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# frozen_string_literal: true
module Gitlab
module Database
module Partitioning
class PartitionManager
UnsafeToDetachPartitionError = Class.new(StandardError)
LEASE_TIMEOUT = 1.minute
MANAGEMENT_LEASE_KEY = 'database_partition_management_%s'
RETAIN_DETACHED_PARTITIONS_FOR = 1.week
def initialize(model)
@model = model
end
def sync_partitions
Gitlab::AppLogger.info(message: "Checking state of dynamic postgres partitions", table_name: model.table_name)
# Double-checking before getting the lease:
# The prevailing situation is no missing partitions and no extra partitions
return if missing_partitions.empty? && extra_partitions.empty?
only_with_exclusive_lease(model, lease_key: MANAGEMENT_LEASE_KEY) do
partitions_to_create = missing_partitions
create(partitions_to_create) unless partitions_to_create.empty?
partitions_to_detach = extra_partitions
detach(partitions_to_detach) unless partitions_to_detach.empty?
end
rescue StandardError => e
Gitlab::AppLogger.error(message: "Failed to create / detach partition(s)",
table_name: model.table_name,
exception_class: e.class,
exception_message: e.message)
end
private
attr_reader :model
delegate :connection, to: :model
def missing_partitions
return [] unless connection.table_exists?(model.table_name)
model.partitioning_strategy.missing_partitions
end
def extra_partitions
return [] unless connection.table_exists?(model.table_name)
model.partitioning_strategy.extra_partitions
end
def only_with_exclusive_lease(model, lease_key:)
lease = Gitlab::ExclusiveLease.new(lease_key % model.table_name, timeout: LEASE_TIMEOUT)
yield if lease.try_obtain
ensure
lease&.cancel
end
def create(partitions)
# with_lock_retries starts a requires_new transaction most of the time, but not on the last iteration
with_lock_retries do
connection.transaction(requires_new: false) do # so we open a transaction here if not already in progress
# Partitions might not get created (IF NOT EXISTS) so explicit locking will not happen.
# This LOCK TABLE ensures to have exclusive lock as the first step.
connection.execute "LOCK TABLE #{connection.quote_table_name(model.table_name)} IN ACCESS EXCLUSIVE MODE"
partitions.each do |partition|
connection.execute partition.to_sql
Gitlab::AppLogger.info(message: "Created partition",
partition_name: partition.partition_name,
table_name: partition.table)
end
model.partitioning_strategy.after_adding_partitions
end
end
end
def detach(partitions)
# with_lock_retries starts a requires_new transaction most of the time, but not on the last iteration
with_lock_retries do
connection.transaction(requires_new: false) do # so we open a transaction here if not already in progress
partitions.each { |p| detach_one_partition(p) }
end
end
end
def detach_one_partition(partition)
assert_partition_detachable!(partition)
connection.execute partition.to_detach_sql
Postgresql::DetachedPartition.create!(table_name: partition.partition_name,
drop_after: RETAIN_DETACHED_PARTITIONS_FOR.from_now)
Gitlab::AppLogger.info(message: "Detached Partition",
partition_name: partition.partition_name,
table_name: partition.table)
end
def assert_partition_detachable!(partition)
parent_table_identifier = "#{connection.current_schema}.#{partition.table}"
if (example_fk = PostgresForeignKey.by_referenced_table_identifier(parent_table_identifier).first)
raise UnsafeToDetachPartitionError, "Cannot detach #{partition.partition_name}, it would block while checking foreign key #{example_fk.name} on #{example_fk.constrained_table_identifier}"
end
end
def with_lock_retries(&block)
Gitlab::Database::WithLockRetries.new(
klass: self.class,
logger: Gitlab::AppLogger,
connection: connection
).run(&block)
end
end
end
end
end
|
