variable ADDITIONAL_SERVICES: add proxy backends outside current project

README.md

@@ -152,6 +152,7 @@ Settings in this part is immutable, you have to redeploy HAProxy service to make
 |STATS_AUTH|stats:stats|username and password required to access the Haproxy stats.|
 |STATS_PORT|1936|port for the HAProxy stats section. If this port is published, stats can be accessed at `http://<host-ip>:<STATS_PORT>/`
 |TIMEOUT|connect 5000, client 50000, server 50000|comma-separated list of HAProxy `timeout` entries to the `default` section.|
+|ADDITIONAL_SERVICES||List of additional services to balance (es: `prj1:web,prj2:sql`). Discovery will be based on `com.docker.compose.[project|service]` container labels. This environment variable only works on compose v2, and the referenced services must be on a network accessible to this containers.|
 
 ### Settings in linked application services###
 

haproxy/haproxycfg.py

@@ -80,6 +80,17 @@ def _init_new_links():
             logger.info("Docker API error, regressing to legacy links mode: ", e)
             return None
         links, Haproxy.cls_linked_services = NewLinkHelper.get_new_links(docker, haproxy_container)
+
+        try:
+            additional_services_str = os.environ.get("ADDITIONAL_SERVICES", "")
+            if additional_services_str!="":
+                additional_services = additional_services_str.split(",")
+                NewLinkHelper.get_additional_links(docker, additional_services, haproxy_container, \
+                                                   links, Haproxy.cls_linked_services)
+        except Exception as e:
+            logger.info("Error loading ADDITIONAL_SERVICES: %s" % str(e))
+            return None
+
         logger.info("Linked service: %s", ", ".join(NewLinkHelper.get_service_links_str(links)))
         logger.info("Linked container: %s", ", ".join(NewLinkHelper.get_container_links_str(links)))
         return links

haproxy/helper/new_link_helper.py

@@ -15,6 +15,41 @@ def get_new_links(docker, haproxy_container):
     links = _calc_links(docker, linked_compose_services, project)
     return links, ["%s_%s" % (project, service) for service in linked_compose_services]
 
+def get_additional_links(docker, additional_services, haproxy_container, links, linked_services):
+    networks_data = docker.networks()
+    haproxy_networks_ids = _find_container_networks_ids(haproxy_container, networks_data)
+    import pprint
+    for _container in docker.containers():
+        container_id = _container.get("Id", "")
+        container = docker.inspect_container(container_id)
+        compose_project = container.get("Config", {}).get("Labels", {}).get("com.docker.compose.project", "")
+        compose_service = container.get("Config", {}).get("Labels", {}).get("com.docker.compose.service", "")
+        for _service in additional_services:
+            terms = _service.strip().split(":")
+            if len(terms) == 2:
+              if terms[0].strip() == compose_project and terms[1].strip() == compose_service:
+                  container_networks_ids = _find_container_networks_ids(container, networks_data)
+                  if set(container_networks_ids).intersection(haproxy_networks_ids):
+                      if _service not in linked_services:
+                          linked_services.append(_service)
+                      container_name = container.get("Name").lstrip("/")
+                      container_evvvars = _get_container_envvars(container)
+                      endpoints = _get_container_endpoints(container, container_name)
+                      links[container_id] = {"service_name": _service,
+                                             "container_envvars": container_evvvars,
+                                             "container_name": container_name,
+                                             "endpoints": endpoints,
+                                             "compose_service": compose_service,
+                                             "compose_project": compose_project}
+                  else:
+                      logger.info("Ignoring container '%s': no shared network with haproxy")
+
+def _find_container_networks_ids(container, networks_data):
+    ids = []
+    for network in networks_data:
+        if container['Id'] in network['Containers'].keys():
+            ids.append(network['Id'])
+    return ids
 
 def _calc_links(docker, linked_compose_services, project):
     links = {}
@@ -76,7 +111,9 @@ def _get_linked_compose_services(networks, project):
 
     haproxy_links = []
     for network in networks.itervalues():
-        haproxy_links.extend(network.get("Links", []))
+        network_links=network.get("Links", [])
+        if network_links:
+          haproxy_links.extend(network_links)
 
     linked_services = []
     for link in haproxy_links: