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// Copyright 2020 Google LLC.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package grpc
import (
"context"
"fmt"
"sync/atomic"
"google.golang.org/api/internal"
"google.golang.org/grpc"
)
// ConnPool is a pool of grpc.ClientConns.
type ConnPool = internal.ConnPool // NOTE(cbro): type alias to export the type. It must live in internal to avoid a circular dependency.
var _ ConnPool = &roundRobinConnPool{}
var _ ConnPool = &singleConnPool{}
// singleConnPool is a special case for a single connection.
type singleConnPool struct {
*grpc.ClientConn
}
func (p *singleConnPool) Conn() *grpc.ClientConn { return p.ClientConn }
func (p *singleConnPool) Num() int { return 1 }
type roundRobinConnPool struct {
conns []*grpc.ClientConn
idx uint32 // access via sync/atomic
}
func (p *roundRobinConnPool) Num() int {
return len(p.conns)
}
func (p *roundRobinConnPool) Conn() *grpc.ClientConn {
i := atomic.AddUint32(&p.idx, 1)
return p.conns[i%uint32(len(p.conns))]
}
func (p *roundRobinConnPool) Close() error {
var errs multiError
for _, conn := range p.conns {
if err := conn.Close(); err != nil {
errs = append(errs, err)
}
}
if len(errs) == 0 {
return nil
}
return errs
}
func (p *roundRobinConnPool) Invoke(ctx context.Context, method string, args interface{}, reply interface{}, opts ...grpc.CallOption) error {
return p.Conn().Invoke(ctx, method, args, reply, opts...)
}
func (p *roundRobinConnPool) NewStream(ctx context.Context, desc *grpc.StreamDesc, method string, opts ...grpc.CallOption) (grpc.ClientStream, error) {
return p.Conn().NewStream(ctx, desc, method, opts...)
}
// multiError represents errors from mulitple conns in the group.
//
// TODO: figure out how and whether this is useful to export. End users should
// not be depending on the transport/grpc package directly, so there might need
// to be some service-specific multi-error type.
type multiError []error
func (m multiError) Error() string {
s, n := "", 0
for _, e := range m {
if e != nil {
if n == 0 {
s = e.Error()
}
n++
}
}
switch n {
case 0:
return "(0 errors)"
case 1:
return s
case 2:
return s + " (and 1 other error)"
}
return fmt.Sprintf("%s (and %d other errors)", s, n-1)
}