Files
Tim Deeb-SwihartandGitHub be7b5514a5 Reconnect to SQL databases when connections fail (#5926)
## What changed?

Both our PostgreSQL and MySQL database backends will now automatically
reconnect to the database when certain errors occur: all errors chosen
have been experienced when testing this behavior through an AWS Aurora
RDS failover of either MySQL or PostgreSQL.

For both backends we will reconnect when we see:
- `ECONNRESET`
- `ECONNABORTED`
- `ECONNREFUSED`
- `io.EOF`
- `io.ErrUnexpectedEOF`
- `database/sql/driver.ErrBadConn`

for postgres we will also reconnect on the following SQLStates:
- `25006` read-only transaction
- `57P03` cannot connect now
- `0A000` feature not supported, but ONLY when the message is `cannot
set transaction read-write mode during recovery`

for mysql we will also reconnect when we see the following error codes:
- `1040` too many connections 
- `1792` read-only transaction (SQLstate `25006`)
- `1836` running in read-only mode

This logic is easily extensible should we discover more failure modes
over time

## Why?

We've had multiple community reports of Temporal problems during RDS
failover. One part of this is the fact that we wouldn't necessarily
reconnect; we were at the whims of our chosen SQL abstraction's
connection pooling logic.

## How did you test it?

I manually tested this functionality in the presence of repeated RDS
failovers: 

- [x] postgres12 plugin with pq driver
- [x] postgres12 plugin with pgx driver
- [x] mysql plugin

Automated testing will be added to our regular testing pipelines once
our infrastructure friends have added the support I need (it's in
progress)

## Potential risks

We're concerned there's a correctness issue in our PostgreSQL backend
that's related to our behavior during an RDS failover. If we merge this
before I figure out what's going on, we could hide the issue and make it
harder to reproduce.

## Documentation
N/A

## Is hotfix candidate?
Yes?
2024-05-17 16:59:15 -07:00

149 lines
5.3 KiB
Go

// The MIT License
//
// Copyright (c) 2020 Temporal Technologies Inc. All rights reserved.
//
// Copyright (c) 2020 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package mysql
import (
"fmt"
"time"
)
const (
readSchemaVersionQuery = `SELECT curr_version from schema_version where version_partition=0 and db_name=?`
writeSchemaVersionQuery = `INSERT into schema_version(version_partition, db_name, creation_time, curr_version, min_compatible_version) ` +
`VALUES (0,?,?,?,?) ` +
`ON DUPLICATE KEY UPDATE ` +
`creation_time=VALUES(creation_time), curr_version=VALUES(curr_version), min_compatible_version=VALUES(min_compatible_version)`
writeSchemaUpdateHistoryQuery = `INSERT into schema_update_history(version_partition, year, month, update_time, old_version, new_version, manifest_md5, description) VALUES(0,?,?,?,?,?,?,?)`
createSchemaVersionTableQuery = `CREATE TABLE IF NOT EXISTS schema_version(version_partition INT not null, ` +
`db_name VARCHAR(255) not null, ` +
`creation_time DATETIME(6), ` +
`curr_version VARCHAR(64), ` +
`min_compatible_version VARCHAR(64), ` +
`PRIMARY KEY (version_partition, db_name));`
createSchemaUpdateHistoryTableQuery = `CREATE TABLE IF NOT EXISTS schema_update_history(` +
`version_partition INT not null, ` +
`year int not null, ` +
`month int not null, ` +
`update_time DATETIME(6) not null, ` +
`description VARCHAR(255), ` +
`manifest_md5 VARCHAR(64), ` +
`new_version VARCHAR(64), ` +
`old_version VARCHAR(64), ` +
`PRIMARY KEY (version_partition, year, month, update_time));`
// NOTE: we have to use %v because somehow mysql doesn't work with ? here
createDatabaseQuery = "CREATE DATABASE IF NOT EXISTS %v CHARACTER SET utf8mb4"
dropDatabaseQuery = "DROP DATABASE IF EXISTS %v"
listTablesQuery = "SHOW TABLES FROM %v"
dropTableQuery = "DROP TABLE %v"
)
// CreateSchemaVersionTables sets up the schema version tables
func (mdb *db) CreateSchemaVersionTables() error {
if err := mdb.Exec(createSchemaVersionTableQuery); err != nil {
return err
}
return mdb.Exec(createSchemaUpdateHistoryTableQuery)
}
// ReadSchemaVersion returns the current schema version for the keyspace
func (mdb *db) ReadSchemaVersion(database string) (string, error) {
var version string
db, err := mdb.handle.DB()
if err != nil {
return "", err
}
err = db.Get(&version, readSchemaVersionQuery, database)
return version, mdb.handle.ConvertError(err)
}
// UpdateSchemaVersion updates the schema version for the keyspace
func (mdb *db) UpdateSchemaVersion(database string, newVersion string, minCompatibleVersion string) error {
return mdb.Exec(writeSchemaVersionQuery, database, time.Now().UTC(), newVersion, minCompatibleVersion)
}
// WriteSchemaUpdateLog adds an entry to the schema update history table
func (mdb *db) WriteSchemaUpdateLog(oldVersion string, newVersion string, manifestMD5 string, desc string) error {
now := time.Now().UTC()
return mdb.Exec(writeSchemaUpdateHistoryQuery, now.Year(), int(now.Month()), now, oldVersion, newVersion, manifestMD5, desc)
}
// Exec executes a sql statement
func (mdb *db) Exec(stmt string, args ...interface{}) error {
db, err := mdb.handle.DB()
if err != nil {
return err
}
_, err = db.Exec(stmt, args...)
return mdb.handle.ConvertError(err)
}
// ListTables returns a list of tables in this database
func (mdb *db) ListTables(database string) ([]string, error) {
var tables []string
db, err := mdb.handle.DB()
if err != nil {
return nil, err
}
err = db.Select(&tables, fmt.Sprintf(listTablesQuery, database))
return tables, mdb.handle.ConvertError(err)
}
// DropTable drops a given table from the database
func (mdb *db) DropTable(name string) error {
return mdb.Exec(fmt.Sprintf(dropTableQuery, name))
}
// DropAllTables drops all tables from this database
func (mdb *db) DropAllTables(database string) error {
tables, err := mdb.ListTables(database)
if err != nil {
return err
}
for _, tab := range tables {
if err := mdb.DropTable(tab); err != nil {
return err
}
}
return nil
}
// CreateDatabase creates a database if it doesn't exist
func (mdb *db) CreateDatabase(name string) error {
return mdb.Exec(fmt.Sprintf(createDatabaseQuery, name))
}
// DropDatabase drops a database
func (mdb *db) DropDatabase(name string) error {
return mdb.Exec(fmt.Sprintf(dropDatabaseQuery, name))
}