Add a namegenerator package

Adds a namegenerator package which generates
readable names for instances.
This will go with a small change in the API
where we expect instance names and will generate
the names if they are not provided.

Issue-ID: MULTICLOUD-716
Change-Id: I69d8b7fb62667b8b60f3e02eb26dc937961d26d2
Signed-off-by: Kiran Kamineni <kiran.k.kamineni@intel.com>

1 files changed, 148 insertions, 0 deletions

diff --git a/src/k8splugin/internal/namegenerator/namegenerator.go b/src/k8splugin/internal/namegenerator/namegenerator.go
new file mode 100644
index 00000000..1980944f
--- /dev/null
+++ b/src/k8splugin/internal/namegenerator/namegenerator.go
@@ -0,0 +1,148 @@
+/*
+ * Copyright 2019 Intel Corporation, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package namegenerator
+
+import (
+	"encoding/json"
+	"log"
+	"strings"
+	"sync"
+
+	"github.com/onap/multicloud-k8s/src/k8splugin/internal/db"
+
+	"github.com/moby/moby/pkg/namesgenerator"
+	pkgerrors "github.com/pkg/errors"
+)
+
+const (
+	storeName = "instanceNames"
+	tag       = "names"
+)
+
+var (
+	nameCache      = &cache{}
+	cacheKeyGlobal = cacheKey{"k8sPluginCacheKey"}
+)
+
+type cache struct {
+	cache map[string]bool
+	mux   sync.Mutex
+}
+
+type cacheKey struct {
+	Key string `json:"key"`
+}
+
+func (c cacheKey) String() string {
+
+	out, err := json.Marshal(c)
+	if err != nil {
+		return ""
+	}
+
+	return string(out)
+}
+
+func (c *cache) init() {
+
+	// We have either restarted or this is the first time
+	// that a name is being requested since the service came
+	// up.
+	if c.cache == nil {
+		c.cache = make(map[string]bool)
+		err := c.readCacheFromDB()
+		if err != nil {
+			log.Println("Error Reading from DB: ", err.Error())
+			return
+		}
+	}
+}
+
+func (c *cache) isAlreadyUsed(name string) bool {
+
+	if _, ok := c.cache[name]; ok {
+		return true
+	}
+	return false
+}
+
+func (c *cache) readCacheFromDB() error {
+
+	// Read the latest from cache
+	data, err := db.DBconn.Read(storeName, cacheKeyGlobal, tag)
+	if err != nil {
+		log.Println("Error reading name cache from Database: ", err)
+		return pkgerrors.Wrap(err, "Reading cache from DB")
+	}
+
+	err = db.DBconn.Unmarshal(data, &c.cache)
+	if err != nil {
+		log.Println("Error unmarshaling data into cache: ", err)
+		return pkgerrors.Wrap(err, "Unmarshaling cache from DB")
+	}
+
+	return nil
+}
+
+// writeCacheToDB will update the DB with the updated cache
+func (c *cache) writeCacheToDB() {
+
+	//Update the database as well
+	err := db.DBconn.Update(storeName, cacheKeyGlobal, tag, c.cache)
+	if err != nil {
+		// TODO: Replace with DBconn variable
+		if strings.Contains(err.Error(), "Error finding master table") {
+			err = db.DBconn.Create(storeName, cacheKeyGlobal, tag, c.cache)
+			if err != nil {
+				log.Println("Error creating the entry in DB. Will try later...")
+				return
+			}
+		} else {
+			log.Println("Error updating DB: ", err.Error())
+			return
+		}
+	}
+}
+
+func (c *cache) generateName() string {
+	c.mux.Lock()
+	defer c.mux.Unlock()
+
+	c.init()
+
+	for {
+		//Call moby package here to generate name
+		name := namesgenerator.GetRandomName(0)
+		if c.isAlreadyUsed(name) {
+			// Generate another name
+			log.Printf("Name %s already used", name)
+			continue
+		}
+
+		c.cache[name] = true
+
+		// Update the cache and db
+		c.writeCacheToDB()
+		return name
+	}
+}
+
+// Generate returns an autogenerated name
+func Generate() string {
+
+	return nameCache.generateName()
+}