Prepare for parallelizable [secondary index queries][../secondary-indexes/] by requesting a coverage plan. The response will be multiple slices of the cluster, as identified by a TCP endpoint and an opaque binary to be included with each 2i query.
Request
message RpbCoverageReq { optional bytes type = 1; required bytes bucket = 2; optional uint32 min_partitions = 3; optional bytes replace_cover = 4; repeated bytes unavailable_cover = 5; }
Required Parameters
| Parameter | Description |
bucket | The name of the bucket in which the data is stored |
Optional Parameters
| Parameter | Description |
type | The name of the bucket type, if this bucket is not in the default (pre-2.0) bucket type. |
min_partitions | The minimum number of cluster slices. undefined results in a direct map of the internal coverage plan, which targets the minimum number of nodes necessary to retrieve all data. An integer will be rounded up to the nearest power of 2 greater than or equal to the ring size. |
replace_cover | If a client cannot reach the server designated by a previous coverage response, the opaque binary can be sent with a new coverage request via this parameter and a new plan component will be calculated and returned. |
unavailable_cover | List of opaque binaries representing other unreachable endpoints to help Riak determine what servers the client cannot currently use. |
Response
The results of a coverage query are returned as a list of endpoints with opaque binaries to be included with secondary index queries.
message RpbCoverageResp { repeated RpbCoverageEntry entries = 1; } message RpbCoverageEntry { required bytes ip = 1; required uint32 port = 2; optional bytes keyspace_desc = 3; required bytes cover_context = 4; }
Values
| Parameter | Description |
ip | The IP address of the server containing a subset of the data. Depending on the environment, this address may require local translation to deal with routing or firewall constraints. |
port | The port to contact on the server. |
keyspace_desc | A human-readable description of the keyspace. Not intended to be used programmatically except potentially for logging. |
cover_context | The opaque binary to be used in secondary index queries (and possibly future coverage queries to indicate that this server appears offline or otherwise non-functional to the client). |
