This implements the new algorithm for deciding which resources must be deleted due to a delete-before-replace operation. We need to compute the set of resources that may be replaced by a change to the resource under consideration. We do this by taking the complete set of transitive dependents on the resource under consideration and removing any resources that would not be replaced by changes to their dependencies. We determine whether or not a resource may be replaced by substituting unknowns for input properties that may change due to deletion of the resources their value depends on and calling the resource provider's Diff method. This is perhaps clearer when described by example. Consider the following dependency graph: A __|__ B C | _|_ D E F In this graph, all of B, C, D, E, and F transitively depend on A. It may be the case, however, that changes to the specific properties of any of those resources R that would occur if a resource on the path to A were deleted and recreated may not cause R to be replaced. For example, the edge from B to A may be a simple dependsOn edge such that a change to B does not actually influence any of B's input properties. In that case, neither B nor D would need to be deleted before A could be deleted. In order to make the above algorithm a reality, the resource monitor interface has been updated to include a map that associates an input property key with the list of resources that input property depends on. Older clients of the resource monitor will leave this map empty, in which case all input properties will be treated as depending on all dependencies of the resource. This is probably overly conservative, but it is less conservative than what we currently implement, and is certainly correct.
583 lines
23 KiB
Go
583 lines
23 KiB
Go
// Copyright 2016-2018, Pulumi Corporation.
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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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package backend
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import (
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"reflect"
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"sort"
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"time"
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"github.com/pkg/errors"
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"github.com/pulumi/pulumi/pkg/engine"
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"github.com/pulumi/pulumi/pkg/resource"
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"github.com/pulumi/pulumi/pkg/resource/deploy"
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"github.com/pulumi/pulumi/pkg/util/contract"
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"github.com/pulumi/pulumi/pkg/util/logging"
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"github.com/pulumi/pulumi/pkg/version"
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"github.com/pulumi/pulumi/pkg/workspace"
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)
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// SnapshotPersister is an interface implemented by our backends that implements snapshot
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// persistence. In order to fit into our current model, snapshot persisters have two functions:
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// saving snapshots and invalidating already-persisted snapshots.
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type SnapshotPersister interface {
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// Persists the given snapshot. Returns an error if the persistence failed.
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Save(snapshot *deploy.Snapshot) error
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}
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// SnapshotManager is an implementation of engine.SnapshotManager that inspects steps and performs
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// mutations on the global snapshot object serially. This implementation maintains two bits of state: the "base"
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// snapshot, which is completely immutable and represents the state of the world prior to the application
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// of the current plan, and a "new" list of resources, which consists of the resources that were operated upon
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// by the current plan.
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//
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// Important to note is that, although this SnapshotManager is designed to be easily convertible into a thread-safe
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// implementation, the code as it is today is *not thread safe*. In particular, it is not legal for there to be
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// more than one `SnapshotMutation` active at any point in time. This is because this SnapshotManager invalidates
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// the last persisted snapshot in `BeginSnapshot`. This is designed to match existing behavior and will not
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// be the state of things going forward.
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//
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// The resources stored in the `resources` slice are pointers to resource objects allocated by the engine.
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// This is subtle and a little confusing. The reason for this is that the engine directly mutates resource objects
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// that it creates and expects those mutations to be persisted directly to the snapshot.
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type SnapshotManager struct {
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persister SnapshotPersister // The persister responsible for invalidating and persisting the snapshot
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baseSnapshot *deploy.Snapshot // The base snapshot for this plan
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resources []*resource.State // The list of resources operated upon by this plan
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operations []resource.Operation // The set of operations known to be outstanding in this plan
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dones map[*resource.State]bool // The set of resources that have been operated upon already by this plan
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completeOps map[*resource.State]bool // The set of resources that have completed their operation
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doVerify bool // If true, verify the snapshot before persisting it
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plugins []workspace.PluginInfo // The list of plugins loaded by the plan, to be saved in the manifest
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mutationRequests chan<- mutationRequest // The queue of mutation requests, to be retired serially by the manager
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cancel chan bool // A channel used to request cancellation of any new mutation requests.
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done <-chan error // A channel that sends a single result when the manager has shut down.
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}
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var _ engine.SnapshotManager = (*SnapshotManager)(nil)
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type mutationRequest struct {
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mutator func() bool
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result chan<- error
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}
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func (sm *SnapshotManager) Close() error {
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close(sm.cancel)
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return <-sm.done
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}
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// If you need to understand what's going on in this file, start here!
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//
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// mutate is the serialization point for reads and writes of the global snapshot state.
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// The given function will be, at the time of its invocation, the only function allowed to
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// mutate state within the SnapshotManager.
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//
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// Serialization is performed by pushing the mutator function onto a channel, where another
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// goroutine is polling the channel and executing the mutation functions as they come.
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// This function optionally verifies the integrity of the snapshot before and after mutation.
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//
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// The mutator may indicate that its corresponding checkpoint write may be safely elided by
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// returning `false`. As of this writing, we only elide writes after same steps with no
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// meaningful changes (see sameSnapshotMutation.mustWrite for details). Any elided writes
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// are flushed by the next non-elided write or the next call to Close.
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//
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// You should never observe or mutate the global snapshot without using this function unless
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// you have a very good justification.
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func (sm *SnapshotManager) mutate(mutator func() bool) error {
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result := make(chan error)
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select {
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case sm.mutationRequests <- mutationRequest{mutator: mutator, result: result}:
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return <-result
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case <-sm.cancel:
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return errors.New("snapshot manager closed")
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}
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}
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// RegisterResourceOutputs handles the registering of outputs on a Step that has already
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// completed. This is accomplished by doing an in-place mutation of the resources currently
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// resident in the snapshot.
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//
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// Due to the way this is currently implemented, the engine directly mutates output properties
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// on the resource State object that it created. Since we are storing pointers to these objects
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// in the `resources` slice, we need only to do a no-op mutation in order to flush these new
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// mutations to disk.
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//
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// Note that this is completely not thread-safe and defeats the purpose of having a `mutate` callback
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// entirely, but the hope is that this state of things will not be permament.
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func (sm *SnapshotManager) RegisterResourceOutputs(step deploy.Step) error {
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return sm.mutate(func() bool { return true })
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}
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// RecordPlugin records that the current plan loaded a plugin and saves it in the snapshot.
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func (sm *SnapshotManager) RecordPlugin(plugin workspace.PluginInfo) error {
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logging.V(9).Infof("SnapshotManager: RecordPlugin(%v)", plugin)
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return sm.mutate(func() bool {
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sm.plugins = append(sm.plugins, plugin)
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return true
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})
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}
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// BeginMutation signals to the SnapshotManager that the engine intends to mutate the global snapshot
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// by performing the given Step. This function gives the SnapshotManager a chance to record the
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// intent to mutate before the mutation occurs.
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func (sm *SnapshotManager) BeginMutation(step deploy.Step) (engine.SnapshotMutation, error) {
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contract.Require(step != nil, "step != nil")
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logging.V(9).Infof("SnapshotManager: Beginning mutation for step `%s` on resource `%s`", step.Op(), step.URN())
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switch step.Op() {
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case deploy.OpSame:
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return &sameSnapshotMutation{sm}, nil
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case deploy.OpCreate, deploy.OpCreateReplacement:
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return sm.doCreate(step)
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case deploy.OpUpdate:
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return sm.doUpdate(step)
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case deploy.OpDelete, deploy.OpDeleteReplaced:
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return sm.doDelete(step)
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case deploy.OpReplace:
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return &replaceSnapshotMutation{sm}, nil
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case deploy.OpRead, deploy.OpReadReplacement:
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return sm.doRead(step)
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case deploy.OpRefresh:
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return &refreshSnapshotMutation{sm}, nil
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case deploy.OpRemovePendingReplace:
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return &removePendingReplaceSnapshotMutation{sm}, nil
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}
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contract.Failf("unknown StepOp: %s", step.Op())
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return nil, nil
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}
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// All SnapshotMutation implementations in this file follow the same basic formula:
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// mark the "old" state as done and mark the "new" state as new. The two special
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// cases are Create (where the "old" state does not exist) and Delete (where the "new" state
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// does not exist).
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//
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// Marking a resource state as old prevents it from being persisted to the snapshot in
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// the `snap` function. Marking a resource state as new /enables/ it to be persisted to
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// the snapshot in `snap`. See the comments in `snap` for more details.
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type sameSnapshotMutation struct {
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manager *SnapshotManager
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}
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// mustWrite returns true if any semantically meaningful difference exists between the old and new states of a same
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// step that forces us to write the checkpoint. If no such difference exists, the checkpoint write that corresponds to
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// this step can be elided.
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func (ssm *sameSnapshotMutation) mustWrite(old, new *resource.State) bool {
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contract.Assert(old.Type == new.Type)
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contract.Assert(old.URN == new.URN)
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contract.Assert(old.Delete == new.Delete)
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contract.Assert(old.External == new.External)
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// If the kind of this resource has changed, we must write the checkpoint.
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if old.Custom != new.Custom {
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return true
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}
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contract.Assert(old.ID == new.ID)
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contract.Assert(old.Provider == new.Provider)
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// If this resource's parent has changed, we must write the checkpoint.
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if old.Parent != new.Parent {
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return true
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}
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// If the protection attribute of this resource has changed, we must write the checkpoint.
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if old.Protect != new.Protect {
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return true
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}
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// If the inputs or outputs of this resource have changed, we must write the checkpoint. Note that it is possible
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// for the inputs of a "same" resource to have changed even if the contents of the input bags are different if the
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// resource's provider deems the physical change to be semantically irrelevant.
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if !reflect.DeepEqual(old.Inputs, new.Inputs) || !reflect.DeepEqual(old.Outputs, new.Outputs) {
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return true
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}
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// Sort dependencies before comparing them. If the dependencies have changed, we must write the checkpoint.
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//
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// Init errors are strictly advisory, so we do not consider them when deciding whether or not to write the
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// checkpoint.
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sortDeps := func(deps []resource.URN) {
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sort.Slice(deps, func(i, j int) bool { return deps[i] < deps[j] })
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}
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sortDeps(old.Dependencies)
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sortDeps(new.Dependencies)
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return !reflect.DeepEqual(old.Dependencies, new.Dependencies)
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}
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func (ssm *sameSnapshotMutation) End(step deploy.Step, successful bool) error {
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contract.Require(step != nil, "step != nil")
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contract.Require(step.Op() == deploy.OpSame, "step.Op() == deploy.OpSame")
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contract.Assert(successful)
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logging.V(9).Infof("SnapshotManager: sameSnapshotMutation.End(..., %v)", successful)
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return ssm.manager.mutate(func() bool {
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ssm.manager.markDone(step.Old())
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ssm.manager.markNew(step.New())
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// Note that "Same" steps only consider input and provider diffs, so it is possible to see a same step for a
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// resource with new dependencies, outputs, parent, protection. etc.
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//
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// As such, we diff all of the non-input properties of the resource here and write the snapshot if we find any
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// changes.
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if !ssm.mustWrite(step.Old(), step.New()) {
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logging.V(9).Infof("SnapshotManager: sameSnapshotMutation.End() eliding write")
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return false
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}
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return true
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})
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}
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func (sm *SnapshotManager) doCreate(step deploy.Step) (engine.SnapshotMutation, error) {
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logging.V(9).Infof("SnapshotManager.doCreate(%s)", step.URN())
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err := sm.mutate(func() bool {
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sm.markOperationPending(step.New(), resource.OperationTypeCreating)
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return true
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})
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if err != nil {
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return nil, err
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}
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return &createSnapshotMutation{sm}, nil
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}
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type createSnapshotMutation struct {
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manager *SnapshotManager
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}
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func (csm *createSnapshotMutation) End(step deploy.Step, successful bool) error {
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contract.Require(step != nil, "step != nil")
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logging.V(9).Infof("SnapshotManager: createSnapshotMutation.End(..., %v)", successful)
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return csm.manager.mutate(func() bool {
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csm.manager.markOperationComplete(step.New())
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if successful {
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// There is some very subtle behind-the-scenes magic here that
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// comes into play whenever this create is a CreateReplacement.
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//
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// Despite intending for the base snapshot to be immutable, the engine
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// does in fact mutate it by setting a `Delete` flag on resources
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// being replaced as part of a Create-Before-Delete replacement sequence.
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// Since we are storing the base snapshot and all resources by reference
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// (we have pointers to engine-allocated objects), this transparently
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// "just works" for the SnapshotManager.
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csm.manager.markNew(step.New())
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// If we had an old state that was marked as pending-replacement, mark its replacement as complete such
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// that it is flushed from the state file.
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if old := step.Old(); old != nil && old.PendingReplacement {
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csm.manager.markDone(old)
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}
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}
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return true
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})
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}
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func (sm *SnapshotManager) doUpdate(step deploy.Step) (engine.SnapshotMutation, error) {
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logging.V(9).Infof("SnapshotManager.doUpdate(%s)", step.URN())
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err := sm.mutate(func() bool {
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sm.markOperationPending(step.New(), resource.OperationTypeUpdating)
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return true
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})
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if err != nil {
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return nil, err
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}
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return &updateSnapshotMutation{sm}, nil
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}
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type updateSnapshotMutation struct {
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manager *SnapshotManager
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}
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func (usm *updateSnapshotMutation) End(step deploy.Step, successful bool) error {
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contract.Require(step != nil, "step != nil")
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logging.V(9).Infof("SnapshotManager: updateSnapshotMutation.End(..., %v)", successful)
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return usm.manager.mutate(func() bool {
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usm.manager.markOperationComplete(step.New())
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if successful {
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usm.manager.markDone(step.Old())
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usm.manager.markNew(step.New())
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}
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return true
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})
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}
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func (sm *SnapshotManager) doDelete(step deploy.Step) (engine.SnapshotMutation, error) {
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logging.V(9).Infof("SnapshotManager.doDelete(%s)", step.URN())
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err := sm.mutate(func() bool {
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sm.markOperationPending(step.Old(), resource.OperationTypeDeleting)
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return true
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})
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if err != nil {
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return nil, err
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}
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return &deleteSnapshotMutation{sm}, nil
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}
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type deleteSnapshotMutation struct {
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manager *SnapshotManager
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}
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func (dsm *deleteSnapshotMutation) End(step deploy.Step, successful bool) error {
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contract.Require(step != nil, "step != nil")
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logging.V(9).Infof("SnapshotManager: deleteSnapshotMutation.End(..., %v)", successful)
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return dsm.manager.mutate(func() bool {
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dsm.manager.markOperationComplete(step.Old())
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if successful {
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contract.Assert(!step.Old().Protect)
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if !step.Old().PendingReplacement {
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dsm.manager.markDone(step.Old())
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}
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}
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return true
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})
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}
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type replaceSnapshotMutation struct {
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manager *SnapshotManager
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}
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func (rsm *replaceSnapshotMutation) End(step deploy.Step, successful bool) error {
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logging.V(9).Infof("SnapshotManager: replaceSnapshotMutation.End(..., %v)", successful)
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return nil
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}
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func (sm *SnapshotManager) doRead(step deploy.Step) (engine.SnapshotMutation, error) {
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logging.V(9).Infof("SnapshotManager.doRead(%s)", step.URN())
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err := sm.mutate(func() bool {
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sm.markOperationPending(step.New(), resource.OperationTypeReading)
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return true
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})
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if err != nil {
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return nil, err
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}
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return &readSnapshotMutation{sm}, nil
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}
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type readSnapshotMutation struct {
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manager *SnapshotManager
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}
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func (rsm *readSnapshotMutation) End(step deploy.Step, successful bool) error {
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contract.Require(step != nil, "step != nil")
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logging.V(9).Infof("SnapshotManager: readSnapshotMutation.End(..., %v)", successful)
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return rsm.manager.mutate(func() bool {
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rsm.manager.markOperationComplete(step.New())
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if successful {
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if step.Old() != nil {
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rsm.manager.markDone(step.Old())
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}
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|
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rsm.manager.markNew(step.New())
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}
|
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return true
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})
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}
|
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|
|
type refreshSnapshotMutation struct {
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manager *SnapshotManager
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}
|
|
|
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func (rsm *refreshSnapshotMutation) End(step deploy.Step, successful bool) error {
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contract.Require(step != nil, "step != nil")
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contract.Require(step.Op() == deploy.OpRefresh, "step.Op() == deploy.OpRefresh")
|
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logging.V(9).Infof("SnapshotManager: refreshSnapshotMutation.End(..., %v)", successful)
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return rsm.manager.mutate(func() bool {
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// We always elide refreshes. The expectation is that all of these run before any actual mutations and that
|
|
// some other component will rewrite the base snapshot in-memory, so there's no action the snapshot
|
|
// manager needs to take other than to remember that the base snapshot--and therefore the actual snapshot--may
|
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// have changed.
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return false
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})
|
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}
|
|
|
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type removePendingReplaceSnapshotMutation struct {
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manager *SnapshotManager
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}
|
|
|
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func (rsm *removePendingReplaceSnapshotMutation) End(step deploy.Step, successful bool) error {
|
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contract.Require(step != nil, "step != nil")
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contract.Require(step.Op() == deploy.OpRemovePendingReplace, "step.Op() == deploy.OpRemovePendingReplace")
|
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return rsm.manager.mutate(func() bool {
|
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res := step.Old()
|
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contract.Assert(res.PendingReplacement)
|
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rsm.manager.markDone(res)
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return true
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})
|
|
}
|
|
|
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// markDone marks a resource as having been processed. Resources that have been marked
|
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// in this manner won't be persisted in the snapshot.
|
|
func (sm *SnapshotManager) markDone(state *resource.State) {
|
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contract.Assert(state != nil)
|
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sm.dones[state] = true
|
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logging.V(9).Infof("Marked old state snapshot as done: %v", state.URN)
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|
}
|
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|
|
// markNew marks a resource as existing in the new snapshot. This occurs on
|
|
// successful non-deletion operations where the given state is the new state
|
|
// of a resource that will be persisted to the snapshot.
|
|
func (sm *SnapshotManager) markNew(state *resource.State) {
|
|
contract.Assert(state != nil)
|
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sm.resources = append(sm.resources, state)
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logging.V(9).Infof("Appended new state snapshot to be written: %v", state.URN)
|
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}
|
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|
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// markOperationPending marks a resource as undergoing an operation that will now be considered pending.
|
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func (sm *SnapshotManager) markOperationPending(state *resource.State, op resource.OperationType) {
|
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contract.Assert(state != nil)
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sm.operations = append(sm.operations, resource.NewOperation(state, op))
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logging.V(9).Infof("SnapshotManager.markPendingOperation(%s, %s)", state.URN, string(op))
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}
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|
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// markOperationComplete marks a resource as having completed the operation that it previously was performing.
|
|
func (sm *SnapshotManager) markOperationComplete(state *resource.State) {
|
|
contract.Assert(state != nil)
|
|
sm.completeOps[state] = true
|
|
logging.V(9).Infof("SnapshotManager.markOperationComplete(%s)", state.URN)
|
|
}
|
|
|
|
// snap produces a new Snapshot given the base snapshot and a list of resources that the current
|
|
// plan has created.
|
|
func (sm *SnapshotManager) snap() *deploy.Snapshot {
|
|
// At this point we have two resource DAGs. One of these is the base DAG for this plan; the other is the current DAG
|
|
// for this plan. Any resource r may be present in both DAGs. In order to produce a snapshot, we need to merge these
|
|
// DAGs such that all resource dependencies are correctly preserved. Conceptually, the merge proceeds as follows:
|
|
//
|
|
// - Begin with an empty merged DAG.
|
|
// - For each resource r in the current DAG, insert r and its outgoing edges into the merged DAG.
|
|
// - For each resource r in the base DAG:
|
|
// - If r is in the merged DAG, we are done: if the resource is in the merged DAG, it must have been in the
|
|
// current DAG, which accurately captures its current dependencies.
|
|
// - If r is not in the merged DAG, insert it and its outgoing edges into the merged DAG.
|
|
//
|
|
// Physically, however, each DAG is represented as list of resources without explicit dependency edges. In place of
|
|
// edges, it is assumed that the list represents a valid topological sort of its source DAG. Thus, any resource r at
|
|
// index i in a list L must be assumed to be dependent on all resources in L with index j s.t. j < i. Due to this
|
|
// representation, we implement the algorithm above as follows to produce a merged list that represents a valid
|
|
// topological sort of the merged DAG:
|
|
//
|
|
// - Begin with an empty merged list.
|
|
// - For each resource r in the current list, append r to the merged list. r must be in a correct location in the
|
|
// merged list, as its position relative to its assumed dependencies has not changed.
|
|
// - For each resource r in the base list:
|
|
// - If r is in the merged list, we are done by the logic given in the original algorithm.
|
|
// - If r is not in the merged list, append r to the merged list. r must be in a correct location in the merged
|
|
// list:
|
|
// - If any of r's dependencies were in the current list, they must already be in the merged list and their
|
|
// relative order w.r.t. r has not changed.
|
|
// - If any of r's dependencies were not in the current list, they must already be in the merged list, as
|
|
// they would have been appended to the list before r.
|
|
|
|
// Start with a copy of the resources produced during the evaluation of the current plan.
|
|
resources := make([]*resource.State, len(sm.resources))
|
|
copy(resources, sm.resources)
|
|
|
|
// Append any resources from the base plan that were not produced by the current plan.
|
|
if base := sm.baseSnapshot; base != nil {
|
|
for _, res := range base.Resources {
|
|
if !sm.dones[res] {
|
|
resources = append(resources, res)
|
|
}
|
|
}
|
|
}
|
|
|
|
// Record any pending operations, if there are any outstanding that have not completed yet.
|
|
var operations []resource.Operation
|
|
for _, op := range sm.operations {
|
|
if !sm.completeOps[op.Resource] {
|
|
operations = append(operations, op)
|
|
}
|
|
}
|
|
|
|
manifest := deploy.Manifest{
|
|
Time: time.Now(),
|
|
Version: version.Version,
|
|
Plugins: sm.plugins,
|
|
}
|
|
|
|
manifest.Magic = manifest.NewMagic()
|
|
return deploy.NewSnapshot(manifest, resources, operations)
|
|
}
|
|
|
|
// saveSnapshot persists the current snapshot and optionally verifies it afterwards.
|
|
func (sm *SnapshotManager) saveSnapshot() error {
|
|
snap := sm.snap()
|
|
if err := sm.persister.Save(snap); err != nil {
|
|
return errors.Wrap(err, "failed to save snapshot")
|
|
}
|
|
if sm.doVerify {
|
|
if err := snap.VerifyIntegrity(); err != nil {
|
|
return errors.Wrapf(err, "failed to verify snapshot")
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// NewSnapshotManager creates a new SnapshotManager for the given stack name, using the given persister
|
|
// and base snapshot.
|
|
//
|
|
// It is *very important* that the baseSnap pointer refers to the same Snapshot
|
|
// given to the engine! The engine will mutate this object and correctness of the
|
|
// SnapshotManager depends on being able to observe this mutation. (This is not ideal...)
|
|
func NewSnapshotManager(persister SnapshotPersister, baseSnap *deploy.Snapshot) *SnapshotManager {
|
|
mutationRequests, cancel, done := make(chan mutationRequest), make(chan bool), make(chan error)
|
|
|
|
manager := &SnapshotManager{
|
|
persister: persister,
|
|
baseSnapshot: baseSnap,
|
|
dones: make(map[*resource.State]bool),
|
|
completeOps: make(map[*resource.State]bool),
|
|
doVerify: true,
|
|
mutationRequests: mutationRequests,
|
|
cancel: cancel,
|
|
done: done,
|
|
}
|
|
|
|
go func() {
|
|
// True if we have elided writes since the last actual write.
|
|
hasElidedWrites := false
|
|
|
|
// Service each mutation request in turn.
|
|
serviceLoop:
|
|
for {
|
|
select {
|
|
case request := <-mutationRequests:
|
|
var err error
|
|
if request.mutator() {
|
|
err = manager.saveSnapshot()
|
|
hasElidedWrites = false
|
|
} else {
|
|
hasElidedWrites = true
|
|
}
|
|
request.result <- err
|
|
case <-cancel:
|
|
break serviceLoop
|
|
}
|
|
}
|
|
|
|
// If we still have elided writes once the channel has closed, flush the snapshot.
|
|
var err error
|
|
if hasElidedWrites {
|
|
logging.V(9).Infof("SnapshotManager: flushing elided writes...")
|
|
err = manager.saveSnapshot()
|
|
}
|
|
done <- err
|
|
}()
|
|
|
|
return manager
|
|
}
|