Plack is a

Perl Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offic ...

web application programming framework inspired by

Rack Rack or racks may refer to: Storage and installation * Amp rack, short for amplifier rack, a piece of furniture in which amplifiers are mounted * Bicycle rack, a frame for storing bicycles when not in use * Bustle rack, a type of storage bin ...

for

Ruby A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called ...

and

WSGI The Web Server Gateway Interface (WSGI, pronounced ''whiskey'' or ) is a simple calling convention for web servers to forward requests to web applications or frameworks written in the Python programming language. The current version of WSGI, ...

for Python, and it is the project behind the PSGI specification used by other frameworks such as

Catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

and

Dancer Dance is a performing art form consisting of sequences of movement, either improvised or purposefully selected. This movement has aesthetic and often symbolic value. Dance can be categorized and described by its choreography, by its repertoire ...

. Plack allows for testing of Perl web applications without a live web server. Plackup is a

command line utility A console application is a computer program designed to be used via a text-only computer interface, such as a text terminal, the command-line interface of some operating systems (Unix, DOS, etc.) or the text-based interface included with most gr ...

to run PSGI applications from the command line.

PSGI

PSGI or Perl Web Server Gateway Interface is an interface between

web server A web server is computer software and underlying hardware that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, commonly a web browser or web crawler, initia ...

s and

web application A web application (or web app) is application software that is accessed using a web browser. Web applications are delivered on the World Wide Web to users with an active network connection. History In earlier computing models like client-serv ...

s and

frameworks A framework is a generic term commonly referring to an essential supporting structure which other things are built on top of. Framework may refer to: Computing * Application framework, used to implement the structure of an application for an op ...

written in the

programming language that allows writing portable applications that can be run as standalone servers or using CGI,

FastCGI FastCGI is a binary protocol for interfacing interactive programs with a web server. It is a variation on the earlier Common Gateway Interface (CGI). FastCGI's main aim is to reduce the overhead related to interfacing between web server and CGI ...

, mod_perl, et al. It is inspired by the

Web Server Gateway Interface The Web Server Gateway Interface (WSGI, pronounced ''whiskey'' or ) is a simple calling convention for web servers to forward requests to web applications or frameworks written in the Python programming language. The current version of WSGI, ...

for Python,

for

and JSGI for

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...

. A PSGI application is a Perl

subroutine In computer programming, a function or subroutine is a sequence of program instructions that performs a specific task, packaged as a unit. This unit can then be used in programs wherever that particular task should be performed. Functions may ...

that accepts arguments as a single

hash Hash, hashes, hash mark, or hashing may refer to: Substances * Hash (food), a coarse mixture of ingredients * Hash, a nickname for hashish, a cannabis product Hash mark *Hash mark (sports), a marking on hockey rinks and gridiron football fiel ...

reference and returns a reference to an array of three elements: an

HTTP status code This is a list of Hypertext Transfer Protocol (HTTP) response status codes. Status codes are issued by a server in response to a client's request made to the server. It includes codes from IETF Request for Comments (RFCs), other specification ...

, a reference to an array of HTTP headers and a reference to an array of HTTP body lines (usually a generated

HTML The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaS ...

document) or a

filehandle In Unix and Unix-like computer operating systems, a file descriptor (FD, less frequently fildes) is a process-unique identifier ( handle) for a file or other input/output resource, such as a pipe or network socket. File descriptors typicall ...

-like

object Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Object (abstract), an object which does not exist at any particular time or place ** Physical object, an identifiable collection of matter * Goal, an ...

Supported backends

Plack::Handler modules on CPAN
/ref> Plack supports the following server backends: * CGI *

SCGI The Simple Common Gateway Interface (SCGI) is a protocol for applications to interface with HTTP servers, as an alternative to the CGI protocol. It is similar to FastCGI but is designed to be easier to parse. Unlike CGI, it permits a long-running ...

* mod_perl under

Apache The Apache () are a group of culturally related Native American tribes in the Southwestern United States, which include the Chiricahua, Jicarilla, Lipan, Mescalero, Mimbreño, Ndendahe (Bedonkohe or Mogollon and Nednhi or Carrizaleño a ...

1.3 and 2.0
Standalone
HTTP server included in Plack
HTTP::Server::Simple

Corona

Starman

Twiggy

AnyEvent::HTTPD

AnyEvent::ReverseHTTP

Examples

Using the default standalone HTTP server: $ plackup app.psgi HTTP::Server::PSGI: Accepting connections at http://0:5000/ Running as a FastCGI daemon listening on a Unix socket, ready to be used by any

Web server A web server is computer software and underlying hardware that accepts requests via HTTP (the network protocol created to distribute web content) or its secure variant HTTPS. A user agent, commonly a web browser or web crawler, initia ...

with FastCGI support: $ plackup -s FCGI -listen /tmp/fcgi.sock app.psgi FastCGI: manager (pid 3336): initialized FastCGI: manager (pid 3336): server (pid 3337) started FastCGI: server (pid 3337): initialized A working Hello world application run as a one-liner: $ plackup -e 'sub ' HTTP::Server::PSGI: Accepting connections at http://0:5000/ The command above starts an HTTP server listening on

port A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as H ...

5000 of every local interface (

IP address An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...

) and returns this 200 OK response to every HTTP request: HTTP/1.0 200 OK Date: Fri, 19 Mar 2010 23:34:10 GMT Server: HTTP::Server::PSGI Content-Type: text/plain Content-Length: 13 Hello, world!

References

External links

PSGI and Plack website

Plack documentation

plackup manual
{{Use dmy dates, date=May 2019 Perl software