Matchmaker improvements, support for party matchmaking. (#521)

The format is based on [keep a changelog](http://keepachangelog.com) and this project uses [semantic versioning](http://semver.org).

## [Unreleased]

### Added

- Add party matching support to matchmaker.

- Add options to matchmaker to control how long tickets are allowed to wait for their preferred match.

### Changed

- Matchmaker improvements to quality of matching and player count range handling.

- Build with Go 1.15.6 release.

## [2.15.0] - 2020-11-28

	github.com/gorilla/mux v1.7.4

	github.com/gorilla/websocket v1.4.2

	github.com/grpc-ecosystem/grpc-gateway/v2 v2.0.1

	github.com/heroiclabs/nakama-common v1.10.1-0.20201216142705-136e6c0d214f

	github.com/heroiclabs/nakama-common v1.10.1-0.20210112124918-da701a0f7020

	github.com/jackc/fake v0.0.0-20150926172116-812a484cc733 // indirect

	github.com/jackc/pgx v3.5.0+incompatible

	github.com/jmhodges/levigo v1.0.0 // indirect

github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=

github.com/heroiclabs/nakama-common v1.10.1-0.20201216142705-136e6c0d214f h1:RTKN7L8sWQjsyBEv4fW65MsHbLxnO/NbgR/l+M3uaF4=

github.com/heroiclabs/nakama-common v1.10.1-0.20201216142705-136e6c0d214f/go.mod h1:li7bMQwOYA0NjT3DM4NKQBNruULPa2hrqdiSaaTwui4=

github.com/heroiclabs/nakama-common v1.10.1-0.20210112124918-da701a0f7020 h1:6jaVk2j7QSdSb4APKMQjDDa/s6FgxcZF+vAKszoCbkg=

github.com/heroiclabs/nakama-common v1.10.1-0.20210112124918-da701a0f7020/go.mod h1:li7bMQwOYA0NjT3DM4NKQBNruULPa2hrqdiSaaTwui4=

github.com/hpcloud/tail v1.0.0 h1:nfCOvKYfkgYP8hkirhJocXT2+zOD8yUNjXaWfTlyFKI=

github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=

github.com/ianlancetaylor/demangle v0.0.0-20181102032728-5e5cf60278f6/go.mod h1:aSSvb/t6k1mPoxDqO4vJh6VOCGPwU4O0C2/Eqndh1Sc=

	// Start up server components.

	metrics := server.NewMetrics(logger, startupLogger, config)

	matchmaker := server.NewLocalMatchmaker(startupLogger, config.GetName())

	sessionRegistry := server.NewLocalSessionRegistry(metrics)

	tracker := server.StartLocalTracker(logger, config, sessionRegistry, metrics, jsonpbMarshaler)

	router := server.NewLocalMessageRouter(sessionRegistry, tracker, jsonpbMarshaler)

	if err != nil {

		startupLogger.Fatal("Failed initializing runtime modules", zap.Error(err))

	}

	matchmaker := server.NewLocalMatchmaker(logger, startupLogger, config, router, runtime)

	leaderboardScheduler.Start(runtime)

	apiServer.Stop()

	consoleServer.Stop()

	metrics.Stop(logger)

	matchmaker.Stop()

	leaderboardScheduler.Stop()

	tracker.Stop()

	sessionRegistry.Stop()

	GetTracker() *TrackerConfig

	GetConsole() *ConsoleConfig

	GetLeaderboard() *LeaderboardConfig

	GetMatchmaker() *MatchmakerConfig

	Clone() (Config, error)

}

	if config.GetLeaderboard().CallbackQueueWorkers < 1 {

		logger.Fatal("Leaderboard callback queue workers must be >= 1", zap.Int("leaderboard.callback_queue_workers", config.GetLeaderboard().CallbackQueueWorkers))

	}

	if config.GetMatchmaker().MaxTickets < 1 {

		logger.Fatal("Matchmaker maximum ticket count must be >= 1", zap.Int("matchmaker.max_tickets", config.GetMatchmaker().MaxTickets))

	}

	if config.GetMatchmaker().IntervalSec < 1 {

		logger.Fatal("Matchmaker interval time seconds must be >= 1", zap.Int("matchmaker.interval_sec", config.GetMatchmaker().IntervalSec))

	}

	if config.GetMatchmaker().MaxIntervals < 1 {

		logger.Fatal("Matchmaker max intervals must be >= 1", zap.Int("matchmaker.max_intervals", config.GetMatchmaker().MaxIntervals))

	}

	// If the runtime path is not overridden, set it to `datadir/modules`.

	if config.GetRuntime().Path == "" {

	Tracker          *TrackerConfig     `yaml:"tracker" json:"tracker" usage:"Presence tracker properties."`

	Console          *ConsoleConfig     `yaml:"console" json:"console" usage:"Console settings."`

	Leaderboard      *LeaderboardConfig `yaml:"leaderboard" json:"leaderboard" usage:"Leaderboard settings."`

	Matchmaker       *MatchmakerConfig  `yaml:"matchmaker" json:"matchmaker" usage:"Matchmaker settings."`

}

// NewConfig constructs a Config struct which represents server settings, and populates it with default values.

		Tracker:          NewTrackerConfig(),

		Console:          NewConsoleConfig(),

		Leaderboard:      NewLeaderboardConfig(),

		Matchmaker:       NewMatchmakerConfig(),

	}

}

	configTracker := *(c.Tracker)

	configConsole := *(c.Console)

	configLeaderboard := *(c.Leaderboard)

	configMatchmaker := *(c.Matchmaker)

	nc := &config{

		Name:             c.Name,

		Datadir:          c.Datadir,

		Tracker:          &configTracker,

		Console:          &configConsole,

		Leaderboard:      &configLeaderboard,

		Matchmaker:       &configMatchmaker,

	}

	nc.Socket.CertPEMBlock = make([]byte, len(c.Socket.CertPEMBlock))

	copy(nc.Socket.CertPEMBlock, c.Socket.CertPEMBlock)

	return c.Leaderboard

}

func (c *config) GetMatchmaker() *MatchmakerConfig {

	return c.Matchmaker

}

// LoggerConfig is configuration relevant to logging levels and output.

type LoggerConfig struct {

	Level    string `yaml:"level" json:"level" usage:"Log level to set. Valid values are 'debug', 'info', 'warn', 'error'. Default 'info'."`

		CallbackQueueWorkers: 8,

	}

}

type MatchmakerConfig struct {

	MaxTickets   int `yaml:"max_tickets" json:"max_tickets" usage:"Maximum number of concurrent matchmaking tickets allowed per session. Default 3."`

	IntervalSec  int `yaml:"interval_sec" json:"interval_sec" usage:"How quickly the matchmaker attempts to form matches, in seconds. Default 15."`

	MaxIntervals int `yaml:"max_intervals" json:"max_intervals" usage:"How many intervals the matchmaker attempts to find matches at the max player count, before allowing min count. Default 2."`

}

func NewMatchmakerConfig() *MatchmakerConfig {

	return &MatchmakerConfig{

		MaxTickets:   3,

		IntervalSec:  15,

		MaxIntervals: 2,

	}

}