Andrzej Bialecki created SOLR-15019:
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Summary: Replica placement API needs a way to fetch existing
replica metrics
Key: SOLR-15019
URL: https://issues.apache.org/jira/browse/SOLR-15019
Project: Solr
Issue Type: Improvement
Security Level: Public (Default Security Level. Issues are Public)
Reporter: Andrzej Bialecki
Replica placement API was introduced in SOLR-14613. It offers a few sample (and
simple) implementations of placement plugins.
However, this API doesn't offer support for retrieving per-replica metrics,
which are required for calculating more realistic placements. For example, when
calculating placements for ADDREPLICA on an already existing collection the
plugin should know what is the size of replica in order to avoid placing large
replicas on nodes with insufficient free disk space.
After discussing this with [~ilan] we propose the following additions to the
API:
* use the existing {{AttributeFetcher}} interface as a facade for retrieving
per-replica values (currently it only retrieves per-node values)
* add {{ShardValues}} interface to represent strongly-typed API for key
metrics, such as replica size, number of docs, number of update and search
requests.
Plugins could then use this API like this:
{code}
AttributeFetcher attributeFetcher = ...
SolrCollection solrCollection = ...
Set<String> metricNames = ...
attributeFetcher.requestCollectionMetrics(solrCollection,
solrCollection.getShardNames(), metricNames);
AttributeValues attributeValues = attributeFetcher.fetchAttributes();
ShardValues shardValues =
attributeValues.getShardMetrics(solrCollection.getName(), shardName);
int sizeInGB = shardValues.getSizeInGB(); // retrieves shard leader metrics
int replicaSizeInGB = shardValues.getSizeInGB(replica);
{code}
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