Adds cache TTL and routing/caching strategy (per plugin)

* Moves caching to the plugin pool (from plugin client)
* Moves routing strategy to the plugin pool (from availableplugins)

Resolves intelsdi-x#601
Partially addresses intelsdi-x#539

control/available_plugin.go

@@ -36,8 +36,10 @@ import (
 	"github.com/intelsdi-x/gomit"
 	"github.com/intelsdi-x/snap/control/plugin"
 	"github.com/intelsdi-x/snap/control/plugin/client"
-	"github.com/intelsdi-x/snap/control/routing"
+	"github.com/intelsdi-x/snap/control/strategy"
+	"github.com/intelsdi-x/snap/core"
 	"github.com/intelsdi-x/snap/core/control_event"
+	"github.com/intelsdi-x/snap/core/ctypes"
 	"github.com/intelsdi-x/snap/core/serror"
 )
 
@@ -51,12 +53,11 @@ const (
 )
 
 var (
-	// ErrPoolNotFound - error message when the plugin pool not found
 	ErrPoolNotFound = errors.New("plugin pool not found")
-	// ErrBadKey - error message when a bad key used
-	ErrBadKey = errors.New("bad key")
-	// ErrBadType - error message when a bad plugin type used
-	ErrBadType = errors.New("bad plugin type")
+	ErrPoolEmpty    = errors.New("plugin pool is empty")
+	ErrBadKey       = errors.New("bad key")
+	ErrBadType      = errors.New("bad plugin type")
+	ErrBadStrategy  = errors.New("bad strategy")
 
 	// This defines the maximum running instances of a loaded plugin.
 	// It is initialized at runtime via the cli.
@@ -307,6 +308,9 @@ type apPool struct {
 
 	// The number of subscriptions per running instance
 	concurrencyCount int
+
+	// The routing and caching strategy declared by the plugin.
+	strategy strategy.RoutingAndCaching
 }
 
 func newPool(key string, plugins ...*availablePlugin) (*apPool, error) {
@@ -327,20 +331,8 @@ func newPool(key string, plugins ...*availablePlugin) (*apPool, error) {
 
 	if len(plugins) > 0 {
 		for _, plg := range plugins {
-			plg.id = p.generatePID()
-			p.plugins[plg.id] = plg
-		}
-		// Because plugin metadata is a singleton and immutable (in static code)
-		// it is safe to take the first item.  Reloading an identical plugin
-		// with new metadata is protected by plugin loading.
-
-		// Checking if plugin is exclusive
-		// (only one instance should be running).
-		if plugins[0].meta.Exclusive {
-			p.max = 1
+			p.insert(plg)
 		}
-		// set concurrency count
-		p.concurrencyCount = plugins[0].meta.ConcurrencyCount
 	}
 
 	return p, nil
@@ -350,17 +342,46 @@ func (p *apPool) insert(ap *availablePlugin) error {
 	if ap.pluginType != plugin.CollectorPluginType && ap.pluginType != plugin.ProcessorPluginType && ap.pluginType != plugin.PublisherPluginType {
 		return ErrBadType
 	}
-	ap.id = p.generatePID()
-	p.plugins[ap.id] = ap
-
 	// If an empty pool is created, it does not have
 	// any available plugins from which to retrieve
 	// concurrency count or exclusivity.  We ensure it
 	// is set correctly on an insert.
+	if len(p.plugins) == 0 {
+		if err := p.applyPluginMeta(ap); err != nil {
+			return err
+		}
+	}
+
+	ap.id = p.generatePID()
+	p.plugins[ap.id] = ap
+
+	return nil
+}
+
+func (p *apPool) applyPluginMeta(ap *availablePlugin) error {
+	// Checking if plugin is exclusive
+	// (only one instance should be running).
 	if ap.meta.Exclusive {
 		p.max = 1
 	}
+
+	// Set the cache TTL
+	cacheTTL := strategy.GlobalCacheExpiration
+	if ap.meta.CacheTTL != 0 {
+		cacheTTL = ap.meta.CacheTTL
+	}
+
+	// Set the routing and caching strategy
+	switch ap.meta.RoutingStrategy {
+	case plugin.DefaultRouting:
+		p.strategy = strategy.NewLRU(cacheTTL)
+	default:
+		return ErrBadStrategy
+	}
+
+	// set concurrency count
 	p.concurrencyCount = ap.meta.ConcurrencyCount
+
 	return nil
 }
 
@@ -484,17 +505,17 @@ func (p *apPool) subscriptionCount() int {
 	return len(p.subs)
 }
 
-func (p *apPool) selectAP(strat RoutingStrategy) (*availablePlugin, serror.SnapError) {
+func (p *apPool) selectAP() (*availablePlugin, serror.SnapError) {
 	p.RLock()
 	defer p.RUnlock()
 
-	sp := make([]routing.SelectablePlugin, p.count())
+	sp := make([]strategy.SelectablePlugin, p.count())
 	i := 0
 	for _, plg := range p.plugins {
 		sp[i] = plg
 		i++
 	}
-	sap, err := strat.Select(p, sp)
+	sap, err := p.strategy.Select(sp)
 	if err != nil || sap == nil {
 		return nil, serror.New(err)
 	}
@@ -506,10 +527,6 @@ func (p *apPool) generatePID() uint32 {
 	return p.pidCounter
 }
 
-func (p *apPool) release() {
-	p.RUnlock()
-}
-
 func (p *apPool) moveSubscriptions(to *apPool) []subscription {
 	var subs []subscription
 
@@ -532,24 +549,58 @@ type subscription struct {
 	taskID  string
 }
 
+func (p *apPool) CheckCache(mts []core.Metric) ([]core.Metric, []core.Metric) {
+	return p.strategy.CheckCache(mts)
+}
+
+func (p *apPool) UpdateCache(mts []core.Metric) {
+	p.strategy.UpdateCache(mts)
+}
+
+func (p *apPool) CacheHits(ns string, ver int) (uint64, error) {
+	return p.strategy.CacheHits(ns, ver)
+}
+
+func (p *apPool) CacheMisses(ns string, ver int) (uint64, error) {
+	return p.strategy.CacheMisses(ns, ver)
+}
+func (p *apPool) AllCacheHits() uint64 {
+	return p.strategy.AllCacheHits()
+}
+
+func (p *apPool) AllCacheMisses() uint64 {
+	return p.strategy.AllCacheMisses()
+}
+
+func (p *apPool) CacheTTL() (time.Duration, error) {
+	if len(p.plugins) == 0 {
+		return 0, ErrPoolEmpty
+	}
+	return p.strategy.CacheTTL(), nil
+}
+
 type availablePlugins struct {
 	// Used to coordinate operations on the table.
 	*sync.RWMutex
-
-	// the strategy used to select a plugin for execution
-	routingStrategy RoutingStrategy
-
 	// table holds all the plugin pools.
 	// The Pools' primary keys are equal to
 	// {plugin_type}:{plugin_name}:{plugin_version}
 	table map[string]*apPool
 }
 
-func newAvailablePlugins(routingStrategy RoutingStrategy) *availablePlugins {
+type requestedMetrics struct {
+	plugin      *availablePlugin
+	metricTypes []core.Metric
+}
+
+type selectsAvailablePlugins interface {
+	get(metricTypes []core.Metric) (*requestedMetrics, serror.SnapError)
+}
+
+func newAvailablePlugins() *availablePlugins {
 	return &availablePlugins{
-		RWMutex:         &sync.RWMutex{},
-		table:           make(map[string]*apPool),
-		routingStrategy: routingStrategy,
+		RWMutex: &sync.RWMutex{},
+		table:   make(map[string]*apPool),
 	}
 }
 
@@ -606,16 +657,127 @@ func (ap *availablePlugins) getPool(key string) (*apPool, serror.SnapError) {
 	return pool, nil
 }
 
-func (ap *availablePlugins) holdPool(key string) (*apPool, serror.SnapError) {
-	pool, err := ap.getPool(key)
+func (ap *availablePlugins) collectMetrics(pluginKey string, metricTypes []core.Metric) ([]core.Metric, error) {
+	var results []core.Metric
+	pool, serr := ap.getPool(pluginKey)
+	if serr != nil {
+		return nil, serr
+	}
+	if pool == nil {
+		return nil, serror.New(ErrPoolNotFound, map[string]interface{}{"pool-key": pluginKey})
+	}
+
+	metricsToCollect, metricsFromCache := pool.CheckCache(metricTypes)
+
+	if len(metricsToCollect) == 0 {
+		return metricsFromCache, nil
+	}
+
+	pool.RLock()
+	defer pool.RUnlock()
+	p, serr := pool.selectAP()
+	if serr != nil {
+		return nil, serr
+	}
+
+	// cast client to PluginCollectorClient
+	cli, ok := p.client.(client.PluginCollectorClient)
+	if !ok {
+		return nil, serror.New(errors.New("unable to cast client to PluginCollectorClient"))
+	}
+
+	// get a metrics
+	metrics, err := cli.CollectMetrics(metricsToCollect)
 	if err != nil {
-		return nil, err
+		return nil, serror.New(err)
 	}
 
-	if pool != nil {
-		pool.RLock()
+	pool.UpdateCache(metrics)
+
+	results = make([]core.Metric, len(metricsFromCache)+len(metrics))
+	idx := 0
+	for _, m := range metrics {
+		results[idx] = m
+		idx++
 	}
-	return pool, nil
+	for _, m := range metricsFromCache {
+		results[idx] = m
+		idx++
+	}
+
+	// update statics about plugin
+	p.hitCount++
+	p.lastHitTime = time.Now()
+
+	return metrics, nil
+}
+
+func (ap *availablePlugins) publishMetrics(contentType string, content []byte, pluginName string, pluginVersion int, config map[string]ctypes.ConfigValue) []error {
+	var errs []error
+	key := strings.Join([]string{plugin.PublisherPluginType.String(), pluginName, strconv.Itoa(pluginVersion)}, ":")
+	pool, serr := ap.getPool(key)
+	if serr != nil {
+		errs = append(errs, serr)
+		return errs
+	}
+	if pool == nil {
+		return []error{serror.New(ErrPoolNotFound, map[string]interface{}{"pool-key": key})}
+	}
+
+	pool.RLock()
+	defer pool.RUnlock()
+	p, err := pool.selectAP()
+	if err != nil {
+		errs = append(errs, err)
+		return errs
+	}
+
+	cli, ok := p.client.(client.PluginPublisherClient)
+	if !ok {
+		return []error{errors.New("unable to cast client to PluginPublisherClient")}
+	}
+
+	errp := cli.Publish(contentType, content, config)
+	if errp != nil {
+		return []error{errp}
+	}
+	p.hitCount++
+	p.lastHitTime = time.Now()
+	return nil
+}
+
+func (ap *availablePlugins) processMetrics(contentType string, content []byte, pluginName string, pluginVersion int, config map[string]ctypes.ConfigValue) (string, []byte, []error) {
+	var errs []error
+	key := strings.Join([]string{plugin.ProcessorPluginType.String(), pluginName, strconv.Itoa(pluginVersion)}, ":")
+	pool, serr := ap.getPool(key)
+	if serr != nil {
+		errs = append(errs, serr)
+		return "", nil, errs
+	}
+	if pool == nil {
+		return "", nil, []error{serror.New(ErrPoolNotFound, map[string]interface{}{"pool-key": key})}
+	}
+
+	pool.RLock()
+	defer pool.RUnlock()
+	p, err := pool.selectAP()
+	if err != nil {
+		errs = append(errs, err)
+		return "", nil, errs
+	}
+
+	cli, ok := p.client.(client.PluginProcessorClient)
+	if !ok {
+		return "", nil, []error{errors.New("unable to cast client to PluginProcessorClient")}
+	}
+
+	ct, c, errp := cli.Process(contentType, content, config)
+	if errp != nil {
+		return "", nil, []error{errp}
+	}
+	p.hitCount++
+	p.lastHitTime = time.Now()
+	return ct, c, nil
 }
 
 func (ap *availablePlugins) findLatestPool(pType, name string) (*apPool, serror.SnapError) {
@@ -664,7 +826,7 @@ func (ap *availablePlugins) selectAP(key string) (*availablePlugin, serror.SnapE
 		return nil, err
 	}
 
-	return pool.selectAP(ap.routingStrategy)
+	return pool.selectAP()
 }
 
 func (ap *availablePlugins) pools() map[string]*apPool {