Concurrent Limit Servlet Filter

Provides concurrent control in a Servlet container like Tomcat. Open Source Java project under Apache License v2.0

Current Development Version is 1.0.0

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DOC

This filter works limiting access for specified URI.

1. Check if the IP has been seen in the last X milliseconds.
2. If not seen, try to acquire access (concurrent) for resource.
3. If any of this checks fail, HTTP code 429 (Too Many Requests) is returned to the client as described in RFC-6585.

Usage Example

<!-- Servlet Filter -->
<!-- WEB-INF/web.xml -->
<filter>
    <filter-name>ConcurrentLimitFilter</filter-name>
    <filter-class>org.javastack.servlet.filters.ConcurrentLimitFilter</filter-class>
    <!-- Example 5 concurrent updates, same IP allowed one time every 5 seconds -->
    <init-param>
        <param-name>/rest/update</param-name>
        <!-- concurrent-limit[:ip-time-limit-millis] -->
        <param-value>5:5000</param-value>
    </init-param>
    <!-- Example one delete per second from same IP -->
    <init-param>
        <param-name>/rest/delete</param-name>
        <param-value>0:1000</param-value>
    </init-param>
    <!-- How many IPs are remembered for each URI, default: 8192 -->
    <init-param>
        <param-name>ipMaxSize</param-name>
        <param-value>4096</param-value>
    </init-param>
</filter>
<filter-mapping>
    <filter-name>ConcurrentLimitFilter</filter-name>
    <url-pattern>/rest/*</url-pattern>
</filter-mapping>

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MAVEN

Add the dependency to your pom.xml:

<dependency>
    <groupId>org.javastack</groupId>
    <artifactId>concurrentlimit-servlet-filter</artifactId>
    <version>1.0.0</version>
</dependency>

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Inspired in mod_ratelimit, this code is Java-minimalistic version.