diff options
Diffstat (limited to 'lib/gitlab/database/load_balancing/host.rb')
| -rw-r--r-- | lib/gitlab/database/load_balancing/host.rb | 81 |
1 files changed, 61 insertions, 20 deletions
diff --git a/lib/gitlab/database/load_balancing/host.rb b/lib/gitlab/database/load_balancing/host.rb index bdbb80d6f31..f8ed5fcd4cc 100644 --- a/lib/gitlab/database/load_balancing/host.rb +++ b/lib/gitlab/database/load_balancing/host.rb @@ -16,6 +16,43 @@ module Gitlab PG::Error ].freeze + # This query checks that the current user has permissions before we try and query logical replication status. We + # also only allow >= PG14 because these views are only accessible to superuser before PG14 even if the + # has_table_privilege says otherwise. + CAN_TRACK_LOGICAL_LSN_QUERY = <<~SQL.squish.freeze + SELECT + has_table_privilege('pg_replication_origin_status', 'select') + AND + has_function_privilege('pg_show_replication_origin_status()', 'execute') + AND current_setting('server_version_num', true)::int >= 140000 + AS allowed + SQL + + # The following is necessary to handle a mix of logical and physical replicas. We assume that if they have + # pg_replication_origin_status then they are a logical replica. In a logical replica we need to use + # `remote_lsn` rather than `pg_last_wal_replay_lsn` in order for our LSN to be comparable to the source + # cluster. This logic would be broken if we have 2 logical subscriptions or if we have a logical subscription + # in the source primary cluster. Read more at https://gitlab.com/gitlab-org/gitlab/-/merge_requests/121621 + LATEST_LSN_WITH_LOGICAL_QUERY = <<~SQL.squish.freeze + CASE + WHEN (SELECT TRUE FROM pg_replication_origin_status) THEN + (SELECT remote_lsn FROM pg_replication_origin_status) + WHEN pg_is_in_recovery() THEN + pg_last_wal_replay_lsn() + ELSE + pg_current_wal_insert_lsn() + END + SQL + + LATEST_LSN_WITHOUT_LOGICAL_QUERY = <<~SQL.squish.freeze + CASE + WHEN pg_is_in_recovery() THEN + pg_last_wal_replay_lsn() + ELSE + pg_current_wal_insert_lsn() + END + SQL + # host - The address of the database. # load_balancer - The LoadBalancer that manages this Host. def initialize(host, load_balancer, port: nil) @@ -30,6 +67,7 @@ module Gitlab @online = true @last_checked_at = Time.zone.now + # Randomly somewhere in between interval and 2*interval we'll refresh the status of the host interval = load_balancer.configuration.replica_check_interval @intervals = (interval..(interval * 2)).step(0.5).to_a end @@ -91,6 +129,7 @@ module Gitlab end def refresh_status + @latest_lsn_query = nil # Periodically clear the cached @latest_lsn_query value in case permissions change @online = replica_is_up_to_date? @last_checked_at = Time.zone.now end @@ -142,11 +181,11 @@ module Gitlab # primary. # # This method will return nil if no lag size could be calculated. - def replication_lag_size - location = connection.quote(primary_write_location) + def replication_lag_size(location = primary_write_location) + location = connection.quote(location) + row = query_and_release(<<-SQL.squish) - SELECT pg_wal_lsn_diff(#{location}, pg_last_wal_replay_lsn())::float - AS diff + SELECT pg_wal_lsn_diff(#{location}, (#{latest_lsn_query}))::float AS diff SQL row['diff'].to_i if row.any? @@ -173,22 +212,8 @@ module Gitlab # # location - The transaction write location as reported by a primary. def caught_up?(location) - string = connection.quote(location) - - # In case the host is a primary pg_last_wal_replay_lsn/pg_last_xlog_replay_location() returns - # NULL. The recovery check ensures we treat the host as up-to-date in - # such a case. - query = <<-SQL.squish - SELECT NOT pg_is_in_recovery() - OR pg_wal_lsn_diff(pg_last_wal_replay_lsn(), #{string}) >= 0 - AS result - SQL - - row = query_and_release(query) - - ::Gitlab::Utils.to_boolean(row['result']) - rescue *CONNECTION_ERRORS - false + lag = replication_lag_size(location) + lag.present? && lag.to_i <= 0 end def query_and_release(sql) @@ -198,6 +223,22 @@ module Gitlab ensure release_connection end + + private + + def can_track_logical_lsn? + row = query_and_release(CAN_TRACK_LOGICAL_LSN_QUERY) + + ::Gitlab::Utils.to_boolean(row['allowed']) + rescue *CONNECTION_ERRORS + false + end + + # The LATEST_LSN_WITH_LOGICAL query requires permissions that may not be present in self-managed configurations. + # We fallback gracefully to the query that does not correctly handle logical replicas for such configurations. + def latest_lsn_query + @latest_lsn_query ||= can_track_logical_lsn? ? LATEST_LSN_WITH_LOGICAL_QUERY : LATEST_LSN_WITHOUT_LOGICAL_QUERY + end end end end |