下面列出了怎么用com.alibaba.dubbo.rpc.cluster.LoadBalance的API类实例代码及写法，或者点击链接到github查看源代码。
@Test
public void testBindingAttachment() {
final String attachKey = "attach";
final String attachValue = "value";
// setup attachment
RpcContext.getContext().setAttachment(attachKey, attachValue);
Map<String, String> attachments = RpcContext.getContext().getAttachments();
Assert.assertTrue("set attachment failed!", attachments != null && attachments.size() == 1);
cluster = new AbstractClusterInvoker(dic) {
@Override
protected Result doInvoke(Invocation invocation, List invokers, LoadBalance loadbalance)
throws RpcException {
// attachment will be bind to invocation
String value = invocation.getAttachment(attachKey);
Assert.assertTrue("binding attachment failed!", value != null && value.equals(attachValue));
return null;
}
};
// invoke
cluster.invoke(invocation);
}
/**
* 使用loadbalance选择invoker.</br>
* a)先lb选择，如果在selected列表中 或者 不可用且做检验时，进入下一步(重选),否则直接返回</br>
* b)重选验证规则：selected > available .保证重选出的结果尽量不在select中，并且是可用的
*
* @param availablecheck 如果设置true，在选择的时候先选invoker.available == true
* @param selected 已选过的invoker.注意：输入保证不重复
*
*/
protected Invoker<T> select(LoadBalance loadbalance, Invocation invocation, List<Invoker<T>> invokers, List<Invoker<T>> selected) throws RpcException {
if (invokers == null || invokers.size() == 0)
return null;
String methodName = invocation == null ? "" : invocation.getMethodName();
boolean sticky = invokers.get(0).getUrl().getMethodParameter(methodName,Constants.CLUSTER_STICKY_KEY, Constants.DEFAULT_CLUSTER_STICKY) ;
{
//ignore overloaded method
if ( stickyInvoker != null && !invokers.contains(stickyInvoker) ){
stickyInvoker = null;
}
//ignore cucurrent problem
if (sticky && stickyInvoker != null && (selected == null || !selected.contains(stickyInvoker))){
if (availablecheck && stickyInvoker.isAvailable()){
return stickyInvoker;
}
}
}
Invoker<T> invoker = doselect(loadbalance, invocation, invokers, selected);
if (sticky){
stickyInvoker = invoker;
}
return invoker;
}
public Result invoke(final Invocation invocation) throws RpcException {
checkWheatherDestoried();
LoadBalance loadbalance;
List<Invoker<T>> invokers = list(invocation);
if (invokers != null && invokers.size() > 0) {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(invokers.get(0).getUrl()
.getMethodParameter(invocation.getMethodName(),Constants.LOADBALANCE_KEY, Constants.DEFAULT_LOADBALANCE));
} else {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(Constants.DEFAULT_LOADBALANCE);
}
RpcUtils.attachInvocationIdIfAsync(getUrl(), invocation);
return doInvoke(invocation, invokers, loadbalance);
}
/**
* 使用loadbalance选择invoker.</br>
* a)先lb选择，如果在selected列表中 或者 不可用且做检验时，进入下一步(重选),否则直接返回</br>
* b)重选验证规则：selected > available .保证重选出的结果尽量不在select中，并且是可用的
*
* @param availablecheck 如果设置true，在选择的时候先选invoker.available == true
* @param selected 已选过的invoker.注意：输入保证不重复
*
*/
protected Invoker<T> select(LoadBalance loadbalance, Invocation invocation, List<Invoker<T>> invokers, List<Invoker<T>> selected) throws RpcException {
if (invokers == null || invokers.size() == 0)
return null;
String methodName = invocation == null ? "" : invocation.getMethodName();
boolean sticky = invokers.get(0).getUrl().getMethodParameter(methodName,Constants.CLUSTER_STICKY_KEY, Constants.DEFAULT_CLUSTER_STICKY) ;
{
//ignore overloaded method
if ( stickyInvoker != null && !invokers.contains(stickyInvoker) ){
stickyInvoker = null;
}
//ignore cucurrent problem
if (sticky && stickyInvoker != null && (selected == null || !selected.contains(stickyInvoker))){
if (availablecheck && stickyInvoker.isAvailable()){
return stickyInvoker;
}
}
}
Invoker<T> invoker = doselect(loadbalance, invocation, invokers, selected);
if (sticky){
stickyInvoker = invoker;
}
return invoker;
}
public Result invoke(final Invocation invocation) throws RpcException {
checkWheatherDestoried();
LoadBalance loadbalance;
List<Invoker<T>> invokers = list(invocation);
if (invokers != null && invokers.size() > 0) {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(invokers.get(0).getUrl()
.getMethodParameter(invocation.getMethodName(),Constants.LOADBALANCE_KEY, Constants.DEFAULT_LOADBALANCE));
} else {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(Constants.DEFAULT_LOADBALANCE);
}
RpcUtils.attachInvocationIdIfAsync(getUrl(), invocation);
return doInvoke(invocation, invokers, loadbalance);
}
/**
* 使用loadbalance选择invoker.</br>
* a)先lb选择，如果在selected列表中 或者 不可用且做检验时，进入下一步(重选),否则直接返回</br>
* b)重选验证规则：selected > available .保证重选出的结果尽量不在select中，并且是可用的
*
* @param availablecheck 如果设置true，在选择的时候先选invoker.available == true
* @param selected 已选过的invoker.注意：输入保证不重复
*
*/
protected Invoker<T> select(LoadBalance loadbalance, Invocation invocation, List<Invoker<T>> invokers, List<Invoker<T>> selected) throws RpcException {
if (invokers == null || invokers.size() == 0)
return null;
String methodName = invocation == null ? "" : invocation.getMethodName();
boolean sticky = invokers.get(0).getUrl().getMethodParameter(methodName,Constants.CLUSTER_STICKY_KEY, Constants.DEFAULT_CLUSTER_STICKY) ;
{
//ignore overloaded method
if ( stickyInvoker != null && !invokers.contains(stickyInvoker) ){
stickyInvoker = null;
}
//ignore cucurrent problem
if (sticky && stickyInvoker != null && (selected == null || !selected.contains(stickyInvoker))){
if (availablecheck && stickyInvoker.isAvailable()){
return stickyInvoker;
}
}
}
Invoker<T> invoker = doselect(loadbalance, invocation, invokers, selected);
if (sticky){
stickyInvoker = invoker;
}
return invoker;
}
public Result invoke(final Invocation invocation) throws RpcException {
checkWheatherDestoried();
LoadBalance loadbalance;
List<Invoker<T>> invokers = list(invocation);
if (invokers != null && invokers.size() > 0) {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(invokers.get(0).getUrl()
.getMethodParameter(invocation.getMethodName(),Constants.LOADBALANCE_KEY, Constants.DEFAULT_LOADBALANCE));
} else {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(Constants.DEFAULT_LOADBALANCE);
}
RpcUtils.attachInvocationIdIfAsync(getUrl(), invocation);
return doInvoke(invocation, invokers, loadbalance);
}
/**
* 使用loadbalance选择invoker.</br>
* a)先lb选择，如果在selected列表中 或者 不可用且做检验时，进入下一步(重选),否则直接返回</br>
* b)重选验证规则：selected > available .保证重选出的结果尽量不在select中，并且是可用的
*
* @param availablecheck 如果设置true，在选择的时候先选invoker.available == true
* @param selected 已选过的invoker.注意：输入保证不重复
*
*/
protected Invoker<T> select(LoadBalance loadbalance, Invocation invocation, List<Invoker<T>> invokers, List<Invoker<T>> selected) throws RpcException {
if (invokers == null || invokers.size() == 0)
return null;
String methodName = invocation == null ? "" : invocation.getMethodName();
boolean sticky = invokers.get(0).getUrl().getMethodParameter(methodName,Constants.CLUSTER_STICKY_KEY, Constants.DEFAULT_CLUSTER_STICKY) ;
{
//ignore overloaded method
if ( stickyInvoker != null && !invokers.contains(stickyInvoker) ){
stickyInvoker = null;
}
//ignore cucurrent problem
if (sticky && stickyInvoker != null && (selected == null || !selected.contains(stickyInvoker))){
if (availablecheck && stickyInvoker.isAvailable()){
return stickyInvoker;
}
}
}
Invoker<T> invoker = doselect(loadbalance, invocation, invokers, selected);
if (sticky){
stickyInvoker = invoker;
}
return invoker;
}
public Result invoke(final Invocation invocation) throws RpcException {
checkWheatherDestoried();
LoadBalance loadbalance;
List<Invoker<T>> invokers = list(invocation);
if (invokers != null && invokers.size() > 0) {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(invokers.get(0).getUrl()
.getMethodParameter(invocation.getMethodName(),Constants.LOADBALANCE_KEY, Constants.DEFAULT_LOADBALANCE));
} else {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(Constants.DEFAULT_LOADBALANCE);
}
RpcUtils.attachInvocationIdIfAsync(getUrl(), invocation);
return doInvoke(invocation, invokers, loadbalance);
}
public Result invoke(final Invocation invocation) throws RpcException {
checkWhetherDestroyed();
LoadBalance loadbalance;
List<Invoker<T>> invokers = list(invocation);
if (invokers != null && invokers.size() > 0) {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(invokers.get(0).getUrl()
.getMethodParameter(invocation.getMethodName(),Constants.LOADBALANCE_KEY, Constants.DEFAULT_LOADBALANCE));
} else {
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(Constants.DEFAULT_LOADBALANCE);
}
RpcUtils.attachInvocationIdIfAsync(getUrl(), invocation);
return doInvoke(invocation, invokers, loadbalance);
}
@Override
public Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
// 检查invoker是否可用
checkInvokers(invokers, invocation);
// 执行负载均衡策略
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
try {
return invoker.invoke(invocation);
} catch (Throwable e) {
if (e instanceof RpcException && ((RpcException) e).isBiz()) { // biz exception.
throw (RpcException) e;
}
throw new RpcException(e instanceof RpcException ? ((RpcException) e).getCode() : 0, "Failfast invoke providers " + invoker.getUrl() + " " + loadbalance.getClass().getSimpleName() + " select from all providers " + invokers + " for service " + getInterface().getName() + " method " + invocation.getMethodName() + " on consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", but no luck to perform the invocation. Last error is: " + e.getMessage(), e.getCause() != null ? e.getCause() : e);
}
}
@Override
public Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
for (Invoker<T> invoker : invokers) {
if (invoker.isAvailable()) {
return invoker.invoke(invocation);
}
}
throw new RpcException("No provider available in " + invokers);
}
@Override
protected Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
try {
checkInvokers(invokers, invocation);
// 执行负载均衡算法
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
return invoker.invoke(invocation);
} catch (Throwable e) {
logger.error("Failback to invoke method " + invocation.getMethodName() + ", wait for retry in background. Ignored exception: "
+ e.getMessage() + ", ", e);
// 执行失败处理
addFailed(invocation, this);
return new RpcResult(); // ignore
}
}
@Override
protected Result doInvoke(Invocation invocation, List<Invoker<T>> invokers,
LoadBalance loadbalance) throws RpcException {
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
selectedInvoker = invoker;
return null;
}
/**
* Select a invoker using loadbalance policy.</br>
* a)Firstly, select an invoker using loadbalance. If this invoker is in previously selected list, or,
* if this invoker is unavailable, then continue step b (reselect), otherwise return the first selected invoker</br>
* b)Reslection, the validation rule for reselection: selected > available. This rule guarantees that
* the selected invoker has the minimum chance to be one in the previously selected list, and also
* guarantees this invoker is available.
*
* @param loadbalance load balance policy
* @param invocation
* @param invokers invoker candidates
* @param selected exclude selected invokers or not
* @return
* @throws RpcException
* 使用loadbalance策略选择调用程序。a)首先，使用loadbalance选择一个调用程序。如果这个调用程序在前面选择的列表中，或者，如果这个调用程序不可用，那么继续步骤b (reselect)，
* 否则返回第一个选择的调用程序b)Reslection，重新选择的验证规则:选择的>可用。该规则保证所选的调用程序有最小的机会出现在前面选择的列表中，并保证该调用程序可用。
*/
protected Invoker<T> select(LoadBalance loadbalance, Invocation invocation, List<Invoker<T>> invokers, List<Invoker<T>> selected) throws RpcException {
if (invokers == null || invokers.isEmpty())
return null;
// 执行的方法名
String methodName = invocation == null ? "" : invocation.getMethodName();
// 是否是有状态连接，一个客户端一直调用到一个服务端，除非这个服务端不可用
boolean sticky = invokers.get(0).getUrl().getMethodParameter(methodName, Constants.CLUSTER_STICKY_KEY, Constants.DEFAULT_CLUSTER_STICKY);
{
//ignore overloaded method
if (stickyInvoker != null && !invokers.contains(stickyInvoker)) {
stickyInvoker = null;
}
//ignore concurrency problem
if (sticky && stickyInvoker != null && (selected == null || !selected.contains(stickyInvoker))) {
if (availablecheck && stickyInvoker.isAvailable()) {
return stickyInvoker;
}
}
}
// 执行负载均衡策略=》
Invoker<T> invoker = doSelect(loadbalance, invocation, invokers, selected);
if (sticky) {
stickyInvoker = invoker;
}
return invoker;
}
private Invoker<T> doSelect(LoadBalance loadbalance, Invocation invocation, List<Invoker<T>> invokers, List<Invoker<T>> selected) throws RpcException {
if (invokers == null || invokers.isEmpty())
return null;
if (invokers.size() == 1)
return invokers.get(0);
if (loadbalance == null) {
// 默认负载均衡策略 random
loadbalance = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(Constants.DEFAULT_LOADBALANCE);
}
Invoker<T> invoker = loadbalance.select(invokers, getUrl(), invocation);
//If the `invoker` is in the `selected` or invoker is unavailable && availablecheck is true, reselect.
if ((selected != null && selected.contains(invoker))
|| (!invoker.isAvailable() && getUrl() != null && availablecheck)) {
try {
// 如果选择的执行器不可用，重新选择=》
Invoker<T> rinvoker = reselect(loadbalance, invocation, invokers, selected, availablecheck);
if (rinvoker != null) {
invoker = rinvoker;
} else {
//Check the index of current selected invoker, if it's not the last one, choose the one at index+1. 检查当前选定调用程序的索引，如果不是最后一个，则选择index+1处的索引。
int index = invokers.indexOf(invoker);
try {
//Avoid collision
invoker = index < invokers.size() - 1 ? invokers.get(index + 1) : invokers.get(0);
} catch (Exception e) {
logger.warn(e.getMessage() + " may because invokers list dynamic change, ignore.", e);
}
}
} catch (Throwable t) {
logger.error("cluster reselect fail reason is :" + t.getMessage() + " if can not solve, you can set cluster.availablecheck=false in url", t);
}
}
return invoker;
}
@Override
protected Result doInvoke(Invocation invocation, List<Invoker<T>> invokers,
LoadBalance loadbalance) throws RpcException {
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
selectedInvoker = invoker;
return null;
}
@Override
public Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
try {
checkInvokers(invokers, invocation);
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
return invoker.invoke(invocation);
} catch (Throwable e) {
logger.error("Failsafe ignore exception: " + e.getMessage(), e);
return new RpcResult(); // ignore
}
}
/**
* 测试均衡.
*/
@Test
public void testSelectBalance(){
LoadBalance lb = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(RoundRobinLoadBalance.NAME);
initlistsize5();
Map<Invoker,AtomicLong> counter = new ConcurrentHashMap<Invoker,AtomicLong>();
for(Invoker invoker :invokers){
counter.put(invoker, new AtomicLong(0));
}
int runs = 1000;
for(int i=0;i<runs;i++){
selectedInvokers.clear();
Invoker sinvoker = cluster.select(lb, invocation, invokers, selectedInvokers);
counter.get(sinvoker).incrementAndGet();
}
for (Invoker minvoker :counter.keySet() ){
Long count = counter.get(minvoker).get();
// System.out.println(count);
if(minvoker.isAvailable())
Assert.assertTrue("count should > avg", count>runs/invokers.size());
}
Assert.assertEquals(runs, counter.get(invoker2).get()+counter.get(invoker4).get());;
}
@Test
public void testCloseAvailablecheck() {
LoadBalance lb = mock(LoadBalance.class);
given(lb.select(invokers, url, invocation)).willReturn(invoker1);
initlistsize5();
Invoker sinvoker = cluster_nocheck.select(lb, invocation, invokers, selectedInvokers);
Assert.assertEquals(false, sinvoker.isAvailable());
Assert.assertEquals(invoker1, sinvoker);
}
/**
* Test balance.
*/
@Test
public void testSelectBalance() {
LoadBalance lb = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(RoundRobinLoadBalance.NAME);
initlistsize5();
Map<Invoker, AtomicLong> counter = new ConcurrentHashMap<Invoker, AtomicLong>();
for (Invoker invoker : invokers) {
counter.put(invoker, new AtomicLong(0));
}
int runs = 1000;
for (int i = 0; i < runs; i++) {
selectedInvokers.clear();
Invoker sinvoker = cluster.select(lb, invocation, invokers, selectedInvokers);
counter.get(sinvoker).incrementAndGet();
}
for (Invoker minvoker : counter.keySet()) {
Long count = counter.get(minvoker).get();
// System.out.println(count);
if (minvoker.isAvailable())
Assert.assertTrue("count should > avg", count > runs / invokers.size());
}
Assert.assertEquals(runs, counter.get(invoker2).get() + counter.get(invoker4).get());
;
}
@Override
protected Result doInvoke(Invocation invocation, List<Invoker<T>> invokers,
LoadBalance loadbalance) throws RpcException {
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
selectedInvoker = invoker;
return null;
}
public Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
checkInvokers(invokers, invocation);
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
try {
return invoker.invoke(invocation);
} catch (Throwable e) {
if (e instanceof RpcException && ((RpcException)e).isBiz()) { // biz exception.
throw (RpcException) e;
}
throw new RpcException(e instanceof RpcException ? ((RpcException)e).getCode() : 0, "Failfast invoke providers " + invoker.getUrl() + " " + loadbalance.getClass().getSimpleName() + " select from all providers " + invokers + " for service " + getInterface().getName() + " method " + invocation.getMethodName() + " on consumer " + NetUtils.getLocalHost() + " use dubbo version " + Version.getVersion() + ", but no luck to perform the invocation. Last error is: " + e.getMessage(), e.getCause() != null ? e.getCause() : e);
}
}
public Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
for (Invoker<T> invoker : invokers) {
if (invoker.isAvailable()) {
return invoker.invoke(invocation);
}
}
throw new RpcException("No provider available in " + invokers);
}
protected Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
try {
checkInvokers(invokers, invocation);
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
return invoker.invoke(invocation);
} catch (Throwable e) {
logger.error("Failback to invoke method " + invocation.getMethodName() + ", wait for retry in background. Ignored exception: "
+ e.getMessage() + ", ", e);
addFailed(invocation, this);
return new RpcResult(); // ignore
}
}
public <T> Invoker<T> join(Directory<T> directory) throws RpcException {
return new AbstractClusterInvoker<T>(directory) {
public Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
for (Invoker<T> invoker : invokers) {
if (invoker.isAvailable()) {
return invoker.invoke(invocation);
}
}
throw new RpcException("No provider available in " + invokers);
}
};
}
private Invoker<T> doselect(LoadBalance loadbalance, Invocation invocation, List<Invoker<T>> invokers, List<Invoker<T>> selected) throws RpcException {
if (invokers == null || invokers.size() == 0)
return null;
if (invokers.size() == 1)
return invokers.get(0);
// 如果只有两个invoker，退化成轮循
if (invokers.size() == 2 && selected != null && selected.size() > 0) {
return selected.get(0) == invokers.get(0) ? invokers.get(1) : invokers.get(0);
}
Invoker<T> invoker = loadbalance.select(invokers, getUrl(), invocation);
//如果 selected中包含（优先判断） 或者 不可用&&availablecheck=true 则重试.
if( (selected != null && selected.contains(invoker))
||(!invoker.isAvailable() && getUrl()!=null && availablecheck)){
try{
Invoker<T> rinvoker = reselect(loadbalance, invocation, invokers, selected, availablecheck);
if(rinvoker != null){
invoker = rinvoker;
}else{
//看下第一次选的位置，如果不是最后，选+1位置.
int index = invokers.indexOf(invoker);
try{
//最后在避免碰撞
invoker = index <invokers.size()-1?invokers.get(index+1) :invoker;
}catch (Exception e) {
logger.warn(e.getMessage()+" may because invokers list dynamic change, ignore.",e);
}
}
}catch (Throwable t){
logger.error("clustor relselect fail reason is :"+t.getMessage() +" if can not slove ,you can set cluster.availablecheck=false in url",t);
}
}
return invoker;
}
public Result doInvoke(Invocation invocation, List<Invoker<T>> invokers, LoadBalance loadbalance) throws RpcException {
try {
checkInvokers(invokers, invocation);
Invoker<T> invoker = select(loadbalance, invocation, invokers, null);
return invoker.invoke(invocation);
} catch (Throwable e) {
logger.error("Failsafe ignore exception: " + e.getMessage(), e);
return new RpcResult(); // ignore
}
}
public Map<Invoker,AtomicLong> getInvokeCounter(int runs,String loadbalanceName) {
Map<Invoker,AtomicLong> counter = new ConcurrentHashMap<Invoker,AtomicLong>();
LoadBalance lb = ExtensionLoader.getExtensionLoader(LoadBalance.class).getExtension(loadbalanceName);
for(Invoker invoker :invokers){
counter.put(invoker, new AtomicLong(0));
}
for(int i=0;i<runs;i++){
Invoker sinvoker = lb.select(invokers, invokers.get(0).getUrl(), invocation);
counter.get(sinvoker).incrementAndGet();
}
return counter;
}
private Invoker<T> doselect(LoadBalance loadbalance, Invocation invocation, List<Invoker<T>> invokers, List<Invoker<T>> selected) throws RpcException {
if (invokers == null || invokers.size() == 0)
return null;
if (invokers.size() == 1)
return invokers.get(0);
// 如果只有两个invoker，退化成轮循
if (invokers.size() == 2 && selected != null && selected.size() > 0) {
return selected.get(0) == invokers.get(0) ? invokers.get(1) : invokers.get(0);
}
Invoker<T> invoker = loadbalance.select(invokers, getUrl(), invocation);
//如果 selected中包含（优先判断） 或者 不可用&&availablecheck=true 则重试.
if( (selected != null && selected.contains(invoker))
||(!invoker.isAvailable() && getUrl()!=null && availablecheck)){
try{
Invoker<T> rinvoker = reselect(loadbalance, invocation, invokers, selected, availablecheck);
if(rinvoker != null){
invoker = rinvoker;
}else{
//看下第一次选的位置，如果不是最后，选+1位置.
int index = invokers.indexOf(invoker);
try{
//最后在避免碰撞
invoker = index <invokers.size()-1?invokers.get(index+1) :invoker;
}catch (Exception e) {
logger.warn(e.getMessage()+" may because invokers list dynamic change, ignore.",e);
}
}
}catch (Throwable t){
logger.error("clustor relselect fail reason is :"+t.getMessage() +" if can not slove ,you can set cluster.availablecheck=false in url",t);
}
}
return invoker;
}