caddy-frontend: Publish only active slaves from main partition

As some of the nodes can lag behind, the system can be in state, that those
nodes will send inactive (also destroyed) slave publish information. Before
publishing it to master, check if each of slaves is really present on master.

Tasks:

 - [x] prove it really works on simulated environment
 - [x] check impact on massive simulated environment
 - [x] cover with a test (optionally)
 - [ ] check test results with this change

/reviewed-on !519

software/caddy-frontend/buildout.hash.cfg

@@ -26,7 +26,7 @@ md5sum = 6fd023f0d29421d8579f0b3351473bb0
 
 [template-apache-replicate]
 filename = instance-apache-replicate.cfg.in
-md5sum = 86f15c85054800a55a7093d37b03cdce
+md5sum = 15d6b5b00ab1f74d42863c90f2537981
 
 [template-slave-list]
 filename = templates/apache-custom-slave-list.cfg.in
@@ -38,7 +38,7 @@ md5sum = 54ae95597a126ae552c3a913ddf29e5e
 
 [template-replicate-publish-slave-information]
 filename = templates/replicate-publish-slave-information.cfg.in
-md5sum = 01efde8febafcff6dde2ebb43e75a9e4
+md5sum = 73e3d1e55a98a3c4d25a1618aa584fff
 
 [template-caddy-frontend-configuration]
 filename = templates/Caddyfile.in

software/caddy-frontend/instance-apache-replicate.cfg.in

@@ -223,6 +223,13 @@ custom-group = ${dynamic-publish-slave-information:rendered}
 {{ frontend_section }} = {{ "${%s:connection-slave-instance-information-list}" % frontend_section }}
 {% endfor %}
 
+[active-slave-instance]
+{% for slave_instance in slave_instance_list %}
+{# Provide a list of slave titles send by master, in order to filter out already destroyed slaves #}
+{# Note: This functionality is not yet covered by tests, please modify with care #}
+{{ slave_instance['slave_title'] }} = active
+{% endfor %}
+
 [dynamic-publish-slave-information]
 < = jinja2-template-base
 template = {{ template_publish_slave_information }}
@@ -231,6 +238,7 @@ extensions = jinja2.ext.do
 extra-context =
     section slave_information slave-information
     section rejected_slave_information rejected-slave-information
+    section active_slave_instance_dict active-slave-instance
 
 [monitor-conf-parameters]
 monitor-url-list +=

software/caddy-frontend/templates/replicate-publish-slave-information.cfg.in

@@ -36,6 +36,9 @@
 
 # Publish information for each slave
 {% for slave_reference, slave_information in slave_information_dict.iteritems() %}
+{#   Filter out destroyed, so not existing anymore, slaves #}
+{#   Note: This functionality is not yet covered by tests, please modify with care #}
+{%   if slave_reference in active_slave_instance_dict %}
 {%     set publish_section_title = 'publish-%s' % slave_reference %}
 {%     do part_list.append(publish_section_title) %}
 [{{ publish_section_title }}]
@@ -48,6 +51,7 @@ log-access-url = {{ dumps(json_module.dumps(log_access_url)) }}
 {%     for key, value in slave_information.iteritems() %}
 {{ key }} = {{ dumps(value) }}
 {%     endfor %}
+{%   endif %}
 {% endfor %}
 
 [buildout]