[OPS-1711]: user agents to be rate limited

playbooks/roles/nginx/templates/edx/app/nginx/sites-available/lms.j2

@@ -14,6 +14,9 @@ upstream lms-backend {
 {%- if EDXAPP_ENABLE_RATE_LIMITING -%}
 # Make Zone
 limit_req_zone $cookie_{{ EDXAPP_SESSION_COOKIE_NAME }} zone=cookies:10m rate={{ EDXAPP_COURSES_REQUEST_RATE }};
+{% for agent in EDXAPP_COURSES_USER_AGENTS %}
+limit_req_zone {{ agent.agent_name }} $binary_remote_addr zone=agents:10m rate={{ agent.rate }};
+{% endfor %}
 {%- endif %}
 
 
@@ -205,6 +208,7 @@ error_page {{ k }} {{ v }};
     {%- if EDXAPP_ENABLE_RATE_LIMITING -%}
     # Set Limit
     limit_req zone=cookies burst={{ EDXAPP_COURSES_REQUEST_BURST_RATE }};
+    limit_req zone=agents burst={{ EDXAPP_COURSES_USER_AGENT_BURST_RATE }};
     error_page  503 = /server/rate-limit.html;
     {%- endif -%}