Add InproxyPersonalPairingMaxBrokerSpecCount

psiphon/common/parameters/parameters.go

@@ -409,6 +409,7 @@ const (
 	InproxyAllBrokerSpecs                              = "InproxyAllBrokerSpecs"
 	InproxyBrokerSpecs                                 = "InproxyBrokerSpecs"
 	InproxyPersonalPairingBrokerSpecs                  = "InproxyPersonalPairingBrokerSpecs"
+	InproxyPersonalPairingMaxBrokerSpecCount           = "InproxyPersonalPairingMaxBrokerSpecCount"
 	InproxyProxyBrokerSpecs                            = "InproxyProxyBrokerSpecs"
 	InproxyProxyPersonalPairingBrokerSpecs             = "InproxyProxyPersonalPairingBrokerSpecs"
 	InproxyClientBrokerSpecs                           = "InproxyClientBrokerSpecs"
@@ -1041,6 +1042,7 @@ var defaultParameters = map[string]struct {
 	InproxyAllBrokerSpecs:                              {value: InproxyBrokerSpecsValue{}, flags: serverSideOnly},
 	InproxyBrokerSpecs:                                 {value: InproxyBrokerSpecsValue{}},
 	InproxyPersonalPairingBrokerSpecs:                  {value: InproxyBrokerSpecsValue{}},
+	InproxyPersonalPairingMaxBrokerSpecCount:           {value: 3, minimum: 1},
 	InproxyProxyBrokerSpecs:                            {value: InproxyBrokerSpecsValue{}},
 	InproxyProxyPersonalPairingBrokerSpecs:             {value: InproxyBrokerSpecsValue{}},
 	InproxyClientBrokerSpecs:                           {value: InproxyBrokerSpecsValue{}},

psiphon/config.go

@@ -1114,6 +1114,7 @@ type Config struct {
 	InproxyPersonalPairingBrokerSpecs                       parameters.InproxyBrokerSpecsValue               `json:",omitempty"`
 	InproxyProxyBrokerSpecs                                 parameters.InproxyBrokerSpecsValue               `json:",omitempty"`
 	InproxyProxyPersonalPairingBrokerSpecs                  parameters.InproxyBrokerSpecsValue               `json:",omitempty"`
+	InproxyPersonalPairingMaxBrokerSpecCount                *int                                             `json:",omitempty"`
 	InproxyClientBrokerSpecs                                parameters.InproxyBrokerSpecsValue               `json:",omitempty"`
 	InproxyClientPersonalPairingBrokerSpecs                 parameters.InproxyBrokerSpecsValue               `json:",omitempty"`
 	InproxyReplayBrokerDialParametersTTLSeconds             *int                                             `json:",omitempty"`
@@ -2788,6 +2789,10 @@ func (config *Config) makeConfigParameters() map[string]interface{} {
 		applyParameters[parameters.InproxyProxyPersonalPairingBrokerSpecs] = config.InproxyProxyPersonalPairingBrokerSpecs
 	}
 
+	if config.InproxyPersonalPairingMaxBrokerSpecCount != nil {
+		applyParameters[parameters.InproxyPersonalPairingMaxBrokerSpecCount] = *config.InproxyPersonalPairingMaxBrokerSpecCount
+	}
+
 	if len(config.InproxyClientBrokerSpecs) > 0 {
 		applyParameters[parameters.InproxyClientBrokerSpecs] = config.InproxyClientBrokerSpecs
 	}
@@ -3797,6 +3802,10 @@ func (config *Config) setDialParametersHash() {
 		hash.Write([]byte("InproxyProxyPersonalPairingBrokerSpecs"))
 		hash.Write([]byte(fmt.Sprintf("%+v", config.InproxyProxyPersonalPairingBrokerSpecs)))
 	}
+	if config.InproxyPersonalPairingMaxBrokerSpecCount != nil {
+		hash.Write([]byte("InproxyPersonalPairingMaxBrokerSpecCount"))
+		binary.Write(hash, binary.LittleEndian, int64(*config.InproxyPersonalPairingMaxBrokerSpecCount))
+	}
 	if len(config.InproxyClientBrokerSpecs) > 0 {
 		hash.Write([]byte("InproxyClientBrokerSpecs"))
 		hash.Write([]byte(fmt.Sprintf("%+v", config.InproxyClientBrokerSpecs)))

psiphon/inproxy.go

@@ -434,6 +434,28 @@ func NewInproxyBrokerClientInstance(
 		PRNG := prng.NewPRNGWithSeed(&seed)
 
 		permutedIndexes := PRNG.Perm(len(brokerSpecs))
+
+		// Minimize rendezvous time by reducing the number of brokers this
+		// personal compartment ID maps over to. With a reduced number of
+		// possible brokers, the client and proxy have fewer brokers to check
+		// after fail overs.
+		//
+		// Given that permutedIndexes is a randomized shuffle, each personal
+		// compartment ID will map to a different set of reduced brokers,
+		// preserving overall broker load balancing.
+		//
+		// InproxyPersonalPairingMaxBrokerSpecCount will be configured high
+		// enough to also preserve reasonable availability when brokers fail.
+		// When InproxyPersonalPairingMaxBrokerSpecCount is 0, there is no max.
+		//
+		// This scheme depends on the len(personalCompartmentIDs) <= 1
+		// constraint checked above.
+
+		maxBrokerSpecs := p.Int(parameters.InproxyPersonalPairingMaxBrokerSpecCount)
+		if maxBrokerSpecs > 0 && len(permutedIndexes) > maxBrokerSpecs {
+			permutedIndexes = permutedIndexes[:maxBrokerSpecs]
+		}
+
 		selectedIndex := permutedIndexes[brokerSelectCount%len(permutedIndexes)]
 		brokerSpecs = brokerSpecs[selectedIndex : selectedIndex+1]