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/backoff.go

@@ -0,0 +1,148 @@
+// 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 (
+	"math"
+	"math/rand"
+	"sync"
+	"time"
+)
+
+// BackoffFunc specifies the signature of a function that returns the
+// time to wait before the next call to a resource. To stop retrying
+// return false in the 2nd return value.
+type BackoffFunc func(retry int) (time.Duration, bool)
+
+// Backoff allows callers to implement their own Backoff strategy.
+type Backoff interface {
+	// Next implements a BackoffFunc.
+	Next(retry int) (time.Duration, bool)
+}
+
+// -- ZeroBackoff --
+
+// ZeroBackoff is a fixed backoff policy whose backoff time is always zero,
+// meaning that the operation is retried immediately without waiting,
+// indefinitely.
+type ZeroBackoff struct{}
+
+// Next implements BackoffFunc for ZeroBackoff.
+func (b ZeroBackoff) Next(retry int) (time.Duration, bool) {
+	return 0, true
+}
+
+// -- StopBackoff --
+
+// StopBackoff is a fixed backoff policy that always returns false for
+// Next(), meaning that the operation should never be retried.
+type StopBackoff struct{}
+
+// Next implements BackoffFunc for StopBackoff.
+func (b StopBackoff) Next(retry int) (time.Duration, bool) {
+	return 0, false
+}
+
+// -- ConstantBackoff --
+
+// ConstantBackoff is a backoff policy that always returns the same delay.
+type ConstantBackoff struct {
+	interval time.Duration
+}
+
+// NewConstantBackoff returns a new ConstantBackoff.
+func NewConstantBackoff(interval time.Duration) *ConstantBackoff {
+	return &ConstantBackoff{interval: interval}
+}
+
+// Next implements BackoffFunc for ConstantBackoff.
+func (b *ConstantBackoff) Next(retry int) (time.Duration, bool) {
+	return b.interval, true
+}
+
+// -- Exponential --
+
+// ExponentialBackoff implements the simple exponential backoff described by
+// Douglas Thain at http://dthain.blogspot.de/2009/02/exponential-backoff-in-distributed.html.
+type ExponentialBackoff struct {
+	t float64 // initial timeout (in msec)
+	f float64 // exponential factor (e.g. 2)
+	m float64 // maximum timeout (in msec)
+}
+
+// NewExponentialBackoff returns a ExponentialBackoff backoff policy.
+// Use initialTimeout to set the first/minimal interval
+// and maxTimeout to set the maximum wait interval.
+func NewExponentialBackoff(initialTimeout, maxTimeout time.Duration) *ExponentialBackoff {
+	return &ExponentialBackoff{
+		t: float64(int64(initialTimeout / time.Millisecond)),
+		f: 2.0,
+		m: float64(int64(maxTimeout / time.Millisecond)),
+	}
+}
+
+// Next implements BackoffFunc for ExponentialBackoff.
+func (b *ExponentialBackoff) Next(retry int) (time.Duration, bool) {
+	r := 1.0 + rand.Float64() // random number in [1..2]
+	m := math.Min(r*b.t*math.Pow(b.f, float64(retry)), b.m)
+	if m >= b.m {
+		return 0, false
+	}
+	d := time.Duration(int64(m)) * time.Millisecond
+	return d, true
+}
+
+// -- Simple Backoff --
+
+// SimpleBackoff takes a list of fixed values for backoff intervals.
+// Each call to Next returns the next value from that fixed list.
+// After each value is returned, subsequent calls to Next will only return
+// the last element. The values are optionally "jittered" (off by default).
+type SimpleBackoff struct {
+	sync.Mutex
+	ticks  []int
+	jitter bool
+}
+
+// NewSimpleBackoff creates a SimpleBackoff algorithm with the specified
+// list of fixed intervals in milliseconds.
+func NewSimpleBackoff(ticks ...int) *SimpleBackoff {
+	return &SimpleBackoff{
+		ticks:  ticks,
+		jitter: false,
+	}
+}
+
+// Jitter enables or disables jittering values.
+func (b *SimpleBackoff) Jitter(flag bool) *SimpleBackoff {
+	b.Lock()
+	b.jitter = flag
+	b.Unlock()
+	return b
+}
+
+// jitter randomizes the interval to return a value of [0.5*millis .. 1.5*millis].
+func jitter(millis int) int {
+	if millis <= 0 {
+		return 0
+	}
+	return millis/2 + rand.Intn(millis)
+}
+
+// Next implements BackoffFunc for SimpleBackoff.
+func (b *SimpleBackoff) Next(retry int) (time.Duration, bool) {
+	b.Lock()
+	defer b.Unlock()
+
+	if retry >= len(b.ticks) {
+		return 0, false
+	}
+
+	ms := b.ticks[retry]
+	if b.jitter {
+		ms = jitter(ms)
+	}
+	return time.Duration(ms) * time.Millisecond, true
+}