89 lines
2.8 KiB
Ruby
89 lines
2.8 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module Database
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module LoadBalancing
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# Rack middleware to handle sticking when serving Rails requests. Grape
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# API calls are handled separately as different API endpoints need to
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# stick based on different objects.
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class RackMiddleware
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STICK_OBJECT = 'load_balancing.stick_object'
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def initialize(app)
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@app = app
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end
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def call(env)
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# Ensure that any state that may have run before the first request
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# doesn't linger around.
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clear
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unstick_or_continue_sticking(env)
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result = @app.call(env)
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ActiveSupport::Notifications.instrument('web_transaction_completed.load_balancing')
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stick_if_necessary(env)
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result
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ensure
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clear
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end
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# Determine if we need to stick based on currently available user data.
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#
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# Typically this code will only be reachable for Rails requests as
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# Grape data is not yet available at this point.
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def unstick_or_continue_sticking(env)
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namespaces_and_ids = sticking_namespaces(env)
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namespaces_and_ids.each do |(sticking, namespace, id)|
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sticking.unstick_or_continue_sticking(namespace, id)
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end
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end
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# Determine if we need to stick after handling a request.
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def stick_if_necessary(env)
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namespaces_and_ids = sticking_namespaces(env)
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namespaces_and_ids.each do |sticking, namespace, id|
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sticking.stick_if_necessary(namespace, id)
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end
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end
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def clear
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::Gitlab::Database::LoadBalancing.release_hosts
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::Gitlab::Database::LoadBalancing::Session.clear_session
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end
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# Determines the sticking namespace and identifier based on the Rack
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# environment.
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#
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# For Rails requests this uses warden, but Grape and others have to
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# manually set the right environment variable.
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def sticking_namespaces(env)
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warden = env['warden']
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if warden && warden.user
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# When sticking per user, _only_ sticking the main connection could
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# result in the application trying to read data from a different
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# connection, while that data isn't available yet.
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#
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# To prevent this from happening, we scope sticking to all the
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# models that support load balancing. In the future (if we
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# determined this to be OK) we may be able to relax this.
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::Gitlab::Database::LoadBalancing.base_models.map do |model|
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[model.sticking, :user, warden.user.id]
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end
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elsif env[STICK_OBJECT].present?
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env[STICK_OBJECT].to_a
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else
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[]
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end
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end
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end
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end
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end
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end
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