# locus
[](https://hex.pm/packages/locus)
[](https://github.com/g-andrade/locus/actions?query=workflow%3Abuild)
`locus` is library for Erlang/OTP and Elixir that allows you to pinpoint
the country, city or ASN of IP addresses using [MaxMind
GeoIP2](https://dev.maxmind.com/geoip/geoip2/geolite2/) and [other
providers](#alternative-providers).
The databases will be loaded on-demand and, when retrieved from the
network, cached on the filesystem and updated automatically.
> ⚠️ For instructions on how to upgrade to 2.x, check
> [`MIGRATION.md`](https://github.com/g-andrade/locus/blob/master/MIGRATION.md)
#### Usage
##### 1\. Configure your license key
**Skip this step if you're not loading databases directly from
MaxMind.**
Get a free [license key](https://www.maxmind.com/en/geolite2/signup)
from MaxMind if you haven't one already. Once logged in, you'll find the
page to generate it on the left menu, under "My License Key".
Then clone the repository, run `make shell` and declare your key:
``` erlang
application:set_env(locus, license_key, "YOUR_LICENSE_KEY").
```
##### 2\. Start the database loader
``` erlang
ok = locus:start_loader(country, {maxmind, "GeoLite2-Country"}).
% You can also use:
% * an HTTP(S) URL,
% * or a local path, e.g. "/usr/share/GeoIP/GeoLite2-City.mmdb"
% * or a {custom, Module, Args} tuple, with Module
% implementing the locus_custom_fetcher behaviour.
```
##### 3\. Wait for the database to load (optional)
``` erlang
{ok, _DatabaseVersion} = locus:await_loader(country). % or `{error, Reason}'
```
##### 4\. Look up IP addresses
``` erlang
% > locus:lookup(country, "93.184.216.34").
% > locus:lookup(country, "2606:2800:220:1:248:1893:25c8:1946").
% * '{ok, Entry}' in case of success;
% * 'not_found' if no entry was found
% * '{error, _}' if something bad happened
{ok,#{<<"continent">> =>
#{<<"code">> => <<"NA">>,
<<"geoname_id">> => 6255149,
<<"names">> =>
#{<<"de">> => <<"Nordamerika">>,
<<"en">> => <<"North America">>,
<<"es">> => <<"Norteamérica"/utf8>>,
<<"fr">> => <<"Amérique du Nord"/utf8>>,
<<"ja">> => <<"北アメリカ"/utf8>>,
<<"pt-BR">> => <<"América do Norte"/utf8>>,
<<"ru">> => <<"Северная Америка"/utf8>>,
<<"zh-CN">> => <<"北美洲"/utf8>>}},
<<"country">> =>
#{<<"geoname_id">> => 6252001,
<<"iso_code">> => <<"US">>,
<<"names">> =>
#{<<"de">> => <<"USA">>,
<<"en">> => <<"United States">>,
<<"es">> => <<"Estados Unidos">>,
<<"fr">> => <<"États-Unis"/utf8>>,
<<"ja">> => <<"アメリカ合衆国"/utf8>>,
<<"pt-BR">> => <<"Estados Unidos">>,
<<"ru">> => <<"США"/utf8>>,
<<"zh-CN">> => <<"美国"/utf8>>}},
<<"registered_country">> =>
#{<<"geoname_id">> => 6252001,
<<"iso_code">> => <<"US">>,
<<"names">> =>
#{<<"de">> => <<"USA">>,
<<"en">> => <<"United States">>,
<<"es">> => <<"Estados Unidos">>,
<<"fr">> => <<"États-Unis"/utf8>>,
<<"ja">> => <<"アメリカ合衆国"/utf8>>,
<<"pt-BR">> => <<"Estados Unidos">>,
<<"ru">> => <<"США"/utf8>>,
<<"zh-CN">> => <<"美国"/utf8>>}}}}
```
#### Documentation
1. [Supported File Formats](#supported-file-formats)
2. [Database Types and Loading](#database-types-and-loading)
3. [Database Validation](#database-validation)
4. [Remote sources: Downloading and
Updating](#remote-sources-downloading-and-updating)
5. [Remote sources: Caching](#remote-sources-caching)
6. [Local sources: Loading and
Updating](#local-sources-loading-and-updating)
7. [Logging](#logging)
8. [Event Subscriptions](#event-subscriptions)
9. [API Reference](#api-reference)
10. [Tested Setup](#tested-setup)
11. [License](#license)
12. [Alternative Providers](#alternative-providers)
13. [Alternative Libraries (Erlang)](#alternative-libraries-erlang)
14. [Alternative Libraries (Elixir)](#alternative-libraries-elixir)
##### Supported File Formats
- gzip-compressed tarballs (`.tar.gz`, `.tgz`)
- plain tarballs (`.tar`)
- MMDB files (`.mmdb`)
- gzip-compressed MMDB files (`.mmdb.gz`)
For tarball files, the first file to be found within it with an `.mmdb`
extension is the one that's chosen for loading.
The implementation of [MaxMind DB
format](https://maxmind.github.io/MaxMind-DB/) is complete except for
the [`data cache
container`](https://maxmind.github.io/MaxMind-DB/#data-cache-container---12)
data type.
##### Database Types and Loading
- The free GeoLite2 [Country, City and ASN
databases](https://dev.maxmind.com/geoip/geoip2/geolite2/) were all
successfully tested; presumably `locus` can deal with [any MMDB
database](#alternative-providers) that maps IP address prefixes to
arbitrary data
- The databases are loaded into memory (mostly) as is; reference
counted binaries are shared with the application callers using
[`persistent_term`](https://erlang.org/doc/man/persistent_term.html),
and the original binary search tree is used to lookup addresses. The
data for each entry is decoded on the fly upon successful lookups.
##### Database Validation
Databases, local or remote, can have their compatibility validated
through the `locus:check/1` function after they've been loaded (see
[function reference](#api-reference).)
Alternatively, they can also be checked from the command line by use of
the `locus` CLI utility:
1. Run `make cli` to build the script, named `locus`, which will be
deployed to the current directory.
2. Check the database:
``` shell
./locus check GeoLite2-City.mmdb
# Loading database from "GeoLite2-City.mmdb"...
# Database version {{2019,11,6},{11,58,0}} successfully loaded
# Checking database for flaws...
# Database is wholesome.
```
The script will exit with code 1 in case of failure, and 0 otherwise.
Warnings can produce failure through the `--warnings-as-errors` flag.
Run `./locus check --help` for a description of supported options and
arguments.
##### Remote sources: Downloading and Updating
- The downloaded database files, when compressed, are inflated in
memory
- For MaxMind and HTTP downloads, the `last-modified` response header,
if present, is used to condition subsequent download attempts (using
`if-modified-since` request headers) in order to save bandwidth
- The downloaded databases are cached on the filesystem in order to
more quickly achieve readiness on future launches of the database
loader
- Database download attempts are retried upon error according to an
exponential backoff policy - quickly at first (every few seconds)
but gradually slowing down to every 15 minutes. Successful and
dismissed download attempts will be checked for update after 6
hours. Both of these behaviours can be tweaked through the
`error_retries` and `update_period` loader settings (see [function
reference](#api-reference).)
- When downloading from a MaxMind edition or an HTTP URL, the remote
certificate will be authenticated against [a list of known
Certification
Authorities](https://hexdocs.pm/tls_certificate_check/) and
connection negotiation will fail in case of an expired certificate,
mismatched hostname, self-signed certificate or unknown
certification authority. These checks can be disabled by specifying
the `insecure` loader option.
##### Remote sources: Caching
- Caching is a best effort; the system falls back to relying
exclusively on the network if needed
- A caching directory named `locus_erlang` is created under the
['user\_cache'
basedir](http://erlang.org/doc/man/filename.html#basedir-3)
- A cached database is named after either:
- the MaxMind database edition name (when explicitly downloading
from MaxMind), or
- the SHA256 hash of the HTTP(S) URL, or
- for `{custom_fetcher, Module, Args}` sources, a filesystem-safe
version of `Module`'s name concatenated with the 32-bit
[`erlang:phash2/2`](https://erlang.org/doc/man/erlang.html#phash2-2)
value of the opaque database source as returned by the
callbacks.
- Modification time of the databases is retrieved from either:
- the `last-modified` response header (when present, for MaxMind
and HTTP(S) sources)
- the `modified_on` metadata property for successful
`locus_custom_fetcher:fetch/1` and ``:conditionally_fetch/2`
callbacks (for databases loaded with `locus_custom_fetcher``)
- Caching can be disabled by specifying the `no_cache` option when
running `:start_loader`
##### Local sources: Loading and Updating
- The loaded database files, when compressed, are inflated in memory
- The database modification timestamp is used to condition subsequent
load attempts in order to lower I/O activity
- Database load attempts are retried upon error according to an
exponential backoff policy - quickly at first (every few seconds)
but gradually slowing down to every 30 seconds. Successful and
dismissed load attempts will be checked for update after 30 seconds.
Both of these behaviours can be tweaked through the `error_retries`
and `update_period` loader settings (see [function
reference](#api-reference).)
##### Logging
- Five logging levels are supported: `debug`, `info`, `warning`,
`error` and `none`
- The chosen backend is
[logger](http://erlang.org/doc/man/logger.html) *if*
[lager](https://github.com/erlang-lager/lager/) is either missing or
it hasn't
[removed](https://github.com/erlang-lager/lager/issues/492)
`logger`'s default handler.
- The default log level is `error`; it can be changed in the
application's `env` config
- To tweak the log level in runtime, use `locus_logger:set_loglevel/1`
##### Event Subscriptions
- Any number of event subscribers can be attached to a database loader
by specifying the `{event_subscriber, Subscriber}` option when
starting the database
- A `Subscriber` can be either a module implementing the
`locus_event_subscriber` behaviour or an arbitrary `pid()`
- The format and content of reported events can be consulted in detail
on the `locus_event_subscriber` module documentation; most key steps
in the loader pipeline are reported (download started, download
succeeded, download failed, caching succeeded, loading failed, etc.)
##### API Reference
The API reference can be found on [HexDocs](https://hexdocs.pm/locus/).
##### Tested setup
- Erlang/OTP 22 or newer
- rebar3
##### License
MIT License
Copyright (c) 2017-2021 Guilherme Andrade
Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be included
in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
`locus` is an independent project and has not been authorized,
sponsored, or otherwise approved by MaxMind.
##### Alternative Providers
- [DB-IP.com](https://db-ip.com/db/): lite databases seem to work but
setting up auto-update for them is not practical, as there's no
"latest" URL.
##### Alternative Libraries (Erlang)
- [egeoip](https://github.com/mochi/egeoip): IP Geolocation module,
currently supporting the MaxMind GeoLite City Database
- [geodata2](https://github.com/brigadier/geodata2): Application for
working with MaxMind geoip2 (.mmdb) databases
- [geoip](https://github.com/manifest/geoip): Returns the location of
an IP address; based on the ipinfodb.com web service
- [geolite2data](https://hex.pm/packages/geolite2data): Periodically
fetches the free MaxMind GeoLite2 databases
- [ip2location-erlang](https://github.com/ip2location/ip2location-erlang):
Uses IP2Location geolocation database
##### Alternative Libraries (Elixir)
- [asn](https://hex.pm/packages/asn): IP-to-AS-to-ASname lookup
- [freegeoip](https://hex.pm/packages/freegeoip): Simple wrapper for
freegeoip.net HTTP API
- [freegeoipx](https://hex.pm/packages/freegeoipx): API Client for
freegeoip.net
- [geoip](https://hex.pm/packages/geoip): Lookup the geo location for
a given IP address, hostname or Plug.Conn instance
- [geolix](https://hex.pm/packages/geolix): MaxMind GeoIP2 database
reader/decoder
- [plug\_geoip2](https://hex.pm/packages/plug_geoip2): Adds geo
location to a Plug connection based upon the client IP address by
using MaxMind's GeoIP2 database
- [tz\_world](https://hex.pm/packages/tz_world): Resolve timezones
from a location efficiently using PostGIS and Ecto
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