Not enough servers or node capacity

I am trying to test my druid set-up on a local machine with ofcourse very less amount of data (just one instance of the data).

I am using tranquility server to ingest real time data into druid.

All my nodes use by default config files provided in the druid bundle. I have just modified the ingestion spec according to my needs.

Since I am just testing it , I am trying to ingest just one instance of the data.

It do get ingested and everything seems to be working fine but when I checked my co-ordinator console , the real time ingestion task is in the running state for more than two hours before it goes to the completed status.

I checked my coordinator console log n saw a warning: Not enough servers or node capacity to assign segment.

Is it because of the memory related issue or is it because of something else. What does it mean when it says: expected replicants [2]. Thank You in advance for the help and the explanation.