通过从Solaris(SmartOS)切换到用于memcached服务器的Ubuntu,“解决了”.现在我们将负载乘以约5倍,并再次遇到问题.

我们正在运行一个大约1000个请求/分钟的站点,每个请求命中Memcached大约3次读取和1次写入.因此负载大约是每秒65个请求.缓存中的总数据大约为37M,每个密钥包含非常少量的数据(JSON编码的整数数组小于1K).

我们在这些页面上设置了基准测试脚本,并将数据输入StatsD进行日志记录.问题是Memcached需要很长时间才能响应.这些似乎与流量高峰无关.

什么可能导致这些尖峰？为什么memcached会接管一秒钟回复？我们刚刚启动了第二台服务器进入池中,并没有在峰值的频率或严重程度上产生任何明显的差异.

这是服务器上getStats()的输出：

Array
(
    [-----------] => Array
        (
            [pid] => 1364
            [uptime] => 3715684
            [threads] => 4
            [time] => 1336596719
            [pointer_size] => 64
            [rusage_user_seconds] => 7924
            [rusage_user_microseconds] => 170000
            [rusage_system_seconds] => 187214
            [rusage_system_microseconds] => 190000
            [curr_items] => 12578
            [total_items] => 53516300
            [limit_maxbytes] => 943718400
            [curr_connections] => 14
            [total_connections] => 72550117
            [connection_structures] => 165
            [bytes] => 2616068
            [cmd_get] => 450388258
            [cmd_set] => 53493365
            [get_hits] => 450388258
            [get_misses] => 2244297
            [evictions] => 0
            [bytes_read] => 2138744916
            [bytes_written] => 745275216
            [version] => 1.4.2
        )

    [-----------:11211] => Array
        (
            [pid] => 8099
            [uptime] => 4687
            [threads] => 4
            [time] => 1336596719
            [pointer_size] => 64
            [rusage_user_seconds] => 7
            [rusage_user_microseconds] => 170000
            [rusage_system_seconds] => 290
            [rusage_system_microseconds] => 990000
            [curr_items] => 2384
            [total_items] => 225964
            [limit_maxbytes] => 943718400
            [curr_connections] => 7
            [total_connections] => 588097
            [connection_structures] => 91
            [bytes] => 562641
            [cmd_get] => 1012562
            [cmd_set] => 225778
            [get_hits] => 1012562
            [get_misses] => 125161
            [evictions] => 0
            [bytes_read] => 91270698
            [bytes_written] => 350071516
            [version] => 1.4.2
        )

)

编辑：这是设置和检索10,000个值的结果.

正常：

Stored 10000 values in 5.6118 seconds.
Average: 0.0006
High: 0.1958
Low: 0.0003

Fetched 10000 values in 5.1215 seconds.
Average: 0.0005
High: 0.0141
Low: 0.0003

当Spiking：

Stored 10000 values in 16.5074 seconds.
Average: 0.0017
High: 0.9288
Low: 0.0003

Fetched 10000 values in 19.8771 seconds.
Average: 0.0020
High: 0.9478
Low: 0.0003