序
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"; } };}- 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; }}- 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; }}- 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
doc
- Node selector