Add keepalive configs as templated values

Author: JDPrabasha

router/src/main/resources/Dockerfile

@@ -47,6 +47,10 @@ ENV ROUTER_LABEL="Default"
 ENV ROUTER_PRIVATE_KEY_PATH=/home/wso2/security/keystore/mg.key
 ENV ROUTER_PUBLIC_CERT_PATH=/home/wso2/security/keystore/mg.pem
 
+ENV KEEPALIVE_PROBES=3
+ENV KEEPALIVE_TIMEOUT=60
+ENV KEEPALIVE_INTERVAL=30
+
 ENV ADAPTER_HOST=adapter
 ENV ADAPTER_PORT=18000
 ENV ADAPTER_CA_CERT_PATH=/home/wso2/security/truststore/mg.pem

router/src/main/resources/envoy.yaml.template

@@ -42,9 +42,9 @@ static_resources:
       connect_timeout: 1s
       upstream_connection_options:
         tcp_keepalive:
-          keepalive_probes: 3
-          keepalive_time: 300
-          keepalive_interval: 30
+          keepalive_probes: '${KEEPALIVE_PROBES}'
+          keepalive_time: '${KEEPALIVE_TIMEOUT}'
+          keepalive_interval: '${KEEPALIVE_INTERVAL}'
       load_assignment:
         cluster_name: xds_cluster
         endpoints: