Gerrit Code Review - Reverse Proxy

Description

Gerrit can be configured to run behind a third-party web server. This allows the other web server to bind to the privileged port 80 (or 443 for SSL), as well as offloads the SSL processing overhead from Java to optimized native C code.

Gerrit Configuration

Ensure '$site_path'/etc/gerrit.config has the property httpd.listenUrl configured to use proxy-http:// or proxy-https:// and a free port number. This may have already been configured if proxy support was enabled during init.

  [httpd]
        listenUrl = proxy-http://127.0.0.1:8081/r/

Apache 2 Configuration

To run Gerrit behind an Apache server using mod_proxy, enable the necessary Apache2 modules:

  a2enmod proxy_http
  a2enmod ssl          ; # optional, needed for HTTPS / SSL

Configure an Apache VirtualHost to proxy to the Gerrit daemon, setting the ProxyPass line to use the http:// URL configured above. Ensure the path of ProxyPass and httpd.listenUrl match, or links will redirect to incorrect locations.

        <VirtualHost *>
          ServerName review.example.com

          ProxyRequests Off
          ProxyVia Off
          ProxyPreserveHost On

          <Proxy *>
            Order deny,allow
            Allow from all
            # Use following line instead of the previous two on Apache >= 2.4
            # Require all granted
          </Proxy>

          AllowEncodedSlashes On
          ProxyPass /r/ http://127.0.0.1:8081/r/ nocanon
        </VirtualHost>

The two options AllowEncodedSlashes On and ProxyPass .. nocanon are required since Gerrit 2.6.

SSL

To enable Apache to perform the SSL processing, use proxy-https:// in httpd.listenUrl within Gerrit’s configuration file, and enable the SSL engine in the Apache VirtualHost block:

        <VirtualHost *:443>
          SSLEngine on
          SSLCertificateFile    conf/server.crt
          SSLCertificateKeyFile conf/server.key

          ... same as above ...
        </VirtualHost>

See the Apache mod_ssl documentation for more details on how to configure SSL within the server, like controlling how strong of an encryption algorithm is required.

Troubleshooting

If you are encountering Page Not Found errors when opening the change screen, your Apache proxy is very likely decoding the passed URL. Make sure to either use AllowEncodedSlashes On together with ProxyPass .. nocanon or alternatively a mod_rewrite configuration with AllowEncodedSlashes NoDecode set.

Nginx Configuration

To run Gerrit behind an Nginx server, use a server statement such as this one:

        server {
          listen 80;
          server_name review.example.com;

          location ^~ /r/ {
            proxy_pass        http://127.0.0.1:8081;
            proxy_set_header  X-Forwarded-For $remote_addr;
            proxy_set_header  Host $host;
          }
        }

SSL

To enable Nginx to perform the SSL processing, use proxy-https:// in httpd.listenUrl within Gerrit’s configuration file, and enable the SSL engine in the Nginx server statement:

        server {
          listen 443;
          server_name review.example.com;

          ssl  on;
          ssl_certificate      conf/server.crt;
          ssl_certificate_key  conf/server.key;

          ... same as above ...
        }

See the Nginx http ssl module documentation for more details on how to configure SSL within the server, like controlling how strong of an encryption algorithm is required.

Troubleshooting

If you are encountering Page Not Found errors when opening the change screen, your Nginx proxy is very likely decoding the passed URL. Make sure to use a proxy_pass URL without any path (esp. no trailing / after the host:port).

If you are using Apache httpd server with mod_jk and AJP connector, add the following option to your httpd.conf directly or included from another file:

JkOptions +ForwardURICompatUnparsed

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