Initial release

src/cache.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+	"sync"
+	"time"
+)
+
+// Cache defines an interface to implement caching structure
+type Cache interface {
+	Startup()
+	Get(string) (interface{}, error)
+	Set(string, interface{}) error
+}
+
+// MemoryCache caches data in an in-memory key-value store with a ttl in seconds
+type MemoryCache struct {
+	mutex       sync.Mutex
+	enabled     bool
+	datastore   map[string]interface{}
+	expireStore map[string]time.Time
+	ttl         float64
+	interval    float64
+}
+
+// NewCache creates a Cache instance
+func NewCache(config CacheConfig) (Cache, error) {
+	enabled := false
+	if config.TTL > 0 {
+		enabled = true
+	}
+	if config.Interval == 0 {
+		config.Interval = 0.25
+	}
+	return &MemoryCache{
+		ttl:      config.TTL,
+		interval: config.Interval,
+		enabled:  enabled,
+	}, nil
+}
+
+// Startup starts cache management threads
+func (c *MemoryCache) Startup() {
+	Debug("starting memory cache")
+	c.datastore = make(map[string]interface{})
+	c.expireStore = make(map[string]time.Time)
+	go c.expireThread()
+}
+
+// expireThread flushes datastore every ttl seconds
+func (c *MemoryCache) expireThread() {
+	Debug("starting cache expire thread")
+	if c.enabled {
+		for {
+			c.mutex.Lock()
+			for key := range c.expireStore {
+				if time.Since(c.expireStore[key]).Seconds() > c.ttl {
+					Debug("deleting key '%s' from cache", key)
+					delete(c.datastore, key)
+					delete(c.expireStore, key)
+				}
+			}
+			c.mutex.Unlock()
+			time.Sleep(time.Duration(c.interval*1000) * time.Millisecond)
+		}
+	}
+	Debug("ending cache expire thread")
+}
+
+// Get a value from cache datastore
+func (c *MemoryCache) Get(key string) (interface{}, error) {
+	if !c.enabled {
+		return nil, nil
+	}
+	value, ok := c.datastore[key]
+	if ok {
+		Debug("value for key '%s' found in cache", key)
+		return value, nil
+	}
+	Debug("value for key '%s' not found in cache", key)
+	return nil, nil
+}
+
+// Set a value into cache datastore with a key
+func (c *MemoryCache) Set(key string, value interface{}) error {
+	if !c.enabled {
+		return nil
+	}
+	Debug("setting value for key '%s' in cache", key)
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	c.datastore[key] = value
+	c.expireStore[key] = time.Now()
+	return nil
+}