org.qbroker.node

Class ScreenNode

java.lang.Object

org.qbroker.node.Node

org.qbroker.node.ScreenNode

All Implemented Interfaces:

MessageNode

public class ScreenNode
extends Node

ScreenNode picks up the JMS messages from an input XQ and screens them according to their content and the pre-defined rulesets. It filters them out into four outlinks: done for the messages passing through the screening process, nohit for those messages do not belong to any pre-defined rulesets, failure for the messages failed in the screening process and bypass for the those messages falling out of screen process. Since ScreenNode does not consume any messages, any in-coming messages has to find a way out via one of the four outlinks.

ScreenNode contains a number of pre-defined rulesets. These rulesets categorize messages into non-overlapping groups. Therefore, each ruleset defines a unique message group. The ruleset also defines the screening options for the messages in each group as well as other parameters used in the screening process, such as TimeToLive and XAMode. With different screen options, ScreenNode withholds messages until their sessions time out. Therefore, each group maintains its own cache and the session to withhold messages temporarily. KeyTemplate is used to extract the keys from of the messages. These keys will be used to track the withheld messages in the cache. TimeToLive determines when to expire the session for the cache. Further more, ScreenNode always creates one extra ruleset, nohit. The ruleset of nohit is for all the messages not hitting any of the patterns.

ScreenNode will not consume any messages. But it may remove the withheld messages from the uplink for certain rulesets. If EXTERNAL_XA bit is set on the uplink, those removed messages will be acknowledged as well. Eventually, those removed and withheld messages will continue to propagate downstreams as usual. This feature is controlled by XAMode of the ruleset. If XAMode is not defined in a ruleset, the ruleset will inherit it from the node, which will be 1 by default. If it is set to 0, all the withheld messages for the ruleset will be acknowledged and removed from the uplink. There is a big consequence to disable XA on a ruleset. Please be extremely careful if you wnat to disable XA on any ruleset.

Here are considerations on when to disable XA on a ruleset. First, you may want ScreenNode to withhold more messages than the capacity of the uplink. Second, the source JMS servers may not be able to handle large amount of unacknowledged messages. In these cases, XAMode of certain rulesets may be set to zero explicitly to disable the XA. As you know, most of the JMS vendors implement message acknowledgement via sessions. The acknowledgement by ScreenNode may upset the XA control of the message flow.

ScreenNode also supports the termination rulesets. A terminate ruleset is similar to a screen ruleset. The only difference is that the former has also defined TargetRule that specifies the name of a screen ruleset for caching terminations. Its KeyTemplate is used to generate the screen key so that the withheld message will be flushed to terminate its session. Each message of a termination ruleset will be routed to the outlink of done.
ScreenNode is also able to monitor the load level report of its first outlink if its report is defined. In this case, all cache sessions will be frozen temporarily if the load level is too high. It means ScreenNode will ignore all TTLs and treats all cache sessions without expirations.

You are free to choose any names for the four fixed outlinks. But ScreenNode always assumes the first outlink for done, the second for bypass, the third for failure and the last for nohit. Any two or more outlinks can share the same outlink name. It means these outlinks are sharing the same output channel.

Author:

yannanlu@yahoo.com

Field Summary

Fields

Modifier and Type	Field and Description
static int	OPTION_END
static int	OPTION_FIRST
static int	OPTION_FIRST_LAST
static int	OPTION_FIRST_MAX
static int	OPTION_FIRST_MIN
static int	OPTION_LAST
static int	OPTION_MAX
static int	OPTION_MIN
static int	OPTION_NONE

Fields inherited from class org.qbroker.node.Node

assetList, bufferSize, callbackMethod, capacity, cbw, cells, cfgList, chkptExpiration, debug, DEBUG_COLL, DEBUG_DIFF, DEBUG_FBAK, DEBUG_INIT, DEBUG_PASS, DEBUG_PROP, DEBUG_REPT, DEBUG_UPDT, displayMask, displayPropertyName, linkName, LOAD_HIGH, LOAD_LOW, LOAD_MEDIUM, msgList, name, operation, RESET_ALL, RESET_MAP, RESET_NONE, RESET_SOME, ruleList, status, TYPE_ACTION, TYPE_AGGREGATE, TYPE_BYPASS, TYPE_CACHE, TYPE_COLLECT, TYPE_DELIVER, TYPE_FORMAT, TYPE_JSONPATH, TYPE_JSONT, TYPE_MAPREDUCE, TYPE_NONE, TYPE_PARSER, TYPE_PICKUP, TYPE_PIPE, TYPE_PUBLISH, TYPE_ROUNDROBIN, TYPE_SCREEN, TYPE_SCRIPT, TYPE_SERVICE, TYPE_SORT, TYPE_SPLIT, TYPE_SPREAD, TYPE_WEIGHTED, TYPE_XPATH, TYPE_XSLT, waitTime, xaMode

Fields inherited from interface org.qbroker.node.MessageNode

ASSET_THR, ASSET_URI, ASSET_XQ, META_MAP, META_MSG, META_OUT, META_RULE, META_XQ, MSG_BID, MSG_CID, MSG_OID, MSG_RID, MSG_TID, MSG_TIME, NODE_CLOSED, NODE_DISABLED, NODE_PAUSE, NODE_READY, NODE_RETRYING, NODE_RUNNING, NODE_STANDBY, NODE_STOPPED, OUT_CAPACITY, OUT_COUNT, OUT_DEQ, OUT_EXTRA, OUT_LENGTH, OUT_MODE, OUT_NRULE, OUT_OFFSET, OUT_ORULE, OUT_QDEPTH, OUT_QIPPS, OUT_QSTATUS, OUT_QTIME, OUT_SIZE, OUT_STATUS, OUT_TIME, RULE_COUNT, RULE_DMASK, RULE_EXTRA, RULE_GID, RULE_MODE, RULE_OID, RULE_OPTION, RULE_PEND, RULE_PID, RULE_SIZE, RULE_STATUS, RULE_TIME, RULE_TTL

Constructor Summary

Constructors

Constructor and Description
ScreenNode(java.util.Map props)

Method Summary

Modifier and Type	Method and Description
void	close() It closes all resources and cleans up all list, cache, metadata, etc.
protected void	finalize()
protected java.util.Map<java.lang.String,java.lang.Object>	initRuleset(long tm, java.util.Map ph, long[] ruleInfo) It initializes a new ruleset with the ruleInfo and returns the rule upon success.
java.util.Map<java.lang.String,java.lang.String>	listPendings(XQueue xq, int type) lists all propagating and withheld messages or keys
void	propagate(XQueue in, XQueue[] out) picks up a message from input queue and evaluates its content to decide which output queue to propagate
int	removeRule(java.lang.String key, XQueue in) It removes the rule from the ruleList and returns the rule id upon success.
int	replaceRule(java.lang.String key, java.util.Map ph, XQueue in) It replaces the existing rule of the key and returns its id upon success.
void	resetMetaData(XQueue in, XQueue[] out) It cleans up MetaData for all XQueues and messages.
int	updateParameters(java.util.Map props) It updates the parameters of the node with the given property map.

Methods inherited from class org.qbroker.node.Node

addRule, callback, checkpoint, collectAll, containsRule, containsXQ, feedback, forcethru, getCapacity, getCapacity, getDebugMode, getDisplayMask, getDisplayProperties, getLinkName, getLinkName, getMetaData, getName, getNumberOfOutLinks, getNumberOfRules, getOperation, getOutLinkBoundary, getRuleName, getStatus, getXAMode, getXAMode, internalXQSupported, list, passthru, refreshRule, renameRule, restore, rotateRule, setDebugMode, setDisplayMask, setDisplayProperties, setStatus, show, takeback, takebackEnabled

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

OPTION_NONE

public static final int OPTION_NONE

See Also:

Constant Field Values

OPTION_MIN

public static final int OPTION_MIN

See Also:

Constant Field Values

OPTION_MAX

public static final int OPTION_MAX

See Also:

Constant Field Values

OPTION_FIRST

public static final int OPTION_FIRST

See Also:

Constant Field Values

OPTION_LAST

public static final int OPTION_LAST

See Also:

Constant Field Values

OPTION_FIRST_MIN

public static final int OPTION_FIRST_MIN

See Also:

Constant Field Values

OPTION_FIRST_MAX

public static final int OPTION_FIRST_MAX

See Also:

Constant Field Values

OPTION_FIRST_LAST

public static final int OPTION_FIRST_LAST

See Also:

Constant Field Values

OPTION_END

public static final int OPTION_END

See Also:

Constant Field Values

Constructor Detail

ScreenNode

public ScreenNode(java.util.Map props)

Method Detail

updateParameters

public int updateParameters(java.util.Map props)

Description copied from class: Node

It updates the parameters of the node with the given property map. Upon success, it returns the number of parameters modified. It is not MT-Safe.

Specified by:

updateParameters in interface MessageNode

Overrides:

updateParameters in class Node

initRuleset

protected java.util.Map<java.lang.String,java.lang.Object> initRuleset(long tm,
                                                                       java.util.Map ph,
                                                                       long[] ruleInfo)

It initializes a new ruleset with the ruleInfo and returns the rule upon success. Otherwise, it throws an exception or returns null.

Specified by:

initRuleset in class Node

removeRule

public int removeRule(java.lang.String key,
                      XQueue in)

It removes the rule from the ruleList and returns the rule id upon success. It is not MT-Safe.

Specified by:

removeRule in interface MessageNode

Overrides:

removeRule in class Node

replaceRule

public int replaceRule(java.lang.String key,
                       java.util.Map ph,
                       XQueue in)

It replaces the existing rule of the key and returns its id upon success. It is not MT-Safe.

Specified by:

replaceRule in interface MessageNode

Overrides:

replaceRule in class Node

propagate

public void propagate(XQueue in,
                      XQueue[] out)
               throws javax.jms.JMSException

picks up a message from input queue and evaluates its content to decide which output queue to propagate

Specified by:

propagate in interface MessageNode

Specified by:

propagate in class Node

Throws:

javax.jms.JMSException

resetMetaData

public void resetMetaData(XQueue in,
                          XQueue[] out)

Description copied from class: Node

It cleans up MetaData for all XQueues and messages.

Specified by:

resetMetaData in interface MessageNode

Overrides:

resetMetaData in class Node

listPendings

public java.util.Map<java.lang.String,java.lang.String> listPendings(XQueue xq,
                                                                     int type)

lists all propagating and withheld messages or keys

Specified by:

listPendings in interface MessageNode

Overrides:

listPendings in class Node

close

public void close()

Description copied from class: Node

It closes all resources and cleans up all list, cache, metadata, etc. Once it is closed, it can not be used any more.

Specified by:

close in interface MessageNode

Overrides:

close in class Node

finalize

protected void finalize()

Overrides:

finalize in class Node