I have add hostname in all the logs, I want create a dashboard which shows No.of logs per hostname.
Do you want a metric, or something else?
I have metric, i want to create a dashboard.
For Eg> api_call:LIST cust_id:1234567A message: This is my message hostname:ip-1-2-1-1
api_call:LIST cust_id:1234567A message: This is my message hostname:ip-1-2-1-2
api_call:LIST cust_id:1234567A message: This is my message hostname:ip-1-2-1-3
api_call:LIST cust_id:1234567A message: This is my message hostname:ip-1-2-1-4
I want to create dashboard based on "hostname"
Right, but what sort of visualisation do you want to create?
A metric, a bar graph, a line chart, a pie chart, something else?
Pie chart would do the job
Just create a pie chart and then use a terms agg on the hostname field, easy! 
The add a field is not present in the drop down list.
Click >> Visualize >> pie Chart >> new search >> split slices >> drop down list aggregation >> significant Terms >> Field >> There is no new filed
How can get the few filed populated in the drop down list??
Should I restart Kibana?
Is there a suitable field in your mappings? Have you refreshed the index in KB?
How to refresh index ? Pls guide
Settings -> Indices -> click your index on the left -> click the orange refresh button.