100 lines
3.9 KiB
Ruby
100 lines
3.9 KiB
Ruby
#
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# Copyright (C) 2012 - present Instructure, Inc.
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#
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# This file is part of Canvas.
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#
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# Canvas is free software: you can redistribute it and/or modify it under
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# the terms of the GNU Affero General Public License as published by the Free
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# Software Foundation, version 3 of the License.
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#
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# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
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# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
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# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
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# details.
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#
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# You should have received a copy of the GNU Affero General Public License along
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# with this program. If not, see <http://www.gnu.org/licenses/>.
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class DelayedJobsUseAdvisoryLocks < ActiveRecord::Migration[4.2]
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tag :predeploy
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def self.connection
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Delayed::Backend::ActiveRecord::Job.connection
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end
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def self.up
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# use an advisory lock based on the name of the strand, instead of locking the whole table
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# note that we're using half of the md5, so collisions are possible, but we don't really
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# care because that would just be the old behavior, whereas for the most part locking will
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# be much smaller
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if connection.adapter_name == 'PostgreSQL'
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execute(<<-CODE)
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CREATE FUNCTION #{connection.quote_table_name('half_md5_as_bigint')}(strand varchar) RETURNS bigint AS $$
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DECLARE
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strand_md5 bytea;
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BEGIN
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strand_md5 := decode(md5(strand), 'hex');
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RETURN (CAST(get_byte(strand_md5, 0) AS bigint) << 56) +
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(CAST(get_byte(strand_md5, 1) AS bigint) << 48) +
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(CAST(get_byte(strand_md5, 2) AS bigint) << 40) +
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(CAST(get_byte(strand_md5, 3) AS bigint) << 32) +
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(CAST(get_byte(strand_md5, 4) AS bigint) << 24) +
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(get_byte(strand_md5, 5) << 16) +
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(get_byte(strand_md5, 6) << 8) +
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get_byte(strand_md5, 7);
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END;
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$$ LANGUAGE plpgsql;
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CODE
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execute(<<-CODE)
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CREATE OR REPLACE FUNCTION #{connection.quote_table_name('delayed_jobs_before_insert_row_tr_fn')} () RETURNS trigger AS $$
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BEGIN
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PERFORM pg_advisory_xact_lock(half_md5_as_bigint(NEW.strand));
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IF (SELECT 1 FROM delayed_jobs WHERE strand = NEW.strand LIMIT 1) = 1 THEN
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NEW.next_in_strand := 'f';
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END IF;
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RETURN NEW;
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END;
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$$ LANGUAGE plpgsql;
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CODE
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execute(<<-CODE)
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CREATE OR REPLACE FUNCTION #{connection.quote_table_name('delayed_jobs_after_delete_row_tr_fn')} () RETURNS trigger AS $$
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BEGIN
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PERFORM pg_advisory_xact_lock(half_md5_as_bigint(OLD.strand));
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UPDATE delayed_jobs SET next_in_strand = 't' WHERE id = (SELECT id FROM delayed_jobs j2 WHERE j2.strand = OLD.strand ORDER BY j2.strand, j2.id ASC LIMIT 1 FOR UPDATE);
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RETURN OLD;
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END;
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$$ LANGUAGE plpgsql;
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CODE
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end
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end
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def self.down
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if connection.adapter_name == 'PostgreSQL'
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execute(<<-CODE)
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CREATE OR REPLACE FUNCTION #{connection.quote_table_name('delayed_jobs_before_insert_row_tr_fn')} () RETURNS trigger AS $$
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BEGIN
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LOCK delayed_jobs IN SHARE ROW EXCLUSIVE MODE;
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IF (SELECT 1 FROM delayed_jobs WHERE strand = NEW.strand LIMIT 1) = 1 THEN
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NEW.next_in_strand := 'f';
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END IF;
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RETURN NEW;
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END;
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$$ LANGUAGE plpgsql;
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CODE
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execute(<<-CODE)
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CREATE OR REPLACE FUNCTION #{connection.quote_table_name('delayed_jobs_after_delete_row_tr_fn')} () RETURNS trigger AS $$
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BEGIN
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UPDATE delayed_jobs SET next_in_strand = 't' WHERE id = (SELECT id FROM delayed_jobs j2 WHERE j2.strand = OLD.strand ORDER BY j2.strand, j2.id ASC LIMIT 1 FOR UPDATE);
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RETURN OLD;
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END;
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$$ LANGUAGE plpgsql;
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CODE
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execute("DROP FUNCTION #{connection.quote_table_name('half_md5_as_bigint')}(varchar)")
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end
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end
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end
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