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An Apache HTTPD module for speaking to redis via HTTP

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README.md

mod_redis

This Apache module uses a rule-based engine (based on regular expression parser) to map URLs to REDIS commands on the fly. It supports an unlimited number of rules and can match on the full URL and the request method (GET, POST, PUT or DELETE) to provide a very flexible option for defining a RESTful interface to REDIS.

By default the module returns an XML representation of the resulting REDIS response. For example configuring a RedisAlias to support the PING command (RedisAlias ^ping$ "PING"), the response would be:

<?xml version="1.0" encoding="UTF-8"?>
<response>
<status>PONG</status></response>

This behavior can be altered by appending .json to the url, for example:

{ "status" : "PONG" }

Alternatively, appending .jsonp and adding a query parameter ‘callback’ respond with:

callback({ "status" : "PONG" });

Installation

  1. Download Hiredis, a minimalistic C client library for the Redis database

    curl https://github.com/antirez/hiredis/zipball/master -L -o hiredis.zip

  2. Unzip the downloaded file

    unzip hiredis.zip

  3. Extract the contents of the zip file (hiredis.zip) and define the base directory. In the example below, the last part of the embedded directory has been obscured so please remember to use the directory created when unzipping the file

    HIREDIS_HOME=pwd/antirez-hiredis-XXXXXXX

  4. Compile the hiredis library

    pushd $HIREDIS_HOME ; make ; popd

  5. Compile mod_redis

    apxs -c -I $HIREDIS_HOME $HIREDIS_HOME/libhiredis.a mod_redis.c

  6. Install the module into the currently installed Apache instance

    sudo apxs -i -a mod_redis.la

  7. Run the tests. This will create a custom httpd.conf and start a new Apache instance on port 8081 for the purposes of testing. Temp files for this test instance can be found in the ./testing directory. By default, the test script will attempt to connect to local REDIS server on the standard REDIS port (6379), this can be modified with command line parameters

    ./test.sh [RedisIPAddress] [RedisPort]

RedisAlias Directive

Description: Defines a rule to match a URL to a REDIS command
Syntax: RedisAlias TestString RedisCommandPattern [Method]

Rules are matched based on the order in which they are defined. Depending on the expression, care should be taken not to define less specific expressions before more specific ones. Consider a configuraton defining two directives in the following order, in the following example the second expression would never be matched because the first expression would evaluate successfully first.

RedisAlias ^([^/]+)$ "GET $1"
RedisAlias ^ping$    "PONG"

TestString

A regular expression defining the elements in the URL to match. This excludes the protocol, hostname, portnumber, module location and query string. Consider an local installation of Apache with mod_redis handler configured for the location /redis/*, in the following contrived example, the element of the URL that can be matched against is in square brackets

http://localhost/redis/[Matchable].json?callback=alert

Round brackets can used used to create a backreference for part of the matching string which can be later referenced in the RedisCommandPattern. This is essential to extract elements of the URL for use in the REDIS command itself.

^([^/]+)/count$

This example matches any characters appearing before the first matching forward slash, followed by a forward slash, the word count and then the end of the string. The round brackets create a backreference, capturing the characters before the forward slash so that it can be used in the RedisCommandPattern, i.e. "ZCARD $1". Using this example the URL <host>/<handler>/myset/count would result in the REDIS command ZCARD myset.

RedisCommandsPattern

The pattern used to create a REDIS command to be executed. The format of this command must confirm to the REDIS command syntax. Additionally the text can contain the following:

  • TestString backreferences: These backreferences take the form $N (0<=N<=9) which provide to the grouped parts (in parentheses) of the TestString.

  • Request variables: These are variables from the current request being processed

    %{DATA} The body content of a PUT or POST request
    ${FORM:field} The value of a form field taken from PUT or POST request. The request must have include the Content-Type header as application/x-www-form-urlencoded
    ${QSA:field} The value of a query string argument taken from the request URL

Method

The HTTP method of the given request, GET, PUT, POST or DELETE. When a method is not specified, GET is assumed as the default. The Method parameter can be used to increase the specificity of the directive. In the following example, the TestString is identical, however the Method determines which directive would successfully match.

RedisAlias ^([^/]+)$ "GET $1"
RedisAlias ^([^/]+)$ "SET $1 %{DATA}" PUT
RedisAlias ^([^/]+)$ "DEL $1" DELETE

Examples

To define alias to add, remove and count the number of entries in a sorted set, you would add the following directives:

RedisAlias ^([^/]+)/([^/]+)$ "ZADD $1 %{DATA} $2" PUT  
RedisAlias ^([^/]+)/([^/]+)$ "ZREM $1 $2" DELETE  
RedisAlias ^([^/]+)/count$ "ZCARD $1"  

To define an alias to retrieve a list of members from a sorted set, you could add the following directive:

RedisAlias ^([^/]+)/range/([^/]+)/([^/]+)$ "ZRANGE $1 $2 $3 WITHSCORES"

To define an alias to create a new member to a sorted set from a POSTed form you could add the following directive:

RedisAlias ^zadd$ "ZADD ${FORM:key} ${FORM:score} ${FORM:member}" POST

To define an alias to determine the rank of a key in a sorted set based on a query parameter, you could add the following directive:

RedisAlias ^([^/]+)/rank$ "ZRANK $1 ${QSA:key}"

RedisIPAddress Directive

Description: Defines the IP address of the REDIS instance to connect to
Syntax: RedisIPAddress IPAddress

The default IPAddress is 127.0.0.1

RedisPort Directive

Description: Defines the port number of the REDIS instance to connect to
Syntax: RedisPort PortNumber

The default PortNumber is 6379

Example httpd.conf

<Location ~ /redis/*>
SetHandler redis
</Location>

<IfModule redis_module>
RedisIPAddress 127.0.0.1
RedisPort 6379
RedisAlias ^ping$ "PING"
</IfModule>
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