MySQL和Redis是兩個(gè)重要的數(shù)據(jù)庫(kù)系統(tǒng)，都有自己的優(yōu)缺點(diǎn)。在實(shí)際應(yīng)用中，我們可能會(huì)同時(shí)使用它們來(lái)存儲(chǔ)數(shù)據(jù)。為了提高數(shù)據(jù)的讀取效率，我們希望在兩個(gè)數(shù)據(jù)庫(kù)之間實(shí)現(xiàn)數(shù)據(jù)同步。雖然這個(gè)問(wèn)題還有很多解決方案，但是本文將著重討論利用MySQL binlog和Redis Pub/Sub機(jī)制實(shí)現(xiàn)數(shù)據(jù)同步的方式。

在MySQL里，binlog是一種二進(jìn)制日志格式，用來(lái)記錄數(shù)據(jù)庫(kù)的更新操作。我們可以利用binlog來(lái)監(jiān)聽(tīng)MySQL數(shù)據(jù)庫(kù)的更新，在Redis中通過(guò)訂閱相應(yīng)的頻道實(shí)現(xiàn)數(shù)據(jù)同步。

USE DATABASE;
SHOW BINLOG EVENTS;

通過(guò)以上的操作，我們可以查看當(dāng)前數(shù)據(jù)庫(kù)的binlog日志記錄。

為了將binlog日志發(fā)送到Redis中，我們可以編寫(xiě)一個(gè)監(jiān)聽(tīng)MySQL binlog并將數(shù)據(jù)發(fā)送到Redis的腳本。如下所示：

import redis
import pymysql
import time
#連接MySQL數(shù)據(jù)庫(kù)
mysql_conn = pymysql.connect(host='localhost', port=3306, user='root', passwd='password', db='test', charset='utf8')
#連接Redis數(shù)據(jù)庫(kù)
redis_conn = redis.Redis(host='localhost', port=6379, db=0)
#監(jiān)聽(tīng)binlog日志
def mysql_listener():
mysql_cursor = mysql_conn.cursor()
mysql_cursor.execute("SHOW MASTER STATUS")
result = mysql_cursor.fetchone()
binlog_file = result[0]
binlog_pos = result[1]
mysql_stream = pymysqlreplication.BinLogStreamReader(
connection_settings={"host": "localhost",
"port": 3306,
"user": "root",
"passwd": "password",
"db": "test"},
server_id=999,
blocking=True,
only_events=[pymysqlreplication.events.DeleteRowsEvent, pymysqlreplication.events.UpdateRowsEvent,
pymysqlreplication.events.WriteRowsEvent])
for binlogevent in mysql_stream:
for row in binlogevent.rows:
event = {"schema": binlogevent.schema, "table": binlogevent.table}
if isinstance(binlogevent, pymysqlreplication.events.DeleteRowsEvent):
event["action"] = "delete"
event["data"] = dict(row["values"].items())
elif isinstance(binlogevent, pymysqlreplication.events.UpdateRowsEvent):
event["action"] = "update"
event["data"] = dict(row["after_values"].items())
elif isinstance(binlogevent, pymysqlreplication.events.WriteRowsEvent):
event["action"] = "insert"
event["data"] = dict(row["values"].items())
redis_conn.publish("mysql_listener", json.dumps(event))
print("sent:", event)
if __name__ == "__main__":
while True:
try:
mysql_listener()
except:
pass
time.sleep(1)

該腳本使用了Python編程語(yǔ)言和pymysqlreplication庫(kù)，可以持續(xù)監(jiān)聽(tīng)MySQL binlog日志，并將修改數(shù)據(jù)發(fā)送到Redis的mysql_listener頻道中。在Redis中，我們可以啟用一個(gè)Pub/Sub進(jìn)程來(lái)接收這些數(shù)據(jù)并執(zhí)行相應(yīng)的操作。如下所示：

import redis
import json
#連接Redis數(shù)據(jù)庫(kù)
redis_conn = redis.Redis(host='localhost', port=6379, db=0)
#定義一個(gè)Pub/Sub進(jìn)程
def redis_listener():
pubsub = redis_conn.pubsub()
pubsub.subscribe("mysql_listener")
for item in pubsub.listen():
try:
event = json.loads(item["data"])
table_name = event["table"]
action = event["action"]
data = event["data"]
if action == "insert":
redis_conn.hmset(table_name + ":" + str(data["id"]), data)
elif action == "update":
redis_conn.hmset(table_name + ":" + str(data["id"]), data)
elif action == "delete":
redis_conn.delete(table_name + ":" + str(data["id"]))
except Exception as e:
pass
if __name__ == "__main__":
redis_listener()

通過(guò)以上的兩段代碼，我們可以實(shí)現(xiàn)MySQL和Redis之間的數(shù)據(jù)同步。通過(guò)監(jiān)聽(tīng)MySQL binlog日志并將數(shù)據(jù)發(fā)送到Redis中，我們可以利用Redis的高效性來(lái)提高數(shù)據(jù)的讀取效率，同時(shí)還可以保證MySQL數(shù)據(jù)在失敗后仍能在Redis中得到保存，提高了系統(tǒng)的可靠性。