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Contents
module PgHero
module Methods
module Replication
def replica?
unless defined?(@replica)
@replica = select_one("SELECT pg_is_in_recovery()")
end
@replica
end
# https://www.postgresql.org/message-id/CADKbJJWz9M0swPT3oqe8f9+tfD4-F54uE6Xtkh4nERpVsQnjnw@mail.gmail.com
def replication_lag
with_feature_support(:replication_lag) do
lag_condition =
if server_version_num >= 100000
"pg_last_wal_receive_lsn() = pg_last_wal_replay_lsn()"
else
"pg_last_xlog_receive_location() = pg_last_xlog_replay_location()"
end
select_one <<~SQL
SELECT
CASE
WHEN NOT pg_is_in_recovery() OR #{lag_condition} THEN 0
ELSE EXTRACT (EPOCH FROM NOW() - pg_last_xact_replay_timestamp())
END
AS replication_lag
SQL
end
end
def replication_slots
if server_version_num >= 90400
with_feature_support(:replication_slots, []) do
select_all <<~SQL
SELECT
slot_name,
database,
active
FROM pg_replication_slots
SQL
end
else
[]
end
end
def replicating?
with_feature_support(:replicating?, false) do
select_all("SELECT state FROM pg_stat_replication").any?
end
end
private
def feature_support
@feature_support ||= {}
end
def with_feature_support(cache_key, default = nil)
# cache feature support to minimize errors in logs
return default if feature_support[cache_key] == false
begin
yield
rescue ActiveRecord::StatementInvalid => e
raise unless e.message.start_with?("PG::FeatureNotSupported:")
feature_support[cache_key] = false
default
end
end
end
end
end
Version data entries
9 entries across 9 versions & 1 rubygems