AliasExists implementation

goes.go

@@ -562,3 +562,17 @@ func (c *Connection) AddAlias(alias string, indexes []string) (Response, error)
 func (c *Connection) RemoveAlias(alias string, indexes []string) (Response, error) {
 	return c.modifyAlias("remove", alias, indexes)
 }
+
+// AliasExists checks whether alias is defined on the server
+func (c *Connection) AliasExists(alias string) (bool, error) {
+
+	r := Request{
+		Conn:   c,
+		method: "HEAD",
+		api:    "_alias/" + alias,
+	}
+
+	resp, err := r.Run()
+
+	return resp.Status == 200, err
+}

goes_test.go

@@ -1363,3 +1363,28 @@ func (s *GoesTestSuite) TestRemoveAlias(c *C) {
 	_, err = conn.Get(aliasName, docType, docId, url.Values{})
 	c.Assert(err.Error(), Equals, "[404] IndexMissingException[["+aliasName+"] missing]")
 }
+
+func (s *GoesTestSuite) TestAliasExists(c *C) {
+	index := "testaliasexist_1"
+	alias := "testaliasexists"
+
+	conn := NewConnection(ES_HOST, ES_PORT)
+	// just in case
+	conn.DeleteIndex(index)
+
+	exists, err := conn.AliasExists(alias)
+	c.Assert(exists, Equals, false)
+
+	_, err = conn.CreateIndex(index, map[string]interface{}{})
+	c.Assert(err, IsNil)
+	defer conn.DeleteIndex(index)
+	time.Sleep(200 * time.Millisecond)
+
+	_, err = conn.AddAlias(alias, []string{index})
+	c.Assert(err, IsNil)
+	time.Sleep(200 * time.Millisecond)
+	defer conn.RemoveAlias(alias, []string{index})
+
+	exists, err = conn.AliasExists(alias)
+	c.Assert(exists, Equals, true)
+}