It may be necessary to set HTTP headers on the Elastica client, for example an Authorization header.
They can be set using the headers configuration key:
# app/config/config.yml
fos_elastica:
clients:
default:
host: example.com
port: 80
headers:
Authorization: "Basic jdumrGK7rY9TMuQOPng7GZycmxyMHNoir=="