Cross Cluster Search简介
cross-cluster search功能允许任何节点作为跨多个群集的federated client(联合客户端),与tribe node不同的是cross-cluster search节点并不会加入remote cluster(远程集群),而是用轻量的方法连接到remote cluster,以便执行federated search(联合搜索)
Remote cluster
要使用cross-cluster search之前需要先了解remote cluster
一个remote cluster中有"name"和seed nodes(种子节点)列表以供引用,注册remote cluster时,会从其中一个seed node来检查其集群状态,以便在默认情况下选择最多三个有资格的节点作为gateway nodes(网关节点), 集群中配置了remote cluster的每个节点都连接到一个或多个gateway nodes,并使用它们将federated search到remote cluster。
可以使用集群设置(可以动态更新)在全局指定remote cluster,也可以在各个节点中的elasticsearch.yml
指定remote cluster 。
如果节点通过elasticsearch.yml文件
配置remote cluster,则可以通过该节点连接到remote cluster。换句话说,federated search只有发送到该节点才能连接到remote cluster。通过cluster settings API 设置的remote cluster集群中的每个节点(设置了cluster.remote.connect: true的节点)都可以连接。
通过elasticsearch.yml设置
:
cluster:
remote:
cluster_one:
seeds: 127.0.0.1:9300
cluster_two:
seeds: 127.0.0.1:9301
cluster_one和cluster_two表示与每个群集连接的任意群集别名。这些名称之后用于区分本地和远程索引
使用cluster settings API设置:
PUT _cluster/settings
{
"persistent": {
"cluster": {
"remote": {
"cluster_one": {
"seeds": [
"127.0.0.1:9300"
]
},
"cluster_two": {
"seeds": [
"127.0.0.1:9301"
]
},
"cluster_three": {
"seeds": [
"127.0.0.1:9302"
]
}
}
}
}
}
删除远程群集:
PUT _cluster/settings
{
"persistent": {
"cluster": {
"remote": {
"cluster_three": {
"seeds": null
}
}
}
}
}
删除cluster_three保留cluster_one和cluster_tow
Remote cluster的设置:
cluster.remote.connections_per_cluster
gateway nodes数量,默认是3
cluster.remote.initial_connect_timeout
节点启动时等待远程节点的超时时间,默认是30s
cluster.remote.node.attr
一个节点属性,用于过滤掉remote cluster中 符合gateway nodes的节点,比如设置cluster.remote.node.attr=gateway,那么将匹配节点属性node.attr.gateway: true
cluster.remote.connect
默认情况下,群集中的任意节点都可以充当federated client并连接到remote cluster,cluster.remote.connect可以设置为 false(默认为true)以防止某些节点连接到remote cluster
cluster.remote.${cluster_alias}.skip_unavailable
在节点中跳过特定的群集别名,默认是false
使用cross-cluster search查询
要搜索远程集群cluster_one上的twitter索引,index名和集群别用冒号分开:
GET /cluster_one:twitter/_search
{
"query": {
"match": {
"user": "kimchy"
}
}
}
与tribe特征相反,cross-cluster search还可以在不同群集上搜索相同名称的index:
GET /cluster_one:twitter,twitter/_search
{
"query": {
"match": {
"user": "kimchy"
}
}
}
搜索结果的歧义与索引在请求中消除歧义的方式相同。即使index名称相同,这些index也会在合并结果时被视为不同的index。从远程index检索的所有结果都将以remote cluster的name为前缀:
{
"took": 150,
"timed_out": false,
"_shards": {
"total": 2,
"successful": 2,
"failed": 0,
"skipped": 0
},
"_clusters": {
"total": 2,
"successful": 2,
"skipped": 0
},
"hits": {
"total": 2,
"max_score": 1,
"hits": [
{
"_index": "cluster_one:twitter",
"_type": "_doc",
"_id": "0",
"_score": 1,
"_source": {
"user": "kimchy",
"date": "2009-11-15T14:12:12",
"message": "trying out Elasticsearch",
"likes": 0
}
},
{
"_index": "twitter",
"_type": "_doc",
"_id": "0",
"_score": 2,
"_source": {
"user": "kimchy",
"date": "2009-11-15T14:12:12",
"message": "trying out Elasticsearch",
"likes": 0
}
}
]
}
}
跳过已经断开连接的集群:
默认情况下,在执行搜索请求时,通过cross-cluster search搜索的所有remote cluster都必须可用,否则整个请求将失败,并且尽管某些群集可用,但不会返回搜索结果。可以通过skip_unavailable设置使remote cluster可选,默认设置为false。
PUT _cluster/settings
{
"persistent": {
"cluster.remote.cluster_two.skip_unavailable": true
}
}
cluster_two就变成可选的了
GET /cluster_one:twitter,cluster_two:twitter,twitter/_search
{
"query": {
"match": {
"user": "kimchy"
}
}
}
在本地、cluster_one
,cluster_two中
搜索索引twitter
{
"took": 150,
"timed_out": false,
"_shards": {
"total": 2,
"successful": 2,
"failed": 0,
"skipped": 0
},
"_clusters": { #clusters部分表示一个群集不可用并被跳过
"total": 3,
"successful": 2,
"skipped": 1
},
"hits": {
"total": 2,
"max_score": 1,
"hits": [
{
"_index": "cluster_one:twitter",
"_type": "_doc",
"_id": "0",
"_score": 1,
"_source": {
"user": "kimchy",
"date": "2009-11-15T14:12:12",
"message": "trying out Elasticsearch",
"likes": 0
}
},
{
"_index": "twitter",
"_type": "_doc",
"_id": "0",
"_score": 2,
"_source": {
"user": "kimchy",
"date": "2009-11-15T14:12:12",
"message": "trying out Elasticsearch",
"likes": 0
}
}
]
}
}