redis服务脚本（支持密码） 

#!/bin/sh
#Configurations injected by install_server below....

EXEC=/usr/local/bin/redis-server
CLIEXEC=/usr/local/bin/redis-cli
PIDFILE=/var/run/redis_6379.pid
CONF="/etc/redis/6379.conf"
REDISPORT="6379"
PASSWORD="**********"
###############
# SysV Init Information
# chkconfig: - 58 74
# description: redis_6379 is the redis daemon.
### BEGIN INIT INFO
# Provides: redis_6379
# Required-Start: $network $local_fs $remote_fs
# Required-Stop: $network $local_fs $remote_fs
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Should-Start: $syslog $named
# Should-Stop: $syslog $named
# Short-Description: start and stop redis_6379
# Description: Redis daemon
### END INIT INFO


case "$1" in
    start)
        if [ -f $PIDFILE ]
        then
            echo "$PIDFILE exists, process is already running or crashed"
        else
            echo "Starting Redis server..."
            $EXEC $CONF
        fi
        ;;
    stop)
        if [ ! -f $PIDFILE ]
        then
            echo "$PIDFILE does not exist, process is not running"
        else
            PID=$(cat $PIDFILE)
            echo "Stopping ..."
            $CLIEXEC -a $PASSWORD -p $REDISPORT shutdown
            while [ -x /proc/${PID} ]
            do
                echo "Waiting for Redis to shutdown ..."
                sleep 1
            done
            echo "Redis stopped"
        fi
        ;;
    status)
        PID=$(cat $PIDFILE)
        if [ ! -x /proc/${PID} ]
        then
            echo 'Redis is not running'
        else
            echo "Redis is running ($PID)"
        fi
        ;;
    restart)
        $0 stop
        $0 start
        ;;
    *)
        echo "Please use start, stop, restart or status as first argument"
        ;;
esac

 

Memcache限制

1. 在 Memcached中可以保存的item数据量是没有限制的，只要内存足够 。

2. Memcached单进程最大使用内存为2G，要使用更多内存，可以分多个端口开启多个Memcached进程，最大30天的数据过期时间,设置为永久的也会在这个时间过期。

3. REALTIME_MAXDELTA：最大键长为250字节，大于该长度无法存储。

4. KEY_MAX_LENGTH：单个item最大数据是1MB，超过1MB数据不予存储。

MySQL忽略已重复数据强制创建唯一索引

常规方法：

CREATE UNIQUE INDEX `idx_m2b_product_photo_pid_sort` ON `m2b`.`m2b_product_photo` (pid, sort) COMMENT ” ALGORITHM DEFAULT LOCK DEFAULT;

忽略已重复数据强制创建唯一索引的方法：

ALTER IGNORE TABLE `m2b_product_photo` ADD UNIQUE `idx_m2b_product_photo_pid_sort` (`pid`, `sort`);