Ciste ("she steh")
Ciste is a Lojban word meaning:
x1 (mass) is a system interrelated by structure x2 among components x3 (set) displaying x4 (ka).
Ciste attempts to provide a structure to Clojure applications.
Ciste is a complete framework for building modular Clojure applications and servers. Ciste contains an app runner, a service initializer, an environment-aware configuration system, an extensible request routing framework, a MVC-like page building mechanism, a dynamic record transformation tool for displaying your resources in multiple response formats, an asynchronous trigger system, support for running and managing independent worker threads, and command system for controlling aspects of the system from remote clients.
Add the following to your project.clj dependencies
Running a Ciste Application
Ciste comes with a -main function specially designed to bootstrap your application and start any required services. Simply add the following to your project.clj file.
There are 2 files that must be present in order to properly configure your Ciste application: ciste.clj and config.clj. These files should be located at the root of your project.
ciste.clj (known as the site config) contains only configuration needed during the initial startup of the application. This file should contain only a properly formatted Clojure hash-map. The site config should contain configuration options that are strictly static for every environment.
There are currently 3 properties defined, but you can add your own.
:environment - This should contain a keyword specifying the default environment of the application. This is the environment that will be run if not otherwise overridden.
:modules - A list of modules to load
:services - A list of services to run
config.clj is also a file containing a Clojure hash-map. Each key in the map specifies a different environment, and the values are another hash containing all the config for the application.
Modules and Services
When Ciste is starting the application, is looks for :modules and :services keys in both the config file and the site config. Each of these keys should have a vector of strings. The loader service will require each namespace.
Modules allow you to create namespaces that change the state of the system in some way, but do not need to be required directly by the rest of your namespaces. Ciste makes use of several different multimethods and protocols. Implementations can be stored in a module and easily included into an application.
Services are similar to Modules, except their start and stop functions will be invoked at the proper point in the application's lifecycle.
Actions for the core API of your application. Any major state change should happen through an Action. Anything that you might want to log (if action logging is enabled), or anything you might want callbacks should be run for should be an Action. In the role of Actions with respect to routing, a traditional function may be substituted.
Action should only have a single arity.
Ciste's routing system allows any request map (usually a ring request, but any map works) to be matched against a sequence of predicates and match info maps and return a response map that can be invoked to generate a full response.
The router will thread the request through each of the predicates applying them against the match info providing parameters for the predicates. The first route to return a non-nil response will be invoked.
The predicates and predicate list can be adapted to any type of request.
Each instance of a router should define a serialization type with with-serialization (specified as a keyword). The serialization type identifies the type of request coming in (used by filters) and to determine a final transformation of returned responses.
When a route is selected, it is first passed to the Action's filter. The filter is a serialization-specific wrapper around the action. The filter is where the request should be parsed, normalized, and passed to the action returning its response.
Ciste is designed to make it easy to serve resources in multiple format. Each router should specify a default format for the interface as a keyword (eg. :html) as well as allow it to be set by route predicates. Formats are used by Views and Sections as well as the formatter as the penultimate step in request processing.
Formatters allow you to deal in easy to manipulate data structures throughout your request, deferring the final transformation till the very end. A formatter might convert a hiccup structure into html or convert a clojure map into a json string or whatever needs to be done for responses of that type.
After the Filter has processed the action and returned the result, it is passed to a view for the given Action and Format. The View returns a map containing parameters for the generation of the response. The :body key of the response should contain the data that should be inserted into the main part of the template and converted by the formatter, but may also contain any other key needed to control the eventual output.
If the View contains the pair :template false, templating will be skipped for this response. This is useful for simple responses, such as redirects or serialization-specific error responses.
Ciste is designed to work best with Records or any type of object where dispatch can function off the class name. There are few functions that directly support this at the moment. An abstraction around using records against various backends is in the works.
Sections allow records to be formatted properly according to their context. Calling a section function with a Record will apply the appropriate multimethod for the currently bound Serialization and Format. This allows you to easily do things like display a sequence of records, display a single record, get the context-appropriate title for that record or link to a record using a common language without needing to define distinct names for each of the many formats you support.
Unless templating has been disabled by the view, a template method will be applied to the response for the given Serialization type. A Template will generally use many different keys from the view to build the page, but will primarily read from the :body key
Triggers and the Action channel
Actions allow triggers to be added that will be run in a different thread. Triggers allow callbacks to be performed in response to an Action.
In addition to Triggers, an event is emitted to a lamina channel. Workers can monitor this channel to perform other actions.
Note: The trigger system is set to be changed soon. In the future, triggers will be run as part of a Worker set to read from the action channel. Use at your own risk.
Workers are functions that are identified by a keyword name. Workers can be started and told to stop. (Workers can check if they've been asked to stop.) The lists of available and running workers can be queried and manipulated. Workers can update a per-worker counter allowing metrics (number of packets processed) to be displayed.
Note: This section is in need of work and will most likely be re-written to be simply a wrapper over a more robust thread manager.
Commands are a special route map and serialization type. Commands allow simple string names to be mapped to actions. Commands exist to work with services that provide an interface to the command system.
The goal of Ciste is to make each part as optional as possible allowing parts to be used without incurring the cost of the whole system.
In addition, there are many supplemental libraries that provide new services, custom formatters, and other tools that work with Ciste. The intention is that you should be able to build up a base application by combining together whatever pieces you need.
While Ciste has been around for quite some time, I have not been able to devote as much time to it as I would like. Ciste has formed the basis of a few highly complex applications, but hasn't been extensively tested by others. If you find Ciste useful to your needs, please let me know so I can take care to limit breaking changes.
In the wild
The prime example of Ciste in action is my OStatus server located at https://github.com/duck1123/jiksnu
Jiksnu has been the primary driver of new features in Ciste and is the best example of a fully functioning Ciste application.
Copyright (C) 2011 KRONK Ltd.
Distributed under the Eclipse Public License, the same as Clojure.