.. program:: nghttpx

nghttpx - HTTP/2 proxy - HOW-TO
===============================

:doc:`nghttpx.1` is a proxy translating protocols between HTTP/2 and
other protocols (e.g., HTTP/1, SPDY).  It operates in several modes
and each mode may require additional programs to work with.  This
article describes each operation mode and explains the intended
use-cases.  It also covers some useful options later.

Default mode
------------

If nghttpx is invoked without :option:`--http2-proxy`, it operates in
default mode.  In this mode, it works as reverse proxy (gateway) for
both HTTP/2 and HTTP/1 clients to backend servers.  This is also known
as "HTTP/2 router".  If nghttpx is linked with spdylay library and
frontend connection is SSL/TLS, the frontend also supports SPDY
protocol.

By default, frontend connection is encrypted using SSL/TLS.  So
server's private key and certificate must be supplied to the command
line (or through configuration file).  In this case, the frontend
protocol selection will be done via ALPN or NPN.

With :option:`--frontend-no-tls` option, user can turn off SSL/TLS in
frontend connection.  In this case, SPDY protocol is not available
even if spdylay library is liked to nghttpx.  HTTP/2 and HTTP/1 are
available on the frontend, and an HTTP/1 connection can be upgraded to
HTTP/2 using HTTP Upgrade.  Starting HTTP/2 connection by sending
HTTP/2 connection preface is also supported.

By default, backend connections are not encrypted.  To enable TLS
encryption on backend connections, use :option:`--backend-tls` option.
Using patterns and ``proto`` keyword in :option:`--backend` option,
backend application protocol can be specified per host/request path
pattern.  It means that you can use both HTTP/2 and HTTP/1 in backend
connections at the same time.  Note that default backend protocol is
HTTP/1.1.  To use HTTP/2 in backend, you have to specify ``h2`` in
``proto`` keyword in :option:`--backend` explicitly.

The backend is supposed to be Web server.  For example, to make
nghttpx listen to encrypted HTTP/2 requests at port 8443, and a
backend Web server is configured to listen to HTTP request at port
8080 in the same host, run nghttpx command-line like this::

    $ nghttpx -f0.0.0.0,8443 -b127.0.0.1,8080 /path/to/server.key /path/to/server.crt

Then HTTP/2 enabled client can access to the nghttpx in HTTP/2.  For
example, you can send GET request to the server using nghttp::

    $ nghttp -nv https://localhost:8443/

HTTP/2 proxy mode
-----------------

If nghttpx is invoked with :option:`--http2-proxy` (or its shorthand
:option:`-s`) option, it operates in HTTP/2 proxy mode.  The supported
protocols in frontend and backend connections are the same in `default
mode`_.  The difference is that this mode acts like forward proxy and
assumes the backend is HTTP proxy server (e.g., Squid, Apache Traffic
Server).  HTTP/1 request must include absolute URI in request line.

By default, frontend connection is encrypted.  So this mode is also
called secure proxy.  If nghttpx is linked with spdylay, it supports
SPDY protocols and it works as so called SPDY proxy.

With :option:`--frontend-no-tls` option, SSL/TLS is turned off in
frontend connection, so the connection gets insecure.

The backend must be HTTP proxy server.  nghttpx supports multiple
backend server addresses.  It translates incoming requests to HTTP
request to backend server.  The backend server performs real proxy
work for each request, for example, dispatching requests to the origin
server and caching contents.

The backend connection is not encrypted by default.  To enable
encryption, use :option:`--backend-tls` option.  The default backend
protocol is HTTP/1.1.  To use HTTP/2 in backend connection, use
:option:`--backend` option, and specify ``h2`` in ``proto`` keyword
explicitly.

For example, to make nghttpx listen to encrypted HTTP/2 requests at
port 8443, and a backend HTTP proxy server is configured to listen to
HTTP/1 request at port 8080 in the same host, run nghttpx command-line
like this::

    $ nghttpx -s -f'*,8443' -b127.0.0.1,8080 /path/to/server.key /path/to/server.crt

At the time of this writing, Firefox 41 and Chromium v46 can use
nghttpx as HTTP/2 proxy.

To make Firefox or Chromium use nghttpx as HTTP/2 or SPDY proxy, user
has to create proxy.pac script file like this:

.. code-block:: javascript

    function FindProxyForURL(url, host) {
        return "HTTPS SERVERADDR:PORT";
    }

``SERVERADDR`` and ``PORT`` is the hostname/address and port of the
machine nghttpx is running.  Please note that both Firefox and
Chromium require valid certificate for secure proxy.

For Firefox, open Preference window and select Advanced then click
Network tab.  Clicking Connection Settings button will show the
dialog.  Select "Automatic proxy configuration URL" and enter the path
to proxy.pac file, something like this:

.. code-block:: text

    file:///path/to/proxy.pac

For Chromium, use following command-line::

    $ google-chrome --proxy-pac-url=file:///path/to/proxy.pac --use-npn

As HTTP/1 proxy server, Squid may work as out-of-box.  Traffic server
requires to be configured as forward proxy.  Here is the minimum
configuration items to edit::

    CONFIG proxy.config.reverse_proxy.enabled INT 0
    CONFIG proxy.config.url_remap.remap_required INT 0

Consult Traffic server `documentation
<http://trafficserver.readthedocs.org/en/latest/admin-guide/configuration/transparent-forward-proxying.en.html>`_
to know how to configure traffic server as forward proxy and its
security implications.

Disable frontend SSL/TLS
------------------------

The frontend connections are encrypted with SSL/TLS by default.  To
turn off SSL/TLS, use :option:`--frontend-no-tls` option.  If this
option is used, the private key and certificate are not required to
run nghttpx.

Enable backend SSL/TLS
----------------------

The backend connections are not encrypted by default.  To enable
SSL/TLS encryption, :option:`--backend-tls` option.

Enable SSL/TLS on memcached connection
--------------------------------------

By default, memcached connection is not encrypted.  To enable
encryption, use :option:`--tls-ticket-key-memcached-tls` for TLS
ticket key, and use :option:`--tls-session-cache-memcached-tls` for
TLS session cache.

Specifying additional server certificates
-----------------------------------------

nghttpx accepts additional server private key and certificate pairs
using :option:`--subcert` option.  It can be used multiple times.

Specifying additional CA certificate
------------------------------------

By default, nghttpx tries to read CA certificate from system.  But
depending on the system you use, this may fail or is not supported.
To specify CA certificate manually, use :option:`--cacert` option.
The specified file must be PEM format and can contain multiple
certificates.

By default, nghttpx validates server's certificate.  If you want to
turn off this validation, knowing this is really insecure and what you
are doing, you can use :option:`--insecure` option to disable
certificate validation.

Read/write rate limit
---------------------

nghttpx supports transfer rate limiting on frontend connections.  You
can do rate limit per frontend connection for reading and writing
individually.

To perform rate limit for reading, use :option:`--read-rate` and
:option:`--read-burst` options.  For writing, use
:option:`--write-rate` and :option:`--write-burst`.

Please note that rate limit is performed on top of TCP and nothing to
do with HTTP/2 flow control.

Rewriting location header field
-------------------------------

nghttpx automatically rewrites location response header field if the
following all conditions satisfy:

* URI in location header field is not absolute URI or is not https URI.
* URI in location header field includes non empty host component.
* host (without port) in URI in location header field must match the
  host appearing in :authority or host header field.

When rewrite happens, URI scheme and port are replaced with the ones
used in frontend, and host is replaced with which appears in
:authority or host request header field.  :authority header field has
precedence.  If the above conditions are not met with the host value
in :authority header field, rewrite is retried with the value in host
header field.

Hot swapping
------------

nghttpx supports hot swapping using signals.  The hot swapping in
nghttpx is multi step process.  First send USR2 signal to nghttpx
process.  It will do fork and execute new executable, using same
command-line arguments and environment variables.  At this point, both
current and new processes can accept requests.  To gracefully shutdown
current process, send QUIT signal to current nghttpx process.  When
all existing frontend connections are done, the current process will
exit.  At this point, only new nghttpx process exists and serves
incoming requests.

Re-opening log files
--------------------

When rotating log files, it is desirable to re-open log files after
log rotation daemon renamed existing log files.  To tell nghttpx to
re-open log files, send USR1 signal to nghttpx process.  It will
re-open files specified by :option:`--accesslog-file` and
:option:`--errorlog-file` options.

Multiple backend addresses
--------------------------

nghttpx supports multiple backend addresses.  To specify them, just
use :option:`--backend` (or its shorthand :option:`-b`) option
repeatedly.  For example, to use ``192.168.0.10:8080`` and
``192.168.0.11:8080``, use command-line like this:
``-b192.168.0.10,8080 -b192.168.0.11,8080``.  In configuration file,
this looks like:

.. code-block:: text

   backend=192.168.0.10,8080
   backend=192.168.0.11,8008

nghttpx can route request to different backend according to request
host and path.  For example, to route request destined to host
``doc.example.com`` to backend server ``docserv:3000``, you can write
like so:

.. code-block:: text

   backend=docserv,3000;doc.example.com/

When you write this option in command-line, you should enclose
argument with single or double quotes, since the character ``;`` has a
special meaning in shell.

To route, request to request path whose prefix is ``/foo`` to backend
server ``[::1]:8080``, you can write like so:

.. code-block:: text

   backend=::1,8080;/foo

Of course, you can specify both host and request path at the same
time:

.. code-block:: text

   backend=192.168.0.10,8080;example.com/foo

We can use ``*`` in the left most position of host to achieve wildcard
suffix match.  If ``*`` is the left most character, then the remaining
string should match the request host suffix.  ``*`` must match at
least one character.  For example, ``*.example.com`` matches
``www.example.com`` and ``dev.example.com``, and does not match
``example.com`` and ``nghttp2.org``.  The exact match (without ``*``)
always takes precedence over wildcard match.

One important thing you have to remember is that we have to specify
default routing pattern for so called "catch all" pattern.  To write
"catch all" pattern, just specify backend server address, without
pattern.

Usually, host is the value of ``Host`` header field.  In HTTP/2, the
value of ``:authority`` pseudo header field is used.

When you write multiple backend addresses sharing the same routing
pattern, they are used as load balancing.  For example, to use 2
servers ``serv1:3000`` and ``serv2:3000`` for request host
``example.com`` and path ``/myservice``, you can write like so:

.. code-block:: text

   backend=serv1,3000;example.com/myservice
   backend=serv2,3000;example.com/myservice

You can also specify backend application protocol in
:option:`--backend` option using ``proto`` keyword after pattern.
Utilizing this allows ngttpx to route certain request to HTTP/2, other
requests to HTTP/1.  For example, to route requests to ``/ws/`` in
backend HTTP/1.1 connection, and use backend HTTP/2 for other
requests, do this:

.. code-block:: text

   backend=serv1,3000;/;proto=h2
   backend=serv1,3000;/ws/;proto=http/1.1

Note that the backends share the same pattern must have the same
backend protocol.  The default backend protocol is HTTP/1.1.

Deprecated modes
----------------

As of nghttpx 1.9.0, ``--http2-bridge``, ``--client`` and
``--client-proxy`` options were removed.  These functionality can be
used using combinations of options.

* ``--http2-bridge``: Use ``--backend='<ADDR>,<PORT>;;proto=h2'``, and
  ``--backend-tls``.

* ``--client``: Use ``--frontend-no-tls``,
  ``--backend='<ADDR>,<PORT>;;proto=h2'``, and ``--backend-tls``.

* ``--client-proxy``: Use ``--http2-proxy``, ``--frontend-no-tls``,
  ``--backend='<ADDR>,<PORT>;;proto=h2'``, and ``--backend-tls``.
