org.qbroker.node

Class CollectNode

java.lang.Object

org.qbroker.node.Node

org.qbroker.node.CollectNode

All Implemented Interfaces:

MessageNode

public class CollectNode
extends Node

CollectNode listens to an input XQ for JMS messages and assigns them to various destinations as the requests according to their content and preconfigured rulesets. It then collects the responses for each outstanding requests and routes them to their next destinations. It has two types of outlinks, position-fixed and non-fixed. There are three position-fixed outlinks: done for all completed requests, failure for the messages failed in the collecting process, nohit for those messages not covered by any rulesets. The non-fixed outlinks are called collectibles for responses.

CollectNode also contains a number of predefined rulesets. These rulesets categorize requests into non-overlapping groups. Therefore, each rule defines a unique request group. The ruleset also specifies the the initial outlink for the group. It may also contains a task list that defines the association between each task and its next outlink. Therefore a ruleset is just like a workflow. For those messages falling off all defined rulesets, CollectNode always creates an extra ruleset, nohit, to handle them. All the nohit requests will be routed to nohit outlink.

For each incoming request, CollectNode sends it to its associated worker via the initial outlink. Then CollectNode frequently checks the response for each outstanding requests. The response is supposed to have the return code and the requested content. Once the response is collected, CollectNode proceeds the next task of the proconfigured task list, based on the return code of the response. A task list is a sequence of tasks just like a workflow. Each task contains three outlinks for three different scenarios: success, failure and exception, respectively. It evalues the return code of the previous task and determines which outlink to route the message. In case of success, the message will be routed to the outlink of success before executing the current task. In case of failure or exception, the routing behavior depends on the outlink for the situation. If the outlink is one of the fixed outlinks, the message will be routed to that outlink. As the result, the current task aborts and the workflow terminates. If the outlink is a collectible and it is same as the one for success, CollectNode will just ignore any failure or exception. As the result, it proceeds the current task as if the previous task is a success. Otherwise, CollectNode branches the workflow and jumps to the first leading task of the task list. A leading task of a branch is the task immediately behind any exit task. An exit task is the task with non-collectible outlink on success. In this case, CollectNode will find the first leading task with the same outlink on success for the branch, skips all tasks in between. Therefore a request message will be able to go through a list of outlinks step by step as configured.

As an option, a task can also specify a single data field of the message to be formattable. In order to do that, you need to define a single Template and/or a single TextSubstitution for that field. If the response of the previous task is a success, the message will be formatted before it is put to next outlink for success. If the response is a failure or an exception, the formatter rule will be bypassed. However, a task may define an ErrorCode to overwrite the return code of its response on a failure or an exception scenario. In this case, CollectNode will store the defined ErrorCode into the ReturnCode property of the message before putting it into the outlink for either failure or exception. Since the ruleset itself is the default task, it can also have the data field, the template and the substitution defined. If all tasks have completed without errors, the ReturnCode property of the message will be reset to null before its final exit.

In an MT env, it may get deadlocked due to circular dependencies among the task outlinks. CollectNode implements walk-sweep method to collect messages with circular dependencies. But it may take long time for an outlink to have vacancies. If a new message can not find vacancy in its next task queue, CollectNode will keep retry up to 10 times and then roll the message back to the input XQueue. The message will be dequeued again and the same format rule will be applied once more before to put it to its task queue. Therefore, please make sure the first format rule of a ruleset is stateless. If you have a stateful format rule as the default task, please create a stateless task and add the new task before it.

You are free to choose any names for the three fixed outlinks. But CollectNode always assumes the first outlink for done, the second for failure and the third for nohit. The rest of the outlinks are for workers. It is OK for those three fixed outlinks to share the same name. Please make sure the first fixed outlink has the actual capacity no less than that of the uplink.

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
CollectNode(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 int	feedback(XQueue in, long milliSec) returns the number of done messages removed from in
protected void	finalize()
int	getOutLinkBoundary() returns the BOUNDARY which is the lowest id of outlinks for collectibles so that any outlink with either the same id or a higher id is for collectibles.
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.
protected int	passthru(long currentTime, javax.jms.Message msg, XQueue in, int rid, int oid, int cid, int tid) It passes the message from the input XQueue over to an output XQueue and returns 1 upon success or 0 otherwise.
void	propagate(XQueue in, XQueue[] out) picks up a message from input queue and evaluates its content to decide which output queue to propagate

Methods inherited from class org.qbroker.node.Node

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

Methods inherited from class java.lang.Object

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

Constructor Detail

CollectNode

public CollectNode(java.util.Map props)

Method Detail

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

passthru

protected int passthru(long currentTime,
                       javax.jms.Message msg,
                       XQueue in,
                       int rid,
                       int oid,
                       int cid,
                       int tid)

It passes the message from the input XQueue over to an output XQueue and returns 1 upon success or 0 otherwise.

Overrides:

passthru in class Node

feedback

protected int feedback(XQueue in,
                       long milliSec)

returns the number of done messages removed from in

Overrides:

feedback in class Node

getOutLinkBoundary

public int getOutLinkBoundary()

returns the BOUNDARY which is the lowest id of outlinks for collectibles so that any outlink with either the same id or a higher id is for collectibles. The EXTERNAL_XA bit of all outlinks for collectibles has to be disabled by the container to stop ack propagations downsstream.

Specified by:

getOutLinkBoundary in interface MessageNode

Overrides:

getOutLinkBoundary 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