Warcprox is an HTTP proxy designed for web archiving applications. When used in parallel with `brozzler <https://github.com/internetarchive/brozzler>`_ it supports a comprehensive, modern, and distributed archival web capture system. Warcprox stores its traffic to disk in the `Web ARChive (WARC) file format <https://iipc.github.io/warc-specifications/specifications/warc-format/warc-1.1/>`_, which may then be accessed with web archival replay software like `OpenWayback <https://github.com/iipc/openwayback>`_ and `pywb <https://github.com/webrecorder/pywb>`_. It captures encrypted HTTPS traffic by using the "man-in-the-middle" technique (see the `Man-in-the-middle`_ section for more info).
Warcprox was originally based on `pymiproxy <https://github.com/allfro/pymiproxy>`_ by Nadeem Douba.
Normally, HTTP proxies can't read encrypted HTTPS traffic. The browser uses the HTTP ``CONNECT`` method to establish a tunnel through the proxy, and the proxy merely routes raw bytes between the client and server. Since the bytes are encrypted, the proxy can't make sense of the information that it proxies. This nonsensical encrypted data is not typically useful for web archiving purposes.
In order to capture HTTPS traffic, warcprox acts as a "man-in-the-middle" (MITM). When it receives a ``CONNECT`` directive from a client, it generates a public key certificate for the requested site, presents to the client, and proceeds to establish an encrypted connection with the client. It then makes a separate, normal HTTPS connection to the remote site. It decrypts, archives, and re-encrypts traffic in both directions.
Configuring a warcprox instance as a browser’s HTTP proxy will result in security certificate warnings because none of the certificates will be signed by trusted authorities. However, there is nothing malicious about warcprox functions. To use warcprox effectively, the client needs to disable certificate verification or add the CA certification generated by warcprox as a trusted authority. When using the latter, remember to undo this change when finished using warcprox.
Warcprox avoids archiving redundant content by "deduplicating" it. The process for deduplication works similarly to deduplication by `Heritrix <https://github.com/internetarchive/heritrix3>`_ and other web archiving tools:
2. Look up digest in deduplication database (warcprox currently supports `sqlite <https://sqlite.org/>`_ by default, `rethinkdb <https://github.com/rethinkdb/rethinkdb>`_ with two different schemas, and `trough <https://github.com/internetarchive/trough>`_)
3. If found, write warc ``revisit`` record referencing the url and capture time of the previous capture
The deduplication database is partitioned into different "buckets". URLs are deduplicated only against other captures in the same bucket. If specified, the ``dedup-bucket`` field of the `Warcprox-Meta HTTP request header <api.rst#warcprox-meta-http-request-header>`_ determines the bucket. Otherwise, the default bucket is used.
Warcprox stores some crawl statistics to sqlite or rethinkdb. These are consulted for enforcing ``limits`` and ``soft-limits`` (see `Warcprox-Meta fields <api.rst#warcprox-meta-fields>`_), and can also be consulted by other processes outside of warcprox, such as for crawl job reporting.
Statistics are grouped by "bucket". Every capture is counted as part of the ``__all__`` bucket. Other buckets can be specified in the ``Warcprox-Meta`` request header. The fallback bucket in case none is specified is called ``__unspecified__``.
Warcprox supports a limited notion of plugins by way of the ``--plugin`` command line argument. Plugin classes are loaded from the regular python module search path. They are instantiated with one argument that contains the values of all command line arguments, ``warcprox.Options``. Legacy plugins with constructors that take no arguments are also supported. Plugins should either have a method ``notify(self, recorded_url, records)`` or should subclass ``warcprox.BasePostfetchProcessor``. More than one plugin can be configured by specifying ``--plugin`` multiples times.
See a minimal example `here <https://github.com/internetarchive/warcprox/blob/318405e795ac0ab8760988a1a482cf0a17697148/warcprox/__init__.py#L165>`__.
