cl-migratum
2024-10-12
Database schema migration system for Common Lisp
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Author
Maintainer
License
Database Schema Migration System for Common Lisp
cl-migratum
is a Common Lisp system, which provides facilities for
performing database schema
migrations.
Requirements
Systems
The following systems are available as part of this repo.
System | Description |
---|---|
cl-migratum | Core system |
cl-migratum.provider.local-path | Provider which discovers migrations from local-path |
cl-migratum.driver.dbi | cl-dbi database driver |
cl-migratum.driver.rmdbs-postgresql | PostgreSQL driver based on hu.dwim.rdbms |
cl-migratum.driver.postmodern-postgresql | PostgreSQL driver based on postmodern |
cl-migratum.driver.mixins | Various mixin classes used by drivers |
cl-migratum.test | Test suite for cl-migratum |
cl-migratum.cli | CLI application of migratum |
Installation
Installation is possible via roswell. This will also build the migratum
binary (see section CLI):
ros install cl-migratum
The latest development version can be installed from the Git repo.
Clone the cl-migratum repo in your Quicklisp local-projects directory.
git clone https://github.com/dnaeon/cl-migratum.git
CLI
You can install the CLI application of migratum
by executing the
following command.
make cli
The migratum
binary will be built into the bin/migratum
directory. You can now install the binary somewhere in your PATH
.
Once the migratum
binary is built you can also generate the Zsh
completions by executing the following command.
migratum zsh-completions > ~/.zsh-completions/_migratum
Make sure that ~/.zsh-completions
is part of your Zsh FPATH
.
In order to generate the Markdown documentation of the CLI app use the
cli-doc
target:
make cli-doc
Or you can build a Docker image instead.
docker build -t migratum.cli:latest -f Dockerfile.cli .
Concepts
The cl-migratum
system uses the following concepts to describe
the process of discovering and applying schema migrations, so it is
important that you get familiar with them first.
Migration
A migration
represents a resource that provides information about a
schema change, e.g. it provides the unique id of the change, the
required scripts that can be used to upgrade and/or downgrade the
database.
Migration resources are discovered via providers
and are being
used by drivers
during the upgrade or downgrade process.
Provider
The provider
is responsible for discovering migration resources.
For example a provider can discover migrations from a local path by scanning for files that match a given pattern or fetch migrations from a remote endpoint (e.g. HTTP service).
The provider
is also responsible for creating new migration
sequences.
The following providers are supported by cl-migratum
.
Name | Description | System |
---|---|---|
local-path | Provider that can discover migration resources from a local path | cl-migratum.provider.local-path |
Driver
The driver
carries out the communication with the database against
which schema changes will be applied.
It is responsible for applying schema changes, registering successfully applied migrations and unregistering them when reverting back to a previous state.
A driver
internally uses a provider
in order to discover
migrations
, which can be applied against the database it is
connected to.
The following drivers are currently supported by cl-migratum
.
Name | Description | System | Migration Registration |
---|---|---|---|
dbi | Driver for performing schema migrations against a SQL database using CL-DBI | cl-migratum.driver.dbi | In table migration |
rdbms-postgresql | Driver for performing schema migrations against a SQL database using hu.dwim.rdbms | cl-migratum.driver.rdbms-postgresql | In table migration |
Usage
The following section contains some examples to get you started.
In order to use cl-migratum
you will need to load the core system,
along with any provider
and driver
systems.
Load the core system.
CL-USER> (ql:quickload :cl-migratum)
Create Provider
First, we will create a new provider
that can discover migration
files from a local path. In order to create a local-path
provider we
need to load the respective system.
CL-USER> (ql:quickload :cl-migratum.provider.local-path)
Once you load the system we can create a local-path
provider. The
local-path
provider can discover migrations from multiple paths.
Typical example where having multiple paths with migration resources
might be useful is when you have a set of base migrations you want to
apply to all environments, and then have a separate path for each
environment with their own migrations. For example you might want to
run specific migrations only in your dev
environment, but don't want
them in your production
environment.
In that case it makes sense to separate the migration resources in multiple paths, for each environment respectively.
CL-USER> (defparameter *provider* (migratum.provider.local-path:make-provider (list #P"/path/to/cl-migratum/t/migrations/"))) *PROVIDER*
The LOCAL-PATH-PROVIDER
discovers migration files which match the
following pattern.
Pattern | Description |
---|---|
<id>-<description>.up.<kind> | Upgrade script |
<id>-<description>.down.<kind> | Downgrade script |
In above pattern <id>
is a monotonically increasing integer, which
represents the timestamp the migration has been created. The format of
<id>
is YYYYMMDDHHMMSS
.
The supported migration kinds by LOCAL-PATH-PROVIDER
are these.
Extension | Kind | Description |
---|---|---|
.sql | :sql | SQL migration resource |
.lisp | :lisp | Migration resource which invokes a Lisp function |
A provider can optionally be initialized, which can be done using the
MIGRATUM:PROVIDER-INIT
generic function. Not all providers would
require initialization, but some will and therefore it is good that
you always initialize them first.
In order to list the migrations provided by a provider
you can use
the MIGRATUM:PROVIDER-LIST-MIGRATIONS
function, e.g.
CL-USER> (migratum:provider-list-migrations *provider*) (#<CL-MIGRATUM.PROVIDER.LOCAL-PATH:LISP-MIGRATION {1004713F73}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {1004603BE3}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {1004603B03}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {10046039B3}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {1004603733}>)
The following generic functions can be used to interact with discovered migrations.
Method | Description |
---|---|
MIGRATUM:MIGRATION-ID | Returns the unique migration id |
MIGRATUM:MIGRATION-DESCRIPTION | Returns the description of the migration |
MIGRATUM:MIGRATION-APPLIED | Returns the timestamp of when the migration was applied |
MIGRATUM:MIGRATION-LOAD | Loads the :up or :down migration |
MIGRATUM:MIGRATION-KIND | Returns the kind of the migration, e.g. :sql , :lisp , etc. |
For example in order to collect the unique IDs of all migration resources you can evaluate the following while at the REPL.
CL-USER> (mapcar #'migratum:migration-id (migratum:provider-list-migrations *provider*)) (20200421180337 20200421173908 20200421173657 ...)
Create Driver
Once we have a provider for discovering migration resources we need to create a driver, which can be used to communicate with the database we want to apply migrations on.
DBI Driver
Here is how we can create a dbi
driver. First, lets load the system,
which provides that driver.
CL-USER> (ql:quickload :cl-migratum.driver.dbi)
The dbi
driver uses CL-DBI
interface to communicate with the database, so we will need to create
a database connection in order to initialize it.
CL-USER> (defparameter *conn* (dbi:connect :sqlite3 :database-name "/path/to/migratum.db")) *CONN*
And now we can instantiate our SQL driver using the previously created provider and connection.
CL-USER> (defparameter *driver* (migratum.driver.dbi:make-driver *provider* *conn*)) *DRIVER*
RDBMS PostgreSQL Driver
The process to create an rdbms-postgresql
driver is analogous. The
driver needs a connection specification to create a DB connection. In
this example we use the same environment variables which are used by
the PostgreSQL client psql
to override the defaults:
(ql:quickload :cl-migratum.driver.rdbms-postgresql) (defparameter *driver* (migratum.driver.rdbms-postgresql:make-driver *provider* `(:host ,(or (uiop:getenv "PGHOST") "localhost") :database ,(or (uiop:getenv "PGDATABASE") "migratum") :user-name ,(or (uiop:getenv "PGUSER") "migratum") :password ,(or (uiop:getenv "PGPASSWORD") "tiger"))))
Initialization
A driver
and provider
may require some initialization steps to be
executed before being able to apply migrations, so make sure that you
initialize them.
In order to initialize your provider
use the
MIGRATUM:PROVIDER-INIT
function.
CL-USER> (migratum:provider-init *provider*)
An example requirement for a driver might be to create some required database schema used to track which migrations have been applied already, so lets initialize our driver first.
CL-USER> (migratum:driver-init *driver*)
Pending Migrations
In order to get the list of pending (not applied yet) migrations we can
use the MIGRATUM:LIST-PENDING
function, e.g.
CL-USER> (migratum:list-pending *driver*) (#<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {100363DFC3}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {100363E0A3}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {100363E183}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {100363E263}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:LISP-MIGRATION {100363E343}>)
Or, we can display a table of the pending migrations using the
MIGRATUM:DISPLAY-PENDING
function instead.
CL-USER> (migratum:display-pending *driver*) .---------------------------------------------. | PENDING MIGRATIONS | +----------------+---------------------+------+ | ID | DESCRIPTION | KIND | +----------------+---------------------+------+ | 20200421173657 | create_table_foo | SQL | | 20200421173908 | create_table_bar | SQL | | 20200421180337 | create_table_qux | SQL | | 20200605144633 | multiple_statements | SQL | | 20220327224455 | lisp_code_migration | LISP | +----------------+---------------------+------+ | | TOTAL | 5 | +----------------+---------------------+------+ NIL
The migrations will be sorted in the order they need to be applied.
Applying Migrations
The following functions are used for applying pending migrations.
MIGRATUM:APPLY-PENDING
- applies all pending migrationsMIGRATUM:APPLY-NEXT
- applies the next pending migration
This is how we can apply all pending migrations for example.
CL-USER> (migratum:apply-pending *driver*) <INFO> [21:20:51] cl-migratum.core core.lisp (apply-pending base-driver) - Found 5 pending migration(s) to be applied <INFO> [21:20:51] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20200421173657 - create_table_foo (SQL) <INFO> [21:20:51] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20200421173908 - create_table_bar (SQL) <INFO> [21:20:51] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20200421180337 - create_table_qux (SQL) <INFO> [21:20:51] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20200605144633 - multiple_statements (SQL) <INFO> [21:20:51] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20220327224455 - lisp_code_migration (LISP) NIL
Get Latest Migration
You can use the MIGRATUM:LATEST-MIGRATION
function to get the latest
applied migration, e.g.
CL-USER> (migratum:migration-id (migratum:latest-migration *driver*)) 20220327224455 (45 bits, #x1263E96BE487)
The MIGRATUM:CONTAINS-APPLIED-MIGRATIONS-P
predicate can be used to
query whether there are any migrations applied, e.g.
CL-USER> (migratum:contains-applied-migrations-p *driver*) T
Displaying Applied Migrations
The following functions can be used to get and display the list of applied database migrations.
Function | Description |
---|---|
MIGRATUM:DRIVER-LIST-APPLIED | Returns the list of applied migrations |
MIGRATUM:DISPLAY-APPLIED | Display a table of applied migrations |
This is how we can get the list of applied migrations.
CL-USER> (migratum:driver-list-applied *driver*) (#<CL-MIGRATUM.CORE:BASE-MIGRATION {1002175993}> #<CL-MIGRATUM.CORE:BASE-MIGRATION {10021759D3}> #<CL-MIGRATUM.CORE:BASE-MIGRATION {1002175A13}> #<CL-MIGRATUM.CORE:BASE-MIGRATION {1002175A53}> #<CL-MIGRATUM.CORE:BASE-MIGRATION {1002175A93}>)
Or we can display a nice table of the applied migrations instead.
CL-USER> (migratum:display-applied *driver*) .-------------------------------------------------------------------. | APPLIED MIGRATIONS | +----------------+---------------------+---------------------+------+ | ID | DESCRIPTION | APPLIED | KIND | +----------------+---------------------+---------------------+------+ | 20220327224455 | lisp_code_migration | 2022-03-29 18:20:53 | LISP | | 20200605144633 | multiple_statements | 2022-03-29 18:20:51 | SQL | | 20200421180337 | create_table_qux | 2022-03-29 18:20:51 | SQL | | 20200421173908 | create_table_bar | 2022-03-29 18:20:51 | SQL | | 20200421173657 | create_table_foo | 2022-03-29 18:20:51 | SQL | +----------------+---------------------+---------------------+------+ | | | TOTAL | 5 | +----------------+---------------------+---------------------+------+ NIL
The output of these functions will be the applied migrations in descending order by their id, first one being the most recent one.
The dbi
and rdbms-postgresql
drivers by default will fetch the
last 100 applied migrations. You can control this behaviour by using
the :offset
and :limit
keyword parameters, which allows you to
fetch applied migrations in pages.
For example, if you are interested only in the last ten applied migrations you can evaluate the following expression.
CL-USER> (migratum:display-applied *driver* :limit 10)
Or if you want to skip the first ten migrations, you can evaluate this expression instead.
CL-USER> (migratum:display-applied *driver* :offset 10 :limit 10)
Stepping through migrations
Using the following functions you can step through migrations.
Function | Description |
---|---|
MIGRATUM:APPLY-NEXT | Apply the next pending migration(s) |
MIGRATUM:REVERT-LAST | Revert the last applied migration(s) |
This is useful in situations when you don't want to apply
all migrations at once, but rather do it one at a time. Both of these
functions accept a keyword parameter :count
which specifies the
number of migrations to apply or revert.
Consider the following pending migrations.
CL-USER> (migratum:display-pending *driver*) .---------------------------------------------. | PENDING MIGRATIONS | +----------------+---------------------+------+ | ID | DESCRIPTION | KIND | +----------------+---------------------+------+ | 20200421173657 | create_table_foo | SQL | | 20200421173908 | create_table_bar | SQL | | 20200421180337 | create_table_qux | SQL | | 20200605144633 | multiple_statements | SQL | | 20220327224455 | lisp_code_migration | LISP | +----------------+---------------------+------+ | | TOTAL | 5 | +----------------+---------------------+------+ NIL
We can apply them one by one and verify them as we go.
CL-USER> (migratum:apply-next *driver*) <INFO> [21:25:45] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20200421173657 - create_table_foo (SQL) NIL CL-USER> (migratum:apply-next *driver*) <INFO> [21:25:47] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20200421173908 - create_table_bar (SQL) NIL CL-USER> (migratum:apply-next *driver*) <INFO> [21:25:48] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20200421180337 - create_table_qux (SQL) NIL CL-USER> (migratum:apply-next *driver*) <INFO> [21:25:49] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20200605144633 - multiple_statements (SQL) NIL CL-USER> (migratum:apply-next *driver*) <INFO> [21:25:50] cl-migratum.core core.lisp (apply-and-register base-driver) - Applying migration 20220327224455 - lisp_code_migration (LISP) NIL
If we want to revert the last three migrations we can use the
MIGRATUM:REVERT-LAST
function, e.g.
CL-USER> (migratum:revert-last *driver* :count 3) <INFO> [21:26:14] cl-migratum.core core.lisp (revert-and-unregister base-driver) - Reverting migration 20220327224455 - lisp_code_migration (LISP) <INFO> [21:26:14] cl-migratum.core core.lisp (revert-and-unregister base-driver) - Reverting migration 20200605144633 - multiple_statements (SQL) <INFO> [21:26:14] cl-migratum.core core.lisp (revert-and-unregister base-driver) - Reverting migration 20200421180337 - create_table_qux (SQL) NIL
Now, we should have 3 pending migrations again.
CL-USER> (migratum:display-pending *driver*) .---------------------------------------------. | PENDING MIGRATIONS | +----------------+---------------------+------+ | ID | DESCRIPTION | KIND | +----------------+---------------------+------+ | 20200421180337 | create_table_qux | SQL | | 20200605144633 | multiple_statements | SQL | | 20220327224455 | lisp_code_migration | LISP | +----------------+---------------------+------+ | | TOTAL | 3 | +----------------+---------------------+------+ NIL
Creating New Migrations
The MIGRATUM:PROVIDER-CREATE-MIGRATION
generic function creates a
new migration sequence. The arguments it expects are the direction
(e.g. :up
or :down
), the migration kind
(e.g. :sql
, :lisp
,
etc.), an instance of a provider
, id
, description
and content
.
Knowing migratum:provider-create-migration
by the documentation
below, you can also use the wrapper
migratum.provider.local-path:touch-migration
to create a pair of
up-and-down empty migrations with a LOCAL-PATH
provider.
SQL migrations
Here's an example of using the LOCAL-PATH
provider for creating a
new SQL migration.
CL-USER> (defparameter *migration-id* (migratum:make-migration-id)) *MIGRATION-ID* CL-USER> CL-USER> (migratum:provider-create-migration :up ;; <- direction :sql ;; <- kind *provider* ;; <- provider *migration-id* ;; <- the migration id "fubar" ;; <- description "CREATE ...") ;; <- contents #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:SQL-MIGRATION {1009570AD3}>
The downgrade migration is created in a similar way. Simply use the
:down
direction and the appropriate contents for it. Also, make sure
that the description and id are the same when creating a pair of
upgrade/downgrade migrations.
Lisp migrations
The :lisp
migration kind allows invoking a handler, which performs
the upgrade and downgrade.
The handler is a regular Lisp function, which accepts a single
argument that is an instance of a driver
.
In order to create a :lisp
migration you need to create a spec,
which specifies the Common Lisp system
, package
, upgrade
and
downgrade
handler.
Here's an example of a spec, which is a regular property list.
(:system :my-system :package :my-system.package :handler :upgrade-handler)
And here's a full example of creating an :up
and :down
migration.
CL-USER> (let ((id (migratum:make-migration-id)) (desc "my lisp migration") (up-spec '(:system :my-system :package :my-system.package :handler :upgrade-handler)) (down-spec '(:system :my-system :package :my-system.package :handler :downgrade-handler))) (values (migratum:provider-create-migration :up :lisp *provider* id desc up-spec) (migratum:provider-create-migration :down :lisp *provider* id desc down-spec))) #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:LISP-MIGRATION {100A39C083}> #<CL-MIGRATUM.PROVIDER.LOCAL-PATH:LISP-MIGRATION {100A39D6C3}>
Multiple SQL Statements
If you need to run multiple SQL statements when using the dbi
or
rdbms-postgresql
driver you can separate each statement in the
migration using the --;;
separator.
The following example migration would create two tables as part of a single transaction.
CREATE TABLE foo ( id INTEGER PRIMARY KEY ); --;; CREATE TABLE bar ( id INTEGER PRIMARY KEY );
Debug logging
cl-migratum
uses log4cl,
so you can enable debug logging, if needed.
CL-USER> (log:config :debug)
Shutdown / Teardown
Once done with the migrations you should call the cleanup functions of
the provider
and driver
.
CL-USER> (migratum:provider-shutdown *provider*) CL-USER> (migratum:driver-shutdown *driver*)
Implemeting new migration resources
Generally new migration resources will be implemented along with a
provider
, which discovers them.
You can implement a new migration resource by inheriting from the
MIGRATUM:BASE-MIGRATION
class.
The following generic functions should be implemented on the newly defined class.
Method | Description |
---|---|
MIGRATUM:MIGRATION-LOAD | Loads the :up and :down scripts |
MIGRATUM:MIGRATION-KIND | Returns the kind of the migration |
The following generic functions can be overriden, if needed.
Method | Description |
---|---|
MIGRATUM:MIGRATION-ID | Returns the unique migration id |
MIGRATUM:MIGRATION-DESCRIPTION | Returns description of the migration |
MIGRATUM:MIGRATION-APPLIED | Returns timestamp of when the migration was applied |
Example implementation that loads migration resources from a remote HTTP server might look like this. The following code uses Dexador as the HTTP client.
(defun http-get (url) "HTTP GETs the given URL" (let ((contents (dex:get url :force-string t))) contents)) (defclass http-migration (base-migration) ((up-script-url :initarg :up-script-url :initform (error "Must specify URL to upgrade script") :accessor http-migration-up-script-url :documentation "URL to the upgrade script") (down-script-url :initarg :down-script-url :initform (error "Must specify URL to downgrade script") :accessor http-migration-down-script-url :documentation "URL to the downgrade script")) (:documentation "HTTP migration resource")) (defmethod migration-load ((direction (eql :up)) (migration http-migration)) (http-get (http-migration-up-script-url migration))) (defmethod migration-load ((direction (eql :down)) (migration http-migration)) (http-get (http-migration-down-script-url migration)))
A provider should simply MAKE-INSTANCE
of the HTTP-MIGRATION
class by
providing values for the required slots while discovering migrations via
the PROVIDER-LIST-MIGRATIONS
function.
Implementing new providers
You can implement custom providers
, which can discover migration
resources from various sources, e.g. local path, remote HTTP endpoints,
etc.
Each provider
determines the rules, which identify a resource as a
valid migration, so custom logic for discovering them can be
implemented by using your own provider. For example the local-path
provider considers files to be valid migrations, if they match a given
regex pattern.
In order to create a new provider you should inherit from the
MIGRATUM:BASE-PROVIDER
class and implement the following generic
functions on your newly defined class.
Method | Description |
---|---|
MIGRATUM:PROVIDER-LIST-MIGRATIONS | Responsible for discovering migrations |
MIGRATUM:PROVIDER-CREATE-MIGRATION | Creates a new migration using the provider |
The following methods can be overriden, if needed.
Method | Description |
---|---|
MIGRATUM:PROVIDER-NAME | Returns a human-friendly name of the provider |
MIGRATUM:PROVIDER-INIT | Initializes the provider, if needed |
MIGRATUM:PROVIDER-INITIALIZED | Returns T if provider is initialized, NIL otherwise |
MIGRATUM:PROVIDER-SHUTDOWN | Shutdowns the provider and cleans up any allocated resources |
You can also check the local-path provider implementation for some example code.
Implementing new drivers
A driver
is responsible for communicating with the database we are
migrating and executes the upgrade and downgrade scripts.
The driver also takes care of registering applied migrations after
applying an upgrade script and also unregistering them during
downgrade, thus it is the drivers' decision how to implement
registering and unregistering. For example the dbi
builtin driver
registers applied migrations in the same database it is migrating, but
a custom driver could choose a different stategy instead, e.g. use a
key/value store, local files, or some remote endpoint instead.
New drivers can be implemented by inheriting from the
MIGRATUM:BASE-DRIVER
class. The following methods should be
implemented on new drivers.
Method | Description |
---|---|
MIGRATUM:DRIVER-LIST-APPLIED | Returns the list of applied migrations |
MIGRATUM:DRIVER-REGISTER-MIGRATION | Registers/unregister a successfully applied migration |
MIGRATUM:DRIVER-APPLY-MIGRATION | Applies a migration according to the given direction |
The following methods can be overriden, if needed.
Method | Description |
---|---|
MIGRATUM:DRIVER-INIT | Initializes the driver, if needed |
MIGRATUM:DRIVER-NAME | Returns the human-friendly name of the driver |
MIGRATUM:DRIVER-PROVIDER | Returns the provider used by the driver |
MIGRATUM:DRIVER-INITIALIZED | Returns T if driver is initialized, NIL otherwise |
MIGRATUM:DRIVER-SHUTDOWN | Shutdowns the driver and cleans up any allocated resources |
You can check the dbi driver implementation for some example code.
Additional methods can also be overriden, if needed. For example if
you need to have a different representation for the pending migrations
you can override the MIGRATUM:DISPLAY-PENDING
method.
Tests
Tests are provided as part of the cl-migratum.test
system.
In order to run the tests you can execute.
make test
Or you can run the tests in a Docker container instead.
Contributing
cl-migratum
is hosted on
Github. Please contribute by
reporting issues, suggesting features or by sending patches using pull
requests.
Authors
- Marin Atanasov Nikolov (dnaeon@gmail.com)
License
This project is Open Source and licensed under the BSD License.