Last updated 31st March 2021
Web PaaS supports building and deploying applications written in Lisp using Common Lisp (the SBCL version) with ASDF and Quick Lisp support. They are compiled during the Build phase, and support both committed dependencies and download-on-demand.
To specify a Lisp container, use the
type property in your
Web PaaS is making assumptions about your application to provide a more streamlined experience. These assumptions are the following:
.asdfile is named like your system name. E.g.
(defsystem example ...).
Web PaaS will then run
(asdf:make :example) on your system to build a binary.
If you don't want these assumptions, you can disable this behavior by specifying in your
build: flavor: none
The recommended way to handle Lisp dependencies on Web PaaS is using ASDF. Commit a
.asd file in your repository and the system will automatically download the dependencies using QuickLisp.
If you wish to change the distributions that QuickLisp is using, you can specify those as follows, specifying a distribution name, its URL and, an optional version:
runtime: quicklisp: <distribution name>: url: "..." version: "..."
runtime: quicklisp: quicklisp: url: 'http://beta.quicklisp.org/dist/quicklisp.txt' version: '2019-07-11'
Web PaaS variables
Web PaaS exposes relationships and other configuration as environment variables. Most notably, it allows a program to determine at runtime what HTTP port it should listen on and what the credentials are to access other services.
To get the
PORT environment variable (the port on which your web application is supposed to listen) you would:
(parse-integer (uiop:getenv "PORT"))
Building and running the application
example.asd are present in your repository, the application will be automatically built on push. You can then start it from the
web.commands.start directive. Note that the start command must run in the foreground. Should the program terminate for any reason it will be automatically restarted. In the example below we sleep for a very, very long time. You could also choose to join the thread of your web server, or use other methods to make sure the program does not terminate.
The following basic
.platform.app.yaml file is sufficient to run most Lisp applications.
name: app type: lisp:1.5 web: commands: start: ./example locations: /: allow: false passthru: true disk: 512
Note that there will still be a proxy server in front of your application. If desired, certain paths may be served directly by our router without hitting your application (for static files, primarily) or you may route all requests to the Lisp application unconditionally, as in the example above.
The services configuration is available in the environment variable
To parse them, add the dependencies to your
:depends-on (:jsown :babel :s-base64)
The following is an example of accessing a PostgreSQL instance:
(defun relationships () (jsown:parse (babel:octets-to-string (with-input-from-string (in (uiop:getenv "PLATFORM_RELATIONSHIPS")) (s-base64:decode-base64-bytes in)))))
Given a relationship defined in
relationships: pg: postgresql:postgresql
The following would access that relationship, and provide your Lisp program the credentials to connect to a PostgreSQL instance. Add this to your
Then in your program you could access the PostgreSQL instance as follows:
(defvar *pg-spec* nil) (defun setup-postgresql () (let* ((pg-relationship (first (jsown:val (relationships) "pg"))) (database (jsown:val pg-relationship "path")) (username (jsown:val pg-relationship "username")) (password (jsown:val pg-relationship "password")) (host (jsown:val pg-relationship "host"))) (setf *pg-spec* (list database username password host))) (postmodern:with-connection *pg-spec* (unless (member "example_table" (postmodern:list-tables t) :test #'string=) (postmodern:execute "create table example_table ( a_field TEXT NOT NULL UNIQUE, another_field TEXT NOT NULL UNIQUE "))))
Web PaaS offers a project template for Lisp applications using the structure described above. It can be used as a starting point or reference for building your own website or web application.
The following is a simple example of a Hunchentoot based web application (you can find the corresponding
.asd and Web PaaS
.yaml files in the linked Github repository):
(defpackage #:example (:use :hunchentoot :cl-who :cl) (:export main)) (in-package #:example) (define-easy-handler (greet :uri "/hello") (name) (../../(with-html-output-to-string (s) (htm (:body (:h1 "hello, " (str name)))))) (defun main () (let ((acceptor (make-instance 'easy-acceptor :port (parse-integer (uiop:getenv "PORT"))))) (start acceptor) (sleep most-positive-fixnum)))
Notice how we get the
PORT from the environment, and how we sleep at the end, as
(start acceptor) will immediately yield and Web PaaS requires applications to run in the foreground.
This template provides the most basic configuration for running a Lisp Huchentoot web server for Web PaaS. It can be used to build a very rudimentary application but is intended primarily as a documentation reference. It is meant to be a starting point and can be modified to fit your own needs.
This template builds a simple Lisp Hunchentoot web server for Web PaaS. It includes a minimalist application for demonstration, but you are free to alter it as needed.
Hunchentoot is a web server written in Common Lisp and at the same time a toolkit for building dynamic websites.
- Lisp 1.5
- Automatic TLS certificates
View the repository on GitHub.
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