Repository: mailru/go-clickhouse (go)

Issue:
Trace context propagation support in client
ClickHouse accepts trace context HTTP headers, as described by the [W3C recommendation](https://www.w3.org/TR/trace-context). It also accepts trace context over a native protocol that is used for communication between ClickHouse servers or between the client and server. 
 Is there any plans to support sending trace trace to Clickhouse for query tracing?

Pull request:
Add support to send trace context to clickhouse server
This PR contains following:

1. Added support to send trace context to clickhouse server using OTEL SDK v1.7.0(highest version compatible with go1.16)
2. updated go version from 1.11 to 1.16. This was needed since OTEL SDK with 1.11 support was not found 

Note: golang version was updated to go1.16 since we need a client with go version<=1.16

This PR fixes #187 

Patch:
diff --git a/README.md b/README.md
index 61007f8..3bb5bdd 100644
--- a/README.md
+++ b/README.md
@@ -297,7 +297,69 @@ func main() {
 }
 
 ```
+Trace context propogation using OTEL SDK
+```go
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/trace"
+	oteltrace "go.opentelemetry.io/otel/trace"
+
+	"database/sql"
+
+	_ "github.com/mailru/go-clickhouse/v2"
+)
+
+func startTracing() (oteltrace.TracerProvider, error) {
+	return trace.NewTracerProvider(), nil
+}
+
+func main() {
+	// Open DB connection
+	connect, err := sql.Open("chhttp", "http://127.0.0.1:8123/default")
+	if err != nil {
+		log.Fatal(err)
+	}
+	ctx := context.Background()
+
+	// Get trace provider
+	tp, err := startTracing()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Set MapPropagator
+	otel.SetTextMapPropagator(propagation.TraceContext{})
+
+	if err := connect.PingContext(ctx); err != nil {
+		log.Fatal(err)
+	}
+
+	// start span
+	trCtx, span := tp.Tracer("test").Start(ctx, "app-query")
 
+	// execute query with span context
+	rows, err := connect.QueryContext(trCtx, "SELECT COUNT() FROM (SELECT number FROM system.numbers LIMIT 5)")
+	if err != nil {
+		log.Fatal(err)
+	}
+	span.End()
+	var count uint64
+	for rows.Next() {
+		if err := rows.Scan(&count); err != nil {
+			log.Fatal(err)
+		}
+	}
+	fmt.Printf("count: %d\n", count)
+}
+
+```
 ## Go versions
 Officially support last 4 golang releases
 
diff --git a/conn.go b/conn.go
index bf132ab..4115757 100644
--- a/conn.go
+++ b/conn.go
@@ -19,6 +19,9 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/trace"
 )
 
 type key int
@@ -374,6 +377,12 @@ func (c *conn) buildRequest(ctx context.Context, query string, params []driver.V
 		req.Header.Set("Content-Encoding", "gzip")
 	}
 
+	parentSpan := trace.SpanFromContext(ctx)
+	if parentSpan.SpanContext().IsValid() {
+		carrier := propagation.HeaderCarrier(req.Header)
+		otel.GetTextMapPropagator().Inject(ctx, carrier)
+	}
+
 	return req, nil
 }
 
diff --git a/go.mod b/go.mod
index 0ac266c..9e1c282 100644
--- a/go.mod
+++ b/go.mod
@@ -2,7 +2,10 @@ module github.com/mailru/go-clickhouse/v2
 
 require (
 	github.com/google/uuid v1.2.0
-	github.com/stretchr/testify v1.3.0
+	github.com/stretchr/testify v1.7.1
+	go.opentelemetry.io/otel v1.7.0
+	go.opentelemetry.io/otel/sdk v1.7.0
+	go.opentelemetry.io/otel/trace v1.7.0
 )
 
-go 1.11
+go 1.16
diff --git a/go.sum b/go.sum
index 479de1f..a957be4 100644
--- a/go.sum
+++ b/go.sum
@@ -1,9 +1,29 @@
 github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/go-logr/logr v1.2.2/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
+github.com/go-logr/logr v1.2.3 h1:2DntVwHkVopvECVRSlL5PSo9eG+cAkDCuckLubN+rq0=
+github.com/go-logr/logr v1.2.3/go.mod h1:jdQByPbusPIv2/zmleS9BjJVeZ6kBagPoEUsqbVz/1A=
+github.com/go-logr/stdr v1.2.2 h1:hSWxHoqTgW2S2qGc0LTAI563KZ5YKYRhT3MFKZMbjag=
+github.com/go-logr/stdr v1.2.2/go.mod h1:mMo/vtBO5dYbehREoey6XUKy/eSumjCCveDpRre4VKE=
+github.com/google/go-cmp v0.5.7 h1:81/ik6ipDQS2aGcBfIN5dHDB36BwrStyeAQquSYCV4o=
+github.com/google/go-cmp v0.5.7/go.mod h1:n+brtR0CgQNWTVd5ZUFpTBC8YFBDLK/h/bpaJ8/DtOE=
 github.com/google/uuid v1.2.0 h1:qJYtXnJRWmpe7m/3XlyhrsLrEURqHRM2kxzoxXqyUDs=
 github.com/google/uuid v1.2.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
-github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.7.1 h1:5TQK59W5E3v0r2duFAb7P95B6hEeOyEnHRa8MjYSMTY=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+go.opentelemetry.io/otel v1.7.0 h1:Z2lA3Tdch0iDcrhJXDIlC94XE+bxok1F9B+4Lz/lGsM=
+go.opentelemetry.io/otel v1.7.0/go.mod h1:5BdUoMIz5WEs0vt0CUEMtSSaTSHBBVwrhnz7+nrD5xk=
+go.opentelemetry.io/otel/sdk v1.7.0 h1:4OmStpcKVOfvDOgCt7UriAPtKolwIhxpnSNI/yK+1B0=
+go.opentelemetry.io/otel/sdk v1.7.0/go.mod h1:uTEOTwaqIVuTGiJN7ii13Ibp75wJmYUDe374q6cZwUU=
+go.opentelemetry.io/otel/trace v1.7.0 h1:O37Iogk1lEkMRXewVtZ1BBTVn5JEp8GrJvP92bJqC6o=
+go.opentelemetry.io/otel/trace v1.7.0/go.mod h1:fzLSB9nqR2eXzxPXb2JW9IKE+ScyXA48yyE4TNvoHqU=
+golang.org/x/sys v0.0.0-20210423185535-09eb48e85fd7 h1:iGu644GcxtEcrInvDsQRCwJjtCIOlT2V7IRt6ah2Whw=
+golang.org/x/sys v0.0.0-20210423185535-09eb48e85fd7/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=


Test patch:
diff --git a/conn_test.go b/conn_test.go
index c633f06..611b40f 100644
--- a/conn_test.go
+++ b/conn_test.go
@@ -13,6 +13,10 @@ import (
 
 	"github.com/google/uuid"
 	"github.com/stretchr/testify/suite"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/trace"
+	oteltrace "go.opentelemetry.io/otel/trace"
 )
 
 var (
@@ -377,6 +381,72 @@ func (s *connSuite) TestBuildRequestWithQueryIdAndQuotaKey() {
 		}
 	}
 }
+
+func (s *connSuite) TestBuildRequestWithTraceContext() {
+	cn := newConn(NewConfig())
+	testCases := []struct {
+		name                       string
+		traceProvider              oteltrace.TracerProvider
+		propagator                 propagation.TextMapPropagator
+		expectedValidSpan          bool
+		expectedTraceHeaderPresent bool
+	}{
+		{
+			name:                       "trace context",
+			traceProvider:              trace.NewTracerProvider(),
+			propagator:                 propagation.TraceContext{},
+			expectedTraceHeaderPresent: true,
+			expectedValidSpan:          true,
+		},
+		{
+			name:                       "trace context with noop trace provider",
+			traceProvider:              oteltrace.NewNoopTracerProvider(),
+			propagator:                 propagation.TraceContext{},
+			expectedTraceHeaderPresent: false,
+			expectedValidSpan:          false,
+		},
+		{
+			name:                       "trace context with noop propagator",
+			traceProvider:              trace.NewTracerProvider(),
+			propagator:                 propagation.NewCompositeTextMapPropagator(),
+			expectedTraceHeaderPresent: false,
+			expectedValidSpan:          false,
+		},
+		{
+			name:                       "trace context with noop provider and propagator",
+			traceProvider:              oteltrace.NewNoopTracerProvider(),
+			propagator:                 propagation.NewCompositeTextMapPropagator(),
+			expectedTraceHeaderPresent: false,
+			expectedValidSpan:          false,
+		},
+	}
+	for _, tc := range testCases {
+		ctx := context.Background()
+		otel.SetTextMapPropagator(tc.propagator)
+		// start span
+		trCtx, expectedSpan := tc.traceProvider.Tracer("go test").Start(ctx, tc.name)
+		req, err := cn.buildRequest(trCtx, "SELECT 1", nil)
+		expectedSpan.End()
+		if s.NoError(err) {
+			// check TraceParent header present in request header
+			traceHeader := req.Header.Get("TraceParent")
+			traceHeaderPresent := len(traceHeader) > 0
+			s.Equal(tc.expectedTraceHeaderPresent, traceHeaderPresent)
+
+			reqCtx := context.Background()
+			reqTrCtx := otel.GetTextMapPropagator().Extract(reqCtx, propagation.HeaderCarrier(req.Header))
+			reqSpan := oteltrace.SpanFromContext(reqTrCtx).SpanContext()
+
+			// check if request span valid
+			s.Equal(tc.expectedValidSpan, reqSpan.IsValid())
+			if tc.expectedValidSpan {
+				s.Equal(expectedSpan.SpanContext().SpanID(), reqSpan.SpanID())
+				s.Equal(expectedSpan.SpanContext().TraceID(), reqSpan.TraceID())
+			}
+		}
+	}
+}
+
 func (s *connSuite) TestBuildRequestParamsInterpolation() {
 	query := `INSERT INTO test (str) VALUES ("Question?")`
 	cn := newConn(NewConfig())