From cb0bc0cbb4e8b3ff36f639a0fc8c8c59dc3e4960 Mon Sep 17 00:00:00 2001
From: Tonis Tiigi <tonistiigi@gmail.com>
Date: Mon, 14 Jun 2021 11:03:15 -0700
Subject: [PATCH] allow otlp clients to use existing grpc connection

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
---
 CHANGELOG.md                                              | 4 ++++
 .../otlp/otlpmetric/internal/connection/connection.go     | 4 ++++
 exporters/otlp/otlpmetric/internal/otlpconfig/options.go  | 1 +
 exporters/otlp/otlpmetric/otlpmetricgrpc/options.go       | 8 ++++++++
 .../otlp/otlptrace/internal/connection/connection.go      | 4 ++++
 exporters/otlp/otlptrace/internal/otlpconfig/options.go   | 1 +
 exporters/otlp/otlptrace/otlptracegrpc/options.go         | 8 ++++++++
 7 files changed, 30 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2cb46459cc5..81cc34e5d9e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,10 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## [Unreleased]
 
+### Added
+
+- Adds `otlptracegrpc.WithGRPCConn` and `otlpmetricgrpc.WithGRPCConn` for reusing existing gRPC connection. (#2002)
+
 ### Changed
 
 - NoopMeterProvider is now private and NewNoopMeterProvider must be used to obtain a noopMeterProvider. (#2237)
diff --git a/exporters/otlp/otlpmetric/internal/connection/connection.go b/exporters/otlp/otlpmetric/internal/connection/connection.go
index edfd07d34a1..4ace51f2201 100644
--- a/exporters/otlp/otlpmetric/internal/connection/connection.go
+++ b/exporters/otlp/otlpmetric/internal/connection/connection.go
@@ -220,6 +220,10 @@ func (c *Connection) setConnection(cc *grpc.ClientConn) bool {
 }
 
 func (c *Connection) dialToCollector(ctx context.Context) (*grpc.ClientConn, error) {
+	if c.cfg.GRPCConn != nil {
+		return c.cfg.GRPCConn, nil
+	}
+
 	dialOpts := []grpc.DialOption{}
 	if c.cfg.ServiceConfig != "" {
 		dialOpts = append(dialOpts, grpc.WithDefaultServiceConfig(c.cfg.ServiceConfig))
diff --git a/exporters/otlp/otlpmetric/internal/otlpconfig/options.go b/exporters/otlp/otlpmetric/internal/otlpconfig/options.go
index cc46fc775ca..b5fb9ce2e67 100644
--- a/exporters/otlp/otlpmetric/internal/otlpconfig/options.go
+++ b/exporters/otlp/otlpmetric/internal/otlpconfig/options.go
@@ -75,6 +75,7 @@ type (
 		ReconnectionPeriod time.Duration
 		ServiceConfig      string
 		DialOptions        []grpc.DialOption
+		GRPCConn           *grpc.ClientConn
 		RetrySettings      RetrySettings
 	}
 )
diff --git a/exporters/otlp/otlpmetric/otlpmetricgrpc/options.go b/exporters/otlp/otlpmetric/otlpmetricgrpc/options.go
index 57b1a2ec08b..6b64145dd5e 100644
--- a/exporters/otlp/otlpmetric/otlpmetricgrpc/options.go
+++ b/exporters/otlp/otlpmetric/otlpmetricgrpc/options.go
@@ -116,6 +116,14 @@ func WithDialOption(opts ...grpc.DialOption) Option {
 	})}
 }
 
+// WithGRPCConn allows reusing existing gRPC connection when it has already been
+// established for other services. When set, other dial options will be ignored.
+func WithGRPCConn(conn *grpc.ClientConn) Option {
+	return wrappedOption{otlpconfig.NewGRPCOption(func(cfg *otlpconfig.Config) {
+		cfg.GRPCConn = conn
+	})}
+}
+
 // WithTimeout tells the client the max waiting time for the backend to process
 // each metrics batch. If unset, the default will be 10 seconds.
 func WithTimeout(duration time.Duration) Option {
diff --git a/exporters/otlp/otlptrace/internal/connection/connection.go b/exporters/otlp/otlptrace/internal/connection/connection.go
index b2b94731fd6..67e06888c89 100644
--- a/exporters/otlp/otlptrace/internal/connection/connection.go
+++ b/exporters/otlp/otlptrace/internal/connection/connection.go
@@ -221,6 +221,10 @@ func (c *Connection) setConnection(cc *grpc.ClientConn) bool {
 }
 
 func (c *Connection) dialToCollector(ctx context.Context) (*grpc.ClientConn, error) {
+	if c.cfg.GRPCConn != nil {
+		return c.cfg.GRPCConn, nil
+	}
+
 	dialOpts := []grpc.DialOption{}
 	if c.cfg.ServiceConfig != "" {
 		dialOpts = append(dialOpts, grpc.WithDefaultServiceConfig(c.cfg.ServiceConfig))
diff --git a/exporters/otlp/otlptrace/internal/otlpconfig/options.go b/exporters/otlp/otlptrace/internal/otlpconfig/options.go
index 0ec2c879eae..8e21250c674 100644
--- a/exporters/otlp/otlptrace/internal/otlpconfig/options.go
+++ b/exporters/otlp/otlptrace/internal/otlpconfig/options.go
@@ -58,6 +58,7 @@ type (
 		ReconnectionPeriod time.Duration
 		ServiceConfig      string
 		DialOptions        []grpc.DialOption
+		GRPCConn           *grpc.ClientConn
 	}
 )
 
diff --git a/exporters/otlp/otlptrace/otlptracegrpc/options.go b/exporters/otlp/otlptrace/otlptracegrpc/options.go
index d2cf76461cc..86bfc1dc8a5 100644
--- a/exporters/otlp/otlptrace/otlptracegrpc/options.go
+++ b/exporters/otlp/otlptrace/otlptracegrpc/options.go
@@ -116,6 +116,14 @@ func WithDialOption(opts ...grpc.DialOption) Option {
 	})}
 }
 
+// WithGRPCConn allows reusing existing gRPC connection when it has already been
+// established for other services. When set, other dial options will be ignored.
+func WithGRPCConn(conn *grpc.ClientConn) Option {
+	return wrappedOption{otlpconfig.NewGRPCOption(func(cfg *otlpconfig.Config) {
+		cfg.GRPCConn = conn
+	})}
+}
+
 // 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 {