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本文主要研究一下Elasticsearch RestClient的NodeSelector
NodeSelector
elasticsearch-7.0.1/client/rest/src/main/java/org/elasticsearch/client/NodeSelector.java
public interface NodeSelector {
/**
* Select the {@link Node}s to which to send requests. This is called with
* a mutable {@link Iterable} of {@linkplain Node}s in the order that the
* rest client would prefer to use them and implementers should remove
* nodes from the that should not receive the request. Implementers may
* iterate the nodes as many times as they need.
* <p>
* This may be called twice per request: first for "living" nodes that
* have not been blacklisted by previous errors. If the selector removes
* all nodes from the list or if there aren't any living nodes then the
* {@link RestClient} will call this method with a list of "dead" nodes.
* <p>
* Implementers should not rely on the ordering of the nodes.
*/
void select(Iterable<Node> nodes);
/*
* We were fairly careful with our choice of Iterable here. The caller has
* a List but reordering the list is likely to break round robin. Luckily
* Iterable doesn't allow any reordering.
*/
/**
* Selector that matches any node.
*/
NodeSelector ANY = new NodeSelector() {
@Override
public void select(Iterable<Node> nodes) {
// Intentionally does nothing
}
@Override
public String toString() {
return "ANY";
}
};
/**
* Selector that matches any node that has metadata and doesn't
* have the {@code master} role OR it has the data {@code data}
* role.
*/
NodeSelector SKIP_DEDICATED_MASTERS = new NodeSelector() {
@Override
public void select(Iterable<Node> nodes) {
for (Iterator<Node> itr = nodes.iterator(); itr.hasNext();) {
Node node = itr.next();
if (node.getRoles() == null) continue;
if (node.getRoles().isMasterEligible()
&& false == node.getRoles().isData()
&& false == node.getRoles().isIngest()) {
itr.remove();
}
}
}
@Override
public String toString() {
return "SKIP_DEDICATED_MASTERS";
}
};
}
复制代码- NodeSelector接口定义了select方法，它接收mutable的Iterable，然后具体实现会选择性删除node；它定义了ANY、SKIP_DEDICATED_MASTERS两个匿名实现类，其中ANY的select方法不做任何操作；SKIP_DEDICATED_MASTERS的select方法会删除date为false、ingest为false的master node；除此之外还有HasAttributeNodeSelector、PreferHasAttributeNodeSelector两个实现类
HasAttributeNodeSelector
elasticsearch-7.0.1/client/rest/src/main/java/org/elasticsearch/client/HasAttributeNodeSelector.java
public final class HasAttributeNodeSelector implements NodeSelector {
private final String key;
private final String value;
public HasAttributeNodeSelector(String key, String value) {
this.key = key;
this.value = value;
}
@Override
public void select(Iterable<Node> nodes) {
Iterator<Node> itr = nodes.iterator();
while (itr.hasNext()) {
Map<String, List<String>> allAttributes = itr.next().getAttributes();
if (allAttributes == null) continue;
List<String> values = allAttributes.get(key);
if (values == null || false == values.contains(value)) {
itr.remove();
}
}
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
HasAttributeNodeSelector that = (HasAttributeNodeSelector) o;
return Objects.equals(key, that.key) &&
Objects.equals(value, that.value);
}
@Override
public int hashCode() {
return Objects.hash(key, value);
}
@Override
public String toString() {
return key + "=" + value;
}
}
复制代码- HasAttributeNodeSelector实现了NodeSelector接口，其构造器接收key、value参数，其select方法会删除node的attributes没有该key或者该key对应的value为null的node
PreferHasAttributeNodeSelector
elasticsearch-7.0.1/client/rest/src/main/java/org/elasticsearch/client/PreferHasAttributeNodeSelector.java
public final class PreferHasAttributeNodeSelector implements NodeSelector {
private final String key;
private final String value;
public PreferHasAttributeNodeSelector(String key, String value) {
this.key = key;
this.value = value;
}
@Override
public void select(Iterable<Node> nodes) {
boolean foundAtLeastOne = false;
for (Node node : nodes) {
Map<String, List<String>> attributes = node.getAttributes();
if (attributes == null) {
continue;
}
List<String> values = attributes.get(key);
if (values == null) {
continue;
}
if (values.contains(value)) {
foundAtLeastOne = true;
break;
}
}
if (foundAtLeastOne) {
Iterator<Node> nodeIterator = nodes.iterator();
while (nodeIterator.hasNext()) {
Map<String, List<String>> attributes = nodeIterator.next().getAttributes();
if (attributes == null) {
continue;
}
List<String> values = attributes.get(key);
if (values == null || !values.contains(value)) {
nodeIterator.remove();
}
}
}
}
@Override
public boolean equals(Object o) {
if (this == o) {
return
true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
PreferHasAttributeNodeSelector that = (PreferHasAttributeNodeSelector) o;
return Objects.equals(key, that.key) &&
Objects.equals(value, that.value);
}
@Override
public int hashCode() {
return Objects.hash(key, value);
}
@Override
public String toString() {
return key + "=" + value;
}
}
复制代码- PreferHasAttributeNodeSelector实现了NodeSelector接口，其构造器接收key、value参数，其select方法会先遍历nodes设置foundAtLeastOne，如果foundAtLeastOne为true才会删除node的attributes没有该key或者该key对应的value为null的node
小结
- NodeSelector接口定义了select方法，它接收mutable的Iterable，然后具体实现会选择性删除node；它定义了ANY、SKIP_DEDICATED_MASTERS两个匿名实现类，其中ANY的select方法不做任何操作；SKIP_DEDICATED_MASTERS的select方法会删除date为false、ingest为false的master node
- HasAttributeNodeSelector实现了NodeSelector接口，其构造器接收key、value参数，其select方法会删除node的attributes没有该key或者该key对应的value为null的node
- PreferHasAttributeNodeSelector实现了NodeSelector接口，其构造器接收key、value参数，其select方法会先遍历nodes设置foundAtLeastOne，如果foundAtLeastOne为true才会删除node的attributes没有该key或者该key对应的value为null的node
