``kawipiko`` is a simple static HTTP server written in Go_, whose main purpose is to serve static content as fast as possible.
However "simple" doesn't imply "dumb" or "limited", instead it implies "efficiency" and removal of superfluous features, inline with UNIX's philosophy of `do one thing and do it well <https://en.wikipedia.org/wiki/Unix_philosophy#Do_One_Thing_and_Do_It_Well>`__.
As such ``kawipiko`` basically supports only ``GET`` (and ``HEAD``) requests and does not provide features like dynamic content, authentication, reverse proxying, etc.
However, ``kawipiko`` does provide something unique, that no other HTTP server offers: the static content is served from a CDB_ database with almost zero latency.
Moreover, the static content can be compressed (with either ``gzip`` or ``brotli``) ahead of time, thus reducing not only CPU but also bandwith and latency.
CDB_ databases are binary files that provide efficient read-only key-value lookup tables, initially used in some DNS and SMTP servers, mainly for their low overhead lookup operations, zero locking in multi-threaded / multi-process scenarios, and "atomic" multi-record updates.
This also makes them suitable for low-latency static content serving over HTTP, which this project provides.
With regard to performance, as described in the `benchmarks section <#benchmarks>`__, ``kawipiko`` is on par with NGinx, sustaining 72k requests / second with 0.4ms latency for 99% of the requests even on my 6 years old laptop.
However the main advantage over NGinx is not raw performance, but deployment and configuration simplicity, plus efficient management and storage of large collections of many small static files.
The path to the input folder that is the root of the website.
``--archive``
The path to the output CDB file that will contain the archived website.
``--compress``
Each individual file (and consequently of the corresponding HTTP response body) is compressed with either ``gzip`` or Brotli_; by default (or alternatively ``identity``) no compression is used.
Even if compression is explicitly requested, if the compression ratio is bellow a certain threshold (depending on the uncompressed size), the file is stored without any compression.
(It's senseless to force the client to spend time and decompress the response body if that time is not recovered during network transmission.)
``--exclude-index``
Disables using ``index.*`` files (where ``.*`` is one of ``.html``, ``.htm``, ``.xhtml``, ``.xht``, ``.txt``, ``.json``, and ``.xml``) to respond to a request whose URL ends in ``/`` (corresponding to the folder wherein ``index.*`` file is located).
(This can be used to implement "slash" blog style URL's like ``/blog/whatever/`` which maps to ``/blog/whatever/index.html``.)
``--exclude-strip``
Disables using a file with the suffix ``.html``, ``.htm``, ``.xhtml``, ``.xht``, and ``.txt`` to respond to a rquest whose URL does not exactly match an existing file.
(This can be used to implement "suffix-less" blog style URL's like ``/blog/whatever`` which maps to ``/blog/whatever.html``.)
``--exclude-etag``
Disables adding an ``ETag`` response header that contains the SHA256 of the response body.
(At this moment it does not support HTTP conditional requests, i.e. the ``If-None-Match``, ``If-Modified-Since`` and their counterparts; however this ``ETag`` header might be used in conjuction with ``HEAD`` requests to see if the resource has changed.)
``--exclude-file-listing``
Disables the creation of an internal list of files that can be used in conjunction with the ``--index-all`` flag of the ``kawipiko-server``.
``--include-folder-listing``
Enables the creation of an internal list of folders. (Currently not used by the ``kawipiko-server`` tool.)
Ignored files
.............
* any file with the following prefixes: ``.``, ``#``;
* any file with the following suffixes: ``~``, ``#``, ``.log``, ``.tmp``, ``.temp``, ``.lock``;
* any file that contains the following: ``#``;
* any file that exactly matches the following:: ``Thumbs.db``, ``.DS_Store``;
* (at the moment these rules are not configurable through flags;)
``_wildcard.*`` files
.....................
By placing a file whose name matches ``_wildcard.*`` (i.e. with the prefix ``_wildcard.`` and any other suffix), it will be used to respond to any request whose URL fails to find a "better" match.
These wildcard files respect the folder hierarchy, in that wildcard files in (direct or transitive) subfolders override the wildcard file in their parents (direct or transitive).
Symlinks, hardlinks, loops, and duplicated files
................................................
You freely use symlinks (including pointing outside of the website root) and they will be crawled during archival respecting the "logical" hierarchy they introduce.
(Any loop that you introduce into the hierarchy will be ignored and a warning will be issued.)
You can safely symlink or hardlink the same file (or folder) in multiple places (within the website root), and its contents will be stored only once.
(The same applies to duplicated files that have exactly the same contents.)
* (optionally) in order to reduce the serving latency even further, one can preload the entire CDB database in memory, or alternatively mapping it in memory (mmap_); this trades memory for CPU;
* "atomic" site content changes; because the entire site content is held in a single CDB database file, and because the file replacement is atomically achieved via the ``rename`` syscall (or the ``mv`` tool), all the site's resources are "changed" at the same time;
*``_wildcard.*`` files (where ``.*`` are the regular extensions like ``.txt``, ``.html``, etc.) which will be used if an actual resource is not found under that folder; (these files respect the hierarchical tree structure, i.e. "deeper" ones override the ones closer to "root";)
* support for custom HTTP response headers (for specific files, for specific folders, etc.); (currently only ``Content-Type``, ``Content-Length``, ``Content-Encoding`` and optionally ``ETag`` is included; additionally ``Cache-Control: public, immutable, max-age=3600`` and a few security related headers are also included;)
* (won't fix) the CDB database **maximum size is 4 GiB**; (however if you have a site this large, you are probabbly doing something extreemly wrong, as large files should be offloaded to something like AWS S3 and served through a CDN like CloudFlare or AWS CloudFront;)
* (won't fix) the server **does not support per-request decompression / recompression**; this implies that if the site content was saved in the CDB database with compression (say ``gzip``), the server will serve all resources compressed (i.e. ``Content-Encoding: gzip``), regardless of what the browser accepts (i.e. ``Accept-Encoding: gzip``); the same applies for uncompressed content; (however always using ``gzip`` compression is safe enough as it is implemented in virtually all browsers and HTTP clients out there;)
* (won't fix) regarding the "atomic" site changes, there is a small time window in which a client that has fetched an "old" version of a resource (say an HTML page), but which has not yet fetched the required resources (say the CSS or JS files), and the CDB database was swapped, it will consequently fetch the "new" version of these required resources; however due to the low latency serving, this time window is extreemly small; (**this is not a limitation of this HTTP server, but a limitation of the way the "web" is built;** always use fingerprints in your resources URL, and perhaps always include the current and previous version on each deploy;)
* under normal conditions (16 concurrent connections), you get around 72k requests / second, at about 0.4ms latency for 99% of the requests;
* under stress conditions (512 concurrent connections), you get arround 74k requests / second, at about 15ms latency for 99% of the requests;
***under extreme conditions (2048 concurrent connections), you get arround 74k requests / second, at about 500ms latency for 99% of the requests (meanwhile the average is 50ms);**
* (the timeout errors are due to the fact that ``wrk`` is configured to timeout after only 1 second of waiting;)
* (the read errors are due to the fact that the server closes a keep-alive connection after serving 256k requests;)
***the raw performance is comparable with NGinx_** (only 20% few requests / second for this "synthetic" benchmark); however for a "real" scenario (i.e. thousand of small files accessed in a random pattern) I think they are on-par; (not to mention how simple it is to configure and deploy ``kawipiko`` as compared to NGinx;)
* (the NGinx configuration file can be found in the `examples folder <./examples>`__; the configuration was obtained after many experiments to squeeze out of NGinx as much performance as possible, given the targeted use-case, namely many small static files;)
* 512 concurrent connections (handled by 2 threads): ::
wrk \
--threads 2 \
--connections 512 \
--timeout 6s \
--duration 30s \
--latency \
http://127.0.0.1:8080/ \
#
* 4096 concurrent connections (handled by 4 threads): ::
wrk \
--threads 4 \
--connections 4096 \
--timeout 6s \
--duration 30s \
--latency \
http://127.0.0.1:8080/ \
#
Methodology notes
.................
* the number of threads for the server plus for ``wkr`` shouldn't be larger than the number of available cores; (or use different machines for the server and the client;)
* also take into account that by default the number of "file descriptors" on most UNIX/Linux machines is 1024, therefore if you want to try with more connections than 1000, you need to raise this limit; (see bellow;)
* additionally, you can try to pin the server and ``wrk`` to specific cores, increase various priorities (scheduling, IO, etc.); (given that Intel processors have HyperThreading which appear to the OS as individual cores, you should make sure that you pin each process on cores part of the same physical processor / core;)
* pinning the server (cores ``0`` and ``1`` are mapped on physical core ``1``): ::
sudo -u root -n -E -P -- \
\
taskset -c 0,1 \
nice -n -19 -- \
ionice -c 2 -n 0 -- \
chrt -r 10 \
prlimit -n16384 -- \
\
sudo -u "${USER}" -n -E -P -- \
\
kawipiko-server \
... \
#
* pinning the client (cores ``2`` and ``3`` are mapped on physical core ``2``): ::
For details about the copyright and licensing, please consult the `notice <./documentation/licensing/notice.txt>`__ file in the `documentation/licensing <./documentation/licensing>`__ folder.
*`Benchmarking LevelDB vs. RocksDB vs. HyperLevelDB vs. LMDB Performance for InfluxDB <https://www.influxdata.com/blog/benchmarking-leveldb-vs-rocksdb-vs-hyperleveldb-vs-lmdb-performance-for-influxdb/>`__ (article);
*`Badger vs LMDB vs BoltDB: Benchmarking key-value databases in Go <https://blog.dgraph.io/post/badger-lmdb-boltdb/>`__ (article);
*`Benchmarking BDB, CDB and Tokyo Cabinet on large datasets <https://www.dmo.ca/blog/benchmarking-hash-databases-on-large-data/>`__ (article);
