/etc/nginx/conf.d/fastcgi_cache.conf

# DoS対策
limit_req_zone $binary_remote_addr zone=limit_zone:10m rate=50r/s;
limit_req zone=limit_zone burst=30 nodelay;


fastcgi_cache_path   /var/run/nginx-fastcgi-cache levels=1:2 keys_zone=fzone:4m max_size=1024m inactive=7d;

# Nginx Helper対応
fastcgi_cache_key "$mobile$scheme$request_method$host$request_uri";

fastcgi_cache_use_stale error timeout invalid_header http_500;
fastcgi_ignore_headers Cache-Control Expires Set-Cookie;


fastcgi_connect_timeout 60;
fastcgi_read_timeout    90;
fastcgi_send_timeout    60;

# upstream sent too big header while reading response header from upstream対策
fastcgi_buffer_size 128k;
fastcgi_buffers 100 256k;

/etc/nginx/sites-available/example.com.conf

(略)

    set $mobile '';

    if ($http_user_agent ~* '(DoCoMo|J-PHONE|Vodafone|MOT-|UP\.Browser|DDIPOCKET|ASTEL|PDXGW|Palmscape|Xiino|sharp pda browser|Windows CE|L-mode|WILLCOM|SoftBank|Semulator|Vemulator|J-EMULATOR|emobile|mixi-mobile-converter)')     {
        set $mobile '@ktai';
    }

    if ($http_user_agent ~* '(iPhone|iPod|incognito|webmate|Android.+Mobile|dream|CUPCAKE|froyo|BlackBerry|webOS|s8000|bada|IEMobile|Googlebot\-Mobile|AdsBot\-Google)') {
        set $mobile '@mobile';
    }

    if ($http_user_agent ~* '(iPad|Android((?!Mobile).)+$)') {
        set $mobile '@tablet';
    }

(略)

    location ~ .php$ {
        try_files $uri /index.php;
        #fastcgi_pass unix:/var/run/php-fpm.sock;
        fastcgi_pass   127.0.0.1:9000;
        fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;
        include fastcgi_params;

        # 変数$mobileをFastCGIサーバーに渡す
        fastcgi_param HTTP_X_UA_MOBILE $mobile;

        fastcgi_cache_bypass $do_not_cache;
        fastcgi_no_cache $do_not_cache;

        fastcgi_cache fzone;
        fastcgi_cache_valid  200 1d;
        fastcgi_cache_valid  any 10s;
    }

(略)

        ## cache purge モジュール設定
        location ~ /nya-n-purge(/.*) {
            #allow 127.0.0.1;
            #allow 150.xxx.yyy.185;
            #deny all;
            fastcgi_cache_purge fzone "$mobile$scheme$request_method$host$1";
        }


(略)

$request_uriを$1に変更するのがポイント。

wp-config.php

// Nginx Helper
define( 'RT_WP_NGINX_HELPER_CACHE_PATH', '/var/run/nginx-fastcgi-cache');

https://ドメイン/nya-n-purge/URI

で削除出来るようになります。

Nginx Helper 設定

更新時にクリアされるようになっています。