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/*
*
* Copyright 2014 gRPC authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* 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
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*/
package grpc
import (
"bytes"
"compress/gzip"
"context"
"encoding/binary"
"fmt"
"io"
"io/ioutil"
"math"
"net/url"
"strings"
"sync"
"time"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/encoding"
"google.golang.org/grpc/encoding/proto"
"google.golang.org/grpc/internal/transport"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/peer"
"google.golang.org/grpc/stats"
"google.golang.org/grpc/status"
)
// Compressor defines the interface gRPC uses to compress a message.
//
// Deprecated: use package encoding.
type Compressor interface {
// Do compresses p into w.
Do(w io.Writer, p []byte) error
// Type returns the compression algorithm the Compressor uses.
Type() string
}
type gzipCompressor struct {
pool sync.Pool
}
// NewGZIPCompressor creates a Compressor based on GZIP.
//
// Deprecated: use package encoding/gzip.
func NewGZIPCompressor() Compressor {
c, _ := NewGZIPCompressorWithLevel(gzip.DefaultCompression)
return c
}
// NewGZIPCompressorWithLevel is like NewGZIPCompressor but specifies the gzip compression level instead
// of assuming DefaultCompression.
//
// The error returned will be nil if the level is valid.
//
// Deprecated: use package encoding/gzip.
func NewGZIPCompressorWithLevel(level int) (Compressor, error) {
if level < gzip.DefaultCompression || level > gzip.BestCompression {
return nil, fmt.Errorf("grpc: invalid compression level: %d", level)
}
return &gzipCompressor{
pool: sync.Pool{
New: func() interface{} {
w, err := gzip.NewWriterLevel(ioutil.Discard, level)
if err != nil {
panic(err)
}
return w
},
},
}, nil
}
func (c *gzipCompressor) Do(w io.Writer, p []byte) error {
z := c.pool.Get().(*gzip.Writer)
defer c.pool.Put(z)
z.Reset(w)
if _, err := z.Write(p); err != nil {
return err
}
return z.Close()
}
func (c *gzipCompressor) Type() string {
return "gzip"
}
// Decompressor defines the interface gRPC uses to decompress a message.
//
// Deprecated: use package encoding.
type Decompressor interface {
// Do reads the data from r and uncompress them.
Do(r io.Reader) ([]byte, error)
// Type returns the compression algorithm the Decompressor uses.
Type() string
}
type gzipDecompressor struct {
pool sync.Pool
}
// NewGZIPDecompressor creates a Decompressor based on GZIP.
//
// Deprecated: use package encoding/gzip.
func NewGZIPDecompressor() Decompressor {
return &gzipDecompressor{}
}
func (d *gzipDecompressor) Do(r io.Reader) ([]byte, error) {
var z *gzip.Reader
switch maybeZ := d.pool.Get().(type) {
case nil:
newZ, err := gzip.NewReader(r)
if err != nil {
return nil, err
}
z = newZ
case *gzip.Reader:
z = maybeZ
if err := z.Reset(r); err != nil {
d.pool.Put(z)
return nil, err
}
}
defer func() {
z.Close()
d.pool.Put(z)
}()
return ioutil.ReadAll(z)
}
func (d *gzipDecompressor) Type() string {
return "gzip"
}
// callInfo contains all related configuration and information about an RPC.
type callInfo struct {
compressorType string
failFast bool
stream ClientStream
maxReceiveMessageSize *int
maxSendMessageSize *int
creds credentials.PerRPCCredentials
contentSubtype string
codec baseCodec
maxRetryRPCBufferSize int
}
func defaultCallInfo() *callInfo {
return &callInfo{
failFast: true,
maxRetryRPCBufferSize: 256 * 1024, // 256KB
}
}
// CallOption configures a Call before it starts or extracts information from
// a Call after it completes.
type CallOption interface {
// before is called before the call is sent to any server. If before
// returns a non-nil error, the RPC fails with that error.
before(*callInfo) error
// after is called after the call has completed. after cannot return an
// error, so any failures should be reported via output parameters.
after(*callInfo)
}
// EmptyCallOption does not alter the Call configuration.
// It can be embedded in another structure to carry satellite data for use
// by interceptors.
type EmptyCallOption struct{}
func (EmptyCallOption) before(*callInfo) error { return nil }
func (EmptyCallOption) after(*callInfo) {}
// Header returns a CallOptions that retrieves the header metadata
// for a unary RPC.
func Header(md *metadata.MD) CallOption {
return HeaderCallOption{HeaderAddr: md}
}
// HeaderCallOption is a CallOption for collecting response header metadata.
// The metadata field will be populated *after* the RPC completes.
// This is an EXPERIMENTAL API.
type HeaderCallOption struct {
HeaderAddr *metadata.MD
}
func (o HeaderCallOption) before(c *callInfo) error { return nil }
func (o HeaderCallOption) after(c *callInfo) {
if c.stream != nil {
*o.HeaderAddr, _ = c.stream.Header()
}
}
// Trailer returns a CallOptions that retrieves the trailer metadata
// for a unary RPC.
func Trailer(md *metadata.MD) CallOption {
return TrailerCallOption{TrailerAddr: md}
}
// TrailerCallOption is a CallOption for collecting response trailer metadata.
// The metadata field will be populated *after* the RPC completes.
// This is an EXPERIMENTAL API.
type TrailerCallOption struct {
TrailerAddr *metadata.MD
}
func (o TrailerCallOption) before(c *callInfo) error { return nil }
func (o TrailerCallOption) after(c *callInfo) {
if c.stream != nil {
*o.TrailerAddr = c.stream.Trailer()
}
}
// Peer returns a CallOption that retrieves peer information for a unary RPC.
// The peer field will be populated *after* the RPC completes.
func Peer(p *peer.Peer) CallOption {
return PeerCallOption{PeerAddr: p}
}
// PeerCallOption is a CallOption for collecting the identity of the remote
// peer. The peer field will be populated *after* the RPC completes.
// This is an EXPERIMENTAL API.
type PeerCallOption struct {
PeerAddr *peer.Peer
}
func (o PeerCallOption) before(c *callInfo) error { return nil }
func (o PeerCallOption) after(c *callInfo) {
if c.stream != nil {
if x, ok := peer.FromContext(c.stream.Context()); ok {
*o.PeerAddr = *x
}
}
}
// WaitForReady configures the action to take when an RPC is attempted on broken
// connections or unreachable servers. If waitForReady is false, the RPC will fail
// immediately. Otherwise, the RPC client will block the call until a
// connection is available (or the call is canceled or times out) and will
// retry the call if it fails due to a transient error. gRPC will not retry if
// data was written to the wire unless the server indicates it did not process
// the data. Please refer to
// https://github.com/grpc/grpc/blob/master/doc/wait-for-ready.md.
//
// By default, RPCs don't "wait for ready".
func WaitForReady(waitForReady bool) CallOption {
return FailFastCallOption{FailFast: !waitForReady}
}
// FailFast is the opposite of WaitForReady.
//
// Deprecated: use WaitForReady.
func FailFast(failFast bool) CallOption {
return FailFastCallOption{FailFast: failFast}
}
// FailFastCallOption is a CallOption for indicating whether an RPC should fail
// fast or not.
// This is an EXPERIMENTAL API.
type FailFastCallOption struct {
FailFast bool
}
func (o FailFastCallOption) before(c *callInfo) error {
c.failFast = o.FailFast
return nil
}
func (o FailFastCallOption) after(c *callInfo) {}
// MaxCallRecvMsgSize returns a CallOption which sets the maximum message size the client can receive.
func MaxCallRecvMsgSize(s int) CallOption {
return MaxRecvMsgSizeCallOption{MaxRecvMsgSize: s}
}
// MaxRecvMsgSizeCallOption is a CallOption that indicates the maximum message
// size the client can receive.
// This is an EXPERIMENTAL API.
type MaxRecvMsgSizeCallOption struct {
MaxRecvMsgSize int
}
func (o MaxRecvMsgSizeCallOption) before(c *callInfo) error {
c.maxReceiveMessageSize = &o.MaxRecvMsgSize
return nil
}
func (o MaxRecvMsgSizeCallOption) after(c *callInfo) {}
// MaxCallSendMsgSize returns a CallOption which sets the maximum message size the client can send.
func MaxCallSendMsgSize(s int) CallOption {
return MaxSendMsgSizeCallOption{MaxSendMsgSize: s}
}
// MaxSendMsgSizeCallOption is a CallOption that indicates the maximum message
// size the client can send.
// This is an EXPERIMENTAL API.
type MaxSendMsgSizeCallOption struct {
MaxSendMsgSize int
}
func (o MaxSendMsgSizeCallOption) before(c *callInfo) error {
c.maxSendMessageSize = &o.MaxSendMsgSize
return nil
}
func (o MaxSendMsgSizeCallOption) after(c *callInfo) {}
// PerRPCCredentials returns a CallOption that sets credentials.PerRPCCredentials
// for a call.
func PerRPCCredentials(creds credentials.PerRPCCredentials) CallOption {
return PerRPCCredsCallOption{Creds: creds}
}
// PerRPCCredsCallOption is a CallOption that indicates the per-RPC
// credentials to use for the call.
// This is an EXPERIMENTAL API.
type PerRPCCredsCallOption struct {
Creds credentials.PerRPCCredentials
}
func (o PerRPCCredsCallOption) before(c *callInfo) error {
c.creds = o.Creds
return nil
}
func (o PerRPCCredsCallOption) after(c *callInfo) {}
// UseCompressor returns a CallOption which sets the compressor used when
// sending the request. If WithCompressor is also set, UseCompressor has
// higher priority.
//
// This API is EXPERIMENTAL.
func UseCompressor(name string) CallOption {
return CompressorCallOption{CompressorType: name}
}
// CompressorCallOption is a CallOption that indicates the compressor to use.
// This is an EXPERIMENTAL API.
type CompressorCallOption struct {
CompressorType string
}
func (o CompressorCallOption) before(c *callInfo) error {
c.compressorType = o.CompressorType
return nil
}
func (o CompressorCallOption) after(c *callInfo) {}
// CallContentSubtype returns a CallOption that will set the content-subtype
// for a call. For example, if content-subtype is "json", the Content-Type over
// the wire will be "application/grpc+json". The content-subtype is converted
// to lowercase before being included in Content-Type. See Content-Type on
// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
// more details.
//
// If CallCustomCodec is not also used, the content-subtype will be used to
// look up the Codec to use in the registry controlled by RegisterCodec. See
// the documentation on RegisterCodec for details on registration. The lookup
// of content-subtype is case-insensitive. If no such Codec is found, the call
// will result in an error with code codes.Internal.
//
// If CallCustomCodec is also used, that Codec will be used for all request and
// response messages, with the content-subtype set to the given contentSubtype
// here for requests.
func CallContentSubtype(contentSubtype string) CallOption {
return ContentSubtypeCallOption{ContentSubtype: strings.ToLower(contentSubtype)}
}
// ContentSubtypeCallOption is a CallOption that indicates the content-subtype
// used for marshaling messages.
// This is an EXPERIMENTAL API.
type ContentSubtypeCallOption struct {
ContentSubtype string
}
func (o ContentSubtypeCallOption) before(c *callInfo) error {
c.contentSubtype = o.ContentSubtype
return nil
}
func (o ContentSubtypeCallOption) after(c *callInfo) {}
// CallCustomCodec returns a CallOption that will set the given Codec to be
// used for all request and response messages for a call. The result of calling
// String() will be used as the content-subtype in a case-insensitive manner.
//
// See Content-Type on
// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for
// more details. Also see the documentation on RegisterCodec and
// CallContentSubtype for more details on the interaction between Codec and
// content-subtype.
//
// This function is provided for advanced users; prefer to use only
// CallContentSubtype to select a registered codec instead.
func CallCustomCodec(codec Codec) CallOption {
return CustomCodecCallOption{Codec: codec}
}
// CustomCodecCallOption is a CallOption that indicates the codec used for
// marshaling messages.
// This is an EXPERIMENTAL API.
type CustomCodecCallOption struct {
Codec Codec
}
func (o CustomCodecCallOption) before(c *callInfo) error {
c.codec = o.Codec
return nil
}
func (o CustomCodecCallOption) after(c *callInfo) {}
// MaxRetryRPCBufferSize returns a CallOption that limits the amount of memory
// used for buffering this RPC's requests for retry purposes.
//
// This API is EXPERIMENTAL.
func MaxRetryRPCBufferSize(bytes int) CallOption {
return MaxRetryRPCBufferSizeCallOption{bytes}
}
// MaxRetryRPCBufferSizeCallOption is a CallOption indicating the amount of
// memory to be used for caching this RPC for retry purposes.
// This is an EXPERIMENTAL API.
type MaxRetryRPCBufferSizeCallOption struct {
MaxRetryRPCBufferSize int
}
func (o MaxRetryRPCBufferSizeCallOption) before(c *callInfo) error {
c.maxRetryRPCBufferSize = o.MaxRetryRPCBufferSize
return nil
}
func (o MaxRetryRPCBufferSizeCallOption) after(c *callInfo) {}
// The format of the payload: compressed or not?
type payloadFormat uint8
const (
compressionNone payloadFormat = 0 // no compression
compressionMade payloadFormat = 1 // compressed
)
// parser reads complete gRPC messages from the underlying reader.
type parser struct {
// r is the underlying reader.
// See the comment on recvMsg for the permissible
// error types.
r io.Reader
// The header of a gRPC message. Find more detail at
// https://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md
header [5]byte
}
// recvMsg reads a complete gRPC message from the stream.
//
// It returns the message and its payload (compression/encoding)
// format. The caller owns the returned msg memory.
//
// If there is an error, possible values are:
// * io.EOF, when no messages remain
// * io.ErrUnexpectedEOF
// * of type transport.ConnectionError
// * an error from the status package
// No other error values or types must be returned, which also means
// that the underlying io.Reader must not return an incompatible
// error.
func (p *parser) recvMsg(maxReceiveMessageSize int) (pf payloadFormat, msg []byte, err error) {
if _, err := p.r.Read(p.header[:]); err != nil {
return 0, nil, err
}
pf = payloadFormat(p.header[0])
length := binary.BigEndian.Uint32(p.header[1:])
if length == 0 {
return pf, nil, nil
}
if int64(length) > int64(maxInt) {
return 0, nil, status.Errorf(codes.ResourceExhausted, "grpc: received message larger than max length allowed on current machine (%d vs. %d)", length, maxInt)
}
if int(length) > maxReceiveMessageSize {
return 0, nil, status.Errorf(codes.ResourceExhausted, "grpc: received message larger than max (%d vs. %d)", length, maxReceiveMessageSize)
}
// TODO(bradfitz,zhaoq): garbage. reuse buffer after proto decoding instead
// of making it for each message:
msg = make([]byte, int(length))
if _, err := p.r.Read(msg); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return 0, nil, err
}
return pf, msg, nil
}
// encode serializes msg and returns a buffer containing the message, or an
// error if it is too large to be transmitted by grpc. If msg is nil, it
// generates an empty message.
func encode(c baseCodec, msg interface{}) ([]byte, error) {
if msg == nil { // NOTE: typed nils will not be caught by this check
return nil, nil
}
b, err := c.Marshal(msg)
if err != nil {
return nil, status.Errorf(codes.Internal, "grpc: error while marshaling: %v", err.Error())
}
if uint(len(b)) > math.MaxUint32 {
return nil, status.Errorf(codes.ResourceExhausted, "grpc: message too large (%d bytes)", len(b))
}
return b, nil
}
// compress returns the input bytes compressed by compressor or cp. If both
// compressors are nil, returns nil.
//
// TODO(dfawley): eliminate cp parameter by wrapping Compressor in an encoding.Compressor.
func compress(in []byte, cp Compressor, compressor encoding.Compressor) ([]byte, error) {
if compressor == nil && cp == nil {
return nil, nil
}
wrapErr := func(err error) error {
return status.Errorf(codes.Internal, "grpc: error while compressing: %v", err.Error())
}
cbuf := &bytes.Buffer{}
if compressor != nil {
z, err := compressor.Compress(cbuf)
if err != nil {
return nil, wrapErr(err)
}
if _, err := z.Write(in); err != nil {
return nil, wrapErr(err)
}
if err := z.Close(); err != nil {
return nil, wrapErr(err)
}
} else {
if err := cp.Do(cbuf, in); err != nil {
return nil, wrapErr(err)
}
}
return cbuf.Bytes(), nil
}
const (
payloadLen = 1
sizeLen = 4
headerLen = payloadLen + sizeLen
)
// msgHeader returns a 5-byte header for the message being transmitted and the
// payload, which is compData if non-nil or data otherwise.
func msgHeader(data, compData []byte) (hdr []byte, payload []byte) {
hdr = make([]byte, headerLen)
if compData != nil {
hdr[0] = byte(compressionMade)
data = compData
} else {
hdr[0] = byte(compressionNone)
}
// Write length of payload into buf
binary.BigEndian.PutUint32(hdr[payloadLen:], uint32(len(data)))
return hdr, data
}
func outPayload(client bool, msg interface{}, data, payload []byte, t time.Time) *stats.OutPayload {
return &stats.OutPayload{
Client: client,
Payload: msg,
Data: data,
Length: len(data),
WireLength: len(payload) + headerLen,
SentTime: t,
}
}
func checkRecvPayload(pf payloadFormat, recvCompress string, haveCompressor bool) *status.Status {
switch pf {
case compressionNone:
case compressionMade:
if recvCompress == "" || recvCompress == encoding.Identity {
return status.New(codes.Internal, "grpc: compressed flag set with identity or empty encoding")
}
if !haveCompressor {
return status.Newf(codes.Unimplemented, "grpc: Decompressor is not installed for grpc-encoding %q", recvCompress)
}
default:
return status.Newf(codes.Internal, "grpc: received unexpected payload format %d", pf)
}
return nil
}
type payloadInfo struct {
wireLength int // The compressed length got from wire.
uncompressedBytes []byte
}
func recvAndDecompress(p *parser, s *transport.Stream, dc Decompressor, maxReceiveMessageSize int, payInfo *payloadInfo, compressor encoding.Compressor) ([]byte, error) {
pf, d, err := p.recvMsg(maxReceiveMessageSize)
if err != nil {
return nil, err
}
if payInfo != nil {
payInfo.wireLength = len(d)
}
if st := checkRecvPayload(pf, s.RecvCompress(), compressor != nil || dc != nil); st != nil {
return nil, st.Err()
}
if pf == compressionMade {
// To match legacy behavior, if the decompressor is set by WithDecompressor or RPCDecompressor,
// use this decompressor as the default.
if dc != nil {
d, err = dc.Do(bytes.NewReader(d))
if err != nil {
return nil, status.Errorf(codes.Internal, "grpc: failed to decompress the received message %v", err)
}
} else {
dcReader, err := compressor.Decompress(bytes.NewReader(d))
if err != nil {
return nil, status.Errorf(codes.Internal, "grpc: failed to decompress the received message %v", err)
}
d, err = ioutil.ReadAll(dcReader)
if err != nil {
return nil, status.Errorf(codes.Internal, "grpc: failed to decompress the received message %v", err)
}
}
}
if len(d) > maxReceiveMessageSize {
// TODO: Revisit the error code. Currently keep it consistent with java
// implementation.
return nil, status.Errorf(codes.ResourceExhausted, "grpc: received message larger than max (%d vs. %d)", len(d), maxReceiveMessageSize)
}
return d, nil
}
// For the two compressor parameters, both should not be set, but if they are,
// dc takes precedence over compressor.
// TODO(dfawley): wrap the old compressor/decompressor using the new API?
func recv(p *parser, c baseCodec, s *transport.Stream, dc Decompressor, m interface{}, maxReceiveMessageSize int, payInfo *payloadInfo, compressor encoding.Compressor) error {
d, err := recvAndDecompress(p, s, dc, maxReceiveMessageSize, payInfo, compressor)
if err != nil {
return err
}
if err := c.Unmarshal(d, m); err != nil {
return status.Errorf(codes.Internal, "grpc: failed to unmarshal the received message %v", err)
}
if payInfo != nil {
payInfo.uncompressedBytes = d
}
return nil
}
type rpcInfo struct {
failfast bool
}
type rpcInfoContextKey struct{}
func newContextWithRPCInfo(ctx context.Context, failfast bool) context.Context {
return context.WithValue(ctx, rpcInfoContextKey{}, &rpcInfo{failfast: failfast})
}
func rpcInfoFromContext(ctx context.Context) (s *rpcInfo, ok bool) {
s, ok = ctx.Value(rpcInfoContextKey{}).(*rpcInfo)
return
}
// Code returns the error code for err if it was produced by the rpc system.
// Otherwise, it returns codes.Unknown.
//
// Deprecated: use status.FromError and Code method instead.
func Code(err error) codes.Code {
if s, ok := status.FromError(err); ok {
return s.Code()
}
return codes.Unknown
}
// ErrorDesc returns the error description of err if it was produced by the rpc system.
// Otherwise, it returns err.Error() or empty string when err is nil.
//
// Deprecated: use status.FromError and Message method instead.
func ErrorDesc(err error) string {
if s, ok := status.FromError(err); ok {
return s.Message()
}
return err.Error()
}
// Errorf returns an error containing an error code and a description;
// Errorf returns nil if c is OK.
//
// Deprecated: use status.Errorf instead.
func Errorf(c codes.Code, format string, a ...interface{}) error {
return status.Errorf(c, format, a...)
}
// toRPCErr converts an error into an error from the status package.
func toRPCErr(err error) error {
if err == nil || err == io.EOF {
return err
}
if err == io.ErrUnexpectedEOF {
return status.Error(codes.Internal, err.Error())
}
if _, ok := status.FromError(err); ok {
return err
}
switch e := err.(type) {
case transport.ConnectionError:
return status.Error(codes.Unavailable, e.Desc)
default:
switch err {
case context.DeadlineExceeded:
return status.Error(codes.DeadlineExceeded, err.Error())
case context.Canceled:
return status.Error(codes.Canceled, err.Error())
}
}
return status.Error(codes.Unknown, err.Error())
}
// setCallInfoCodec should only be called after CallOptions have been applied.
func setCallInfoCodec(c *callInfo) error {
if c.codec != nil {
// codec was already set by a CallOption; use it.
return nil
}
if c.contentSubtype == "" {
// No codec specified in CallOptions; use proto by default.
c.codec = encoding.GetCodec(proto.Name)
return nil
}
// c.contentSubtype is already lowercased in CallContentSubtype
c.codec = encoding.GetCodec(c.contentSubtype)
if c.codec == nil {
return status.Errorf(codes.Internal, "no codec registered for content-subtype %s", c.contentSubtype)
}
return nil
}
// parseDialTarget returns the network and address to pass to dialer
func parseDialTarget(target string) (net string, addr string) {
net = "tcp"
m1 := strings.Index(target, ":")
m2 := strings.Index(target, ":/")
// handle unix:addr which will fail with url.Parse
if m1 >= 0 && m2 < 0 {
if n := target[0:m1]; n == "unix" {
net = n
addr = target[m1+1:]
return net, addr
}
}
if m2 >= 0 {
t, err := url.Parse(target)
if err != nil {
return net, target
}
scheme := t.Scheme
addr = t.Path
if scheme == "unix" {
net = scheme
if addr == "" {
addr = t.Host
}
return net, addr
}
}
return net, target
}
// channelzData is used to store channelz related data for ClientConn, addrConn and Server.
// These fields cannot be embedded in the original structs (e.g. ClientConn), since to do atomic
// operation on int64 variable on 32-bit machine, user is responsible to enforce memory alignment.
// Here, by grouping those int64 fields inside a struct, we are enforcing the alignment.
type channelzData struct {
callsStarted int64
callsFailed int64
callsSucceeded int64
// lastCallStartedTime stores the timestamp that last call starts. It is of int64 type instead of
// time.Time since it's more costly to atomically update time.Time variable than int64 variable.
lastCallStartedTime int64
}
// The SupportPackageIsVersion variables are referenced from generated protocol
// buffer files to ensure compatibility with the gRPC version used. The latest
// support package version is 5.
//
// Older versions are kept for compatibility. They may be removed if
// compatibility cannot be maintained.
//
// These constants should not be referenced from any other code.
const (
SupportPackageIsVersion3 = true
SupportPackageIsVersion4 = true
SupportPackageIsVersion5 = true
)
const grpcUA = "grpc-go/" + Version