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https://github.com/discourse/discourse.git
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e76c583b91
Having a large number of post-deploy migrations running out-of-numerical-sequence with pre-deploy migrations can be problematic. For example, if we have the sequence - db/migrate/2017... - add column - db/post_migrate/2018... - drop the column - db/migrate/2021... - add the same column again It will work fine in numerical order. But if you run the pre-deploy migrations **followed by** the post-deploy migrations, you will not get the same result. Our post-deploy system is designed to allow for seamless upgrades of Discourse. However, it is reasonable for us to only support this totally seamless experience for a limited period of time. This commit moves all post_deploy migrations which are more than 1 year old (i.e. more than 2 major Discourse versions ago) into the regular pre-deploy migrations directory. This limits the impact of any edge cases caused by out-of-numerical-sequence migrations.
164 lines
4.5 KiB
Ruby
164 lines
4.5 KiB
Ruby
# frozen_string_literal: true
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module Migration; end
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class Discourse::InvalidMigration < StandardError; end
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class Migration::SafeMigrate
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module SafeMigration
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@@enable_safe = true
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def self.enable_safe!
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@@enable_safe = true
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end
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def self.disable_safe!
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@@enable_safe = false
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end
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def migrate(direction)
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if direction == :up &&
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version && version > Migration::SafeMigrate.earliest_post_deploy_version &&
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@@enable_safe != false &&
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!is_post_deploy_migration?
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Migration::SafeMigrate.enable!
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end
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super
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ensure
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Migration::SafeMigrate.disable!
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end
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private
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def is_post_deploy_migration?
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instance_methods = self.class.instance_methods(false)
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method =
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if instance_methods.include?(:up)
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:up
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elsif instance_methods.include?(:change)
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:change
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end
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return false if !method
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self.method(method).source_location.first.include?(
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Discourse::DB_POST_MIGRATE_PATH
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)
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end
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end
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module NiceErrors
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def migrate
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super
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rescue => e
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if e.cause.is_a?(Discourse::InvalidMigration)
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def e.cause
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nil
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end
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def e.backtrace
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super.reject do |frame|
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frame =~ /safe_migrate\.rb/ || frame =~ /schema_migration_details\.rb/
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end
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end
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raise e
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else
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raise e
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end
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end
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end
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def self.post_migration_path
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Discourse::DB_POST_MIGRATE_PATH
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end
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def self.enable!
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return if PG::Connection.method_defined?(:exec_migrator_unpatched)
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return if ENV['RAILS_ENV'] == "production"
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PG::Connection.class_eval do
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alias_method :exec_migrator_unpatched, :exec
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alias_method :async_exec_migrator_unpatched, :async_exec
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def exec(*args, &blk)
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Migration::SafeMigrate.protect!(args[0])
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exec_migrator_unpatched(*args, &blk)
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end
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def async_exec(*args, &blk)
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Migration::SafeMigrate.protect!(args[0])
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async_exec_migrator_unpatched(*args, &blk)
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end
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end
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end
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def self.disable!
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return if !PG::Connection.method_defined?(:exec_migrator_unpatched)
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return if ENV['RAILS_ENV'] == "production"
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PG::Connection.class_eval do
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alias_method :exec, :exec_migrator_unpatched
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alias_method :async_exec, :async_exec_migrator_unpatched
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remove_method :exec_migrator_unpatched
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remove_method :async_exec_migrator_unpatched
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end
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end
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def self.patch_active_record!
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return if ENV['RAILS_ENV'] == "production"
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ActiveSupport.on_load(:active_record) do
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ActiveRecord::Migration.prepend(SafeMigration)
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end
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if defined?(ActiveRecord::Tasks::DatabaseTasks)
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ActiveRecord::Tasks::DatabaseTasks.singleton_class.prepend(NiceErrors)
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end
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end
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def self.protect!(sql)
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if sql =~ /^\s*(?:drop\s+table|alter\s+table.*rename\s+to)\s+/i
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$stdout.puts("", <<~STR)
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WARNING
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-------------------------------------------------------------------------------------
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An attempt was made to drop or rename a table in a migration
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SQL used was: '#{sql}'
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Please generate a post deployment migration using `rails g post_migration` to drop
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or rename the table.
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This protection is in place to protect us against dropping tables that are currently
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in use by live applications.
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STR
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raise Discourse::InvalidMigration, "Attempt was made to drop a table"
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elsif sql =~ /^\s*alter\s+table.*(?:rename|drop)\s+/i
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$stdout.puts("", <<~STR)
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WARNING
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-------------------------------------------------------------------------------------
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An attempt was made to drop or rename a column in a migration
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SQL used was: '#{sql}'
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Please generate a post deployment migration using `rails g post_migration` to drop
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or rename columns.
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Note, to minimize disruption use self.ignored_columns = ["column name"] on your
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ActiveRecord model, this can be removed 6 months or so later.
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This protection is in place to protect us against dropping columns that are currently
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in use by live applications.
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STR
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raise Discourse::InvalidMigration, "Attempt was made to rename or delete column"
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end
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end
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def self.earliest_post_deploy_version
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@@earliest_post_deploy_version ||= begin
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first_file = Dir.glob("#{Discourse::DB_POST_MIGRATE_PATH}/*.rb").sort.first
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file_name = File.basename(first_file, ".rb")
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file_name.first(14).to_i
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end
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end
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end
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