我的服务器出了点问题。我正处于高峰期，服务器负载非常高。
我有 3 台服务器，一台用于前端，一台用于数据库（mysql），一台用于传送图像（这台没有问题）
以下是我的当前配置和 1500 名访问者的平均负载：
服务器 1 (前端)：
load average: 143.08, 120.50, 66.99
CentOS 6.3
Apache/2.2.15
8 x Intel(R) Xeon(R) CPU E5645 @ 2.40GHz
16GB RAM
httpd配置文件
PidFile run/httpd.pid
Timeout 60
KeepAlive Off
MaxKeepAliveRequests 1000
KeepAliveTimeout 15
<IfModule prefork.c>
ServerLimit 520
StartServers 16
MinSpareServers 5
MaxSpareServers 20
MaxClients 500
MaxRequestsPerChild 1000
</IfModule>
<IfModule worker.c>
ServerLimit 520
StartServers 16
MaxClients 500
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
MaxRequestsPerChild 0
</IfModule>
ExtendedStatus On
UseCanonicalName Off
HostnameLookups Off
ErrorLog logs/error_log
LogLevel warn
ServerSignature On
IndexOptions FancyIndexing VersionSort NameWidth=* HTMLTable Charset=UTF-8
BrowserMatch "Mozilla/2" nokeepalive
BrowserMatch "MSIE 4\.0b2;" nokeepalive downgrade-1.0 force-response-1.0
BrowserMatch "RealPlayer 4\.0" force-response-1.0
BrowserMatch "Java/1\.0" force-response-1.0
BrowserMatch "JDK/1\.0" force-response-1.0
BrowserMatch "Microsoft Data Access Internet Publishing Provider" redirect-carefully
BrowserMatch "MS FrontPage" redirect-carefully
BrowserMatch "^WebDrive" redirect-carefully
BrowserMatch "^WebDAVFS/1.[0123]" redirect-carefully
BrowserMatch "^gnome-vfs/1.0" redirect-carefully
BrowserMatch "^XML Spy" redirect-carefully
BrowserMatch "^Dreamweaver-WebDAV-SCM1" redirect-carefully
服务器2（MySQL my.cnf）
load average: 12.84, 23.39, 22.85
CentOS 6.4
MYSQL 5.5.34
8 x Intel(R) Xeon(R) CPU E5645 @ 2.40GHz
16GB RAM
我的cnf
[mysqld]
port=3306
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
user=mysql
# Disabling symbolic-links is recommended to prevent assorted security risks
symbolic-links=0
max_connections = 2000
key_buffer = 384M
query_cache_type=1
query_cache_size=512M
query_cache_limit=4M
innodb_buffer_pool_size = 8G
slow_query_log=1
slow_query_log_file=log-slow-queries.log
thread_cache_size=8
table_cache=128k
tmp_table_size=256M
max_heap_table_size=256M
init_connect='SET collation_connection = latin1_swedish_ci'
init_connect='SET NAMES latin1'
character-set-server=latin1
collation-server=latin1_swedish_ci
skip-character-set-client-handshake
log-error=/var/log/mysqld.error.log
[mysqld_safe]
log-error=/var/log/mysqld.log
pid-file=/var/run/mysqld/mysqld.pid
mysqltuner 输出
-------- General Statistics --------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.5.34-log
[OK] Operating on 64-bit architecture
-------- Storage Engine Statistics -------------------------------------------
[--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster
[--] Data in InnoDB tables: 3G (Tables: 57)
[--] Data in PERFORMANCE_SCHEMA tables: 0B (Tables: 17)
[!!] Total fragmented tables: 57
-------- Security Recommendations -------------------------------------------
[OK] All database users have passwords assigned
-------- Performance Metrics -------------------------------------------------
[--] Up for: 5h 11m 15s (4M q [241.514 qps], 537K conn, TX: 11B, RX: 2B)
[--] Reads / Writes: 87% / 13%
[--] Total buffers: 9.1G global + 2.8M per thread (2000 max threads)
[OK] Maximum possible memory usage: 14.5G (46% of installed RAM)
[OK] Slow queries: 1% (55K/4M)
[OK] Highest usage of available connections: 37% (756/2000)
[OK] Key buffer size / total MyISAM indexes: 384.0M/96.0K
[OK] Key buffer hit rate: 100.0% (46K cached / 0 reads)
[!!] Query cache efficiency: 0.0% (0 cached / 2M selects)
[OK] Query cache prunes per day: 0
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 480K sorts)
[OK] Temporary tables created on disk: 16% (112K on disk / 684K total)
[OK] Thread cache hit rate: 83% (87K created / 537K connections)
[OK] Table cache hit rate: 99% (2K open / 2K opened)
[OK] Open file limit used: 0% (19/264K)
[OK] Table locks acquired immediately: 100% (7M immediate / 7M locks)
[OK] InnoDB data size / buffer pool: 3.6G/8.0G
应用详细信息
php 5.4 Symfony 1.2 数据库大小：6GB
你能帮助我吗？
答案1
我在这里看到的主要问题是前端服务器的平均负载过高。MySQL 服务器可以做得更好，但情况并没有那么糟糕。Apache 服务器经常成为瓶颈。如果不知道应用程序在做什么，解决问题就相当困难。一般建议如下：
- 在前端服务器上设置 Munin，其中包含 Apache 的指标。有了这些信息，您可以更轻松地调整 Apache。Munin 还可以帮助您确定平均负载增加的频率和时间。
- 分析 Apache 和应用程序日志。最重和最频繁的请求是什么？可能存在一些与应用程序相关的问题（例如使用 PHP 提供静态文件）。
- 考虑切换到 nginx/php-fpm 而不是 Apache。Apache 是一款非常好的网络服务器，但 nginx 已成为许多现代设置的标准，这些设置不需要某些特定的 Apache 功能。
考虑 MySQL 优化。您只有 96.0K 的 MyISAM 索引，但有 384.0M 的关键缓冲池。您可以安全地降低此参数。您还可以使用 Percona 的 pt-query-digest 检查您的慢查询，它非常方便。