intergrate opensearch v1 (#5135)

opensearchv1

Signed-off-by: chengdehao <dehaocheng@kubesphere.io>

Signed-off-by: chengdehao <dehaocheng@kubesphere.io>
Co-authored-by: chengdehao <dehaocheng@kubesphere.io>

vendor/github.com/opensearch-project/opensearch-go/opensearchtransport/connection.go

@@ -0,0 +1,338 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// The OpenSearch Contributors require contributions made to
+// this file be licensed under the Apache-2.0 license or a
+// compatible open source license.
+//
+// Modifications Copyright OpenSearch Contributors. See
+// GitHub history for details.
+
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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 opensearchtransport
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"net/url"
+	"sort"
+	"sync"
+	"time"
+)
+
+var (
+	defaultResurrectTimeoutInitial      = 60 * time.Second
+	defaultResurrectTimeoutFactorCutoff = 5
+)
+
+// Selector defines the interface for selecting connections from the pool.
+//
+type Selector interface {
+	Select([]*Connection) (*Connection, error)
+}
+
+// ConnectionPool defines the interface for the connection pool.
+//
+type ConnectionPool interface {
+	Next() (*Connection, error)  // Next returns the next available connection.
+	OnSuccess(*Connection) error // OnSuccess reports that the connection was successful.
+	OnFailure(*Connection) error // OnFailure reports that the connection failed.
+	URLs() []*url.URL            // URLs returns the list of URLs of available connections.
+}
+
+// Connection represents a connection to a node.
+//
+type Connection struct {
+	sync.Mutex
+
+	URL       *url.URL
+	IsDead    bool
+	DeadSince time.Time
+	Failures  int
+
+	ID         string
+	Name       string
+	Roles      []string
+	Attributes map[string]interface{}
+}
+
+type singleConnectionPool struct {
+	connection *Connection
+
+	metrics *metrics
+}
+
+type statusConnectionPool struct {
+	sync.Mutex
+
+	live     []*Connection // List of live connections
+	dead     []*Connection // List of dead connections
+	selector Selector
+
+	metrics *metrics
+}
+
+type roundRobinSelector struct {
+	sync.Mutex
+
+	curr int // Index of the current connection
+}
+
+// NewConnectionPool creates and returns a default connection pool.
+//
+func NewConnectionPool(conns []*Connection, selector Selector) (ConnectionPool, error) {
+	if len(conns) == 1 {
+		return &singleConnectionPool{connection: conns[0]}, nil
+	}
+	if selector == nil {
+		selector = &roundRobinSelector{curr: -1}
+	}
+	return &statusConnectionPool{live: conns, selector: selector}, nil
+}
+
+// Next returns the connection from pool.
+//
+func (cp *singleConnectionPool) Next() (*Connection, error) {
+	return cp.connection, nil
+}
+
+// OnSuccess is a no-op for single connection pool.
+func (cp *singleConnectionPool) OnSuccess(c *Connection) error { return nil }
+
+// OnFailure is a no-op for single connection pool.
+func (cp *singleConnectionPool) OnFailure(c *Connection) error { return nil }
+
+// URLs returns the list of URLs of available connections.
+func (cp *singleConnectionPool) URLs() []*url.URL { return []*url.URL{cp.connection.URL} }
+
+func (cp *singleConnectionPool) connections() []*Connection { return []*Connection{cp.connection} }
+
+// Next returns a connection from pool, or an error.
+//
+func (cp *statusConnectionPool) Next() (*Connection, error) {
+	cp.Lock()
+	defer cp.Unlock()
+
+	// Return next live connection
+	if len(cp.live) > 0 {
+		return cp.selector.Select(cp.live)
+	} else if len(cp.dead) > 0 {
+		// No live connection is available, resurrect one of the dead ones.
+		c := cp.dead[len(cp.dead)-1]
+		cp.dead = cp.dead[:len(cp.dead)-1]
+		c.Lock()
+		defer c.Unlock()
+		cp.resurrect(c, false)
+		return c, nil
+	}
+	return nil, errors.New("no connection available")
+}
+
+// OnSuccess marks the connection as successful.
+//
+func (cp *statusConnectionPool) OnSuccess(c *Connection) error {
+	c.Lock()
+	defer c.Unlock()
+
+	// Short-circuit for live connection
+	if !c.IsDead {
+		return nil
+	}
+
+	c.markAsHealthy()
+
+	cp.Lock()
+	defer cp.Unlock()
+	return cp.resurrect(c, true)
+}
+
+// OnFailure marks the connection as failed.
+//
+func (cp *statusConnectionPool) OnFailure(c *Connection) error {
+	cp.Lock()
+	defer cp.Unlock()
+
+	c.Lock()
+
+	if c.IsDead {
+		if debugLogger != nil {
+			debugLogger.Logf("Already removed %s\n", c.URL)
+		}
+		c.Unlock()
+		return nil
+	}
+
+	if debugLogger != nil {
+		debugLogger.Logf("Removing %s...\n", c.URL)
+	}
+	c.markAsDead()
+	cp.scheduleResurrect(c)
+	c.Unlock()
+
+	// Push item to dead list and sort slice by number of failures
+	cp.dead = append(cp.dead, c)
+	sort.Slice(cp.dead, func(i, j int) bool {
+		c1 := cp.dead[i]
+		c2 := cp.dead[j]
+		c1.Lock()
+		c2.Lock()
+		defer c1.Unlock()
+		defer c2.Unlock()
+
+		res := c1.Failures > c2.Failures
+		return res
+	})
+
+	// Check if connection exists in the list, return error if not.
+	index := -1
+	for i, conn := range cp.live {
+		if conn == c {
+			index = i
+		}
+	}
+	if index < 0 {
+		return errors.New("connection not in live list")
+	}
+
+	// Remove item; https://github.com/golang/go/wiki/SliceTricks
+	copy(cp.live[index:], cp.live[index+1:])
+	cp.live = cp.live[:len(cp.live)-1]
+
+	return nil
+}
+
+// URLs returns the list of URLs of available connections.
+//
+func (cp *statusConnectionPool) URLs() []*url.URL {
+	var urls []*url.URL
+
+	cp.Lock()
+	defer cp.Unlock()
+
+	for _, c := range cp.live {
+		urls = append(urls, c.URL)
+	}
+
+	return urls
+}
+
+func (cp *statusConnectionPool) connections() []*Connection {
+	var conns []*Connection
+	conns = append(conns, cp.live...)
+	conns = append(conns, cp.dead...)
+	return conns
+}
+
+// resurrect adds the connection to the list of available connections.
+// When removeDead is true, it also removes it from the dead list.
+// The calling code is responsible for locking.
+//
+func (cp *statusConnectionPool) resurrect(c *Connection, removeDead bool) error {
+	if debugLogger != nil {
+		debugLogger.Logf("Resurrecting %s\n", c.URL)
+	}
+
+	c.markAsLive()
+	cp.live = append(cp.live, c)
+
+	if removeDead {
+		index := -1
+		for i, conn := range cp.dead {
+			if conn == c {
+				index = i
+			}
+		}
+		if index >= 0 {
+			// Remove item; https://github.com/golang/go/wiki/SliceTricks
+			copy(cp.dead[index:], cp.dead[index+1:])
+			cp.dead = cp.dead[:len(cp.dead)-1]
+		}
+	}
+
+	return nil
+}
+
+// scheduleResurrect schedules the connection to be resurrected.
+//
+func (cp *statusConnectionPool) scheduleResurrect(c *Connection) {
+	factor := math.Min(float64(c.Failures-1), float64(defaultResurrectTimeoutFactorCutoff))
+	timeout := time.Duration(defaultResurrectTimeoutInitial.Seconds() * math.Exp2(factor) * float64(time.Second))
+	if debugLogger != nil {
+		debugLogger.Logf("Resurrect %s (failures=%d, factor=%1.1f, timeout=%s) in %s\n", c.URL, c.Failures, factor, timeout, c.DeadSince.Add(timeout).Sub(time.Now().UTC()).Truncate(time.Second))
+	}
+
+	time.AfterFunc(timeout, func() {
+		cp.Lock()
+		defer cp.Unlock()
+
+		c.Lock()
+		defer c.Unlock()
+
+		if !c.IsDead {
+			if debugLogger != nil {
+				debugLogger.Logf("Already resurrected %s\n", c.URL)
+			}
+			return
+		}
+
+		cp.resurrect(c, true)
+	})
+}
+
+// Select returns the connection in a round-robin fashion.
+//
+func (s *roundRobinSelector) Select(conns []*Connection) (*Connection, error) {
+	s.Lock()
+	defer s.Unlock()
+
+	s.curr = (s.curr + 1) % len(conns)
+	return conns[s.curr], nil
+}
+
+// markAsDead marks the connection as dead.
+//
+func (c *Connection) markAsDead() {
+	c.IsDead = true
+	if c.DeadSince.IsZero() {
+		c.DeadSince = time.Now().UTC()
+	}
+	c.Failures++
+}
+
+// markAsLive marks the connection as alive.
+//
+func (c *Connection) markAsLive() {
+	c.IsDead = false
+}
+
+// markAsHealthy marks the connection as healthy.
+//
+func (c *Connection) markAsHealthy() {
+	c.IsDead = false
+	c.DeadSince = time.Time{}
+	c.Failures = 0
+}
+
+// String returns a readable connection representation.
+//
+func (c *Connection) String() string {
+	c.Lock()
+	defer c.Unlock()
+	return fmt.Sprintf("<%s> dead=%v failures=%d", c.URL, c.IsDead, c.Failures)
+}

vendor/github.com/opensearch-project/opensearch-go/opensearchtransport/discovery.go

@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// The OpenSearch Contributors require contributions made to
+// this file be licensed under the Apache-2.0 license or a
+// compatible open source license.
+//
+// Modifications Copyright OpenSearch Contributors. See
+// GitHub history for details.
+
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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 opensearchtransport
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Discoverable defines the interface for transports supporting node discovery.
+//
+type Discoverable interface {
+	DiscoverNodes() error
+}
+
+// nodeInfo represents the information about node in a cluster.
+//
+type nodeInfo struct {
+	ID         string
+	Name       string
+	URL        *url.URL
+	Roles      []string `json:"roles"`
+	Attributes map[string]interface{}
+	HTTP       struct {
+		PublishAddress string `json:"publish_address"`
+	}
+}
+
+// DiscoverNodes reloads the client connections by fetching information from the cluster.
+//
+func (c *Client) DiscoverNodes() error {
+	var conns []*Connection
+
+	nodes, err := c.getNodesInfo()
+	if err != nil {
+		if debugLogger != nil {
+			debugLogger.Logf("Error getting nodes info: %s\n", err)
+		}
+		return fmt.Errorf("discovery: get nodes: %s", err)
+	}
+
+	for _, node := range nodes {
+		var (
+			isMasterOnlyNode bool
+		)
+
+		roles := append(node.Roles[:0:0], node.Roles...)
+		sort.Strings(roles)
+
+		if len(roles) == 1 && roles[0] == "master" {
+			isMasterOnlyNode = true
+		}
+
+		if debugLogger != nil {
+			var skip string
+			if isMasterOnlyNode {
+				skip = "; [SKIP]"
+			}
+			debugLogger.Logf("Discovered node [%s]; %s; roles=%s%s\n", node.Name, node.URL, node.Roles, skip)
+		}
+
+		// Skip master only nodes
+		// TODO: Move logic to Selector?
+		if isMasterOnlyNode {
+			continue
+		}
+
+		conns = append(conns, &Connection{
+			URL:        node.URL,
+			ID:         node.ID,
+			Name:       node.Name,
+			Roles:      node.Roles,
+			Attributes: node.Attributes,
+		})
+	}
+
+	c.Lock()
+	defer c.Unlock()
+
+	if lockable, ok := c.pool.(sync.Locker); ok {
+		lockable.Lock()
+		defer lockable.Unlock()
+	}
+
+	if c.poolFunc != nil {
+		c.pool = c.poolFunc(conns, c.selector)
+	} else {
+		// TODO: Replace only live connections, leave dead scheduled for resurrect?
+		c.pool, err = NewConnectionPool(conns, c.selector)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (c *Client) getNodesInfo() ([]nodeInfo, error) {
+	var (
+		out    []nodeInfo
+		scheme = c.urls[0].Scheme
+	)
+
+	req, err := http.NewRequest("GET", "/_nodes/http", nil)
+	if err != nil {
+		return out, err
+	}
+
+	c.Lock()
+	conn, err := c.pool.Next()
+	c.Unlock()
+	// TODO: If no connection is returned, fallback to original URLs
+	if err != nil {
+		return out, err
+	}
+
+	c.setReqURL(conn.URL, req)
+	c.setReqAuth(conn.URL, req)
+	c.setReqUserAgent(req)
+
+	res, err := c.transport.RoundTrip(req)
+	if err != nil {
+		return out, err
+	}
+	defer res.Body.Close()
+
+	if res.StatusCode > 200 {
+		body, _ := ioutil.ReadAll(res.Body)
+		return out, fmt.Errorf("server error: %s: %s", res.Status, body)
+	}
+
+	var env map[string]json.RawMessage
+	if err := json.NewDecoder(res.Body).Decode(&env); err != nil {
+		return out, err
+	}
+
+	var nodes map[string]nodeInfo
+	if err := json.Unmarshal(env["nodes"], &nodes); err != nil {
+		return out, err
+	}
+
+	for id, node := range nodes {
+		node.ID = id
+		u, err := c.getNodeURL(node, scheme)
+		if err != nil {
+			return out, err
+		}
+		node.URL = u
+		out = append(out, node)
+	}
+
+	return out, nil
+}
+
+func (c *Client) getNodeURL(node nodeInfo, scheme string) (*url.URL, error) {
+	var (
+		host string
+		port string
+
+		addrs = strings.Split(node.HTTP.PublishAddress, "/")
+		ports = strings.Split(node.HTTP.PublishAddress, ":")
+	)
+
+	if len(addrs) > 1 {
+		host = addrs[0]
+	} else {
+		host = strings.Split(addrs[0], ":")[0]
+	}
+	port = ports[len(ports)-1]
+
+	u := &url.URL{
+		Scheme: scheme,
+		Host:   host + ":" + port,
+	}
+
+	return u, nil
+}
+
+func (c *Client) scheduleDiscoverNodes(d time.Duration) {
+	go c.DiscoverNodes()
+
+	c.Lock()
+	defer c.Unlock()
+	if c.discoverNodesTimer != nil {
+		c.discoverNodesTimer.Stop()
+	}
+	c.discoverNodesTimer = time.AfterFunc(c.discoverNodesInterval, func() {
+		c.scheduleDiscoverNodes(c.discoverNodesInterval)
+	})
+}

vendor/github.com/opensearch-project/opensearch-go/opensearchtransport/doc.go

@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// The OpenSearch Contributors require contributions made to
+// this file be licensed under the Apache-2.0 license or a
+// compatible open source license.
+//
+// Modifications Copyright OpenSearch Contributors. See
+// GitHub history for details.
+
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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 opensearchtransport provides the transport layer for the OpenSearch client.
+
+It is automatically included in the client provided by the github.com/opensearch-project/opensearch-go package
+and is not intended for direct use: to configure the client, use the opensearch.Config struct.
+
+The default HTTP transport of the client is http.Transport; use the Transport option to customize it;
+
+The package will automatically retry requests on network-related errors, and on specific
+response status codes (by default 502, 503, 504). Use the RetryOnStatus option to customize the list.
+The transport will not retry a timeout network error, unless enabled by setting EnableRetryOnTimeout to true.
+
+Use the MaxRetries option to configure the number of retries, and set DisableRetry to true
+to disable the retry behaviour altogether.
+
+By default, the retry will be performed without any delay; to configure a backoff interval,
+implement the RetryBackoff option function; see an example in the package unit tests for information.
+
+When multiple addresses are passed in configuration, the package will use them in a round-robin fashion,
+and will keep track of live and dead nodes. The status of dead nodes is checked periodically.
+
+To customize the node selection behaviour, provide a Selector implementation in the configuration.
+To replace the connection pool entirely, provide a custom ConnectionPool implementation via
+the ConnectionPoolFunc option.
+
+The package defines the Logger interface for logging information about request and response.
+It comes with several bundled loggers for logging in text and JSON.
+
+Use the EnableDebugLogger option to enable the debugging logger for connection management.
+
+Use the EnableMetrics option to enable metric collection and export.
+*/
+package opensearchtransport

vendor/github.com/opensearch-project/opensearch-go/opensearchtransport/logger.go

@@ -0,0 +1,461 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// The OpenSearch Contributors require contributions made to
+// this file be licensed under the Apache-2.0 license or a
+// compatible open source license.
+//
+// Modifications Copyright OpenSearch Contributors. See
+// GitHub history for details.
+
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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 opensearchtransport
+
+import (
+	"bufio"
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var debugLogger DebuggingLogger
+
+// Logger defines an interface for logging request and response.
+//
+type Logger interface {
+	// LogRoundTrip should not modify the request or response, except for consuming and closing the body.
+	// Implementations have to check for nil values in request and response.
+	LogRoundTrip(*http.Request, *http.Response, error, time.Time, time.Duration) error
+	// RequestBodyEnabled makes the client pass a copy of request body to the logger.
+	RequestBodyEnabled() bool
+	// ResponseBodyEnabled makes the client pass a copy of response body to the logger.
+	ResponseBodyEnabled() bool
+}
+
+// DebuggingLogger defines the interface for a debugging logger.
+//
+type DebuggingLogger interface {
+	Log(a ...interface{}) error
+	Logf(format string, a ...interface{}) error
+}
+
+// TextLogger prints the log message in plain text.
+//
+type TextLogger struct {
+	Output             io.Writer
+	EnableRequestBody  bool
+	EnableResponseBody bool
+}
+
+// ColorLogger prints the log message in a terminal-optimized plain text.
+//
+type ColorLogger struct {
+	Output             io.Writer
+	EnableRequestBody  bool
+	EnableResponseBody bool
+}
+
+// CurlLogger prints the log message as a runnable curl command.
+//
+type CurlLogger struct {
+	Output             io.Writer
+	EnableRequestBody  bool
+	EnableResponseBody bool
+}
+
+// JSONLogger prints the log message as JSON.
+//
+type JSONLogger struct {
+	Output             io.Writer
+	EnableRequestBody  bool
+	EnableResponseBody bool
+}
+
+// debuggingLogger prints debug messages as plain text.
+//
+type debuggingLogger struct {
+	Output io.Writer
+}
+
+// LogRoundTrip prints the information about request and response.
+//
+func (l *TextLogger) LogRoundTrip(req *http.Request, res *http.Response, err error, start time.Time, dur time.Duration) error {
+	fmt.Fprintf(l.Output, "%s %s %s [status:%d request:%s]\n",
+		start.Format(time.RFC3339),
+		req.Method,
+		req.URL.String(),
+		resStatusCode(res),
+		dur.Truncate(time.Millisecond),
+	)
+	if l.RequestBodyEnabled() && req != nil && req.Body != nil && req.Body != http.NoBody {
+		var buf bytes.Buffer
+		if req.GetBody != nil {
+			b, _ := req.GetBody()
+			buf.ReadFrom(b)
+		} else {
+			buf.ReadFrom(req.Body)
+		}
+		logBodyAsText(l.Output, &buf, ">")
+	}
+	if l.ResponseBodyEnabled() && res != nil && res.Body != nil && res.Body != http.NoBody {
+		defer res.Body.Close()
+		var buf bytes.Buffer
+		buf.ReadFrom(res.Body)
+		logBodyAsText(l.Output, &buf, "<")
+	}
+	if err != nil {
+		fmt.Fprintf(l.Output, "! ERROR: %v\n", err)
+	}
+	return nil
+}
+
+// RequestBodyEnabled returns true when the request body should be logged.
+func (l *TextLogger) RequestBodyEnabled() bool { return l.EnableRequestBody }
+
+// ResponseBodyEnabled returns true when the response body should be logged.
+func (l *TextLogger) ResponseBodyEnabled() bool { return l.EnableResponseBody }
+
+// LogRoundTrip prints the information about request and response.
+//
+func (l *ColorLogger) LogRoundTrip(req *http.Request, res *http.Response, err error, start time.Time, dur time.Duration) error {
+	query, _ := url.QueryUnescape(req.URL.RawQuery)
+	if query != "" {
+		query = "?" + query
+	}
+
+	var (
+		status string
+		color  string
+	)
+
+	status = res.Status
+	switch {
+	case res.StatusCode > 0 && res.StatusCode < 300:
+		color = "\x1b[32m"
+	case res.StatusCode > 299 && res.StatusCode < 500:
+		color = "\x1b[33m"
+	case res.StatusCode > 499:
+		color = "\x1b[31m"
+	default:
+		status = "ERROR"
+		color = "\x1b[31;4m"
+	}
+
+	fmt.Fprintf(l.Output, "%6s \x1b[1;4m%s://%s%s\x1b[0m%s %s%s\x1b[0m \x1b[2m%s\x1b[0m\n",
+		req.Method,
+		req.URL.Scheme,
+		req.URL.Host,
+		req.URL.Path,
+		query,
+		color,
+		status,
+		dur.Truncate(time.Millisecond),
+	)
+
+	if l.RequestBodyEnabled() && req != nil && req.Body != nil && req.Body != http.NoBody {
+		var buf bytes.Buffer
+		if req.GetBody != nil {
+			b, _ := req.GetBody()
+			buf.ReadFrom(b)
+		} else {
+			buf.ReadFrom(req.Body)
+		}
+		fmt.Fprint(l.Output, "\x1b[2m")
+		logBodyAsText(l.Output, &buf, "       »")
+		fmt.Fprint(l.Output, "\x1b[0m")
+	}
+
+	if l.ResponseBodyEnabled() && res != nil && res.Body != nil && res.Body != http.NoBody {
+		defer res.Body.Close()
+		var buf bytes.Buffer
+		buf.ReadFrom(res.Body)
+		fmt.Fprint(l.Output, "\x1b[2m")
+		logBodyAsText(l.Output, &buf, "       «")
+		fmt.Fprint(l.Output, "\x1b[0m")
+	}
+
+	if err != nil {
+		fmt.Fprintf(l.Output, "\x1b[31;1m» ERROR \x1b[31m%v\x1b[0m\n", err)
+	}
+
+	if l.RequestBodyEnabled() || l.ResponseBodyEnabled() {
+		fmt.Fprintf(l.Output, "\x1b[2m%s\x1b[0m\n", strings.Repeat("─", 80))
+	}
+	return nil
+}
+
+// RequestBodyEnabled returns true when the request body should be logged.
+func (l *ColorLogger) RequestBodyEnabled() bool { return l.EnableRequestBody }
+
+// ResponseBodyEnabled returns true when the response body should be logged.
+func (l *ColorLogger) ResponseBodyEnabled() bool { return l.EnableResponseBody }
+
+// LogRoundTrip prints the information about request and response.
+//
+func (l *CurlLogger) LogRoundTrip(req *http.Request, res *http.Response, err error, start time.Time, dur time.Duration) error {
+	var b bytes.Buffer
+
+	var query string
+	qvalues := url.Values{}
+	for k, v := range req.URL.Query() {
+		if k == "pretty" {
+			continue
+		}
+		for _, qv := range v {
+			qvalues.Add(k, qv)
+		}
+	}
+	if len(qvalues) > 0 {
+		query = qvalues.Encode()
+	}
+
+	b.WriteString(`curl`)
+	if req.Method == "HEAD" {
+		b.WriteString(" --head")
+	} else {
+		fmt.Fprintf(&b, " -X %s", req.Method)
+	}
+
+	if len(req.Header) > 0 {
+		for k, vv := range req.Header {
+			if k == "Authorization" || k == "User-Agent" {
+				continue
+			}
+			v := strings.Join(vv, ",")
+			b.WriteString(fmt.Sprintf(" -H '%s: %s'", k, v))
+		}
+	}
+
+	b.WriteString(" 'http://localhost:9200")
+	b.WriteString(req.URL.Path)
+	b.WriteString("?pretty")
+	if query != "" {
+		fmt.Fprintf(&b, "&%s", query)
+	}
+	b.WriteString("'")
+
+	if req != nil && req.Body != nil && req.Body != http.NoBody {
+		var buf bytes.Buffer
+		if req.GetBody != nil {
+			b, _ := req.GetBody()
+			buf.ReadFrom(b)
+		} else {
+			buf.ReadFrom(req.Body)
+		}
+
+		b.Grow(buf.Len())
+		b.WriteString(" -d \\\n'")
+		json.Indent(&b, buf.Bytes(), "", " ")
+		b.WriteString("'")
+	}
+
+	b.WriteRune('\n')
+
+	var status string
+	status = res.Status
+
+	fmt.Fprintf(&b, "# => %s [%s] %s\n", start.UTC().Format(time.RFC3339), status, dur.Truncate(time.Millisecond))
+	if l.ResponseBodyEnabled() && res != nil && res.Body != nil && res.Body != http.NoBody {
+		var buf bytes.Buffer
+		buf.ReadFrom(res.Body)
+
+		b.Grow(buf.Len())
+		b.WriteString("# ")
+		json.Indent(&b, buf.Bytes(), "# ", " ")
+	}
+
+	b.WriteString("\n")
+	if l.ResponseBodyEnabled() && res != nil && res.Body != nil && res.Body != http.NoBody {
+		b.WriteString("\n")
+	}
+
+	b.WriteTo(l.Output)
+
+	return nil
+}
+
+// RequestBodyEnabled returns true when the request body should be logged.
+func (l *CurlLogger) RequestBodyEnabled() bool { return l.EnableRequestBody }
+
+// ResponseBodyEnabled returns true when the response body should be logged.
+func (l *CurlLogger) ResponseBodyEnabled() bool { return l.EnableResponseBody }
+
+// LogRoundTrip prints the information about request and response.
+//
+func (l *JSONLogger) LogRoundTrip(req *http.Request, res *http.Response, err error, start time.Time, dur time.Duration) error {
+	// TODO: Research performance optimization of using sync.Pool
+
+	bsize := 200
+	var b = bytes.NewBuffer(make([]byte, 0, bsize))
+	var v = make([]byte, 0, bsize)
+
+	appendTime := func(t time.Time) {
+		v = v[:0]
+		v = t.AppendFormat(v, time.RFC3339)
+		b.Write(v)
+	}
+
+	appendQuote := func(s string) {
+		v = v[:0]
+		v = strconv.AppendQuote(v, s)
+		b.Write(v)
+	}
+
+	appendInt := func(i int64) {
+		v = v[:0]
+		v = strconv.AppendInt(v, i, 10)
+		b.Write(v)
+	}
+
+	port := req.URL.Port()
+
+	b.WriteRune('{')
+	// -- Timestamp
+	b.WriteString(`"@timestamp":"`)
+	appendTime(start.UTC())
+	b.WriteRune('"')
+	// -- Event
+	b.WriteString(`,"event":{`)
+	b.WriteString(`"duration":`)
+	appendInt(dur.Nanoseconds())
+	b.WriteRune('}')
+	// -- URL
+	b.WriteString(`,"url":{`)
+	b.WriteString(`"scheme":`)
+	appendQuote(req.URL.Scheme)
+	b.WriteString(`,"domain":`)
+	appendQuote(req.URL.Hostname())
+	if port != "" {
+		b.WriteString(`,"port":`)
+		b.WriteString(port)
+	}
+	b.WriteString(`,"path":`)
+	appendQuote(req.URL.Path)
+	b.WriteString(`,"query":`)
+	appendQuote(req.URL.RawQuery)
+	b.WriteRune('}') // Close "url"
+	// -- HTTP
+	b.WriteString(`,"http":`)
+	// ---- Request
+	b.WriteString(`{"request":{`)
+	b.WriteString(`"method":`)
+	appendQuote(req.Method)
+	if l.RequestBodyEnabled() && req != nil && req.Body != nil && req.Body != http.NoBody {
+		var buf bytes.Buffer
+		if req.GetBody != nil {
+			b, _ := req.GetBody()
+			buf.ReadFrom(b)
+		} else {
+			buf.ReadFrom(req.Body)
+		}
+
+		b.Grow(buf.Len() + 8)
+		b.WriteString(`,"body":`)
+		appendQuote(buf.String())
+	}
+	b.WriteRune('}') // Close "http.request"
+	// ---- Response
+	b.WriteString(`,"response":{`)
+	b.WriteString(`"status_code":`)
+	appendInt(int64(resStatusCode(res)))
+	if l.ResponseBodyEnabled() && res != nil && res.Body != nil && res.Body != http.NoBody {
+		defer res.Body.Close()
+		var buf bytes.Buffer
+		buf.ReadFrom(res.Body)
+
+		b.Grow(buf.Len() + 8)
+		b.WriteString(`,"body":`)
+		appendQuote(buf.String())
+	}
+	b.WriteRune('}') // Close "http.response"
+	b.WriteRune('}') // Close "http"
+	// -- Error
+	if err != nil {
+		b.WriteString(`,"error":{"message":`)
+		appendQuote(err.Error())
+		b.WriteRune('}') // Close "error"
+	}
+	b.WriteRune('}')
+	b.WriteRune('\n')
+	b.WriteTo(l.Output)
+
+	return nil
+}
+
+// RequestBodyEnabled returns true when the request body should be logged.
+func (l *JSONLogger) RequestBodyEnabled() bool { return l.EnableRequestBody }
+
+// ResponseBodyEnabled returns true when the response body should be logged.
+func (l *JSONLogger) ResponseBodyEnabled() bool { return l.EnableResponseBody }
+
+// Log prints the arguments to output in default format.
+//
+func (l *debuggingLogger) Log(a ...interface{}) error {
+	_, err := fmt.Fprint(l.Output, a...)
+	return err
+}
+
+// Logf prints formats the arguments and prints them to output.
+//
+func (l *debuggingLogger) Logf(format string, a ...interface{}) error {
+	_, err := fmt.Fprintf(l.Output, format, a...)
+	return err
+}
+
+func logBodyAsText(dst io.Writer, body io.Reader, prefix string) {
+	scanner := bufio.NewScanner(body)
+	for scanner.Scan() {
+		s := scanner.Text()
+		if s != "" {
+			fmt.Fprintf(dst, "%s %s\n", prefix, s)
+		}
+	}
+}
+
+func duplicateBody(body io.ReadCloser) (io.ReadCloser, io.ReadCloser, error) {
+	var (
+		b1 bytes.Buffer
+		b2 bytes.Buffer
+		tr = io.TeeReader(body, &b2)
+	)
+	_, err := b1.ReadFrom(tr)
+	if err != nil {
+		return ioutil.NopCloser(io.MultiReader(&b1, errorReader{err: err})), ioutil.NopCloser(io.MultiReader(&b2, errorReader{err: err})), err
+	}
+	defer func() { body.Close() }()
+
+	return ioutil.NopCloser(&b1), ioutil.NopCloser(&b2), nil
+}
+
+func resStatusCode(res *http.Response) int {
+	if res == nil {
+		return -1
+	}
+	return res.StatusCode
+}
+
+type errorReader struct{ err error }
+
+func (r errorReader) Read(p []byte) (int, error) { return 0, r.err }

vendor/github.com/opensearch-project/opensearch-go/opensearchtransport/metrics.go

@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// The OpenSearch Contributors require contributions made to
+// this file be licensed under the Apache-2.0 license or a
+// compatible open source license.
+//
+// Modifications Copyright OpenSearch Contributors. See
+// GitHub history for details.
+
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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 opensearchtransport
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+)
+
+// Measurable defines the interface for transports supporting metrics.
+//
+type Measurable interface {
+	Metrics() (Metrics, error)
+}
+
+// connectionable defines the interface for transports returning a list of connections.
+//
+type connectionable interface {
+	connections() []*Connection
+}
+
+// Metrics represents the transport metrics.
+//
+type Metrics struct {
+	Requests  int         `json:"requests"`
+	Failures  int         `json:"failures"`
+	Responses map[int]int `json:"responses"`
+
+	Connections []fmt.Stringer `json:"connections"`
+}
+
+// ConnectionMetric represents metric information for a connection.
+//
+type ConnectionMetric struct {
+	URL       string     `json:"url"`
+	Failures  int        `json:"failures,omitempty"`
+	IsDead    bool       `json:"dead,omitempty"`
+	DeadSince *time.Time `json:"dead_since,omitempty"`
+
+	Meta struct {
+		ID    string   `json:"id"`
+		Name  string   `json:"name"`
+		Roles []string `json:"roles"`
+	} `json:"meta"`
+}
+
+// metrics represents the inner state of metrics.
+//
+type metrics struct {
+	sync.RWMutex
+
+	requests  int
+	failures  int
+	responses map[int]int
+
+	connections []*Connection
+}
+
+// Metrics returns the transport metrics.
+//
+func (c *Client) Metrics() (Metrics, error) {
+	if c.metrics == nil {
+		return Metrics{}, errors.New("transport metrics not enabled")
+	}
+	c.metrics.RLock()
+	defer c.metrics.RUnlock()
+
+	if lockable, ok := c.pool.(sync.Locker); ok {
+		lockable.Lock()
+		defer lockable.Unlock()
+	}
+
+	m := Metrics{
+		Requests:  c.metrics.requests,
+		Failures:  c.metrics.failures,
+		Responses: c.metrics.responses,
+	}
+
+	if pool, ok := c.pool.(connectionable); ok {
+		for _, c := range pool.connections() {
+			c.Lock()
+
+			cm := ConnectionMetric{
+				URL:      c.URL.String(),
+				IsDead:   c.IsDead,
+				Failures: c.Failures,
+			}
+
+			if !c.DeadSince.IsZero() {
+				cm.DeadSince = &c.DeadSince
+			}
+
+			if c.ID != "" {
+				cm.Meta.ID = c.ID
+			}
+
+			if c.Name != "" {
+				cm.Meta.Name = c.Name
+			}
+
+			if len(c.Roles) > 0 {
+				cm.Meta.Roles = c.Roles
+			}
+
+			m.Connections = append(m.Connections, cm)
+			c.Unlock()
+		}
+	}
+
+	return m, nil
+}
+
+// String returns the metrics as a string.
+//
+func (m Metrics) String() string {
+	var (
+		i int
+		b strings.Builder
+	)
+	b.WriteString("{")
+
+	b.WriteString("Requests:")
+	b.WriteString(strconv.Itoa(m.Requests))
+
+	b.WriteString(" Failures:")
+	b.WriteString(strconv.Itoa(m.Failures))
+
+	if len(m.Responses) > 0 {
+		b.WriteString(" Responses: ")
+		b.WriteString("[")
+
+		for code, num := range m.Responses {
+			b.WriteString(strconv.Itoa(code))
+			b.WriteString(":")
+			b.WriteString(strconv.Itoa(num))
+			if i+1 < len(m.Responses) {
+				b.WriteString(", ")
+			}
+			i++
+		}
+		b.WriteString("]")
+	}
+
+	b.WriteString(" Connections: [")
+	for i, c := range m.Connections {
+		b.WriteString(c.String())
+		if i+1 < len(m.Connections) {
+			b.WriteString(", ")
+		}
+		i++
+	}
+	b.WriteString("]")
+
+	b.WriteString("}")
+	return b.String()
+}
+
+// String returns the connection information as a string.
+//
+func (cm ConnectionMetric) String() string {
+	var b strings.Builder
+	b.WriteString("{")
+	b.WriteString(cm.URL)
+	if cm.IsDead {
+		fmt.Fprintf(&b, " dead=%v", cm.IsDead)
+	}
+	if cm.Failures > 0 {
+		fmt.Fprintf(&b, " failures=%d", cm.Failures)
+	}
+	if cm.DeadSince != nil {
+		fmt.Fprintf(&b, " dead_since=%s", cm.DeadSince.Local().Format(time.Stamp))
+	}
+	b.WriteString("}")
+	return b.String()
+}

vendor/github.com/opensearch-project/opensearch-go/opensearchtransport/opensearchtransport.go

@@ -0,0 +1,521 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// The OpenSearch Contributors require contributions made to
+// this file be licensed under the Apache-2.0 license or a
+// compatible open source license.
+//
+// Modifications Copyright OpenSearch Contributors. See
+// GitHub history for details.
+
+// Licensed to Elasticsearch B.V. under one or more contributor
+// license agreements. See the NOTICE file distributed with
+// this work for additional information regarding copyright
+// ownership. Elasticsearch B.V. licenses this file to you 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 opensearchtransport
+
+import (
+	"bytes"
+	"compress/gzip"
+	"crypto/x509"
+	"errors"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"os"
+	"regexp"
+	"runtime"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"github.com/opensearch-project/opensearch-go/signer"
+
+	"github.com/opensearch-project/opensearch-go/internal/version"
+)
+
+const (
+	// Version returns the package version as a string.
+	Version = version.Client
+
+	// esCompatHeader defines the env var for Compatibility header.
+	esCompatHeader = "ELASTIC_CLIENT_APIVERSIONING"
+)
+
+var (
+	userAgent           string
+	compatibilityHeader bool
+	reGoVersion         = regexp.MustCompile(`go(\d+\.\d+\..+)`)
+
+	defaultMaxRetries    = 3
+	defaultRetryOnStatus = [...]int{502, 503, 504}
+)
+
+func init() {
+	userAgent = initUserAgent()
+
+	compatHeaderEnv := os.Getenv(esCompatHeader)
+	compatibilityHeader, _ = strconv.ParseBool(compatHeaderEnv)
+}
+
+// Interface defines the interface for HTTP client.
+//
+type Interface interface {
+	Perform(*http.Request) (*http.Response, error)
+}
+
+// Config represents the configuration of HTTP client.
+//
+type Config struct {
+	URLs     []*url.URL
+	Username string
+	Password string
+
+	Header http.Header
+	CACert []byte
+
+	Signer signer.Signer
+
+	RetryOnStatus        []int
+	DisableRetry         bool
+	EnableRetryOnTimeout bool
+	MaxRetries           int
+	RetryBackoff         func(attempt int) time.Duration
+
+	CompressRequestBody bool
+
+	EnableMetrics     bool
+	EnableDebugLogger bool
+
+	DiscoverNodesInterval time.Duration
+
+	Transport http.RoundTripper
+	Logger    Logger
+	Selector  Selector
+
+	ConnectionPoolFunc func([]*Connection, Selector) ConnectionPool
+}
+
+// Client represents the HTTP client.
+//
+type Client struct {
+	sync.Mutex
+
+	urls     []*url.URL
+	username string
+	password string
+	header   http.Header
+
+	signer signer.Signer
+
+	retryOnStatus         []int
+	disableRetry          bool
+	enableRetryOnTimeout  bool
+	maxRetries            int
+	retryBackoff          func(attempt int) time.Duration
+	discoverNodesInterval time.Duration
+	discoverNodesTimer    *time.Timer
+
+	compressRequestBody bool
+
+	metrics *metrics
+
+	transport http.RoundTripper
+	logger    Logger
+	selector  Selector
+	pool      ConnectionPool
+	poolFunc  func([]*Connection, Selector) ConnectionPool
+}
+
+// New creates new transport client.
+//
+// http.DefaultTransport will be used if no transport is passed in the configuration.
+//
+func New(cfg Config) (*Client, error) {
+	if cfg.Transport == nil {
+		cfg.Transport = http.DefaultTransport
+	}
+
+	if cfg.CACert != nil {
+		httpTransport, ok := cfg.Transport.(*http.Transport)
+		if !ok {
+			return nil, fmt.Errorf("unable to set CA certificate for transport of type %T", cfg.Transport)
+		}
+
+		httpTransport = httpTransport.Clone()
+		httpTransport.TLSClientConfig.RootCAs = x509.NewCertPool()
+
+		if ok := httpTransport.TLSClientConfig.RootCAs.AppendCertsFromPEM(cfg.CACert); !ok {
+			return nil, errors.New("unable to add CA certificate")
+		}
+
+		cfg.Transport = httpTransport
+	}
+
+	if len(cfg.RetryOnStatus) == 0 {
+		cfg.RetryOnStatus = defaultRetryOnStatus[:]
+	}
+
+	if cfg.MaxRetries == 0 {
+		cfg.MaxRetries = defaultMaxRetries
+	}
+
+	var conns []*Connection
+	for _, u := range cfg.URLs {
+		conns = append(conns, &Connection{URL: u})
+	}
+
+	client := Client{
+		urls:     cfg.URLs,
+		username: cfg.Username,
+		password: cfg.Password,
+		header:   cfg.Header,
+
+		signer: cfg.Signer,
+
+		retryOnStatus:         cfg.RetryOnStatus,
+		disableRetry:          cfg.DisableRetry,
+		enableRetryOnTimeout:  cfg.EnableRetryOnTimeout,
+		maxRetries:            cfg.MaxRetries,
+		retryBackoff:          cfg.RetryBackoff,
+		discoverNodesInterval: cfg.DiscoverNodesInterval,
+
+		compressRequestBody: cfg.CompressRequestBody,
+
+		transport: cfg.Transport,
+		logger:    cfg.Logger,
+		selector:  cfg.Selector,
+		poolFunc:  cfg.ConnectionPoolFunc,
+	}
+
+	if client.poolFunc != nil {
+		client.pool = client.poolFunc(conns, client.selector)
+	} else {
+		client.pool, _ = NewConnectionPool(conns, client.selector)
+	}
+
+	if cfg.EnableDebugLogger {
+		debugLogger = &debuggingLogger{Output: os.Stdout}
+	}
+
+	if cfg.EnableMetrics {
+		client.metrics = &metrics{responses: make(map[int]int)}
+		// TODO(karmi): Type assertion to interface
+		if pool, ok := client.pool.(*singleConnectionPool); ok {
+			pool.metrics = client.metrics
+		}
+		if pool, ok := client.pool.(*statusConnectionPool); ok {
+			pool.metrics = client.metrics
+		}
+	}
+
+	if client.discoverNodesInterval > 0 {
+		time.AfterFunc(client.discoverNodesInterval, func() {
+			client.scheduleDiscoverNodes(client.discoverNodesInterval)
+		})
+	}
+
+	return &client, nil
+}
+
+// Perform executes the request and returns a response or error.
+//
+func (c *Client) Perform(req *http.Request) (*http.Response, error) {
+	var (
+		res *http.Response
+		err error
+	)
+
+	// Compatibility Header
+	if compatibilityHeader {
+		if req.Body != nil {
+			req.Header.Set("Content-Type", "application/vnd.elasticsearch+json;compatible-with=7")
+		}
+		req.Header.Set("Accept", "application/vnd.elasticsearch+json;compatible-with=7")
+	}
+
+	// Record metrics, when enabled
+	if c.metrics != nil {
+		c.metrics.Lock()
+		c.metrics.requests++
+		c.metrics.Unlock()
+	}
+
+	// Update request
+	c.setReqUserAgent(req)
+	c.setReqGlobalHeader(req)
+
+	if req.Body != nil && req.Body != http.NoBody {
+		if c.compressRequestBody {
+			var buf bytes.Buffer
+			zw := gzip.NewWriter(&buf)
+			if _, err := io.Copy(zw, req.Body); err != nil {
+				return nil, fmt.Errorf("failed to compress request body: %s", err)
+			}
+			if err := zw.Close(); err != nil {
+				return nil, fmt.Errorf("failed to compress request body (during close): %s", err)
+			}
+
+			req.GetBody = func() (io.ReadCloser, error) {
+				r := buf
+				return ioutil.NopCloser(&r), nil
+			}
+			req.Body, _ = req.GetBody()
+
+			req.Header.Set("Content-Encoding", "gzip")
+			req.ContentLength = int64(buf.Len())
+
+		} else if req.GetBody == nil {
+			if !c.disableRetry || (c.logger != nil && c.logger.RequestBodyEnabled()) {
+				var buf bytes.Buffer
+				buf.ReadFrom(req.Body)
+
+				req.GetBody = func() (io.ReadCloser, error) {
+					r := buf
+					return ioutil.NopCloser(&r), nil
+				}
+				req.Body, _ = req.GetBody()
+			}
+		}
+	}
+
+	for i := 0; i <= c.maxRetries; i++ {
+		var (
+			conn            *Connection
+			shouldRetry     bool
+			shouldCloseBody bool
+		)
+
+		// Get connection from the pool
+		c.Lock()
+		conn, err = c.pool.Next()
+		c.Unlock()
+		if err != nil {
+			if c.logger != nil {
+				c.logRoundTrip(req, nil, err, time.Time{}, time.Duration(0))
+			}
+			return nil, fmt.Errorf("cannot get connection: %s", err)
+		}
+
+		// Update request
+		c.setReqURL(conn.URL, req)
+		c.setReqAuth(conn.URL, req)
+
+		if err = c.signRequest(req); err != nil {
+			return nil, fmt.Errorf("failed to sign request: %s", err)
+		}
+
+		if !c.disableRetry && i > 0 && req.Body != nil && req.Body != http.NoBody {
+			body, err := req.GetBody()
+			if err != nil {
+				return nil, fmt.Errorf("cannot get request body: %s", err)
+			}
+			req.Body = body
+		}
+
+		// Set up time measures and execute the request
+		start := time.Now().UTC()
+		res, err = c.transport.RoundTrip(req)
+		dur := time.Since(start)
+
+		// Log request and response
+		if c.logger != nil {
+			if c.logger.RequestBodyEnabled() && req.Body != nil && req.Body != http.NoBody {
+				req.Body, _ = req.GetBody()
+			}
+			c.logRoundTrip(req, res, err, start, dur)
+		}
+
+		if err != nil {
+			// Record metrics, when enabled
+			if c.metrics != nil {
+				c.metrics.Lock()
+				c.metrics.failures++
+				c.metrics.Unlock()
+			}
+
+			// Report the connection as unsuccessful
+			c.Lock()
+			c.pool.OnFailure(conn)
+			c.Unlock()
+
+			// Retry on EOF errors
+			if err == io.EOF {
+				shouldRetry = true
+			}
+
+			// Retry on network errors, but not on timeout errors, unless configured
+			if err, ok := err.(net.Error); ok {
+				if (!err.Timeout() || c.enableRetryOnTimeout) && !c.disableRetry {
+					shouldRetry = true
+				}
+			}
+		} else {
+			// Report the connection as succesfull
+			c.Lock()
+			c.pool.OnSuccess(conn)
+			c.Unlock()
+		}
+
+		if res != nil && c.metrics != nil {
+			c.metrics.Lock()
+			c.metrics.responses[res.StatusCode]++
+			c.metrics.Unlock()
+		}
+
+		// Retry on configured response statuses
+		if res != nil && !c.disableRetry {
+			for _, code := range c.retryOnStatus {
+				if res.StatusCode == code {
+					shouldRetry = true
+					shouldCloseBody = true
+				}
+			}
+		}
+
+		// Break if retry should not be performed
+		if !shouldRetry {
+			break
+		}
+
+		// Drain and close body when retrying after response
+		if shouldCloseBody && i < c.maxRetries {
+			if res.Body != nil {
+				io.Copy(ioutil.Discard, res.Body)
+				res.Body.Close()
+			}
+		}
+
+		// Delay the retry if a backoff function is configured
+		if c.retryBackoff != nil {
+			time.Sleep(c.retryBackoff(i + 1))
+		}
+	}
+
+	// TODO(karmi): Wrap error
+	return res, err
+}
+
+// URLs returns a list of transport URLs.
+//
+//
+func (c *Client) URLs() []*url.URL {
+	return c.pool.URLs()
+}
+
+func (c *Client) setReqURL(u *url.URL, req *http.Request) *http.Request {
+	req.URL.Scheme = u.Scheme
+	req.URL.Host = u.Host
+
+	if u.Path != "" {
+		var b strings.Builder
+		b.Grow(len(u.Path) + len(req.URL.Path))
+		b.WriteString(u.Path)
+		b.WriteString(req.URL.Path)
+		req.URL.Path = b.String()
+	}
+
+	return req
+}
+
+func (c *Client) setReqAuth(u *url.URL, req *http.Request) *http.Request {
+	if _, ok := req.Header["Authorization"]; !ok {
+		if u.User != nil {
+			password, _ := u.User.Password()
+			req.SetBasicAuth(u.User.Username(), password)
+			return req
+		}
+
+		if c.username != "" && c.password != "" {
+			req.SetBasicAuth(c.username, c.password)
+			return req
+		}
+	}
+
+	return req
+}
+
+func (c *Client) signRequest(req *http.Request) error {
+	if c.signer != nil {
+		return c.signer.SignRequest(req)
+	}
+	return nil
+}
+
+func (c *Client) setReqUserAgent(req *http.Request) *http.Request {
+	req.Header.Set("User-Agent", userAgent)
+	return req
+}
+
+func (c *Client) setReqGlobalHeader(req *http.Request) *http.Request {
+	if len(c.header) > 0 {
+		for k, v := range c.header {
+			if req.Header.Get(k) != k {
+				for _, vv := range v {
+					req.Header.Add(k, vv)
+				}
+			}
+		}
+	}
+	return req
+}
+
+func (c *Client) logRoundTrip(
+	req *http.Request,
+	res *http.Response,
+	err error,
+	start time.Time,
+	dur time.Duration,
+) {
+	var dupRes http.Response
+	if res != nil {
+		dupRes = *res
+	}
+	if c.logger.ResponseBodyEnabled() {
+		if res != nil && res.Body != nil && res.Body != http.NoBody {
+			b1, b2, _ := duplicateBody(res.Body)
+			dupRes.Body = b1
+			res.Body = b2
+		}
+	}
+	c.logger.LogRoundTrip(req, &dupRes, err, start, dur) // errcheck exclude
+}
+
+func initUserAgent() string {
+	var b strings.Builder
+
+	b.WriteString("opensearch-go")
+	b.WriteRune('/')
+	b.WriteString(Version)
+	b.WriteRune(' ')
+	b.WriteRune('(')
+	b.WriteString(runtime.GOOS)
+	b.WriteRune(' ')
+	b.WriteString(runtime.GOARCH)
+	b.WriteString("; ")
+	b.WriteString("Go ")
+	if v := reGoVersion.ReplaceAllString(runtime.Version(), "$1"); v != "" {
+		b.WriteString(v)
+	} else {
+		b.WriteString(runtime.Version())
+	}
+	b.WriteRune(')')
+
+	return b.String()
+}