Nginx 大流量负载均衡

Question

在过去的 3 周里，我们一直在测试 Nginx 作为负载平衡。 目前，我们无法成功处理超过 1000 个请求/秒和 18K 个活动连接。 当我们达到上述数字时，Nginx 开始挂起，并返回超时代码。 获得响应的唯一方法是大幅减少连接数。

我必须注意，我的服务器可以并且确实每天处理这么多的流量，我们目前使用简单的轮询 DNS 平衡。

我们正在使用具有以下硬件的专用服务器：

• 英特尔至强 E5620 CPU
• 16GB 内存
• 2T SATA 硬盘
• 1Gb/s 连接
• 操作系统：CentOS 5.8

我们需要负载平衡 7 个运行 Tomcat6 并在 peek 时间上处理超过 2000 req/sec 的后端服务器，处理 HTTP 和 HTTPS 请求。

在运行 Nginx 时，cpu 消耗约为 15%，使用的 RAM 约为 100MB。

我的问题是：

1. 有没有人尝试过使用 nginx 对这种流量进行负载均衡？
2. 你认为 nginx 可以处理这样的流量吗？
3. 您知道导致挂起的原因吗？
4. 我的配置是否遗漏了什么？

以下是我的配置文件：

nginx.conf：

user  nginx;
worker_processes 10;

worker_rlimit_nofile 200000;

error_log  /var/log/nginx/error.log warn;
pid        /var/run/nginx.pid;


events {
    worker_connections  10000;
    use epoll;
    multi_accept on;
}


http {
    include       /etc/nginx/mime.types;
    default_type  application/octet-stream;

    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  /var/log/nginx/access.log  main;
    access_log off;

    sendfile        on;
    tcp_nopush     on;

    keepalive_timeout  65;
    reset_timedout_connection on;

    gzip  on;
    gzip_comp_level 1;
    include /etc/nginx/conf.d/*.conf;
} 

servers.conf：

#Set the upstream (servers to load balance)
#HTTP stream
upstream adsbar {
  least_conn;
  server xx.xx.xx.34 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.36 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.37 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.39 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.40 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.42 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.43 max_fails=2 fail_timeout=15s;
}      

#HTTPS stream
upstream adsbar-ssl {
  least_conn;
  server xx.xx.xx.34:443 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.36:443 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.37:443 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.39:443 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.40:443 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.42:443 max_fails=2 fail_timeout=15s;
  server xx.xx.xx.43:443 max_fails=2 fail_timeout=15s;
}

#HTTP
server {
  listen xxx.xxx.xxx.xxx:8080;
  server_name www.mycompany.com;
  location / {
      proxy_set_header Host $host;
      # So the original HTTP Host header is preserved
      proxy_set_header X-Real-IP $remote_addr;
      # The IP address of the client (which might be a proxy itself)
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_pass http://adsbar;
  }
}

#HTTPS
server {
  listen xxx.xxx.xxx.xxx:8443;
  server_name www.mycompany.com;
  ssl on;
  ssl_certificate /etc/pki/tls/certs/mycompany.crt;
  # Path to an SSL certificate;
  ssl_certificate_key /etc/pki/tls/private/mycompany.key;
  # Path to the key for the SSL certificate;
  location / {
      proxy_set_header Host $host;
      # So the original HTTP Host header is preserved
      proxy_set_header X-Real-IP $remote_addr;
      # The IP address of the client (which might be a proxy itself)
      proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
      proxy_pass https://adsbar-ssl;
  }
}

server {
    listen xxx.xxx.xxx.xxx:61709;
    location /nginx_status {
        stub_status on;
        access_log off;
        allow 127.0.0.1;
        deny all;
    }
} 

sysctl.conf：

# Kernel sysctl configuration file for Red Hat Linux
#
# For binary values, 

0 is disabled, 1 is enabled.  See sysctl(8) and
# sysctl.conf(5) for more details.

# Controls IP packet forwarding
net.ipv4.ip_forward = 0

# Controls source route verification
net.ipv4.conf.default.rp_filter = 1

# Do not accept source routing
net.ipv4.conf.default.accept_source_route = 0

# Controls the System Request debugging functionality of the kernel
kernel.sysrq = 1

# Controls whether core dumps will append the PID to the core filename
# Useful for debugging multi-threaded applications
kernel.core_uses_pid = 1

# Controls the use of TCP syncookies
net.ipv4.tcp_syncookies = 1

# Controls the maximum size of a message, in bytes
kernel.msgmnb = 65536

# Controls the default maxmimum size of a mesage queue
kernel.msgmax = 65536

# Controls the maximum shared segment size, in bytes
kernel.shmmax = 68719476736

# Controls the maximum number of shared memory segments, in pages
kernel.shmall = 4294967296

fs.file-max = 120000
net.ipv4.ip_conntrack_max = 131072
net.ipv4.tcp_max_syn_backlog = 8196
net.ipv4.tcp_fin_timeout = 25
net.ipv4.tcp_keepalive_time = 3600
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.tcp_rmem = 4096 25165824 25165824
net.core.rmem_max = 25165824
net.core.rmem_default = 25165824
net.ipv4.tcp_wmem = 4096 65536 25165824
net.core.wmem_max = 25165824
net.core.wmem_default = 65536
net.core.optmem_max = 25165824
net.core.netdev_max_backlog = 2500
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1

我们将不胜感激任何帮助、指导和想法。

Answer 1

这里有一些很好的参考：

http://dak1n1.com/blog/12-nginx-performance-tuning

服务器故障： https://serverfault.com/questions/221292/tips-for-maximizing-nginx-requests-sec

来自 dak1n1 链接的详细记录配置：

# This number should be, at maximum, the number of CPU cores on your system. 
# (since nginx doesn't benefit from more than one worker per CPU.)
worker_processes 24;

# Number of file descriptors used for Nginx. This is set in the OS with 'ulimit -n 200000'
# or using /etc/security/limits.conf
worker_rlimit_nofile 200000;


# only log critical errors
error_log /var/log/nginx/error.log crit


# Determines how many clients will be served by each worker process.
# (Max clients = worker_connections * worker_processes)
# "Max clients" is also limited by the number of socket connections available on the system (~64k)
worker_connections 4000;


# essential for linux, optmized to serve many clients with each thread
use epoll;


# Accept as many connections as possible, after nginx gets notification about a new connection.
# May flood worker_connections, if that option is set too low.
multi_accept on;


# Caches information about open FDs, freqently accessed files.
# Changing this setting, in my environment, brought performance up from 560k req/sec, to 904k req/sec.
# I recommend using some varient of these options, though not the specific values listed below.
open_file_cache max=200000 inactive=20s; 
open_file_cache_valid 30s; 
open_file_cache_min_uses 2;
open_file_cache_errors on;


# Buffer log writes to speed up IO, or disable them altogether
#access_log /var/log/nginx/access.log main buffer=16k;
access_log off;


# Sendfile copies data between one FD and other from within the kernel. 
# More efficient than read() + write(), since the requires transferring data to and from the user space.
sendfile on; 


# Tcp_nopush causes nginx to attempt to send its HTTP response head in one packet, 
# instead of using partial frames. This is useful for prepending headers before calling sendfile, 
# or for throughput optimization.
tcp_nopush on;


# don't buffer data-sends (disable Nagle algorithm). Good for sending frequent small bursts of data in real time.
tcp_nodelay on; 


# Timeout for keep-alive connections. Server will close connections after this time.
keepalive_timeout 30;


# Number of requests a client can make over the keep-alive connection. This is set high for testing.
keepalive_requests 100000;


# allow the server to close the connection after a client stops responding. Frees up socket-associated memory.
reset_timedout_connection on;


# send the client a "request timed out" if the body is not loaded by this time. Default 60.
client_body_timeout 10;


# If the client stops reading data, free up the stale client connection after this much time. Default 60.
send_timeout 2;


# Compression. Reduces the amount of data that needs to be transferred over the network
gzip on;
gzip_min_length 10240;
gzip_proxied expired no-cache no-store private auth;
gzip_types text/plain text/css text/xml text/javascript application/x-javascript application/xml;
gzip_disable "MSIE [1-6]\.";

还有更多关于 sysctl.conf 的 linux 系统调优的信息：

# Increase system IP port limits to allow for more connections

net.ipv4.ip_local_port_range = 2000 65000


net.ipv4.tcp_window_scaling = 1


# number of packets to keep in backlog before the kernel starts dropping them 
net.ipv4.tcp_max_syn_backlog = 3240000


# increase socket listen backlog
net.core.somaxconn = 3240000
net.ipv4.tcp_max_tw_buckets = 1440000


# Increase TCP buffer sizes
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216
net.ipv4.tcp_congestion_control = cubic

Answer 2

nginx 肯定能够处理超过 1000 个请求/秒（我在使用 jmeter 的廉价笔记本电脑上使用 2 个内核中的一个和一半时在 nginx 中获得大约 2800 个请求/秒）

据我了解，您正在使用 epoll，这是当前 linux 内核上的最佳选择。

您已经关闭了 acces_log，因此您的磁盘 IO 也不应该成为瓶颈（注意：您还可以将 access_log 设置为具有大缓冲区的缓冲模式，它只在每个 x kb 之后写入，这样可以避免磁盘 io 不断被敲击，但保留日志以供分析）

我的理解是，为了最大化 nginx 性能，您通常将 worker_processes 的数量设置为等于 core/cpu 的数量，然后增加 worker_connections 的数量以允许更多的并发连接（以及打开文件的数量 os限制）。然而，在您上面发布的数据中，您有一个四核 cpu，有 10 个工作进程，每个进程允许 10k 个连接。因此，在 nginx 方面，我会尝试类似的方法：

worker_processes 4;
worker_rlimit_nofile 999999;
events {
  worker_connections 32768;
  use epoll;
  multi_accept on;
}

在内核方面，我会以不同方式调整 tcp 读取和写入缓冲区，您需要较小的最小值、较小的默认值和较大的最大值。

您已经扩大了临时端口范围。

我会增加打开文件的数量限制，因为您将有很多打开的套接字。

在 /etc/sysctl.conf 中添加/更改以下行

net.ipv4.tcp_rmem = 4096 4096 25165824                                
net.ipv4.tcp_wmem = 4096 4096 25165824
fs.file-max=999999

希望对您有所帮助。

Answer 3

我发现使用最小连接算法是有问题的。我换了

hash $remote_addr consistent;

并更快地找到服务。