed in Capistrano 3 and replaced with a similarHOSTSfeature, which sadly doesn't do what we need; it tries to run all tasks on the specified hosts regardless of whether the tasks apply to the role or not.So if for any reason we want to upgrade to Capistrano 3, we'd need to find an alternative solution. I don't imagine that's very likely though, given that we've been on Cap 2 for so many years.
Tested in Integration by making the same change manually on the Jenkins job temporarily.