Allow arbitrary haproxy_server_options to be supplied to HAProxy.

lib/synapse/haproxy.rb

@@ -704,6 +704,16 @@ def generate_backend_stanza(watcher, config)
       # setting the enabled state.
       watcher.backends.each do |backend|
         backend_name = construct_name(backend)
+        # If we have information in the state file that allows us to detect
+        # server option changes, use that to potentially force a restart
+        if backends.has_key?(backend_name)
+          old_backend = backends[backend_name]
+          if (old_backend.fetch('haproxy_server_options', "") !=
+              backend.fetch('haproxy_server_options', ""))
+            log.info "synapse: restart required because haproxy_server_options changed for #{backend_name}"
+            @restart_required = true
+          end
+        end
         backends[backend_name] = backend.merge('enabled' => true)
       end
 
@@ -718,7 +728,8 @@ def generate_backend_stanza(watcher, config)
           backend = backends[backend_name]
           b = "\tserver #{backend_name} #{backend['host']}:#{backend['port']}"
           b = "#{b} cookie #{backend_name}" unless config.include?('mode tcp')
-          b = "#{b} #{watcher.haproxy['server_options']}"
+          b = "#{b} #{watcher.haproxy['server_options']}" if watcher.haproxy['server_options']
+          b = "#{b} #{backend['haproxy_server_options']}" if backend['haproxy_server_options']
           b = "#{b} disabled" unless backend['enabled']
           b }
       ]

lib/synapse/service_watcher/README.md

@@ -1,11 +1,15 @@
 ## Watcher Classes
 
 Watchers are the piece of Synapse that watch an external service registry
-and reflect those changes in the local HAProxy state. Watchers should look
-like:
+and reflect those changes in the local HAProxy state. Watchers should conform
+to the interface specified by `BaseWatcher` and when your watcher has received
+an update from the service registry you should call
+`set_backends(new_backends)` to trigger a sync of your watcher state with local
+HAProxy state. See the [`Backend Interface`](#backend_interface) section for
+what service registrations Synapse understands.
 
 ```ruby
-require "synapse/service\_watcher/base"
+require "synapse/service_watcher/base"
 
 module Synapse::ServiceWatcher
   class MyWatcher < BaseWatcher
@@ -26,7 +30,8 @@ module Synapse::ServiceWatcher
       # here, validate any required options in @discovery
     end
 
-    ...
+    ... setup watches, poll, etc ... and call set_backends when you have new
+    ... backends to set
 
   end
 end
@@ -38,7 +43,7 @@ the watcher configuration.  Every watcher is passed configuration with the
 `method` key, e.g. `zookeeper` or `ec2tag`.
 
 #### Class Location
-Synapse expects to find your class at `synapse/service\_watcher/#{method}`. You
+Synapse expects to find your class at `synapse/service_watcher/#{method}`. You
 must make your watcher available at that path, and Synapse can "just work" and
 find it.
 
@@ -51,24 +56,29 @@ method_class  = method.split('_').map{|x| x.capitalize}.join.concat('Watcher')
 ```
 
 This has the effect of taking the method, splitting on '_', capitalizing each
-part and recombining with an added 'Watcher' on the end. So `zookeeper\_dns`
+part and recombining with an added 'Watcher' on the end. So `zookeeper_dns`
 becomes `ZookeeperDnsWatcher`, and `zookeeper` becomes `Zookeeper`. Make sure
 your class name is correct.
 
-### Watcher Class Interface
-ServiceWatchers should conform to the interface provided by `BaseWatcher`:
+<a name="backend_interface"/>
+### Backend interface
+Synapse understands the following fields in service backends (which are pulled
+from the service registries):
 
-```
-start: start the watcher on a service registry
+`host` (string): The hostname of the service instance
 
-stop: stop the watcher on a service registry
+`port` (integer): The port running the service on `host`
 
-ping?: healthcheck the watcher's connection to the service registry
+`name` (string, optional): The human readable name to refer to this service instance by
 
-private
-validate_discovery_opts: check if the configuration has the right options
-```
+`weight` (float, optional): The weight that this backend should get when load
+balancing to this service instance. Full support for updating HAProxy based on
+this is still a WIP.
 
-When your watcher has received an update from the service registry you should
-call `set\_backends(new\_backends)` to trigger a sync of your watcher state
-with local HAProxy state.
+`haproxy_server_options` (string, optional): Any haproxy server options
+specific to this particular server. They will be applied to the generated
+`server` line in the HAProxy configuration. If you want Synapse to react to
+changes in these lines you will need to enable the `state_file_path` option
+in the main synapse configuration. In general the HAProxy backend level
+`haproxy.server_options` setting is preferred to setting this per server
+in your backends.

spec/lib/synapse/haproxy_spec.rb

@@ -14,6 +14,15 @@ class MockWatcher; end;
     mockWatcher
   end
 
+  let(:mockwatcher_with_server_options) do
+    mockWatcher = double(Synapse::ServiceWatcher)
+    allow(mockWatcher).to receive(:name).and_return('example_service')
+    backends = [{ 'host' => 'somehost', 'port' => '5555', 'haproxy_server_options' => 'backup'}]
+    allow(mockWatcher).to receive(:backends).and_return(backends)
+    allow(mockWatcher).to receive(:haproxy).and_return({'server_options' => "check inter 2000 rise 3 fall 2"})
+    mockWatcher
+  end
+
   it 'updating the config' do
     expect(subject).to receive(:generate_config)
     subject.update_config([mockwatcher])
@@ -29,4 +38,8 @@ class MockWatcher; end;
     expect(subject.generate_backend_stanza(mockwatcher, mockConfig)).to eql(["\nbackend example_service", ["\tmode tcp"], ["\tserver somehost:5555 somehost:5555 check inter 2000 rise 3 fall 2"]])
   end
 
+  it 'respects haproxy_server_options' do
+    mockConfig = []
+    expect(subject.generate_backend_stanza(mockwatcher_with_server_options, mockConfig)).to eql(["\nbackend example_service", [], ["\tserver somehost:5555 somehost:5555 cookie somehost:5555 check inter 2000 rise 3 fall 2 backup"]])
+  end
 end