筆者以筆者自己的項目為例。想達到的目的：
http://by-syk.com:8081/nanoiconpack/watchdog >>> http://nano.by-syk.com/watchdog
并同時保證原來的訪問接口依然能用。

/etc/nginx/sites-enabled/default 舊配置：

server {
  listen 8081;
  server_name by-syk.com www.by-syk.com;

  location / {
    proxy_pass http://nodejs_nanoiconpack_servers;
  }
}

/etc/nginx/sites-enabled/default 新配置：

server {
  listen 80;
  server_name nano.by-syk.com;

  location / {
    proxy_pass http://nodejs_nanoiconpack_servers;
  }
}

server {
  listen 8081;
  server_name by-syk.com www.by-syk.com;

  location / {
    proxy_pass http://nodejs_nanoiconpack_servers;
  }

  // 兼容舊路徑
  location /nanoiconpack/ {
    # 例子說明末尾神奇的“/”：
    # 對于 http://by-syk.com:8081/nanoiconpack/page/query
    # 不加則代理為 http://by-syk.com:8081/nanoiconpack/page/query
    # 加上則代理為 http://by-syk.com:8081/page/query
    proxy_pass http://nodejs_nanoiconpack_servers/;

    # rewrite '^/nanoiconpack(.*)$' $1;
  }
}

同時調整服務器接口定義：

/*
app.get('/nanoiconpack/watchdog', function(req, res) {
  logger.info('GET /nanoiconpack/watchdog');

  res.jsonp(utils.getResRes(0, undefined, {
    port: serverPort,
    time: Date.now()
  }));
});
*/

app.get('/watchdog', function(req, res) {
  logger.info('GET /watchdog');

  res.jsonp(utils.getResRes(0, undefined, {
    port: serverPort,
    time: Date.now()
  }));
});

調整 HTML 頁面內部的調用：

/*
$.get("/nanoiconpack/watchdog", function(data) {
    if (data && data.status == 0) {
      // ...
    }
});
*/

$.get("/watchdog", function(data) {
    if (data && data.status == 0) {
      // ...
    }
});

TODO 這樣配置帶來了一個附加影響，增加了一個訪問通道：http://by-syk.com:8081/watchdog