Nginx Learning (3)

NGINX Load Balancing – TCP and UDP Load Balancer

Configuring Reverse Proxy

For UDP traffic, also include the udp parameter. TCP is the default protocol for the stream context, so there is no tcp parameter to the listen directive

Optionally, you can tune the size of two in‑memory buffers where NGINX can put data from both the client and upstream connections.

stream {
    server {
        listen     12345;
        #TCP traffic will be forwarded to the "stream_backend" upstream group
        proxy_pass stream_backend;
    }
    server {
        listen     12346;
        #TCP traffic will be forwarded to the specified server
        proxy_pass backend.example.com:12346;
        proxy_buffer_size 16k;   
    }
    server {
        listen     53 udp;
        #UDP traffic will be forwarded to the "dns_servers" upstream group
        proxy_pass dns_servers;
    }
    # ...
}

Configuring TCP or UDP Load Balancing

Note that you do not define the protocol for each server, because that is defined for the entire upstream group by the parameter you include on the listen directive in the server block, which you have created earlier.

The health_check directive enables the health‑check functionality, while the health_check_timeout directive overrides the proxy_timeout value for health checks, as for health checks this timeout needs to be significantly shorter.

To enable health checks for UDP traffic, in the health_check directive specify the udp parameter and optionally the match parameter with the name of a corresponding match block of tests for verifying server responses (see Fine‑Tuning UDP Health Checks):

server {
    listen       5053;
    proxy_pass   dns_servers;
    health_check udp match=dns;
    health_check_timeout 5s;
}

Fine‑Tuning Health Checks

By default, NGINX Plus tries to connect to each server in an upstream server group every 5 seconds. If the connection cannot be established, NGINX Plus considers the health check failed, marks the server as unhealthy, and stops forwarding client connections to the server.

To change the default behavior, include these parameters to the health_check directive:

• interval – How often (in seconds) NGINX Plus sends health check requests (default is 5 seconds)
• passes – Number of consecutive health checks the server must respond to to be considered healthy (default is 1)
• fails – Number of consecutive health checks the server must fail to respond to to be considered unhealthy (default is 1)

server {
    listen       12345;
    proxy_pass   stream_backend;
    health_check interval=10 passes=2 fails=3;
}

Fine‑Tuning Health Checks with the match Configuration Block

You can verify server responses to health checks by configuring a number of tests. These tests are defined with the match configuration block placed in the stream context. Specify the match block and set its name (here, tcp_test):

The conditions or tests under which a health check succeeds are set with send and expect parameters:

• send – The text string or hexadecimal literals (/x followed by two hex digits) to send to the server
• expect – Literal string or regular expression that the data returned by the server needs to match

If both the send and expect parameters are specified, then the string from the send parameter must match the regular expression from the expect parameter:

stream {
    upstream stream_backend {
        zone   upstream_backend 64k;
        server backend1.example.com:12345;
    }
    match http {
        send      "GET / HTTP/1.0
Host: localhost

";
        expect ~* "200 OK";
    }
    server {
        listen       12345;
        health_check match=http;
        proxy_pass   stream_backend;
    }
}

Fine-Tuning UDP Health Checks

To fine‑tune health checks for UDP, specify both send and expect parameters:

Example for DNS:

match dns {
    send x00x2ax00x00x00x01x00x00x00x00x00x00x03x73x74x6cx04x75x6dx73x6cx03x65x64x75x00x00x01x00x01;
    expect ~* "health.is.good";
}

On-the-Fly Configuration

Upstream server groups can be easily reconfigured on-the-fly using NGINX Plus REST API. Using this interface, you can view all servers in an upstream group or a particular server, modify server parameters, and add or remove upstream servers.

TODO:

Configuring NGINX to Accept the PROXY Protocol 

NGINX Content Caching