批量请求
The patterns for the mget
and bulk
APIs are similar to those for individual documents. The difference is that the requesting node knows in which shard each document lives. It breaks up the multi-document request into a multi-document request per shard, and forwards these in parallel to each participating node.
Once it receives answers from each node, it collates their responses into a single response, which it returns to the client.
[[img-distrib-mget]] .Retrieving multiple documents with mget
image::images/04-05_mget.png["Retrieving multiple documents with mget"]
Below we list the sequence of steps necessary to retrieve multiple documents with a single mget
request, as depicted in <>:
The client sends an
mget
request toNode_1
.Node 1
builds a multi-get request per shard, and forwards these requests in parallel to the nodes hosting each required primary or replica shard. Once all replies have been received,Node 1
builds the response and returns it to the client.
A routing
parameter can be set for each document in the docs
array, and the preference
parameter can be set for the top-level mget
request.
[[img-distrib-bulk]] .Multiple document changes with bulk
image::images/04-06_bulk.png["Multiple document changes with bulk"]
Below we list the sequence of steps necessary to execute multiple create
, index
, delete
and update
requests within a single bulk
request, as depicted in <>:
The client sends a
bulk
request toNode_1
.Node 1
builds a bulk request per shard, and forwards these requests in parallel to the nodes hosting each involved primary shard.The primary shard executes each action serially, one after another. As each action succeeds, the primary forwards the new document (or deletion) to its replica shards in parallel, then moves on to the next action. Once all replica shards report success for all actions, the node reports success to the requesting node, which collates the responses and returns them to the client.
The bulk
API also accepts the replication
and consistency
parameters at the top-level for the whole bulk
request, and the routing
parameter in the metadata for each request.
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