.. _deploy:

Deploying Simple Bandwidth Scanner
=====================================

To run sbws is needed:

- A machine to run the :term:`scanner`.
- One or more :term:`destination` (s) that serve a large file.

Both the ``scanner`` and your the ``destination`` (s) should be on fast,
well connected machines.

.. _destinations_requirements:

Destination requirements
------------------------

- TLS support to avoid HTTP content caches at the various exit nodes.
- Certificates can be self-signed.
- A fixed IP address or a domain name.
- Bandwidth: at least 12.5MB/s (100 Mbit/s).
- Network traffic: around 12-15GB/day.
- An HTTP Web server, see next subsection.

HTTP server requirements
~~~~~~~~~~~~~~~~~~~~~~~~

- If the consensus parameter ``bwscanner_cc`` is not set or has a value lower
  than 2:

  A Web server installed and running that supports HTTP GET, HEAD and
  Range (:rfc:`7233`) requests.
  ``Apache`` HTTP Server and ``Nginx`` support them.

  It also needs to allow ```keep-alive``, in order to reuse connections between
  the sbws HEAD request and the several GET ones.

  .. Note:: if the server is configured with ``keep-alive`` timeout, it'd need
     to be at least the same timeout as in the sbws HTTP requests, which is 10
     seconds by default (``http_timeout`` variable in the configuration file,
     see  more about in the next section).

  It also needs a large file; at the time of writing, at least 1 GiB in size
  It can be created running::

      head -c $((1024*1024*1024)) /dev/urandom > 1GiB

- If the consensus parameter ``bwscanner_cc`` has value 2:

  A Web server installed and running that supports HTTP POST via
  ``Content-Type application/octet-stream``.

  You can install and run `bwscanner_webserver`_ application, it supports sbws
  uploads and downloads.

You can test your configuration running:

- HEAD request::

    curl https://bwauth.httpd.ip/1G -i -H "Range: bytes=0-1023"

  It should reply::

    HTTP/1.1 206 Partial Content
    Accept-Ranges: bytes
    Content-Length: 1024
    Content-Range: bytes 0-1023/1073741824

- GET request::

    curl -v https://bwauth.httpd.ip/1G

  It should reply::

    < HTTP/1.1 200 OK
    < Accept-Ranges: bytes
    < Content-Length: 1073741824

- POST request::

    dd if=/dev/zero of=post-20MB.zero bs=1k count=20480
    curl -F "sbwstest=@post-20MB.zero" https://bwauth.httpd.ip/postpath -O
    curl -F "sbwstest=<post-20MB.zero" https://bwauth.httpd.ip/postpath -O

  In the `Xferd` column it should show ``20.0M``::

      % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                Dload  Upload   Total   Spent    Left  Speed
      100 20.0M  100   265  100 20.0M      4   346k  0:01:06  0:00:59  0:00:07    64

If you want, use a `Content delivery network`_ (CDN) in order to make the
destination IP closer to the scanner exit.

.. _bwscanner_webserver: https://gitlab.torproject.org/tpo/network-health/bwscanner_webserver

Configuring an HTTP server ``destination`` in a testing network
---------------------------------------------------------------

For development and integration tests, we use `chutney`_ to bootstrap a Tor
network and `a minimal HTTP server`_ in localhost. ``sbws`` only accepts the
``HTTP`` scheme (without TLS) for the destination, when its address is
``127.0.0.1``. In this case, ``sbws`` also `detects`_ that
the Tor network is a ``TestingTorNetwork`` and stops after the first ``loop``.

If you need an HTTP server running in other address other than localhost, you
would need it to support TLS.

For this, you can create a self-signed certificate and configure ``sbws`` to
use it by adding the certificate to its `verify configuration option`_

.. _chutney: https://gitlab.torproject.org/tpo/core/chutney
.. _a minimal HTTP server: https://gitlab.torproject.org/tpo/network-health/sbws/-/blob/3a9f523a410d657f12650f1f8828abc5caf6f93b/tests/integration/async_https_server.py
.. _detects: https://gitlab.torproject.org/tpo/network-health/sbws/-/blob/3a9f523a410d657f12650f1f8828abc5caf6f93b/sbws/core/scanner.py#L987
.. _verify configuration option: https://gitlab.torproject.org/tpo/network-health/sbws/-/blob/3a9f523a410d657f12650f1f8828abc5caf6f93b/docs/source/man_sbws.ini.rst#L76


scanner setup
-------------

.. note:: To facilitate debugging, it is recommended that the system timezone
   is set to UTC.

To set the timezone to UTC in Debian::

  apt-get --reinstall install tzdata
  ln -sf /usr/share/zoneinfo/UTC /etc/localtime
  update-initramfs -u

Install sbws according to `<INSTALL.rst>`_ (in the local directory or Tor
Project Gitlab) or `<INSTALL.html>`_  (local build or Read the Docs).

To run the ``scanner`` it is mandatory to create a configuration file with at
least one ``destination``.
It is recommended to set several ``destinations`` so that the ``scanner`` can
continue if one fails.

If ``sbws`` is installed from the Debian package, then create the configuration
file in ``/etc/sbws/sbws.ini``.
You can see an example with all the possible options here, note that you don't
need to include all of that and that everything that starts with ``#`` and
``;`` is a comment:

.. literalinclude:: /examples/sbws.example.ini
    :caption: Example sbws.example.ini

If ``sbws`` is installed from the sources as a non-root user then create the
configuration file in ``~/.sbws.ini``.

More details about the configuration file can be found in
``./docs/source/man_sbws.ini.rst`` (in the local directory or Tor Project
Gitlab) or `<man_sbws.ini.html>`_  (local build or Read the Docs) or
``man sbws.ini`` (system package).

generator setup
---------------

The Debian package from version 1.6.0 replaces cron jobs by `systemd.timer`_
to run the ``generator`` and the ``cleanup`` command to clean the old data.

After the package is installed, it's needed to enable and start the timers
(Debian policy is not to start/enable services by default)::

  systemctl enable --now sbws_cleanup.timer
  systemctl enable --now sbws_generate.timer

To ensure they are enabled run::

  systemctl list-timers

It should show the next time the ``generator`` or cleanup timer is going to
run::

  Wed 2023-10-18 08:35:00 GMT 19min left    Wed 2023-10-18 07:35:02 GMT 40min ago         sbws_generate.timer          sbws_generate.service

You can check that the timer service is working by invoking it directly::

  systemctl start sbws_generate.service

If sbws is installed in some other way, you would need to create the timers or
cron jobs. Example cron jobs::

  35 *     * * *   sbws  /usr/local/bin/sbws -c /etc/sbws/sbws.ini generate
  05 0     * * *   sbws  /usr/local/bin/sbws -c /etc/sbws/sbws.ini cleanup

You can modify the timers or cron jobs to get emails on failures.
For the cron jobs, use ``MAILTO``, for the timers, use ``OnFailure`` to call an
email service.

If the cron job is configured to send Email alerts on errors, it's probably
better to configure the log level to ``ERROR`` instead of ``WARNING``.

At level ``WARNING``, the first days, the ``generator`` will log every hour
that it hasn't reached enough percentage of relays to report.
After some days, if the scanner is located near fasts exits, it would also log
every hour that it is reporting more than the 50% of the consensus bandwidth.

The log level can be changed in the configuration file, for example::

  to_stdout_level = error

This setup will affect both to the ``generator`` and the ``scanner``, so for
Email alerts, it's probably more convenient to configure it from the command
line, for example::

  /usr/local/bin/sbws --log-level error generate


See also ``./docs/source/man_sbws.rst`` (in the local directory or Tor Project
Gitlab) or `<man_sbws.html>`_ (local build or Read the Docs) or ``man sbws``
(system package).

.. _Content delivery network: https://en.wikipedia.org/wiki/Content_delivery_network
.. _systemd.timer: https://www.freedesktop.org/software/systemd/man/systemd.timer.html


Reading BandwidthFiles from the directory authority
---------------------------------------------------

The directory authority tor's configuration (torrc) must include
``V3BandwidthsFile`` option with the whole path to the ``latest.v3bw`` files
that the ``scanner`` generates.

.. note:: the user running the directory authority tor's daemon must have
   permissions to read this path. If the daemon is launched by a ``systemd``
   service, you would need to add a ``ReadOnlyDirectories`` entry with the
   directory where the ``latest.v3bw`` is generated.

.. note:: During the ~5 first days the ``scanner`` has been running, the
  ``generator`` will mark all the ``RelayLines`` with ``vote=0``
  until the scanner has measured more than the ~60% of the network.
  The directory authority tor's daemon `ignore these lines`_ and warn about
  `Empty bandwidth file`_

.. _ignore these lines: https://gitlab.torproject.org/tpo/core/tor/-/blob/cc31724f409ee5cff10d82ca05d43e04a85a44e1/src/feature/dirauth/bwauth.c#L413
.. _Empty bandwidth file: https://gitlab.torproject.org/tpo/core/tor/-/blob/cc31724f409ee5cff10d82ca05d43e04a85a44e1/src/feature/dirauth/bwauth.c#L258

Troubleshooting
---------------

See ``./docs/source/troubleshooting.rst`` (in the local directory or Tor Project
Gitlab) or `<Troubleshooting.html>`_ (local build or Read the Docs)
