mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-05 01:52:46 +00:00
220 lines
6.9 KiB
Go
220 lines
6.9 KiB
Go
/*
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*
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* Copyright 2017 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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package grpc
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import (
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"context"
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"fmt"
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"io"
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"sync/atomic"
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"google.golang.org/grpc/balancer"
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"google.golang.org/grpc/codes"
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"google.golang.org/grpc/internal/channelz"
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istatus "google.golang.org/grpc/internal/status"
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"google.golang.org/grpc/internal/transport"
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"google.golang.org/grpc/stats"
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"google.golang.org/grpc/status"
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)
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// pickerGeneration stores a picker and a channel used to signal that a picker
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// newer than this one is available.
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type pickerGeneration struct {
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// picker is the picker produced by the LB policy. May be nil if a picker
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// has never been produced.
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picker balancer.Picker
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// blockingCh is closed when the picker has been invalidated because there
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// is a new one available.
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blockingCh chan struct{}
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}
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// pickerWrapper is a wrapper of balancer.Picker. It blocks on certain pick
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// actions and unblock when there's a picker update.
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type pickerWrapper struct {
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// If pickerGen holds a nil pointer, the pickerWrapper is closed.
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pickerGen atomic.Pointer[pickerGeneration]
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statsHandlers []stats.Handler // to record blocking picker calls
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}
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func newPickerWrapper(statsHandlers []stats.Handler) *pickerWrapper {
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pw := &pickerWrapper{
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statsHandlers: statsHandlers,
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}
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pw.pickerGen.Store(&pickerGeneration{
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blockingCh: make(chan struct{}),
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})
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return pw
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}
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// updatePicker is called by UpdateState calls from the LB policy. It
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// unblocks all blocked pick.
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func (pw *pickerWrapper) updatePicker(p balancer.Picker) {
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old := pw.pickerGen.Swap(&pickerGeneration{
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picker: p,
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blockingCh: make(chan struct{}),
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})
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close(old.blockingCh)
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}
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// doneChannelzWrapper performs the following:
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// - increments the calls started channelz counter
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// - wraps the done function in the passed in result to increment the calls
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// failed or calls succeeded channelz counter before invoking the actual
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// done function.
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func doneChannelzWrapper(acbw *acBalancerWrapper, result *balancer.PickResult) {
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ac := acbw.ac
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ac.incrCallsStarted()
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done := result.Done
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result.Done = func(b balancer.DoneInfo) {
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if b.Err != nil && b.Err != io.EOF {
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ac.incrCallsFailed()
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} else {
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ac.incrCallsSucceeded()
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}
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if done != nil {
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done(b)
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}
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}
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}
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// pick returns the transport that will be used for the RPC.
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// It may block in the following cases:
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// - there's no picker
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// - the current picker returns ErrNoSubConnAvailable
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// - the current picker returns other errors and failfast is false.
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// - the subConn returned by the current picker is not READY
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// When one of these situations happens, pick blocks until the picker gets updated.
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func (pw *pickerWrapper) pick(ctx context.Context, failfast bool, info balancer.PickInfo) (transport.ClientTransport, balancer.PickResult, error) {
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var ch chan struct{}
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var lastPickErr error
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for {
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pg := pw.pickerGen.Load()
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if pg == nil {
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return nil, balancer.PickResult{}, ErrClientConnClosing
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}
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if pg.picker == nil {
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ch = pg.blockingCh
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}
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if ch == pg.blockingCh {
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// This could happen when either:
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// - pw.picker is nil (the previous if condition), or
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// - we have already called pick on the current picker.
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select {
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case <-ctx.Done():
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var errStr string
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if lastPickErr != nil {
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errStr = "latest balancer error: " + lastPickErr.Error()
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} else {
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errStr = fmt.Sprintf("received context error while waiting for new LB policy update: %s", ctx.Err().Error())
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}
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switch ctx.Err() {
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case context.DeadlineExceeded:
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return nil, balancer.PickResult{}, status.Error(codes.DeadlineExceeded, errStr)
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case context.Canceled:
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return nil, balancer.PickResult{}, status.Error(codes.Canceled, errStr)
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}
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case <-ch:
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}
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continue
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}
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// If the channel is set, it means that the pick call had to wait for a
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// new picker at some point. Either it's the first iteration and this
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// function received the first picker, or a picker errored with
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// ErrNoSubConnAvailable or errored with failfast set to false, which
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// will trigger a continue to the next iteration. In the first case this
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// conditional will hit if this call had to block (the channel is set).
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// In the second case, the only way it will get to this conditional is
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// if there is a new picker.
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if ch != nil {
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for _, sh := range pw.statsHandlers {
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sh.HandleRPC(ctx, &stats.PickerUpdated{})
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}
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}
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ch = pg.blockingCh
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p := pg.picker
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pickResult, err := p.Pick(info)
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if err != nil {
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if err == balancer.ErrNoSubConnAvailable {
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continue
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}
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if st, ok := status.FromError(err); ok {
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// Status error: end the RPC unconditionally with this status.
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// First restrict the code to the list allowed by gRFC A54.
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if istatus.IsRestrictedControlPlaneCode(st) {
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err = status.Errorf(codes.Internal, "received picker error with illegal status: %v", err)
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}
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return nil, balancer.PickResult{}, dropError{error: err}
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}
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// For all other errors, wait for ready RPCs should block and other
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// RPCs should fail with unavailable.
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if !failfast {
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lastPickErr = err
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continue
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}
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return nil, balancer.PickResult{}, status.Error(codes.Unavailable, err.Error())
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}
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acbw, ok := pickResult.SubConn.(*acBalancerWrapper)
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if !ok {
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logger.Errorf("subconn returned from pick is type %T, not *acBalancerWrapper", pickResult.SubConn)
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continue
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}
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if t := acbw.ac.getReadyTransport(); t != nil {
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if channelz.IsOn() {
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doneChannelzWrapper(acbw, &pickResult)
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return t, pickResult, nil
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}
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return t, pickResult, nil
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}
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if pickResult.Done != nil {
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// Calling done with nil error, no bytes sent and no bytes received.
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// DoneInfo with default value works.
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pickResult.Done(balancer.DoneInfo{})
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}
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logger.Infof("blockingPicker: the picked transport is not ready, loop back to repick")
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// If ok == false, ac.state is not READY.
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// A valid picker always returns READY subConn. This means the state of ac
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// just changed, and picker will be updated shortly.
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// continue back to the beginning of the for loop to repick.
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}
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}
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func (pw *pickerWrapper) close() {
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old := pw.pickerGen.Swap(nil)
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close(old.blockingCh)
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}
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// reset clears the pickerWrapper and prepares it for being used again when idle
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// mode is exited.
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func (pw *pickerWrapper) reset() {
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old := pw.pickerGen.Swap(&pickerGeneration{blockingCh: make(chan struct{})})
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close(old.blockingCh)
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}
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// dropError is a wrapper error that indicates the LB policy wishes to drop the
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// RPC and not retry it.
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type dropError struct {
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error
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}
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