Need a clarification on coordinator mySQL way of use.

HI all.
I have a datasource on which a realtime node are successfully feeding data (from a Kafka firehose).
I am able both to query the broker for data, and also the coordinator to understand if it “knows” about that datasource, and all seems ok:

curl --silent -XGET -H’Content-type: application/json’ “http://mbslbm00.p.rmce.libero.it:8080/druid/coordinator/v1/datasources/sso_tbed_skc”| jq ‘.’

{
“tiers”: {
“_default_tier”: {
“segmentCount”: 4,
“size”: 0
}
},
“segments”: {
“minTime”: “2016-03-01T00:00:00.000Z”,
“count”: 4,
“maxTime”: “2016-03-05T00:00:00.000Z”,
“size”: 0
}
}

Does http://druid.io/docs/latest/ingestion/faq.html help at all?

most common cause: your historical cluster is out of capacity or you have incorrect configuration

Thanks Fangjin,
it was related to

druid.segmentCache.locations
value. I increased it.

Best regards,
Marco