Implement otlploggrpc gRPC client (#5572)

part of #5056

For full usage of this client, check
#5522

---------

Co-authored-by: Damien Mathieu <42@dmathieu.com>

exporters/otlp/otlplog/otlploggrpc/client.go

@@ -4,6 +4,8 @@
 package otlploggrpc // import "go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc"
 
 import (
+	"context"
+	"fmt"
 	"time"
 
 	"google.golang.org/genproto/googleapis/rpc/errdetails"
@@ -16,8 +18,10 @@ import (
 	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/status"
 
+	"go.opentelemetry.io/otel"
 	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc/internal/retry"
 	collogpb "go.opentelemetry.io/proto/otlp/collector/logs/v1"
+	logpb "go.opentelemetry.io/proto/otlp/logs/v1"
 )
 
 // The methods of this type are not expected to be called concurrently.
@@ -107,6 +111,99 @@ func newGRPCDialOptions(cfg config) []grpc.DialOption {
 	return dialOpts
 }
 
+// UploadLogs sends proto logs to connected endpoint.
+//
+// Retryable errors from the server will be handled according to any
+// RetryConfig the client was created with.
+//
+// The otlplog.Exporter synchronizes access to client methods, and
+// ensures this is not called after the Exporter is shutdown. Only thing
+// to do here is send data.
+func (c *client) UploadLogs(ctx context.Context, rl []*logpb.ResourceLogs) error {
+	select {
+	case <-ctx.Done():
+		// Do not upload if the context is already expired.
+		return ctx.Err()
+	default:
+	}
+
+	ctx, cancel := c.exportContext(ctx)
+	defer cancel()
+
+	return c.requestFunc(ctx, func(ctx context.Context) error {
+		resp, err := c.lsc.Export(ctx, &collogpb.ExportLogsServiceRequest{
+			ResourceLogs: rl,
+		})
+		if resp != nil && resp.PartialSuccess != nil {
+			msg := resp.PartialSuccess.GetErrorMessage()
+			n := resp.PartialSuccess.GetRejectedLogRecords()
+			if n != 0 || msg != "" {
+				err := fmt.Errorf("OTLP partial success: %s (%d log records rejected)", msg, n)
+				otel.Handle(err)
+			}
+		}
+		// nil is converted to OK.
+		if status.Code(err) == codes.OK {
+			// Success.
+			return nil
+		}
+		return err
+	})
+}
+
+// Shutdown shuts down the client, freeing all resources.
+//
+// Any active connections to a remote endpoint are closed if they were created
+// by the client. Any gRPC connection passed during creation using
+// WithGRPCConn will not be closed. It is the caller's responsibility to
+// handle cleanup of that resource.
+//
+// The otlplog.Exporter synchronizes access to client methods and
+// ensures this is called only once. The only thing that needs to be done
+// here is to release any computational resources the client holds.
+func (c *client) Shutdown(ctx context.Context) error {
+	c.metadata = nil
+	c.requestFunc = nil
+	c.lsc = nil
+
+	// Release the connection if we created it.
+	err := ctx.Err()
+	if c.ourConn {
+		closeErr := c.conn.Close()
+		// A context timeout error takes precedence over this error.
+		if err == nil && closeErr != nil {
+			err = closeErr
+		}
+	}
+	c.conn = nil
+	return err
+}
+
+// exportContext returns a copy of parent with an appropriate deadline and
+// cancellation function based on the clients configured export timeout.
+//
+// It is the callers responsibility to cancel the returned context once its
+// use is complete, via the parent or directly with the returned CancelFunc, to
+// ensure all resources are correctly released.
+func (c *client) exportContext(parent context.Context) (context.Context, context.CancelFunc) {
+	var (
+		ctx    context.Context
+		cancel context.CancelFunc
+	)
+
+	if c.exportTimeout > 0 {
+		ctx, cancel = context.WithTimeout(parent, c.exportTimeout)
+	} else {
+		ctx, cancel = context.WithCancel(parent)
+	}
+
+	if c.metadata.Len() > 0 {
+		ctx = metadata.NewOutgoingContext(ctx, c.metadata)
+	}
+
+	return ctx, cancel
+}
+
 // retryable returns if err identifies a request that can be retried and a
 // duration to wait for if an explicit throttle time is included in err.
 func retryable(err error) (bool, time.Duration) {