Commit fd7f95ee authored by Stan Hu's avatar Stan Hu

Disable replication lag check for Aurora PostgreSQL databases

Replication slots are not supported in Aurora. Attempting to check
the lag results in the message:

```
ActiveRecord::StatementInvalid: PG::FeatureNotSupported: ERROR:
Replication slots are currently not supported in Aurora : SELECT
pg_xlog_location_diff(pg_current_xlog_insert_location(),
restart_lsn)::...
```

To avoid breaking support for background migrations in Aurora, we just
disable the check if we encounter this error.

This change also now checks whether there are any replication slots
present in the primary before checking the replication lag.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/52176
parent 3cdf7c7e
...@@ -4,6 +4,15 @@ module Postgresql ...@@ -4,6 +4,15 @@ module Postgresql
class ReplicationSlot < ActiveRecord::Base class ReplicationSlot < ActiveRecord::Base
self.table_name = 'pg_replication_slots' self.table_name = 'pg_replication_slots'
# Returns true if there are any replication slots in use.
# PostgreSQL-compatible databases such as Aurora don't support
# replication slots, so this will return false as well.
def self.in_use?
transaction { exists? }
rescue ActiveRecord::StatementInvalid
false
end
# Returns true if the lag observed across all replication slots exceeds a # Returns true if the lag observed across all replication slots exceeds a
# given threshold. # given threshold.
# #
...@@ -11,6 +20,8 @@ module Postgresql ...@@ -11,6 +20,8 @@ module Postgresql
# statistics it takes between 1 and 5 seconds to replicate around # statistics it takes between 1 and 5 seconds to replicate around
# 100 MB of data. # 100 MB of data.
def self.lag_too_great?(max = 100.megabytes) def self.lag_too_great?(max = 100.megabytes)
return false unless in_use?
lag_function = "#{Gitlab::Database.pg_wal_lsn_diff}" \ lag_function = "#{Gitlab::Database.pg_wal_lsn_diff}" \
"(#{Gitlab::Database.pg_current_wal_insert_lsn}(), restart_lsn)::bigint" "(#{Gitlab::Database.pg_current_wal_insert_lsn}(), restart_lsn)::bigint"
......
---
title: Disable replication lag check for Aurora PostgreSQL databases
merge_request: 22786
author:
type: fixed
...@@ -3,7 +3,27 @@ ...@@ -3,7 +3,27 @@
require 'spec_helper' require 'spec_helper'
describe Postgresql::ReplicationSlot, :postgresql do describe Postgresql::ReplicationSlot, :postgresql do
describe '.in_use?' do
it 'returns true when replication slots are present' do
expect(described_class).to receive(:exists?).and_return(true)
expect(described_class.in_use?).to be_truthy
end
it 'returns false when replication slots are not present' do
expect(described_class.in_use?).to be_falsey
end
it 'returns false if the existence check is invalid' do
expect(described_class).to receive(:exists?).and_raise(ActiveRecord::StatementInvalid.new('PG::FeatureNotSupported'))
expect(described_class.in_use?).to be_falsey
end
end
describe '.lag_too_great?' do describe '.lag_too_great?' do
before do
expect(described_class).to receive(:in_use?).and_return(true)
end
it 'returns true when replication lag is too great' do it 'returns true when replication lag is too great' do
expect(described_class) expect(described_class)
.to receive(:pluck) .to receive(:pluck)
......
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