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author | Daniel J Walsh <dwalsh@redhat.com> | 2022-07-11 10:03:44 -0400 |
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committer | Matthew Heon <matthew.heon@pm.me> | 2022-07-26 13:34:38 -0400 |
commit | 9c1de040b36483fed1c331c438d8bce5fd8fab58 (patch) | |
tree | 7423c50dd57336eb045fea31665f4a1fb808acab /vendor/google.golang.org/grpc/internal/balancer | |
parent | 03eaea8bbe4dc7791c2129d64321988d3ec12bb0 (diff) | |
download | podman-9c1de040b36483fed1c331c438d8bce5fd8fab58.tar.gz podman-9c1de040b36483fed1c331c438d8bce5fd8fab58.tar.bz2 podman-9c1de040b36483fed1c331c438d8bce5fd8fab58.zip |
Vendor in containers/(storage,image, common, buildah)
Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>
Diffstat (limited to 'vendor/google.golang.org/grpc/internal/balancer')
-rw-r--r-- | vendor/google.golang.org/grpc/internal/balancer/gracefulswitch/gracefulswitch.go | 382 |
1 files changed, 382 insertions, 0 deletions
diff --git a/vendor/google.golang.org/grpc/internal/balancer/gracefulswitch/gracefulswitch.go b/vendor/google.golang.org/grpc/internal/balancer/gracefulswitch/gracefulswitch.go new file mode 100644 index 000000000..7ba8f4d18 --- /dev/null +++ b/vendor/google.golang.org/grpc/internal/balancer/gracefulswitch/gracefulswitch.go @@ -0,0 +1,382 @@ +/* + * + * Copyright 2022 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 gracefulswitch implements a graceful switch load balancer. +package gracefulswitch + +import ( + "errors" + "fmt" + "sync" + + "google.golang.org/grpc/balancer" + "google.golang.org/grpc/balancer/base" + "google.golang.org/grpc/connectivity" + "google.golang.org/grpc/resolver" +) + +var errBalancerClosed = errors.New("gracefulSwitchBalancer is closed") +var _ balancer.Balancer = (*Balancer)(nil) + +// NewBalancer returns a graceful switch Balancer. +func NewBalancer(cc balancer.ClientConn, opts balancer.BuildOptions) *Balancer { + return &Balancer{ + cc: cc, + bOpts: opts, + } +} + +// Balancer is a utility to gracefully switch from one balancer to +// a new balancer. It implements the balancer.Balancer interface. +type Balancer struct { + bOpts balancer.BuildOptions + cc balancer.ClientConn + + // mu protects the following fields and all fields within balancerCurrent + // and balancerPending. mu does not need to be held when calling into the + // child balancers, as all calls into these children happen only as a direct + // result of a call into the gracefulSwitchBalancer, which are also + // guaranteed to be synchronous. There is one exception: an UpdateState call + // from a child balancer when current and pending are populated can lead to + // calling Close() on the current. To prevent that racing with an + // UpdateSubConnState from the channel, we hold currentMu during Close and + // UpdateSubConnState calls. + mu sync.Mutex + balancerCurrent *balancerWrapper + balancerPending *balancerWrapper + closed bool // set to true when this balancer is closed + + // currentMu must be locked before mu. This mutex guards against this + // sequence of events: UpdateSubConnState() called, finds the + // balancerCurrent, gives up lock, updateState comes in, causes Close() on + // balancerCurrent before the UpdateSubConnState is called on the + // balancerCurrent. + currentMu sync.Mutex +} + +// swap swaps out the current lb with the pending lb and updates the ClientConn. +// The caller must hold gsb.mu. +func (gsb *Balancer) swap() { + gsb.cc.UpdateState(gsb.balancerPending.lastState) + cur := gsb.balancerCurrent + gsb.balancerCurrent = gsb.balancerPending + gsb.balancerPending = nil + go func() { + gsb.currentMu.Lock() + defer gsb.currentMu.Unlock() + cur.Close() + }() +} + +// Helper function that checks if the balancer passed in is current or pending. +// The caller must hold gsb.mu. +func (gsb *Balancer) balancerCurrentOrPending(bw *balancerWrapper) bool { + return bw == gsb.balancerCurrent || bw == gsb.balancerPending +} + +// SwitchTo initializes the graceful switch process, which completes based on +// connectivity state changes on the current/pending balancer. Thus, the switch +// process is not complete when this method returns. This method must be called +// synchronously alongside the rest of the balancer.Balancer methods this +// Graceful Switch Balancer implements. +func (gsb *Balancer) SwitchTo(builder balancer.Builder) error { + gsb.mu.Lock() + if gsb.closed { + gsb.mu.Unlock() + return errBalancerClosed + } + bw := &balancerWrapper{ + gsb: gsb, + lastState: balancer.State{ + ConnectivityState: connectivity.Connecting, + Picker: base.NewErrPicker(balancer.ErrNoSubConnAvailable), + }, + subconns: make(map[balancer.SubConn]bool), + } + balToClose := gsb.balancerPending // nil if there is no pending balancer + if gsb.balancerCurrent == nil { + gsb.balancerCurrent = bw + } else { + gsb.balancerPending = bw + } + gsb.mu.Unlock() + balToClose.Close() + // This function takes a builder instead of a balancer because builder.Build + // can call back inline, and this utility needs to handle the callbacks. + newBalancer := builder.Build(bw, gsb.bOpts) + if newBalancer == nil { + // This is illegal and should never happen; we clear the balancerWrapper + // we were constructing if it happens to avoid a potential panic. + gsb.mu.Lock() + if gsb.balancerPending != nil { + gsb.balancerPending = nil + } else { + gsb.balancerCurrent = nil + } + gsb.mu.Unlock() + return balancer.ErrBadResolverState + } + + // This write doesn't need to take gsb.mu because this field never gets read + // or written to on any calls from the current or pending. Calls from grpc + // to this balancer are guaranteed to be called synchronously, so this + // bw.Balancer field will never be forwarded to until this SwitchTo() + // function returns. + bw.Balancer = newBalancer + return nil +} + +// Returns nil if the graceful switch balancer is closed. +func (gsb *Balancer) latestBalancer() *balancerWrapper { + gsb.mu.Lock() + defer gsb.mu.Unlock() + if gsb.balancerPending != nil { + return gsb.balancerPending + } + return gsb.balancerCurrent +} + +// UpdateClientConnState forwards the update to the latest balancer created. +func (gsb *Balancer) UpdateClientConnState(state balancer.ClientConnState) error { + // The resolver data is only relevant to the most recent LB Policy. + balToUpdate := gsb.latestBalancer() + if balToUpdate == nil { + return errBalancerClosed + } + // Perform this call without gsb.mu to prevent deadlocks if the child calls + // back into the channel. The latest balancer can never be closed during a + // call from the channel, even without gsb.mu held. + return balToUpdate.UpdateClientConnState(state) +} + +// ResolverError forwards the error to the latest balancer created. +func (gsb *Balancer) ResolverError(err error) { + // The resolver data is only relevant to the most recent LB Policy. + balToUpdate := gsb.latestBalancer() + if balToUpdate == nil { + return + } + // Perform this call without gsb.mu to prevent deadlocks if the child calls + // back into the channel. The latest balancer can never be closed during a + // call from the channel, even without gsb.mu held. + balToUpdate.ResolverError(err) +} + +// ExitIdle forwards the call to the latest balancer created. +// +// If the latest balancer does not support ExitIdle, the subConns are +// re-connected to manually. +func (gsb *Balancer) ExitIdle() { + balToUpdate := gsb.latestBalancer() + if balToUpdate == nil { + return + } + // There is no need to protect this read with a mutex, as the write to the + // Balancer field happens in SwitchTo, which completes before this can be + // called. + if ei, ok := balToUpdate.Balancer.(balancer.ExitIdler); ok { + ei.ExitIdle() + return + } + for sc := range balToUpdate.subconns { + sc.Connect() + } +} + +// UpdateSubConnState forwards the update to the appropriate child. +func (gsb *Balancer) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) { + gsb.currentMu.Lock() + defer gsb.currentMu.Unlock() + gsb.mu.Lock() + // Forward update to the appropriate child. Even if there is a pending + // balancer, the current balancer should continue to get SubConn updates to + // maintain the proper state while the pending is still connecting. + var balToUpdate *balancerWrapper + if gsb.balancerCurrent != nil && gsb.balancerCurrent.subconns[sc] { + balToUpdate = gsb.balancerCurrent + } else if gsb.balancerPending != nil && gsb.balancerPending.subconns[sc] { + balToUpdate = gsb.balancerPending + } + gsb.mu.Unlock() + if balToUpdate == nil { + // SubConn belonged to a stale lb policy that has not yet fully closed, + // or the balancer was already closed. + return + } + balToUpdate.UpdateSubConnState(sc, state) +} + +// Close closes any active child balancers. +func (gsb *Balancer) Close() { + gsb.mu.Lock() + gsb.closed = true + currentBalancerToClose := gsb.balancerCurrent + gsb.balancerCurrent = nil + pendingBalancerToClose := gsb.balancerPending + gsb.balancerPending = nil + gsb.mu.Unlock() + + currentBalancerToClose.Close() + pendingBalancerToClose.Close() +} + +// balancerWrapper wraps a balancer.Balancer, and overrides some Balancer +// methods to help cleanup SubConns created by the wrapped balancer. +// +// It implements the balancer.ClientConn interface and is passed down in that +// capacity to the wrapped balancer. It maintains a set of subConns created by +// the wrapped balancer and calls from the latter to create/update/remove +// SubConns update this set before being forwarded to the parent ClientConn. +// State updates from the wrapped balancer can result in invocation of the +// graceful switch logic. +type balancerWrapper struct { + balancer.Balancer + gsb *Balancer + + lastState balancer.State + subconns map[balancer.SubConn]bool // subconns created by this balancer +} + +func (bw *balancerWrapper) UpdateSubConnState(sc balancer.SubConn, state balancer.SubConnState) { + if state.ConnectivityState == connectivity.Shutdown { + bw.gsb.mu.Lock() + delete(bw.subconns, sc) + bw.gsb.mu.Unlock() + } + // There is no need to protect this read with a mutex, as the write to the + // Balancer field happens in SwitchTo, which completes before this can be + // called. + bw.Balancer.UpdateSubConnState(sc, state) +} + +// Close closes the underlying LB policy and removes the subconns it created. bw +// must not be referenced via balancerCurrent or balancerPending in gsb when +// called. gsb.mu must not be held. Does not panic with a nil receiver. +func (bw *balancerWrapper) Close() { + // before Close is called. + if bw == nil { + return + } + // There is no need to protect this read with a mutex, as Close() is + // impossible to be called concurrently with the write in SwitchTo(). The + // callsites of Close() for this balancer in Graceful Switch Balancer will + // never be called until SwitchTo() returns. + bw.Balancer.Close() + bw.gsb.mu.Lock() + for sc := range bw.subconns { + bw.gsb.cc.RemoveSubConn(sc) + } + bw.gsb.mu.Unlock() +} + +func (bw *balancerWrapper) UpdateState(state balancer.State) { + // Hold the mutex for this entire call to ensure it cannot occur + // concurrently with other updateState() calls. This causes updates to + // lastState and calls to cc.UpdateState to happen atomically. + bw.gsb.mu.Lock() + defer bw.gsb.mu.Unlock() + bw.lastState = state + + if !bw.gsb.balancerCurrentOrPending(bw) { + return + } + + if bw == bw.gsb.balancerCurrent { + // In the case that the current balancer exits READY, and there is a pending + // balancer, you can forward the pending balancer's cached State up to + // ClientConn and swap the pending into the current. This is because there + // is no reason to gracefully switch from and keep using the old policy as + // the ClientConn is not connected to any backends. + if state.ConnectivityState != connectivity.Ready && bw.gsb.balancerPending != nil { + bw.gsb.swap() + return + } + // Even if there is a pending balancer waiting to be gracefully switched to, + // continue to forward current balancer updates to the Client Conn. Ignoring + // state + picker from the current would cause undefined behavior/cause the + // system to behave incorrectly from the current LB policies perspective. + // Also, the current LB is still being used by grpc to choose SubConns per + // RPC, and thus should use the most updated form of the current balancer. + bw.gsb.cc.UpdateState(state) + return + } + // This method is now dealing with a state update from the pending balancer. + // If the current balancer is currently in a state other than READY, the new + // policy can be swapped into place immediately. This is because there is no + // reason to gracefully switch from and keep using the old policy as the + // ClientConn is not connected to any backends. + if state.ConnectivityState != connectivity.Connecting || bw.gsb.balancerCurrent.lastState.ConnectivityState != connectivity.Ready { + bw.gsb.swap() + } +} + +func (bw *balancerWrapper) NewSubConn(addrs []resolver.Address, opts balancer.NewSubConnOptions) (balancer.SubConn, error) { + bw.gsb.mu.Lock() + if !bw.gsb.balancerCurrentOrPending(bw) { + bw.gsb.mu.Unlock() + return nil, fmt.Errorf("%T at address %p that called NewSubConn is deleted", bw, bw) + } + bw.gsb.mu.Unlock() + + sc, err := bw.gsb.cc.NewSubConn(addrs, opts) + if err != nil { + return nil, err + } + bw.gsb.mu.Lock() + if !bw.gsb.balancerCurrentOrPending(bw) { // balancer was closed during this call + bw.gsb.cc.RemoveSubConn(sc) + bw.gsb.mu.Unlock() + return nil, fmt.Errorf("%T at address %p that called NewSubConn is deleted", bw, bw) + } + bw.subconns[sc] = true + bw.gsb.mu.Unlock() + return sc, nil +} + +func (bw *balancerWrapper) ResolveNow(opts resolver.ResolveNowOptions) { + // Ignore ResolveNow requests from anything other than the most recent + // balancer, because older balancers were already removed from the config. + if bw != bw.gsb.latestBalancer() { + return + } + bw.gsb.cc.ResolveNow(opts) +} + +func (bw *balancerWrapper) RemoveSubConn(sc balancer.SubConn) { + bw.gsb.mu.Lock() + if !bw.gsb.balancerCurrentOrPending(bw) { + bw.gsb.mu.Unlock() + return + } + bw.gsb.mu.Unlock() + bw.gsb.cc.RemoveSubConn(sc) +} + +func (bw *balancerWrapper) UpdateAddresses(sc balancer.SubConn, addrs []resolver.Address) { + bw.gsb.mu.Lock() + if !bw.gsb.balancerCurrentOrPending(bw) { + bw.gsb.mu.Unlock() + return + } + bw.gsb.mu.Unlock() + bw.gsb.cc.UpdateAddresses(sc, addrs) +} + +func (bw *balancerWrapper) Target() string { + return bw.gsb.cc.Target() +} |