org.jgroups.protocols.rules.SUPERVISOR Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
package org.jgroups.protocols.rules;
import org.jgroups.Address;
import org.jgroups.Event;
import org.jgroups.Message;
import org.jgroups.View;
import org.jgroups.annotations.MBean;
import org.jgroups.annotations.ManagedAttribute;
import org.jgroups.annotations.ManagedOperation;
import org.jgroups.annotations.Property;
import org.jgroups.conf.ConfiguratorFactory;
import org.jgroups.stack.Protocol;
import org.jgroups.util.*;
import org.w3c.dom.*;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import java.io.InputStream;
import java.util.*;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
/**
* Protocol which supervises other protocols. Essentially a rule engine, where rule conditions are checked periodically,
* triggering (optional) actions. Example: start failure detection in FD is it isn't running
* https://issues.jboss.org/browse/JGRP-1557
* @author Bela Ban
* @since 3.3
*/
@MBean(description="Supervises the running stack, taking corrective actions if necessary")
public class SUPERVISOR extends Protocol {
protected Address local_addr;
protected volatile View view;
// The timer used to run the rules on
protected TimeScheduler timer;
// The last 50 executions, can be retrieved with executions()
protected final BoundedList executions=new BoundedList<>(50);
@Property(description="Location of an XML file listing the rules to be installed")
protected String config;
// hashmap of rules, keys are rule names and values futures to the rules
protected final Map>> rules=new HashMap<>();
protected final List event_handlers=new ArrayList<>();
@ManagedAttribute(description="The number of registered EventHandler")
protected volatile int num_event_handlers;
protected static final String RULES = "rules";
protected static final String RULE = "rule";
protected static final String NAME = "name";
protected static final String CLASS = "class";
protected static final String INTERVAL = "interval";
public Address getLocalAddress() {return local_addr;}
public View getView() {return view;}
@ManagedOperation(description="Prints the last N conditions that triggered a rule action")
public String executions() {
StringBuilder sb=new StringBuilder();
for(String execution: executions)
sb.append(execution + "\n");
return sb.toString();
}
public void addCondition(String cond) {
executions.add(new Date() + ": " + cond);
}
@ManagedAttribute(description="The number of rules currently installed")
public int getNumRules() {
return rules.size();
}
@ManagedOperation(description="Prints all currently installed rules")
public String dumpRules() {
StringBuilder sb=new StringBuilder();
for(Map.Entry>> entry: rules.entrySet()) {
String key=entry.getKey();
Tuple> tuple=entry.getValue();
Rule rule=tuple.getVal1();
sb.append(key + ": " + rule.description() + "\n");
}
return sb.toString();
}
public void register(EventHandler handler) {
if(handler != null) {
event_handlers.add(handler);
num_event_handlers=event_handlers.size();
}
}
public void unregister(EventHandler handler) {
if(handler != null) {
event_handlers.remove(handler);
num_event_handlers=event_handlers.size();
}
}
public void init() throws Exception {
super.init();
timer=getTransport().getTimer();
if(timer == null)
throw new IllegalStateException("timer not found");
if(config != null)
parseConfig(config);
}
public void destroy() {
for(Tuple> tuple: rules.values())
tuple.getVal2().cancel(true);
rules.clear();
super.destroy();
}
/**
* Installs a new rule
* @param interval Number of ms between executions of the rule
* @param rule The rule
*/
public void installRule(long interval, Rule rule) {
installRule(null, interval, rule);
}
/**
* Installs a new rule
* @param name The name of the rule
* @param interval Number of ms between executions of the rule
* @param rule The rule
*/
public void installRule(String name, long interval, Rule rule) {
rule.supervisor(this).log(log).init();
Future future=timer.scheduleAtFixedRate(rule, interval, interval, TimeUnit.MILLISECONDS);
Tuple> existing=rules.put(name != null? name : rule.name(), new Tuple>(rule, future));
if(existing != null)
existing.getVal2().cancel(true);
}
@ManagedOperation(description="Installs the given rule with the given classname")
public void installRule(String name, long interval, String classname) throws Exception {
Class clazz=Util.loadClass(classname,getClass());
Rule rule=clazz.newInstance();
installRule(name, interval, rule);
}
@ManagedOperation(description="Installs the given rule with the given classname")
public void installRule(long interval, String classname) throws Exception {
installRule(null, interval, classname);
}
@ManagedOperation(description="Uninstalls the named rule")
public void uninstallRule(String name) {
if(name != null) {
Tuple> tuple=rules.remove(name);
if(tuple != null) {
tuple.getVal2().cancel(true);
tuple.getVal1().destroy();
}
}
}
public Object down(Event evt) {
switch(evt.getType()) {
case Event.SET_LOCAL_ADDRESS:
local_addr=(Address)evt.getArg();
break;
case Event.VIEW_CHANGE:
handleView((View)evt.getArg());
break;
}
if(num_event_handlers > 0) {
for(EventHandler handler: event_handlers) {
try {
handler.down(evt);
}
catch(Throwable t) {
log.error("event handler failed handling down event", t);
}
}
}
return down_prot.down(evt);
}
public Object up(Event evt) {
switch(evt.getType()) {
case Event.VIEW_CHANGE:
handleView((View)evt.getArg());
break;
}
if(num_event_handlers > 0) {
for(EventHandler handler: event_handlers) {
try {
handler.up(evt);
}
catch(Throwable t) {
log.error("event handler failed handling up event", t);
}
}
}
return up_prot.up(evt);
}
public void up(MessageBatch batch) {
if(num_event_handlers > 0) {
for(Message msg: batch) {
for(EventHandler handler: event_handlers) {
try {
handler.up(new Event(Event.MSG, msg));
}
catch(Throwable t) {
log.error("event handler failed handling up event", t);
}
}
}
}
if(!batch.isEmpty())
up_prot.up(batch);
}
protected void handleView(View view) {
this.view=view;
}
protected void parseConfig(String filename) throws Exception {
InputStream input=null;
try {
input=ConfiguratorFactory.getConfigStream(filename);
parseRules(input);
}
finally {
Util.close(input);
}
}
protected void parseRules(InputStream input) throws Exception {
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setValidating(false); // for now
DocumentBuilder builder=factory.newDocumentBuilder();
Document document=builder.parse(input);
Element root=document.getDocumentElement();
match(RULES, root.getNodeName(), true);
NodeList children=root.getChildNodes();
if(children == null || children.getLength() == 0)
return;
for(int i=0; i < children.getLength(); i++) {
Node node=children.item(i);
if(node.getNodeType() != Node.ELEMENT_NODE)
continue;
String element_name=node.getNodeName();
if(RULE.equals(element_name))
parseRule(node);
else
throw new Exception("expected <" + RULE + ">, but got " + "<" + element_name + ">");
}
}
protected void parseRule(Node root) throws Exception {
if(root.getNodeType() != Node.ELEMENT_NODE)
return;
NamedNodeMap attrs=root.getAttributes();
if(attrs == null || attrs.getLength() == 0)
return;
Attr name_attr=(Attr)attrs.getNamedItem(NAME),
classname_attr=(Attr)attrs.getNamedItem(CLASS),
interval_attr=(Attr)attrs.getNamedItem(INTERVAL);
Class clazz=Util.loadClass(classname_attr.getValue(), getClass());
Rule rule=clazz.newInstance();
long interval=Long.parseLong(interval_attr.getValue());
installRule(name_attr.getValue(), interval, rule);
}
protected static void match(String expected_name, String name, boolean is_element) throws Exception {
if(!expected_name.equals(name))
throw new Exception((is_element? "Element " : "Attribute ") + "\"" + name + "\" didn't match \"" + expected_name + "\"");
}
}