PBC Coverage Queries

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).