分佈式文檔存儲
routing a document to a shard
shard = hash(routing) % number_of_primary_shardsrouting value default is document's _id
how primary and replica shards interact
我們可以發送請求到集羣中的任何節點。每個節點完全有能力任何請求服務。每個節點都知道集羣中的每個文檔的位置,所以可以直接請求轉發到所需的節點。在下面的例子中,我們將我們所有的請求發送到節點1,我們將稱之爲請求節點。
When sending requests,
it is good practice to round-robin through all the nodes in the cluster, in order to spread the load.
creating, indexing, and deleting a document
上邊所有的操作都是寫操作，所以必須要再主分片上進行成功之後再同步到複製分片
1.請求發送到master節點。更新文檔存在的shard爲P0。
2。master節點知道P0存在於NODE3所以將請求轉發給node3.
3。node3更新文檔後，複製更新後的文檔到NODE2，與NODE1的複製分片。當複製成功之後，返回請求成功
請求參數設置
replication sync|async 同步或異步複製，默認同步
consistency(數據一致性)
主分片需要一些複製分片來保證數據一致性(不是所有複製分片，因爲有些複製分片所存在的節點網絡不通) 選項爲 one(只有主分片)|all(所有分片)|quorum(指定複製分片個數)
一個主分片的默認一致性複製分片個數爲int( (primary + number_of_replicas) / 2 ) + 1
timeout
如果沒有滿足複製分片的個數，請求將等待 默認1分鐘 1分鐘之後請求超時 100 is
100 milliseconds, and 30s is
30 seconds.
A new index has 1 replica
by default, which means that two active shard copies shouldbe
required in order to satisfy the need for a quorum.
However, these default settings would prevent us from doing anything useful with a single-node cluster. To avoid this problem, the requirement for a quorum is enforced only when number_of_replicas is
greater than 1.
重新取回文檔
For
read requests, the requesting node will choose a different shard copy on every request in order to balance the load; it round-robins through all shard copies.
partial update a document
1.請求發送到master節點。master節點通過計算hash值發現此文檔屬於shard0
2.將請求轉發到Node3
3.從P0主分片中取出文檔，更新文檔
4.複製更新後的文檔到複製分片。
多文檔模式。
因爲ES知道每個文檔所存在的節點與分片，請求將會以分片的形式分組(每一組請求都屬於同一個主分片)，最後將分組後的請求一併轉發到node上