标签：new size space creation 版本 2.4 index back row
http://www.cnblogs.com/bonelee/p/6078947.html 里分析了ES bulk实现，其中路由代码：
ShardId shardId = clusterService.operationRouting().indexShards(clusterState, concreteIndex, request.id(), request.routing()).shardId();
其实现： https://github.com/elastic/elasticsearch/blob/master/core/src/main/java/org/elasticsearch/cluster/routing/OperationRouting.java
public ShardIterator indexShards(ClusterState clusterState, String index, String id, @Nullable String routing) {
return shards(clusterState, index, id, routing).shardsIt();
}
protected IndexShardRoutingTable shards(ClusterState clusterState, String index, String id, String routing) {
int shardId = generateShardId(indexMetaData(clusterState, index), id, routing);
return clusterState.getRoutingTable().shardRoutingTable(index, shardId);
}
static int generateShardId(IndexMetaData indexMetaData, String id, @Nullable String routing) {
final int hash;
if (routing == null) {
hash = Murmur3HashFunction.hash(id);
} else {
hash = Murmur3HashFunction.hash(routing);
}
// we don‘t use IMD#getNumberOfShards since the index might have been shrunk such that we need to use the size
// of original index to hash documents
return Math.floorMod(hash, indexMetaData.getRoutingNumShards()) / indexMetaData.getRoutingFactor();
}
可以看到最新的Es代码实现路由是：
Math.floorMod(hash, indexMetaData.getRoutingNumShards()) / indexMetaData.getRoutingFactor();
在https://github.com/elastic/elasticsearch/blob/master/core/src/main/java/org/elasticsearch/cluster/metadata/IndexMetaData.java 里可以看到getRoutingFactor实现：
/**
* Returns the routing factor for this index. The default is <tt>1</tt>.
*
* @see #getRoutingFactor(IndexMetaData, int) for details
*/
public int getRoutingFactor() {
return routingFactor;
}
构造函数里有：
assert numberOfShards * routingFactor == routingNumShards : routingNumShards + " must be a multiple of " + numberOfShards;
反正默认是1，也就是所有的shard节点都会负责路由！
当心，ES2.4版本的路由实现：https://github.com/elastic/elasticsearch/blob/2.4/core/src/main/java/org/elasticsearch/cluster/routing/
@SuppressForbidden(reason = "Math#abs is trappy") private int generateShardId(ClusterState clusterState, String index, String type, String id, @Nullable String routing) { IndexMetaData indexMetaData = clusterState.metaData().index(index); if (indexMetaData == null) { throw new IndexNotFoundException(index); } final Version createdVersion = indexMetaData.getCreationVersion(); final HashFunction hashFunction = indexMetaData.getRoutingHashFunction(); final boolean useType = indexMetaData.getRoutingUseType(); final int hash; if (routing == null) { if (!useType) { hash = hash(hashFunction, id); } else { hash = hash(hashFunction, type, id); } } else { hash = hash(hashFunction, routing); } if (createdVersion.onOrAfter(Version.V_2_0_0_beta1)) { return MathUtils.mod(hash, indexMetaData.getNumberOfShards()); } else { return Math.abs(hash % indexMetaData.getNumberOfShards()); } }
@Deprecated protected int hash(HashFunction hashFunction, String type, String id) { if (type == null || "_all".equals(type)) { throw new IllegalArgumentException("Can‘t route an operation with no type and having type part of the routing (for backward comp)"); } return hashFunction.hash(type, id); }
而该hash function实现由：
DjbHashFunction.java
SimpleHashFunction.java
Murmur3HashFunction.java
三种。
标签：new size space creation 版本 2.4 index back row
原文地址：http://www.cnblogs.com/bonelee/p/6078956.html
