public class ThrottlingFilter extends Object implements Filter
For servers where there is 1 application with standardized resource restrictions, then this affect can be easily
controlled by limiting the size of the server thread pool
, however
where there are multiple applications, or a single application has different resource requirements for different
URLs, then this filter can assist in managing the number of requests being services at any point in time.
The filter has 3 configurable values, which may be set as init parameters:
maximum
determines the maxmimum number of requests that may be on the filter chain at any point in time.
(See below for a more detailed explanation)block
determines how long (in milliseconds) a request will be queued before it is rejected.
Set this to -1 to block indefinately.queue
determines how many requests can be queued simultaneously - any additional requests will be rejected.
Set this to 0 to turn off queueing.<filter><filter-name>throttle1</filter-name> <filter-class>org.adjective.spiral.filter.ThrottlingFilter</filter-class> <filter><filter-name>throttle2</filter-name> <filter-class>org.adjective.spiral.filter.ThrottlingFilter</filter-class>creates 2 separate filters with individual request counts.
Queueing: When the number of active requests exceed the maximum
requests will be queued. This queue regulates
the flow of connections. Once the number of requests on the queue reached the queue
threshold, then any new requests
will be rejected. Requests are queued for a maximum of block
milliseconds - is no capacity is made available in this
time then the request will be rejected. The oldest pending request is removed from the queue and processed as soon as the number
of pending requests falls below the maximum
value (i.e. when a request is completed)
Rejection: Requests are rejected when the number of requests in progress has reached maximum and either the queue
is full; or a request has been queued for more than block
milliseconds. The rejection is performed by calling the
method rejectRequest(javax.servlet.http.HttpServletRequest, javax.servlet.http.HttpServletResponse)
. By default this method sends the HTTP status code 503
,
but this may be over-ridden in derived classes.
This filter works best with the org.mortbay.jetty.nio.SelectChannelConnector
, as org.mortbay.jetty.RetryRequest
based
Continuation
s can be used to free the thread and other resources associated with the queued requests.
Constructor and Description |
---|
ThrottlingFilter() |
Modifier and Type | Method and Description |
---|---|
void |
destroy() |
void |
doFilter(HttpServletRequest request,
HttpServletResponse response,
FilterChain chain) |
void |
doFilter(ServletRequest request,
ServletResponse response,
FilterChain chain) |
void |
init(FilterConfig filterConfig) |
protected void |
rejectRequest(HttpServletRequest request,
HttpServletResponse response) |
public void init(FilterConfig filterConfig) throws ServletException
init
in interface Filter
ServletException
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException
doFilter
in interface Filter
IOException
ServletException
public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) throws IOException, ServletException
IOException
ServletException
protected void rejectRequest(HttpServletRequest request, HttpServletResponse response) throws IOException
IOException
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