nginx redirect all http to https with one exceptio

Question

I would like to redirect all http traffic to https with one exception. Anything with /preview/ in the url I would like to keep on http.

I have tried with below configuration but it keeps telling me i have a redirect loop.

server {
    listen 80;
    server_name example.com;
    root            /var/www/html/example.com/public;
    index           index.php index.html;


    location /preview {
        try_files $uri $uri/ /index.php?$query_string;
    }

    location / {
        # we are in http server, but want https for normal
        # requests - redirect to https

        return 301 https://$server_name$request_uri;
    }


    location ~ \.php$ {
            try_files $uri =404;
            fastcgi_split_path_info ^(.+\.php)(/.+)$;
            # NOTE: You should have "cgi.fix_pathinfo = 0;" in php.ini

            # With php5-cgi alone:
            #fastcgi_pass 127.0.0.1:9000;
            # With php5-fpm:
            fastcgi_pass unix:/var/run/php-fpm/php-fpm.sock;
            fastcgi_index index.php;
            fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
            include fastcgi_params;
    }
}


 server {
    listen 443;
    server_name example.com;

    ssl on;
    ssl_certificate /etc/nginx/ssl/cert_chain.crt;
    ssl_certificate_key /etc/nginx/ssl/server.key;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

    add_header Strict-Transport-Security max-age=31536000;

    access_log  /var/log/nginx/example.com/access.log;
    error_log   /var/log/nginx/example.com/error.log;

    charset utf-8;


    root            /var/www/html/example.com/public;
    index           index.php index.html;

    location / {
        try_files $uri $uri/ /index.php?$query_string;
    }

    location /preview {
        # we are in http server, but want https for normal
        # requests - redirect to https

        return 301 http://$server_name$request_uri;
    }

    location ~ \.php$ {
            try_files $uri =404;
            fastcgi_split_path_info ^(.+\.php)(/.+)$;
            # NOTE: You should have "cgi.fix_pathinfo = 0;" in php.ini

            # With php5-cgi alone:
            #fastcgi_pass 127.0.0.1:9000;
            # With php5-fpm:
            fastcgi_pass unix:/var/run/php-fpm/php-fpm.sock;
            fastcgi_index index.php;
            fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
            include fastcgi_params;
    }
}

Answer 1

To be absolutely sure that you're not issuing any redirects under any circumstances from within /preview, you might want to always make the redirect conditional, e.g.:

listen 80;
location / {
    if ($request_uri !~ /preview) {
        return 302 https://...;
    }
}