From 99f34b3af762bb304997572caa143ec453ffba25 Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Fri, 22 Dec 2023 16:14:22 +0100
Subject: [PATCH 01/12] Add onfiguration option to override Host header.

---
 CHANGELOG.md                                      |  1 +
 .../otlpmetricgrpc/internal/oconf/options.go      |  8 ++++++++
 .../otlpmetricgrpc/internal/otest/collector.go    | 13 ++++++++++---
 .../otlp/otlpmetric/otlpmetrichttp/client.go      |  5 +++++
 .../otlp/otlpmetric/otlpmetrichttp/client_test.go | 15 ++++++++++++++-
 .../otlp/otlpmetric/otlpmetrichttp/config.go      |  6 ++++++
 .../otlpmetrichttp/internal/oconf/options.go      |  8 ++++++++
 .../otlpmetrichttp/internal/otest/collector.go    | 13 ++++++++++---
 .../otlptracegrpc/internal/otlpconfig/options.go  |  8 ++++++++
 exporters/otlp/otlptrace/otlptracehttp/client.go  |  4 ++++
 .../otlp/otlptrace/otlptracehttp/client_test.go   | 11 +++++++++++
 .../otlptracehttp/internal/otlpconfig/options.go  | 10 +++++++++-
 .../otlptracehttp/mock_collector_test.go          | 12 ++++++++++--
 exporters/otlp/otlptrace/otlptracehttp/options.go |  6 ++++++
 .../shared/otlp/otlpmetric/oconf/options.go.tmpl  |  8 ++++++++
 .../otlp/otlpmetric/otest/collector.go.tmpl       | 13 ++++++++++---
 .../otlp/otlptrace/otlpconfig/options.go.tmpl     |  8 ++++++++
 17 files changed, 136 insertions(+), 13 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c283b9cbebb..25a7a5eeba8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Add `WithResourceAsConstantLabels` option to apply resource attributes for every metric emitted by the Prometheus exporter. (#4733)
 - Experimental cardinality limiting is added to the metric SDK.
   See [metric documentation](./sdk/metric/EXPERIMENTAL.md#cardinality-limit) for more information about this feature and how to enable it. (#4457)
+- Add `WithHostHeader` config option to override Host header in opentelemetry requests (#4777)
 
 ### Changed
 
diff --git a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/options.go b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/options.go
index a85f2712224..6060899c9e2 100644
--- a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/options.go
+++ b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/options.go
@@ -56,6 +56,7 @@ type (
 		Insecure    bool
 		TLSCfg      *tls.Config
 		Headers     map[string]string
+		HostHeader  string
 		Compression Compression
 		Timeout     time.Duration
 		URLPath     string
@@ -331,6 +332,13 @@ func WithHeaders(headers map[string]string) GenericOption {
 	})
 }
 
+func WithHostHeader(host string) GenericOption {
+	return newGenericOption(func(cfg Config) Config {
+		cfg.Metrics.HostHeader = host
+		return cfg
+	})
+}
+
 func WithTimeout(duration time.Duration) GenericOption {
 	return newGenericOption(func(cfg Config) Config {
 		cfg.Metrics.Timeout = duration
diff --git a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
index f08fbd5c5f7..b4bc6bc7313 100644
--- a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
@@ -197,9 +197,10 @@ func (e *HTTPResponseError) Unwrap() error { return e.Err }
 type HTTPCollector struct {
 	plainTextResponse bool
 
-	headersMu sync.Mutex
-	headers   http.Header
-	storage   *Storage
+	headersMu  sync.Mutex
+	headers    http.Header
+	hostHeader string
+	storage    *Storage
 
 	resultCh <-chan ExportResult
 	listener net.Listener
@@ -299,6 +300,10 @@ func (c *HTTPCollector) Headers() map[string][]string {
 	return c.headers.Clone()
 }
 
+func (c *HTTPCollector) HostHeader() string {
+   return c.hostHeader
+}
+
 func (c *HTTPCollector) handler(w http.ResponseWriter, r *http.Request) {
 	c.respond(w, c.record(r))
 }
@@ -334,6 +339,8 @@ func (c *HTTPCollector) record(r *http.Request) ExportResult {
 	}
 	c.headersMu.Unlock()
 
+	c.hostHeader = r.Host
+
 	if c.resultCh != nil {
 		return <-c.resultCh
 	}
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/client.go b/exporters/otlp/otlpmetric/otlpmetrichttp/client.go
index 73463c91d5f..6523982ca77 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/client.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/client.go
@@ -83,6 +83,7 @@ func newClient(cfg oconf.Config) (*client, error) {
 	if cfg.Metrics.Insecure {
 		u.Scheme = "http"
 	}
+
 	// Body is set when this is cloned during upload.
 	req, err := http.NewRequest(http.MethodPost, u.String(), http.NoBody)
 	if err != nil {
@@ -99,6 +100,10 @@ func newClient(cfg oconf.Config) (*client, error) {
 	}
 	req.Header.Set("Content-Type", "application/x-protobuf")
 
+	if cfg.Metrics.HostHeader != "" {
+		req.Host = cfg.Metrics.HostHeader
+	}
+
 	return &client{
 		compression: Compression(cfg.Metrics.Compression),
 		req:         req,
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go b/exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go
index a4ead01c1f1..04f815cca27 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go
@@ -4,7 +4,7 @@
 // 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
+//	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,
@@ -123,6 +123,19 @@ func TestConfig(t *testing.T) {
 		assert.Equal(t, got[key], []string{headers[key]})
 	})
 
+	t.Run("WithHostHeader", func(t *testing.T) {
+		hostHeader := "test-host"
+		exp, coll := factoryFunc("", nil, WithHostHeader(hostHeader))
+		ctx := context.Background()
+		t.Cleanup(func() { require.NoError(t, coll.Shutdown(ctx)) })
+		require.NoError(t, exp.Export(ctx, &metricdata.ResourceMetrics{}))
+		// Ensure everything is flushed.
+		require.NoError(t, exp.Shutdown(ctx))
+
+		got := coll.HostHeader()
+		assert.Equal(t, got, hostHeader)
+	})
+
 	t.Run("WithTimeout", func(t *testing.T) {
 		// Do not send on rCh so the Collector never responds to the client.
 		rCh := make(chan otest.ExportResult)
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/config.go b/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
index 6eae3e1bbda..0b4f12a8e33 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
@@ -149,6 +149,12 @@ func WithHeaders(headers map[string]string) Option {
 	return wrappedOption{oconf.WithHeaders(headers)}
 }
 
+// WithHostHeader overrides Host header in HTTP requests.
+// If unset, the target Endpoint's host will be used as Host header
+func WithHostHeader(host string) Option {
+	return wrappedOption{oconf.WithHostHeader(host)}
+}
+
 // WithTimeout sets the max amount of time an Exporter will attempt an export.
 //
 // This takes precedence over any retry settings defined by WithRetry. Once
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/options.go b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/options.go
index 59468b9a5ed..185807f0dde 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/options.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/options.go
@@ -56,6 +56,7 @@ type (
 		Insecure    bool
 		TLSCfg      *tls.Config
 		Headers     map[string]string
+		HostHeader  string
 		Compression Compression
 		Timeout     time.Duration
 		URLPath     string
@@ -331,6 +332,13 @@ func WithHeaders(headers map[string]string) GenericOption {
 	})
 }
 
+func WithHostHeader(host string) GenericOption {
+	return newGenericOption(func(cfg Config) Config {
+		cfg.Metrics.HostHeader = host
+		return cfg
+	})
+}
+
 func WithTimeout(duration time.Duration) GenericOption {
 	return newGenericOption(func(cfg Config) Config {
 		cfg.Metrics.Timeout = duration
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
index 6398f8ba5ba..c4f96433e0f 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
@@ -197,9 +197,10 @@ func (e *HTTPResponseError) Unwrap() error { return e.Err }
 type HTTPCollector struct {
 	plainTextResponse bool
 
-	headersMu sync.Mutex
-	headers   http.Header
-	storage   *Storage
+	headersMu  sync.Mutex
+	headers    http.Header
+	hostHeader string
+	storage    *Storage
 
 	resultCh <-chan ExportResult
 	listener net.Listener
@@ -299,6 +300,10 @@ func (c *HTTPCollector) Headers() map[string][]string {
 	return c.headers.Clone()
 }
 
+func (c *HTTPCollector) HostHeader() string {
+   return c.hostHeader
+}
+
 func (c *HTTPCollector) handler(w http.ResponseWriter, r *http.Request) {
 	c.respond(w, c.record(r))
 }
@@ -334,6 +339,8 @@ func (c *HTTPCollector) record(r *http.Request) ExportResult {
 	}
 	c.headersMu.Unlock()
 
+	c.hostHeader = r.Host
+
 	if c.resultCh != nil {
 		return <-c.resultCh
 	}
diff --git a/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options.go b/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options.go
index dddb1f334de..370ae769b2b 100644
--- a/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options.go
+++ b/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options.go
@@ -49,6 +49,7 @@ type (
 		Insecure    bool
 		TLSCfg      *tls.Config
 		Headers     map[string]string
+		HostHeader  string
 		Compression Compression
 		Timeout     time.Duration
 		URLPath     string
@@ -317,6 +318,13 @@ func WithHeaders(headers map[string]string) GenericOption {
 	})
 }
 
+func WithHostHeader(host string) GenericOption {
+	return newGenericOption(func(cfg Config) Config {
+		cfg.Traces.HostHeader = host
+		return cfg
+	})
+}
+
 func WithTimeout(duration time.Duration) GenericOption {
 	return newGenericOption(func(cfg Config) Config {
 		cfg.Traces.Timeout = duration
diff --git a/exporters/otlp/otlptrace/otlptracehttp/client.go b/exporters/otlp/otlptrace/otlptracehttp/client.go
index 3b5f3839f27..007a4f08e42 100644
--- a/exporters/otlp/otlptrace/otlptracehttp/client.go
+++ b/exporters/otlp/otlptrace/otlptracehttp/client.go
@@ -228,6 +228,10 @@ func (d *client) newRequest(body []byte) (request, error) {
 	}
 	r.Header.Set("Content-Type", contentTypeProto)
 
+	if d.cfg.HostHeader != "" {
+		r.Host = d.cfg.HostHeader
+	}
+
 	req := request{Request: r}
 	switch Compression(d.cfg.Compression) {
 	case NoCompression:
diff --git a/exporters/otlp/otlptrace/otlptracehttp/client_test.go b/exporters/otlp/otlptrace/otlptracehttp/client_test.go
index 63a4cd4f207..f146fb2ae7c 100644
--- a/exporters/otlp/otlptrace/otlptracehttp/client_test.go
+++ b/exporters/otlp/otlptrace/otlptracehttp/client_test.go
@@ -47,6 +47,8 @@ var (
 	customUserAgentHeader = map[string]string{
 		"user-agent": "custome-user-agent",
 	}
+
+	customHostName = "test-host-name"
 )
 
 func TestEndToEnd(t *testing.T) {
@@ -156,6 +158,15 @@ func TestEndToEnd(t *testing.T) {
 				ExpectedHeaders: customUserAgentHeader,
 			},
 		},
+		{
+			name: "with custom host header",
+			opts: []otlptracehttp.Option{
+				otlptracehttp.WithHostHeader(customHostName),
+			},
+			mcCfg: mockCollectorConfig{
+				ExpectedHostHeader: customHostName,
+			},
+		},
 	}
 
 	for _, tc := range tests {
diff --git a/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go b/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go
index 8401bd7f155..41b175e7230 100644
--- a/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go
+++ b/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go
@@ -15,7 +15,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package otlpconfig // import "go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig"
+package otlpconfig
 
 import (
 	"crypto/tls"
@@ -49,6 +49,7 @@ type (
 		Insecure    bool
 		TLSCfg      *tls.Config
 		Headers     map[string]string
+		HostHeader  string
 		Compression Compression
 		Timeout     time.Duration
 		URLPath     string
@@ -317,6 +318,13 @@ func WithHeaders(headers map[string]string) GenericOption {
 	})
 }
 
+func WithHostHeader(host string) GenericOption {
+	return newGenericOption(func(cfg Config) Config {
+		cfg.Traces.HostHeader = host
+		return cfg
+	})
+}
+
 func WithTimeout(duration time.Duration) GenericOption {
 	return newGenericOption(func(cfg Config) Config {
 		cfg.Traces.Timeout = duration
diff --git a/exporters/otlp/otlptrace/otlptracehttp/mock_collector_test.go b/exporters/otlp/otlptrace/otlptracehttp/mock_collector_test.go
index 2b87215d183..cae09ac1188 100644
--- a/exporters/otlp/otlptrace/otlptracehttp/mock_collector_test.go
+++ b/exporters/otlp/otlptrace/otlptracehttp/mock_collector_test.go
@@ -50,8 +50,9 @@ type mockCollector struct {
 	partial              *collectortracepb.ExportTracePartialSuccess
 	delay                <-chan struct{}
 
-	clientTLSConfig *tls.Config
-	expectedHeaders map[string]string
+	clientTLSConfig    *tls.Config
+	expectedHeaders    map[string]string
+	expectedHostHeader string
 }
 
 func (c *mockCollector) Stop() error {
@@ -95,6 +96,11 @@ func (c *mockCollector) serveTraces(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusBadRequest)
 		return
 	}
+	if c.expectedHostHeader != "" && c.expectedHostHeader != r.Host {
+		w.WriteHeader(http.StatusBadRequest)
+		return
+	}
+
 	response := collectortracepb.ExportTraceServiceResponse{
 		PartialSuccess: c.partial,
 	}
@@ -215,6 +221,7 @@ type mockCollectorConfig struct {
 	Delay                <-chan struct{}
 	WithTLS              bool
 	ExpectedHeaders      map[string]string
+	ExpectedHostHeader   string
 }
 
 func (c *mockCollectorConfig) fillInDefaults() {
@@ -238,6 +245,7 @@ func runMockCollector(t *testing.T, cfg mockCollectorConfig) *mockCollector {
 		partial:              cfg.Partial,
 		delay:                cfg.Delay,
 		expectedHeaders:      cfg.ExpectedHeaders,
+		expectedHostHeader:   cfg.ExpectedHostHeader,
 	}
 	mux := http.NewServeMux()
 	mux.Handle(cfg.TracesURLPath, http.HandlerFunc(m.serveTraces))
diff --git a/exporters/otlp/otlptrace/otlptracehttp/options.go b/exporters/otlp/otlptrace/otlptracehttp/options.go
index e3ed6494c5d..459053baad1 100644
--- a/exporters/otlp/otlptrace/otlptracehttp/options.go
+++ b/exporters/otlp/otlptrace/otlptracehttp/options.go
@@ -100,6 +100,12 @@ func WithHeaders(headers map[string]string) Option {
 	return wrappedOption{otlpconfig.WithHeaders(headers)}
 }
 
+// WithHostHeader allows one to tell the driver to override HTTP host header.
+// If value is unset Endpoint's host is used as Host header.
+func WithHostHeader(host string) Option {
+	return wrappedOption{otlpconfig.WithHostHeader(host)}
+}
+
 // WithTimeout tells the driver the max waiting time for the backend to process
 // each spans batch.  If unset, the default will be 10 seconds.
 func WithTimeout(duration time.Duration) Option {
diff --git a/internal/shared/otlp/otlpmetric/oconf/options.go.tmpl b/internal/shared/otlp/otlpmetric/oconf/options.go.tmpl
index c4f9d0830f4..4878eb87e52 100644
--- a/internal/shared/otlp/otlpmetric/oconf/options.go.tmpl
+++ b/internal/shared/otlp/otlpmetric/oconf/options.go.tmpl
@@ -56,6 +56,7 @@ type (
 		Insecure    bool
 		TLSCfg      *tls.Config
 		Headers     map[string]string
+		HostHeader  string
 		Compression Compression
 		Timeout     time.Duration
 		URLPath     string
@@ -331,6 +332,13 @@ func WithHeaders(headers map[string]string) GenericOption {
 	})
 }
 
+func WithHostHeader(host string) GenericOption {
+	return newGenericOption(func(cfg Config) Config {
+		cfg.Metrics.HostHeader = host
+		return cfg
+	})
+}
+
 func WithTimeout(duration time.Duration) GenericOption {
 	return newGenericOption(func(cfg Config) Config {
 		cfg.Metrics.Timeout = duration
diff --git a/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl b/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
index fba237e68fc..aff6fad65e1 100644
--- a/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
+++ b/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
@@ -197,9 +197,10 @@ func (e *HTTPResponseError) Unwrap() error { return e.Err }
 type HTTPCollector struct {
 	plainTextResponse bool
 
-	headersMu sync.Mutex
-	headers   http.Header
-	storage   *Storage
+	headersMu  sync.Mutex
+	headers    http.Header
+	hostHeader string
+	storage    *Storage
 
 	resultCh <-chan ExportResult
 	listener net.Listener
@@ -299,6 +300,10 @@ func (c *HTTPCollector) Headers() map[string][]string {
 	return c.headers.Clone()
 }
 
+func (c *HTTPCollector) HostHeader() string {
+   return c.hostHeader
+}
+
 func (c *HTTPCollector) handler(w http.ResponseWriter, r *http.Request) {
 	c.respond(w, c.record(r))
 }
@@ -334,6 +339,8 @@ func (c *HTTPCollector) record(r *http.Request) ExportResult {
 	}
 	c.headersMu.Unlock()
 
+	c.hostHeader = r.Host
+
 	if c.resultCh != nil {
 		return <-c.resultCh
 	}
diff --git a/internal/shared/otlp/otlptrace/otlpconfig/options.go.tmpl b/internal/shared/otlp/otlptrace/otlpconfig/options.go.tmpl
index 9270e506a9c..bef29cd739a 100644
--- a/internal/shared/otlp/otlptrace/otlpconfig/options.go.tmpl
+++ b/internal/shared/otlp/otlptrace/otlpconfig/options.go.tmpl
@@ -49,6 +49,7 @@ type (
 		Insecure    bool
 		TLSCfg      *tls.Config
 		Headers     map[string]string
+		HostHeader  string
 		Compression Compression
 		Timeout     time.Duration
 		URLPath     string
@@ -317,6 +318,13 @@ func WithHeaders(headers map[string]string) GenericOption {
 	})
 }
 
+func WithHostHeader(host string) GenericOption {
+	return newGenericOption(func(cfg Config) Config {
+		cfg.Traces.HostHeader = host
+		return cfg
+	})
+}
+
 func WithTimeout(duration time.Duration) GenericOption {
 	return newGenericOption(func(cfg Config) Config {
 		cfg.Traces.Timeout = duration

From ccbd51b197de35c8345ad39bfc348d1d5f65ed56 Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Thu, 4 Jan 2024 16:34:49 +0100
Subject: [PATCH 02/12] Fix linter

---
 .../otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go  | 2 +-
 .../otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
index b4bc6bc7313..8cc131676e7 100644
--- a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
@@ -301,7 +301,7 @@ func (c *HTTPCollector) Headers() map[string][]string {
 }
 
 func (c *HTTPCollector) HostHeader() string {
-   return c.hostHeader
+	return c.hostHeader
 }
 
 func (c *HTTPCollector) handler(w http.ResponseWriter, r *http.Request) {
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
index c4f96433e0f..f143b2f2a8e 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
@@ -301,7 +301,7 @@ func (c *HTTPCollector) Headers() map[string][]string {
 }
 
 func (c *HTTPCollector) HostHeader() string {
-   return c.hostHeader
+	return c.hostHeader
 }
 
 func (c *HTTPCollector) handler(w http.ResponseWriter, r *http.Request) {

From d4f00880f8b5e3540dd5cbc7db1142db39798bfe Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Thu, 4 Jan 2024 16:37:54 +0100
Subject: [PATCH 03/12] Fix linter

---
 internal/shared/otlp/otlpmetric/otest/collector.go.tmpl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl b/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
index aff6fad65e1..d15c895c052 100644
--- a/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
+++ b/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
@@ -42,9 +42,9 @@ import (
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/proto"
 
-	"{{ .oconfImportPath }}"
 	collpb "go.opentelemetry.io/proto/otlp/collector/metrics/v1"
 	mpb "go.opentelemetry.io/proto/otlp/metrics/v1"
+	"{{ .oconfImportPath }}"
 )
 
 // Collector is the collection target a Client sends metric uploads to.
@@ -301,7 +301,7 @@ func (c *HTTPCollector) Headers() map[string][]string {
 }
 
 func (c *HTTPCollector) HostHeader() string {
-   return c.hostHeader
+	return c.hostHeader
 }
 
 func (c *HTTPCollector) handler(w http.ResponseWriter, r *http.Request) {

From f802723d1b92a48f44498365b6832ceb0e9d5aa4 Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Mon, 8 Jan 2024 13:35:05 +0100
Subject: [PATCH 04/12] fix linter: make precommit

---
 .../otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go  | 2 +-
 .../otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
index 8cc131676e7..b5649fcc8cb 100644
--- a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
@@ -42,9 +42,9 @@ import (
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/proto"
 
-	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf"
 	collpb "go.opentelemetry.io/proto/otlp/collector/metrics/v1"
 	mpb "go.opentelemetry.io/proto/otlp/metrics/v1"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf"
 )
 
 // Collector is the collection target a Client sends metric uploads to.
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
index f143b2f2a8e..8f8cb92491c 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
@@ -42,9 +42,9 @@ import (
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/proto"
 
-	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf"
 	collpb "go.opentelemetry.io/proto/otlp/collector/metrics/v1"
 	mpb "go.opentelemetry.io/proto/otlp/metrics/v1"
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf"
 )
 
 // Collector is the collection target a Client sends metric uploads to.

From 590b3ea852764f83a19f9ed5b75ccc0e5d11640a Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <109675364+enuret@users.noreply.github.com>
Date: Mon, 8 Jan 2024 13:38:36 +0100
Subject: [PATCH 05/12] Update CHANGELOG.md

Co-authored-by: Damien Mathieu <42@dmathieu.com>
---
 CHANGELOG.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2ed807eede7..c1ba3498c18 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,7 +21,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Add `WithResourceAsConstantLabels` option to apply resource attributes for every metric emitted by the Prometheus exporter. (#4733)
 - Experimental cardinality limiting is added to the metric SDK.
   See [metric documentation](./sdk/metric/EXPERIMENTAL.md#cardinality-limit) for more information about this feature and how to enable it. (#4457)
-- Add `WithHostHeader` config option to override Host header in opentelemetry requests (#4777)
+- Add `WithHostHeader` config option to override Host header in opentelemetry requests (#4780)
 
 ### Changed
 

From 4b00ca12d76e1f54ac770f4b51f608db0f9a3d70 Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <109675364+enuret@users.noreply.github.com>
Date: Mon, 8 Jan 2024 13:38:48 +0100
Subject: [PATCH 06/12] Update
 exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go

Co-authored-by: Damien Mathieu <42@dmathieu.com>
---
 exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go b/exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go
index 04f815cca27..b3dc928a6d6 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/client_test.go
@@ -4,7 +4,7 @@
 // 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
+//     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,

From d6ee1261393000fe633bcb270b95aa79c0b6a1c7 Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Mon, 8 Jan 2024 13:59:30 +0100
Subject: [PATCH 07/12] options tests

---
 .../otlpmetricgrpc/internal/oconf/options_test.go     |  9 +++++++++
 .../otlpmetrichttp/internal/oconf/options_test.go     |  9 +++++++++
 .../otlptracegrpc/internal/otlpconfig/options_test.go | 11 +++++++++++
 .../otlptracehttp/internal/otlpconfig/options_test.go | 11 +++++++++++
 .../shared/otlp/otlpmetric/oconf/options_test.go.tmpl |  9 +++++++++
 .../otlp/otlptrace/otlpconfig/options_test.go.tmpl    | 11 +++++++++++
 6 files changed, 60 insertions(+)

diff --git a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/options_test.go b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/options_test.go
index 64457efbf08..7dc95d15fc3 100644
--- a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/options_test.go
+++ b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf/options_test.go
@@ -303,6 +303,15 @@ func TestConfigs(t *testing.T) {
 				assert.Equal(t, map[string]string{"m1": "mv1"}, c.Metrics.Headers)
 			},
 		},
+		{
+			name: "Test WithHeaders",
+			opts: []GenericOption{
+				WithHostHeader("th"),
+			},
+			asserts: func(t *testing.T, c *Config, grpcOption bool) {
+				assert.Equal(t, "th", c.Metrics.HostHeader)
+			},
+		},
 
 		// Compression Tests
 		{
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/options_test.go b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/options_test.go
index 1da4a6f2f63..bb533690473 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/options_test.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf/options_test.go
@@ -303,6 +303,15 @@ func TestConfigs(t *testing.T) {
 				assert.Equal(t, map[string]string{"m1": "mv1"}, c.Metrics.Headers)
 			},
 		},
+		{
+			name: "Test WithHeaders",
+			opts: []GenericOption{
+				WithHostHeader("th"),
+			},
+			asserts: func(t *testing.T, c *Config, grpcOption bool) {
+				assert.Equal(t, "th", c.Metrics.HostHeader)
+			},
+		},
 
 		// Compression Tests
 		{
diff --git a/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options_test.go b/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options_test.go
index 567f12f1018..8c58344d8cb 100644
--- a/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options_test.go
+++ b/exporters/otlp/otlptrace/otlptracegrpc/internal/otlpconfig/options_test.go
@@ -300,6 +300,17 @@ func TestConfigs(t *testing.T) {
 			},
 		},
 
+		// Host header test
+		{
+			name: "Test With Host Header",
+			opts: []GenericOption{
+				WithHostHeader("th"),
+			},
+			asserts: func(t *testing.T, c *Config, grpcOption bool) {
+				assert.Equal(t, "th", c.Traces.HostHeader)
+			},
+		},
+
 		// Compression Tests
 		{
 			name: "Test With Compression",
diff --git a/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options_test.go b/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options_test.go
index 4c7a525a996..a2037f9b453 100644
--- a/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options_test.go
+++ b/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options_test.go
@@ -300,6 +300,17 @@ func TestConfigs(t *testing.T) {
 			},
 		},
 
+		// Host header test
+		{
+			name: "Test With Host Header",
+			opts: []GenericOption{
+				WithHostHeader("th"),
+			},
+			asserts: func(t *testing.T, c *Config, grpcOption bool) {
+				assert.Equal(t, "th", c.Traces.HostHeader)
+			},
+		},
+
 		// Compression Tests
 		{
 			name: "Test With Compression",
diff --git a/internal/shared/otlp/otlpmetric/oconf/options_test.go.tmpl b/internal/shared/otlp/otlpmetric/oconf/options_test.go.tmpl
index 7c52efc51d9..578ca89cd5d 100644
--- a/internal/shared/otlp/otlpmetric/oconf/options_test.go.tmpl
+++ b/internal/shared/otlp/otlpmetric/oconf/options_test.go.tmpl
@@ -303,6 +303,15 @@ func TestConfigs(t *testing.T) {
 				assert.Equal(t, map[string]string{"m1": "mv1"}, c.Metrics.Headers)
 			},
 		},
+		{
+			name: "Test WithHeaders",
+			opts: []GenericOption{
+				WithHostHeader("th"),
+			},
+			asserts: func(t *testing.T, c *Config, grpcOption bool) {
+				assert.Equal(t, "th", c.Metrics.HostHeader)
+			},
+		},
 
 		// Compression Tests
 		{
diff --git a/internal/shared/otlp/otlptrace/otlpconfig/options_test.go.tmpl b/internal/shared/otlp/otlptrace/otlpconfig/options_test.go.tmpl
index b83891a89f6..b9d94cafff1 100644
--- a/internal/shared/otlp/otlptrace/otlpconfig/options_test.go.tmpl
+++ b/internal/shared/otlp/otlptrace/otlpconfig/options_test.go.tmpl
@@ -300,6 +300,17 @@ func TestConfigs(t *testing.T) {
 			},
 		},
 
+		// Host header test
+		{
+			name: "Test With Host Header",
+			opts: []GenericOption{
+				WithHostHeader("th"),
+			},
+			asserts: func(t *testing.T, c *Config, grpcOption bool) {
+				assert.Equal(t, "th", c.Traces.HostHeader)
+			},
+		},
+
 		// Compression Tests
 		{
 			name: "Test With Compression",

From 78fa53c8aa117d61a921622945cc32f2fe9492bf Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Mon, 8 Jan 2024 14:22:20 +0100
Subject: [PATCH 08/12] gofmt

---
 .../otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
index b5649fcc8cb..8cc131676e7 100644
--- a/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/otest/collector.go
@@ -42,9 +42,9 @@ import (
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/proto"
 
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf"
 	collpb "go.opentelemetry.io/proto/otlp/collector/metrics/v1"
 	mpb "go.opentelemetry.io/proto/otlp/metrics/v1"
-	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc/internal/oconf"
 )
 
 // Collector is the collection target a Client sends metric uploads to.

From 0c612a8260276933bfa5653e509726c872d2743e Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Mon, 8 Jan 2024 15:24:19 +0100
Subject: [PATCH 09/12] shared file for lint

---
 internal/shared/otlp/otlpmetric/otest/collector.go.tmpl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl b/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
index d15c895c052..083a05011c7 100644
--- a/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
+++ b/internal/shared/otlp/otlpmetric/otest/collector.go.tmpl
@@ -42,9 +42,9 @@ import (
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/proto"
 
+	"{{ .oconfImportPath }}"
 	collpb "go.opentelemetry.io/proto/otlp/collector/metrics/v1"
 	mpb "go.opentelemetry.io/proto/otlp/metrics/v1"
-	"{{ .oconfImportPath }}"
 )
 
 // Collector is the collection target a Client sends metric uploads to.

From ece66a661601827fec2f34abf77791a9bb0d8e9f Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Mon, 8 Jan 2024 15:52:01 +0100
Subject: [PATCH 10/12] Lint for config.go

---
 exporters/otlp/otlpmetric/otlpmetrichttp/config.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/config.go b/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
index 0b4f12a8e33..7a3b2ddde3c 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
@@ -150,7 +150,7 @@ func WithHeaders(headers map[string]string) Option {
 }
 
 // WithHostHeader overrides Host header in HTTP requests.
-// If unset, the target Endpoint's host will be used as Host header
+// If unset, the target Endpoint's host will be used as Host header.
 func WithHostHeader(host string) Option {
 	return wrappedOption{oconf.WithHostHeader(host)}
 }

From 2fbec025f2aed9a823b842228fce21c49cbc477c Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Mon, 8 Jan 2024 16:02:50 +0100
Subject: [PATCH 11/12] run precommit

---
 .../otlpmetric/otlpmetrichttp/internal/otest/collector.go     | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
index 8f8cb92491c..870f2f76b56 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
@@ -15,7 +15,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package otest // import "go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest"
+package otest
 
 import (
 	"bytes"
@@ -42,9 +42,9 @@ import (
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/protobuf/proto"
 
+	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf"
 	collpb "go.opentelemetry.io/proto/otlp/collector/metrics/v1"
 	mpb "go.opentelemetry.io/proto/otlp/metrics/v1"
-	"go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp/internal/oconf"
 )
 
 // Collector is the collection target a Client sends metric uploads to.

From e18a523fcc5fc19cd02817decfb79d7f5806d36a Mon Sep 17 00:00:00 2001
From: Elena Nuretdinova <elena.nuretdinova@booking.com>
Date: Fri, 12 Jan 2024 16:41:38 +0100
Subject: [PATCH 12/12] Add comment & fix lint

---
 exporters/otlp/otlpmetric/otlpmetrichttp/config.go       | 9 +++++++++
 .../otlpmetrichttp/internal/otest/collector.go           | 2 +-
 .../otlptracehttp/internal/otlpconfig/options.go         | 2 +-
 3 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/config.go b/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
index 7a3b2ddde3c..e735dacd8ef 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/config.go
@@ -150,6 +150,15 @@ func WithHeaders(headers map[string]string) Option {
 }
 
 // WithHostHeader overrides Host header in HTTP requests.
+//
+// The example of the use case is using load balancer like envoy between
+// the otel instrumentation library and collector. Typically
+// the call via envoy's route is based on the host header. Example of the usage
+//
+// config.WithEndpoint("myenvoyhost")
+//
+//	.WithHostHeader("mytargetotelcollectorhost")
+//
 // If unset, the target Endpoint's host will be used as Host header.
 func WithHostHeader(host string) Option {
 	return wrappedOption{oconf.WithHostHeader(host)}
diff --git a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
index 870f2f76b56..f143b2f2a8e 100644
--- a/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
+++ b/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest/collector.go
@@ -15,7 +15,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package otest
+package otest // import "go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetrichttp/internal/otest"
 
 import (
 	"bytes"
diff --git a/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go b/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go
index 41b175e7230..460c71dadb9 100644
--- a/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go
+++ b/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig/options.go
@@ -15,7 +15,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package otlpconfig
+package otlpconfig // import "go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp/internal/otlpconfig"
 
 import (
 	"crypto/tls"