Issue search support elasticsearch (#9428)

* Issue search support elasticsearch

* Fix lint

* Add indexer name on app.ini

* add a warnning on SearchIssuesByKeyword

* improve code

vendor/github.com/olivere/elastic/v7/connection.go

@@ -0,0 +1,90 @@
+// Copyright 2012-present Oliver Eilhard. All rights reserved.
+// Use of this source code is governed by a MIT-license.
+// See http://olivere.mit-license.org/license.txt for details.
+
+package elastic
+
+import (
+	"fmt"
+	"sync"
+	"time"
+)
+
+// conn represents a single connection to a node in a cluster.
+type conn struct {
+	sync.RWMutex
+	nodeID    string // node ID
+	url       string
+	failures  int
+	dead      bool
+	deadSince *time.Time
+}
+
+// newConn creates a new connection to the given URL.
+func newConn(nodeID, url string) *conn {
+	c := &conn{
+		nodeID: nodeID,
+		url:    url,
+	}
+	return c
+}
+
+// String returns a representation of the connection status.
+func (c *conn) String() string {
+	c.RLock()
+	defer c.RUnlock()
+	return fmt.Sprintf("%s [dead=%v,failures=%d,deadSince=%v]", c.url, c.dead, c.failures, c.deadSince)
+}
+
+// NodeID returns the ID of the node of this connection.
+func (c *conn) NodeID() string {
+	c.RLock()
+	defer c.RUnlock()
+	return c.nodeID
+}
+
+// URL returns the URL of this connection.
+func (c *conn) URL() string {
+	c.RLock()
+	defer c.RUnlock()
+	return c.url
+}
+
+// IsDead returns true if this connection is marked as dead, i.e. a previous
+// request to the URL has been unsuccessful.
+func (c *conn) IsDead() bool {
+	c.RLock()
+	defer c.RUnlock()
+	return c.dead
+}
+
+// MarkAsDead marks this connection as dead, increments the failures
+// counter and stores the current time in dead since.
+func (c *conn) MarkAsDead() {
+	c.Lock()
+	c.dead = true
+	if c.deadSince == nil {
+		utcNow := time.Now().UTC()
+		c.deadSince = &utcNow
+	}
+	c.failures += 1
+	c.Unlock()
+}
+
+// MarkAsAlive marks this connection as eligible to be returned from the
+// pool of connections by the selector.
+func (c *conn) MarkAsAlive() {
+	c.Lock()
+	c.dead = false
+	c.Unlock()
+}
+
+// MarkAsHealthy marks this connection as healthy, i.e. a request has been
+// successfully performed with it.
+func (c *conn) MarkAsHealthy() {
+	c.Lock()
+	c.dead = false
+	c.deadSince = nil
+	c.failures = 0
+	c.Unlock()
+}