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terraform: Graph nodes for closing ephemeral resource instances
For now these graph nodes don't actually do anything, but the graph shape is at least plausible for what we'll need.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,29 @@ | ||
| // Copyright (c) HashiCorp, Inc. | ||
| // SPDX-License-Identifier: BUSL-1.1 | ||
|
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| package terraform | ||
|
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| import ( | ||
| "github.com/hashicorp/terraform/internal/addrs" | ||
| ) | ||
|
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| // nodeEphemeralResourceClose is the node type for closing the previously-opened | ||
| // instances of a particular ephemeral resource. | ||
| // | ||
| // Although ephemeral resource instances will always all get closed once a | ||
| // graph walk has completed anyway, the inclusion of explicit nodes for this | ||
| // allows closing ephemeral resource instances more promptly after all work | ||
| // that uses them has been completed, rather than always just waiting until | ||
| // the end of the graph walk. | ||
| // | ||
| // This is scoped to config-level resources rather than dynamic resource | ||
| // instances as a concession to allow using the same node type in both the plan | ||
| // and apply graphs, where the former only deals in whole resources while the | ||
| // latter contains individual instances. | ||
| type nodeEphemeralResourceClose struct { | ||
| addr addrs.ConfigResource | ||
| } | ||
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| func (n *nodeEphemeralResourceClose) Name() string { | ||
| return n.addr.String() + " (close)" | ||
| } |
191 changes: 191 additions & 0 deletions
191
internal/terraform/transform_ephemeral_resource_close.go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,191 @@ | ||
| // Copyright (c) HashiCorp, Inc. | ||
| // SPDX-License-Identifier: BUSL-1.1 | ||
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| package terraform | ||
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| import ( | ||
| "fmt" | ||
| "log" | ||
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| "github.com/hashicorp/terraform/internal/addrs" | ||
| "github.com/hashicorp/terraform/internal/collections" | ||
| "github.com/hashicorp/terraform/internal/dag" | ||
| ) | ||
|
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| // graphNodeEphemeralResourceConsumer is implemented by graph node types that | ||
| // can validly refer to ephemeral resources, to announce which ephemeral | ||
| // resources they each depend on. | ||
| // | ||
| // This is used to decide the dependencies for [nodeEphemeralResourceClose] | ||
| // nodes. | ||
| type graphNodeEphemeralResourceConsumer interface { | ||
| // requiredEphemeralResources returns a set of all of the ephemeral | ||
| // resources that the receiver directly depends on when performing | ||
| // the given walk operation. | ||
| // | ||
| // Although the addrs package types can't constrain this statically, | ||
| // this method should return only addresses of mode | ||
| // [addrs.EphemeralResourceMode]. Resources of any other mode are invalid | ||
| // to return. | ||
| // | ||
| // walkOperation is normalized for implementation simplicity: it can be | ||
| // either [walkPlan] or [walkApply], and no other type. | ||
| requiredEphemeralResources(op walkOperation) addrs.Set[addrs.ConfigResource] | ||
| } | ||
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| // requiredEphemeralResourcesForReferencer is a helper for implementing | ||
| // [graphNodeEphemeralResourceConsumer] for any node type which implements | ||
| // [GraphNodeReferencer] and whose reported references can entirely describe | ||
| // the needed ephemeral resources. | ||
| func requiredEphemeralResourcesForReferencer[T GraphNodeReferencer](n T) addrs.Set[addrs.ConfigResource] { | ||
| moduleAddr := n.ModulePath() | ||
| refs := n.References() | ||
| if len(refs) == 0 { | ||
| return nil | ||
| } | ||
| ret := addrs.MakeSet[addrs.ConfigResource]() | ||
| for _, ref := range refs { | ||
| var resourceAddr addrs.Resource | ||
| switch refAddr := ref.Subject.(type) { | ||
| case addrs.Resource: | ||
| resourceAddr = refAddr | ||
| case addrs.ResourceInstance: | ||
| resourceAddr = refAddr.Resource | ||
| default: | ||
| continue | ||
| } | ||
| if resourceAddr.Mode != addrs.EphemeralResourceMode { | ||
| continue // we only care about ephemeral resources here | ||
| } | ||
| ret.Add(resourceAddr.InModule(moduleAddr)) | ||
| } | ||
| return ret | ||
| } | ||
|
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| // ephemeralResourceCloseTransformer is a graph transformer that inserts | ||
| // a [nodeEphemeralResourceClose] node for each ephemeral resource whose "open" | ||
| // is represented by at least one existing node, and arranges for the close | ||
| // node to depend on the open node and on any other node that consumes the | ||
| // relevant ephemeral resource. | ||
| // | ||
| // This transformer also prunes nodes for any ephemeral resources that have | ||
| // no consumers for the given walk operation. In particular this means that | ||
| // Terraform will not open any instances of an ephemeral resource that is | ||
| // only used in resource provisioners if the graph is not being built for the | ||
| // apply phase, because only the apply phase actually executes provisioners. | ||
| // | ||
| // This transformer must run after any other transformer that might introduce | ||
| // an ephemeral resource node into the graph, or that might given an existing | ||
| // node information it needs to properly announce any ephemeral resources it | ||
| // consumes. | ||
| type ephemeralResourceCloseTransformer struct { | ||
| // op must be one of walkValidate, walkPlan, or walkApply. For other walk | ||
| // operations, choose walkApply if the walk will execute resource | ||
| // provisioners or walkPlan otherwise. | ||
| // | ||
| // if op is walkValidate then this transformer does absolutely nothing, | ||
| // because we don't open or close ephemeral resources during the validate | ||
| // walk. | ||
| op walkOperation | ||
| } | ||
|
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| func (t *ephemeralResourceCloseTransformer) Transform(g *Graph) error { | ||
| if t.op != walkApply && t.op != walkPlan { | ||
| // Nothing to do for any other walks, because only plan-like or | ||
| // apply-like walks actually open ephemeral resource instances. | ||
| return nil | ||
| } | ||
|
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| // We'll freeze the set of vertices we started with so that we can | ||
| // visit it multiple times while we're modifying the graph. | ||
| verts := g.Vertices() | ||
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| // First we'll find all of the ephemeral resources that already have | ||
| // at least one node in the graph, and we'll assume those are all | ||
| // "open" nodes. Each distinct ephemeral resource address gets one | ||
| // close node that depends on all of the nodes that might open instances | ||
| // of it. | ||
| openNodes := addrs.MakeMap[addrs.ConfigResource, collections.Set[dag.Vertex]]() | ||
| closeNodes := addrs.MakeMap[addrs.ConfigResource, *nodeEphemeralResourceClose]() | ||
| for _, v := range verts { | ||
| v, ok := v.(GraphNodeConfigResource) | ||
| if !ok { | ||
| continue | ||
| } | ||
| addr := v.ResourceAddr() | ||
| if addr.Resource.Mode != addrs.EphemeralResourceMode { | ||
| continue | ||
| } | ||
| if !openNodes.Has(addr) { | ||
| openNodes.Put(addr, collections.NewSetCmp[dag.Vertex]()) | ||
| } | ||
| openNodes.Get(addr).Add(v) | ||
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| if !closeNodes.Has(addr) { | ||
| closeNode := &nodeEphemeralResourceClose{ | ||
| addr: addr, | ||
| } | ||
| closeNodes.Put(addr, closeNode) | ||
| log.Printf("[TRACE] ephemeralResourceCloseTransformer: adding close node for %s", addr) | ||
| g.Add(closeNode) | ||
| } | ||
| closeNode := closeNodes.Get(addr) | ||
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| // The close node depends on the open node, because we can't | ||
| // close an ephemeral resource instance until we've opened it. | ||
| g.Connect(dag.BasicEdge(closeNode, v)) | ||
| } | ||
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| consumerCount := addrs.MakeMap[addrs.ConfigResource, int]() | ||
| for _, v := range verts { | ||
| v, ok := v.(graphNodeEphemeralResourceConsumer) | ||
| if !ok { | ||
| continue | ||
| } | ||
| for _, consumedAddr := range v.requiredEphemeralResources(t.op) { | ||
| if consumedAddr.Resource.Mode != addrs.EphemeralResourceMode { | ||
| // Should not happen: correct implementations of | ||
| // [graphNodeEphemeralResourceConsumer] only return | ||
| // ephemeral resource addresses. | ||
| panic(fmt.Sprintf("node %s incorrectly reported %s as an ephemeral resource", dag.VertexName(v), consumedAddr)) | ||
| } | ||
| closeNode := closeNodes.Get(consumedAddr) | ||
| if closeNode == nil { | ||
| // Suggests that there's a reference to an ephemeral resource | ||
| // that isn't declared, which is invalid but it's not this | ||
| // transformer's responsibility to detect that invalidity, | ||
| // so we'll just ignore it. | ||
| log.Printf("[TRACE] ephemeralResourceCloseTransformer: %s refers to undeclared ephemeral resource %s", dag.VertexName(v), consumedAddr) | ||
| continue | ||
| } | ||
| consumerCount.Put(consumedAddr, consumerCount.Get(consumedAddr)+1) | ||
|
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| // The close node depends on anything that consumes instances of | ||
| // the ephemeral resource, because we mustn't close it while | ||
| // other components are still using it. | ||
| g.Connect(dag.BasicEdge(closeNode, v)) | ||
| } | ||
| } | ||
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| // Finally, if we found any ephemeral resources that don't have any | ||
| // consumers then we'll prune out all of their open and close nodes | ||
| // to avoid redundantly opening and closing something that we aren't | ||
| // going to use anyway. | ||
| // (We don't use this transformer in the validate walk, | ||
| for _, elem := range openNodes.Elems { | ||
| if consumerCount.Get(elem.Key) == 0 { | ||
| for _, v := range elem.Value.Elems() { | ||
| log.Printf("[TRACE] ephemeralResourceCloseTransformer: pruning %s because it has no consumers", dag.VertexName(v)) | ||
| g.Remove(v) | ||
| } | ||
| } | ||
| } | ||
| for _, elem := range closeNodes.Elems { | ||
| if consumerCount.Get(elem.Key) == 0 { | ||
| log.Printf("[TRACE] ephemeralResourceCloseTransformer: pruning %s because it has no consumers", dag.VertexName(elem.Value)) | ||
| g.Remove(elem.Value) | ||
| } | ||
| } | ||
|
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| return nil | ||
| } |