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/retrier.go

@@ -0,0 +1,68 @@
+// 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 (
+	"context"
+	"net/http"
+	"time"
+)
+
+// RetrierFunc specifies the signature of a Retry function, and is an adapter
+// to allow the use of ordinary Retry functions. If f is a function with the
+// appropriate signature, RetrierFunc(f) is a Retrier that calls f.
+type RetrierFunc func(context.Context, int, *http.Request, *http.Response, error) (time.Duration, bool, error)
+
+// Retry calls f.
+func (f RetrierFunc) Retry(ctx context.Context, retry int, req *http.Request, resp *http.Response, err error) (time.Duration, bool, error) {
+	return f(ctx, retry, req, resp, err)
+}
+
+// Retrier decides whether to retry a failed HTTP request with Elasticsearch.
+type Retrier interface {
+	// Retry is called when a request has failed. It decides whether to retry
+	// the call, how long to wait for the next call, or whether to return an
+	// error (which will be returned to the service that started the HTTP
+	// request in the first place).
+	//
+	// Callers may also use this to inspect the HTTP request/response and
+	// the error that happened. Additional data can be passed through via
+	// the context.
+	Retry(ctx context.Context, retry int, req *http.Request, resp *http.Response, err error) (time.Duration, bool, error)
+}
+
+// -- StopRetrier --
+
+// StopRetrier is an implementation that does no retries.
+type StopRetrier struct {
+}
+
+// NewStopRetrier returns a retrier that does no retries.
+func NewStopRetrier() *StopRetrier {
+	return &StopRetrier{}
+}
+
+// Retry does not retry.
+func (r *StopRetrier) Retry(ctx context.Context, retry int, req *http.Request, resp *http.Response, err error) (time.Duration, bool, error) {
+	return 0, false, nil
+}
+
+// -- BackoffRetrier --
+
+// BackoffRetrier is an implementation that does nothing but return nil on Retry.
+type BackoffRetrier struct {
+	backoff Backoff
+}
+
+// NewBackoffRetrier returns a retrier that uses the given backoff strategy.
+func NewBackoffRetrier(backoff Backoff) *BackoffRetrier {
+	return &BackoffRetrier{backoff: backoff}
+}
+
+// Retry calls into the backoff strategy and its wait interval.
+func (r *BackoffRetrier) Retry(ctx context.Context, retry int, req *http.Request, resp *http.Response, err error) (time.Duration, bool, error) {
+	wait, goahead := r.backoff.Next(retry)
+	return wait, goahead, nil
+}