Top Description Fields Constructors Methods
org.apache.catalina.valves

public Class LoadBalancerDrainingValve

extends ValveBase
Class Inheritance
Imports
java.io.IOException, jakarta.servlet.ServletException, .SessionCookieConfig, jakarta.servlet.http.Cookie, .HttpServletResponse, org.apache.catalina.connector.Request, .Response, org.apache.catalina.util.SessionConfig

A Valve to detect situations where a load-balanced node receiving a request has been deactivated by the load balancer (JK_LB_ACTIVATION=DIS) and the incoming request has no valid session.

In these cases, the user's session cookie should be removed if it exists, any ";jsessionid" parameter should be removed from the request URI, and the client should be redirected to the same URI. This will cause the load-balanced to re-balance the client to another server.

All this work is required because when the activation state of a node is DISABLED, the load-balancer will still send requests to the node if they appear to have a session on that node. Since mod_jk doesn't actually know whether the session id is valid, it will send the request blindly to the disabled node, which makes it take much longer to drain the node than strictly necessary.

For testing purposes, a special cookie can be configured and used by a client to ignore the normal behavior of this Valve and allow a client to get a new session on a DISABLED node. See setIgnoreCookieName and setIgnoreCookieValue to configure those values.

This Valve should be installed earlier in the Valve pipeline than any authentication valves, as the redirection should take place before an authentication valve would save a request to a protected resource.

See Also
Load balancer documentation

Field Summary

Modifier and TypeField and Description
private String
_ignoreCookieName

The name of the cookie which can be set to ignore the "draining" action of this Filter.

private String
_ignoreCookieValue

The value of the cookie which can be set to ignore the "draining" action of this Filter.

private int
_redirectStatusCode

The HTTP response code that will be used to redirect the request back to the load-balancer for re-balancing.

public static final String
ATTRIBUTE_KEY_JK_LB_ACTIVATION

The request attribute key where the load-balancer's activation state can be found.

Inherited from org.apache.catalina.valves.ValveBase:
asyncSupportedcontainercontainerLognextsm

Constructor Summary

AccessConstructor and Description
public
LoadBalancerDrainingValve()

Method Summary

Modifier and TypeMethod and Description
public String

Returns:

The cookie name used to ignore normal processing rules.
getIgnoreCookieName()

Gets the name of the cookie that can be used to override the re-balancing behavior of this Valve when the current node is in the DISABLED activation state.

public String

Returns:

The cookie value used to ignore normal processing rules.
getIgnoreCookieValue()

Gets the expected value of the cookie that can be used to override the re-balancing behavior of this Valve when the current node is in the DISABLED activation state.

public void
invoke(Request
The servlet request to be processed
request, Response
The servlet response to be created
response)

Implements org.apache.catalina.Valve.invoke.

Perform request processing as required by this Valve.

public void
setIgnoreCookieName(String
The cookie name to use to ignore normal processing rules.
cookieName)

Sets the name of the cookie that can be used to override the re-balancing behavior of this Valve when the current node is in the DISABLED activation state.

public void
setIgnoreCookieValue(String
The cookie value to use to ignore normal processing rules.
cookieValue)

Sets the expected value of the cookie that can be used to override the re-balancing behavior of this Valve when the current node is in the DISABLED activation state.

public void
setRedirectStatusCode(int
The code to use for the redirect
code)

Sets the HTTP response code that will be used to redirect the request back to the load-balancer for re-balancing.

Inherited from org.apache.catalina.valves.ValveBase:
backgroundProcessgetContainergetDomainInternalgetNextgetObjectNameKeyPropertiesinitInternalisAsyncSupportedsetAsyncSupportedsetContainersetNextstartInternalstopInternaltoString

Field Detail

_ignoreCookieNameback to summary
private String _ignoreCookieName

The name of the cookie which can be set to ignore the "draining" action of this Filter. This will allow a client to contact the server without being re-balanced to another server. The expected cookie value can be set in the _ignoreCookieValue. The cookie name and value must match to avoid being re-balanced.

_ignoreCookieValueback to summary
private String _ignoreCookieValue

The value of the cookie which can be set to ignore the "draining" action of this Filter. This will allow a client to contact the server without being re-balanced to another server. The expected cookie name can be set in the _ignoreCookieName. The cookie name and value must match to avoid being re-balanced.

_redirectStatusCodeback to summary
private int _redirectStatusCode

The HTTP response code that will be used to redirect the request back to the load-balancer for re-balancing. Defaults to 307 (TEMPORARY_REDIRECT). HTTP status code 305 (USE_PROXY) might be an option, here. too.

ATTRIBUTE_KEY_JK_LB_ACTIVATIONback to summary
public static final String ATTRIBUTE_KEY_JK_LB_ACTIVATION

The request attribute key where the load-balancer's activation state can be found.

Constructor Detail

LoadBalancerDrainingValveback to summary
public LoadBalancerDrainingValve()

Method Detail

getIgnoreCookieNameback to summary
public String getIgnoreCookieName()

Gets the name of the cookie that can be used to override the re-balancing behavior of this Valve when the current node is in the DISABLED activation state.

Returns:String

The cookie name used to ignore normal processing rules.

See Also
setIgnoreCookieValue
getIgnoreCookieValueback to summary
public String getIgnoreCookieValue()

Gets the expected value of the cookie that can be used to override the re-balancing behavior of this Valve when the current node is in the DISABLED activation state.

Returns:String

The cookie value used to ignore normal processing rules.

See Also
setIgnoreCookieValue
invokeback to summary
public void invoke(Request request, Response response) throws IOException, ServletException

Implements org.apache.catalina.Valve.invoke.

Doc from org.apache.catalina.Valve.invoke.

Perform request processing as required by this Valve.

An individual Valve MAY perform the following actions, in the specified order:

  • Examine and/or modify the properties of the specified Request and Response.
  • Examine the properties of the specified Request, completely generate the corresponding Response, and return control to the caller.
  • Examine the properties of the specified Request and Response, wrap either or both of these objects to supplement their functionality, and pass them on.
  • If the corresponding Response was not generated (and control was not returned, call the next Valve in the pipeline (if there is one) by executing getNext().invoke().
  • Examine, but not modify, the properties of the resulting Response (which was created by a subsequently invoked Valve or Container).

A Valve MUST NOT do any of the following things:

  • Change request properties that have already been used to direct the flow of processing control for this request (for instance, trying to change the virtual host to which a Request should be sent from a pipeline attached to a Host or Context in the standard implementation).
  • Create a completed Response AND pass this Request and Response on to the next Valve in the pipeline.
  • Consume bytes from the input stream associated with the Request, unless it is completely generating the response, or wrapping the request before passing it on.
  • Modify the HTTP headers included with the Response after the getNext().invoke() method has returned.
  • Perform any actions on the output stream associated with the specified Response after the getNext().invoke() method has returned.
Parameters
request:Request

The servlet request to be processed

response:Response

The servlet response to be created

Annotations
@Override
Exceptions
IOException:
if an input/output error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
ServletException:
if a servlet error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
setIgnoreCookieNameback to summary
public void setIgnoreCookieName(String cookieName)

Sets the name of the cookie that can be used to override the re-balancing behavior of this Valve when the current node is in the DISABLED activation state. There is no default value for this setting: the ability to override the re-balancing behavior of this Valve is disabled by default.

Parameters
cookieName:String

The cookie name to use to ignore normal processing rules.

See Also
getIgnoreCookieValue
setIgnoreCookieValueback to summary
public void setIgnoreCookieValue(String cookieValue)

Sets the expected value of the cookie that can be used to override the re-balancing behavior of this Valve when the current node is in the DISABLED activation state. The "ignore" cookie's value must be exactly equal to this value in order to allow the client to override the re-balancing behavior.

Parameters
cookieValue:String

The cookie value to use to ignore normal processing rules.

See Also
getIgnoreCookieValue
setRedirectStatusCodeback to summary
public void setRedirectStatusCode(int code)

Sets the HTTP response code that will be used to redirect the request back to the load-balancer for re-balancing. Defaults to 307 (TEMPORARY_REDIRECT).

Parameters
code:int

The code to use for the redirect