fixes #27 update doc for rate limiting

docs/content/middleware/index.md

@@ -59,4 +59,8 @@ Sharing (CORS) handler supports single page applications from another domain to
 A full request/response log handler to dump everything regarding to request and response 
 into log file for developers. 
 
+* [limit](https://networknt.github.io/light-java/middleware/limit/) - 
+A rate limiting handler to limit number of concurrent requests on the server.
+Once the limit is reached, subsequent requests will be queued for later execution. The
+size of the queue is configurable. 
 

docs/content/middleware/limit.md

@@ -0,0 +1,67 @@
+---
+date: 2017-02-17T14:10:28-05:00
+title: Rate Limiting
+---
+
+Although our framework can handle potential millions requests per second, for 
+some public facing APIs, it might be a good idea to enable this handler to 
+limit the concurrent request to certain level in order to avoid DDOS attacks.
+
+As this handler will impact the overall performance a little bit, it is not
+configured as default in the swagger-codegen. You must manually enable it
+in your API with the following steps.
+
+## Dependency
+
+In order to use this handler, the following dependency need to be added to
+pom.xml in your project.
+
+```
+            <dependency>
+                <groupId>com.networknt</groupId>
+                <artifactId>limit</artifactId>
+                <version>${version.light-java}</version>
+            </dependency>
+```
+
+## Service
+
+As this middleware is not plugged in by default, we need to add it into
+com.networknt.handler.MiddlewareHandler in src/main/resources/META-INF/services
+folder. As this rate limiting handler needs to be failed fast, it need to be
+put right after ExceptionHandler and MetricsHandler. The reason it is after
+MetricsHandler is to capture 513 error code in InfluxDB and Grafana for
+monitoring on production.
+
+```
+#Traceability Put traceabilityId into response header from request header if it exists
+com.networknt.traceability.TraceabilityHandler
+#Rate Limiting
+com.networknt.limit.LimitHandler
+#Metrics In order to calculate response time accurately, this needs to be the second.
+com.networknt.metrics.MetricsHandler
+#Exception Global exception handler that needs to be called first.
+com.networknt.exception.ExceptionHandler
+
+```
+
+## Config
+
+Here is the configuration file for rate limiting.
+
+```
+{
+  "description": "Rate Limit Handler",
+  "enabled": false,
+  "concurrentRequest": 1000,
+  "queueSize": -1
+}
+
+```
+
+- enabled true to enable it and false to disable it.
+- concurrentRequest number of concurrent request to be limited.
+- queueSize -1 unlimited queue size which might use a lot of memory. > 1 integer will limit the requests to be queued and once queue is full, 513 will be returned for new requests. 
+
+
+