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# frozen_string_literal: true
require 'spec_helper'
RSpec.describe 'Load balancer behavior with errors inside a transaction', :redis, :delete do
let(:model) { ApplicationRecord }
let(:db_host) { model.connection_pool.db_config.host }
let(:test_table_name) { '_test_foo' }
before do
# Patch in our load balancer config, simply pointing at the test database twice
allow(Gitlab::Database::LoadBalancing::Configuration).to receive(:for_model) do |base_model|
Gitlab::Database::LoadBalancing::Configuration.new(base_model, [db_host, db_host])
end
Gitlab::Database::LoadBalancing::Setup.new(ApplicationRecord).setup
model.connection.execute(<<~SQL)
CREATE TABLE IF NOT EXISTS #{test_table_name} (id SERIAL PRIMARY KEY, value INTEGER)
SQL
end
after do
model.connection.execute(<<~SQL)
DROP TABLE IF EXISTS #{test_table_name}
SQL
end
def execute(conn)
conn.execute("INSERT INTO #{test_table_name} (value) VALUES (1)")
backend_pid = conn.execute("SELECT pg_backend_pid() AS pid").to_a.first['pid']
# This will result in a PG error, which is not raised.
# Instead, we retry the statement on a fresh connection (where the pid is different and it does nothing)
# and the load balancer continues with a fresh connection and no transaction if a transaction was open previously
conn.execute(<<~SQL)
SELECT CASE
WHEN pg_backend_pid() = #{backend_pid} THEN
pg_terminate_backend(#{backend_pid})
END
SQL
# This statement will execute on a new connection, and violate transaction semantics
# if we were in a transaction before
conn.execute("INSERT INTO #{test_table_name} (value) VALUES (2)")
end
it 'logs a warning when violating transaction semantics with writes' do
conn = model.connection
expect(::Gitlab::Database::LoadBalancing::Logger).to receive(:warn).with(hash_including(event: :transaction_leak))
conn.transaction do
expect(conn).to be_transaction_open
execute(conn)
expect(conn).not_to be_transaction_open
end
values = conn.execute("SELECT value FROM #{test_table_name}").to_a.map { |row| row['value'] }
expect(values).to contain_exactly(2) # Does not include 1 because the transaction was aborted and leaked
end
it 'does not log a warning when no transaction is open to be leaked' do
conn = model.connection
expect(::Gitlab::Database::LoadBalancing::Logger)
.not_to receive(:warn).with(hash_including(event: :transaction_leak))
expect(conn).not_to be_transaction_open
execute(conn)
expect(conn).not_to be_transaction_open
values = conn.execute("SELECT value FROM #{test_table_name}").to_a.map { |row| row['value'] }
expect(values).to contain_exactly(1, 2) # Includes both rows because there was no transaction to roll back
end
end
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