Weights support in Synapse

README.md

@@ -273,6 +273,7 @@ This section is its own hash, which should contain the following keys:
 * `backend_order`: optional: how backends should be ordered in the `backend` stanza. (default is shuffling). Setting to `asc` means sorting backends in ascending alphabetical order before generating stanza. `desc` means descending alphabetical order. `no_shuffle` means no shuffling or sorting.
 * `shared_frontend`: optional: haproxy configuration directives for a shared http frontend (see below)
 * `cookie_value_method`: optional: default value is `name`, it defines the way your backends receive a cookie value in http mode. If equal to `hash`, synapse hashes backend names on cookie value assignation of your discovered backends, useful when you want to use haproxy cookie feature but you do not want that your end users receive a Set-Cookie with your server name and ip readable in clear.
+* `ignore_weights`: optional: stops haproxy backend 'weight' options being generated, even if the Nerve registrations contain this information. This will cause all backend servers to be treated equally by haproxy. This defaults to true so weights will *NOT* be used by default.
 
 <a name="haproxy"/>
 ### Configuring HAProxy ###

lib/synapse/haproxy.rb

@@ -714,6 +714,11 @@ def generate_backend_stanza(watcher, config)
             log.info "synapse: restart required because haproxy_server_options changed for #{backend_name}"
             @restart_required = true
           end
+          if (old_backend.fetch('weight', "") !=
+              backend.fetch('weight', ""))
+            log.info "synapse: restart required because weight changed for #{backend_name}"
+            @restart_required = true
+          end
         end
         backends[backend_name] = backend.merge('enabled' => true)
       end
@@ -748,6 +753,17 @@ def generate_backend_stanza(watcher, config)
             end
           end
           b = "#{b} #{watcher.haproxy['server_options']}" if watcher.haproxy['server_options']
+          if backend.has_key?('weight')
+            # Check if server_options/haproxy_server_options already contains weight, if so log a warning
+            if watcher.haproxy.fetch('server_options', '').include? 'weight'
+              log.warn "synapse: weight is defined in both server_options and nerve. nerve weight takes precedence"
+            end
+            if backend['haproxy_server_options'] and backend['haproxy_server_options'].include? 'weight'
+              log.warn "synapse: weight is defined in both haproxy_server_options and nerve. nerve weight takes precedence"
+            end
+            weight = backend['weight'].to_i
+            b = "#{b} weight #{weight}"
+          end
           b = "#{b} #{backend['haproxy_server_options']}" if backend['haproxy_server_options']
           b = "#{b} disabled" unless backend['enabled']
           b }

spec/lib/synapse/haproxy_spec.rb

@@ -5,15 +5,18 @@ class MockWatcher; end;
 describe Synapse::Haproxy do
   subject { Synapse::Haproxy.new(config['haproxy']) }
 
-  let(:mockwatcher) do
+  def createmockwatcher(backends)
     mockWatcher = double(Synapse::ServiceWatcher)
     allow(mockWatcher).to receive(:name).and_return('example_service')
-    backends = [{ 'host' => 'somehost', 'port' => 5555}]
     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
 
+  let(:mockwatcher) do
+    createmockwatcher [{ 'host' => 'somehost', 'port' => '5555'}]
+  end
+
   let(:mockwatcher_with_server_options) do
     mockWatcher = double(Synapse::ServiceWatcher)
     allow(mockWatcher).to receive(:name).and_return('example_service2')
@@ -275,4 +278,24 @@ class MockWatcher; end;
     expect(subject.generate_frontend_stanza(mockwatcher_frontend_with_bind_address, mockConfig)).to eql(["\nfrontend example_service5", [], "\tbind 127.0.0.3:2200", "\tdefault_backend example_service5"])
   end
 
+  it 'generates backend stanza with weight' do
+    mockConfig = []
+    expect(subject.generate_backend_stanza(createmockwatcher([{ 'weight' => 1, 'host' => 'somehost', 'port' => '5555'}]), mockConfig)).to eql(["\nbackend example_service", [], ["\tserver somehost:5555 somehost:5555 cookie somehost:5555 check inter 2000 rise 3 fall 2 weight 1"]])
+  end
+
+  it 'generates backend stanza with bad weight = 0' do
+    mockConfig = []
+    expect(subject.generate_backend_stanza(createmockwatcher([{ 'weight' => 'hi', 'host' => 'somehost', 'port' => '5555'}]), mockConfig)).to eql(["\nbackend example_service", [], ["\tserver somehost:5555 somehost:5555 cookie somehost:5555 check inter 2000 rise 3 fall 2 weight 0"]])
+  end
+
+  it 'generates backend stanza with nil weight = 0' do
+    mockConfig = []
+    expect(subject.generate_backend_stanza(createmockwatcher([{ 'weight' => nil, 'host' => 'somehost', 'port' => '5555'}]), mockConfig)).to eql(["\nbackend example_service", [], ["\tserver somehost:5555 somehost:5555 cookie somehost:5555 check inter 2000 rise 3 fall 2 weight 0"]])
+  end
+
+  it 'generates backend stanza without weight' do
+    mockConfig = []
+    expect(subject.generate_backend_stanza(createmockwatcher([{ 'host' => 'somehost', 'port' => '5555'}]), mockConfig)).to eql(["\nbackend example_service", [], ["\tserver somehost:5555 somehost:5555 cookie somehost:5555 check inter 2000 rise 3 fall 2"]])
+  end
+
 end

spec/lib/synapse/service_watcher_base_spec.rb

@@ -135,5 +135,37 @@ def remove_arg(name)
         expect(subject.backends).to eq(matching_labeled_backends)
       end
     end
+
+    context 'with weights defined' do
+      let(:backends_with_weight)  { [
+        { 'name' => 'server1', 'host' => 'server1', 'port' => 1111, 'weight' => 11 },
+        { 'name' => 'server2', 'host' => 'server2', 'port' => 2222, 'weight' => 22 },
+      ] }
+      let(:non_matching_weight_backends) { [
+        { 'name' => 'server1', 'host' => 'server1', 'port' => 1111, 'weight' => 33 },
+        { 'name' => 'server2', 'host' => 'server2', 'port' => 2222, 'weight' => 22 },
+      ] }
+      let(:backends_with_non_matching_weight_duplicates) { [
+        { 'name' => 'server1', 'host' => 'server1', 'port' => 1111, 'weight' => 11 },
+        { 'name' => 'server1', 'host' => 'server1', 'port' => 1111, 'weight' => 33 },
+        { 'name' => 'server2', 'host' => 'server2', 'port' => 2222, 'weight' => 22 },
+      ] }
+      it 'updates backends only when weights change' do
+        expect(subject).to receive(:'reconfigure!').exactly(:twice)
+        expect(subject.send(:set_backends, backends_with_weight)).to equal(true)
+        expect(subject.backends).to eq(backends_with_weight)
+        expect(subject.send(:set_backends, non_matching_weight_backends)).to equal(true)
+        expect(subject.backends).to eq(non_matching_weight_backends)
+        expect(subject.send(:set_backends, non_matching_weight_backends)).to equal(false)
+        expect(subject.backends).to eq(non_matching_weight_backends)
+      end
+      it 'ignores duplicates even with non-matching weights' do
+        expect(subject).to receive(:'reconfigure!').exactly(:once)
+        expect(subject.send(:set_backends, backends_with_weight)).to equal(true)
+        expect(subject.backends).to eq(backends_with_weight)
+        expect(subject.send(:set_backends, backends_with_non_matching_weight_duplicates)).to equal(false)
+        expect(subject.backends).to eq(backends_with_weight)
+      end
+    end
   end
 end