org.qbroker.node

Class DispatchNode

java.lang.Object

org.qbroker.node.Node

org.qbroker.node.DispatchNode

All Implemented Interfaces:

MessageNode

public class DispatchNode
extends Node

DispatchNode dispatches JMS messages to various destinations according to their content, and preconfigured rulesets. DispatchNode contains one or more outlinks as the destinations. Those outlinks are grouped exclusively according to their group names. Within each group, all the oulinks are equivalent and backing up with each other in case of failure or high load.

DispatchNode uses the predefined rulesets to dispatch incoming messages. These rulesets categorize messages into non-overlapping groups. Therefore, each rule defines a unique message group. The ruleset also specifies the association between the message group and the outlinks. For those messages falling off all defined rulesets, DispatchNode always creates an extra ruleset, nohit, to handle them. By default, nohit ruleset always uses the last outlink unless there is one defined explicitly.

Currently, DispatchNode supports only four types of dynamic switchings: roundrobin, weighted, preferred and sticky. All the switchings are based on the same outlink groups. DispatchNode assumes all the destinations are equivalent and mutually replaceable within the same group. Therefore, there is no fixed association between a ruleset and the outlinks in the same group. For the type of roundrobin, DispatchNode picks up next available outlink in the group for each incoming message roundrobinly. For the type of weighted, DispatchNode looks for the outlink with lowest load in the group for each incoming message. For the type of preferred, the association between the ruleset and the outlinks in the group changes only if there is a failover due to either the load or the availability of the destinations. For the type of sticky, the association between the rulesets and the outlinks is determined by the hash value of the key that is retrieved from the incoming message. If the outlink has a high load or it is not available, sticky messages will be routed to its redirect outlink. For nohit ruleset, the switching type is always preferred.

In case of a high load or a failure from the report on a given outlink, its status will be set to standby mode for load balance and high availability. Meanwhile, DispatchNode will failover all stuck messages to other available outlinks within the group and updates the outlink associations of the rulesets. When the outlink becomes available again, it will failback those outstanding messages to their oringial outlink and resumes the original outlink associations. Dynamic load balance, failover and failback are supported via the sessions and monitor reports. If SessionTimeout is non-zero, please make sure all outlinks having their reports defined. Otherwise, SessionTimeout will be reset to zero to prevent outlinks from being stuck forever. On the other hand, if SessionTimeout is set to zero, it will only do static switching and load balancing. DispatchNode supports static reports with a non-zero SessionTimeout. In this case, the static report must contain ReportType with the value of "static" in lower case.

Threshold contains 3 values for low, medium and high load. The load for each outlink is supposed to be updated by reporters. DispatchNode checks the load for each outlink every heartbeat and controls the pace of the dispatch process. If the load is between low and medium, DispatchNode will skip the outlink every other time to slow down its pace. Meanwhile, it also monitors the session count of dispatched messages so that the total number of dispatched messages plus the load of the destination will not exceed the value of high load within each session. If the load is above medium, the outlink will be marked as standby mode. In the meantime, all the messages in the outlink will be migrated to another outlink with lower load in the group.

In order for DispatchNode to check the report for each outlink, ReportName has to be defined in each OutLink. DispatchNode looks up the report via the report name every heartbeat. First, it checks the timestamp of the report. If the report is newly updated, it will check the status of the report. If the status is 0 (Normal), the node will query the current depth for the destination with the key of CurrentDepth. If it is defined, the number will be treated as the current depth. It will be used for flow control and load balance. Otherwise, it will be assumed to be zero. In case of the static report, DispatchNode will use the local flow rate for each session. Anyway, the reports can be used to control the load balance and flow rate.

There is no limit on the number of outlinks. All the outlinks will take part in the load balance process.

Author:

yannanlu@yahoo.com

Field Summary

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
DispatchNode(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()
int	getMetaData(int type, int id, long[] data) overwrites the method of parent due to the mask stored in OUT_STATUS
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.
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	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, getName, getNumberOfOutLinks, getNumberOfRules, getOperation, getOutLinkBoundary, getRuleName, getStatus, getXAMode, getXAMode, internalXQSupported, list, listPendings, passthru, refreshRule, removeRule, renameRule, replaceRule, resetMetaData, 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

Constructor Detail

DispatchNode

public DispatchNode(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

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

getMetaData

public int getMetaData(int type,
                       int id,
                       long[] data)

overwrites the method of parent due to the mask stored in OUT_STATUS

Specified by:

getMetaData in interface MessageNode

Overrides:

getMetaData 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