terraform/instances/expander.go

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package instances
import (
"fmt"
"sort"
"sync"
"github.com/hashicorp/terraform/addrs"
"github.com/zclconf/go-cty/cty"
)
// Expander instances serve as a coordination point for gathering object
// repetition values (count and for_each in configuration) and then later
// making use of them to fully enumerate all of the instances of an object.
//
// The two repeatable object types in Terraform are modules and resources.
// Because resources belong to modules and modules can nest inside other
// modules, module expansion in particular has a recursive effect that can
// cause deep objects to expand exponentially. Expander assumes that all
// instances of a module have the same static objects inside, and that they
// differ only in the repetition count for some of those objects.
//
// Expander is a synchronized object whose methods can be safely called
// from concurrent threads of execution. However, it does expect a certain
// sequence of operations which is normally obtained by the caller traversing
// a dependency graph: each object must have its repetition mode set exactly
// once, and this must be done before any calls that depend on the repetition
// mode. In other words, the count or for_each expression value for a module
// must be provided before any object nested directly or indirectly inside
// that module can be expanded. If this ordering is violated, the methods
// will panic to enforce internal consistency.
//
// The Expand* methods of Expander only work directly with modules and with
// resources. Addresses for other objects that nest within modules but
// do not themselves support repetition can be obtained by calling ExpandModule
// with the containing module path and then producing one absolute instance
// address per module instance address returned.
type Expander struct {
mu sync.RWMutex
exps *expanderModule
}
// NewExpander initializes and returns a new Expander, empty and ready to use.
func NewExpander() *Expander {
return &Expander{
exps: newExpanderModule(),
}
}
// SetModuleSingle records that the given module call inside the given parent
// module does not use any repetition arguments and is therefore a singleton.
func (e *Expander) SetModuleSingle(parentAddr addrs.ModuleInstance, callAddr addrs.ModuleCall) {
e.setModuleExpansion(parentAddr, callAddr, expansionSingleVal)
}
// SetModuleCount records that the given module call inside the given parent
// module instance uses the "count" repetition argument, with the given value.
func (e *Expander) SetModuleCount(parentAddr addrs.ModuleInstance, callAddr addrs.ModuleCall, count int) {
e.setModuleExpansion(parentAddr, callAddr, expansionCount(count))
}
// SetModuleForEach records that the given module call inside the given parent
// module instance uses the "for_each" repetition argument, with the given
// map value.
//
// In the configuration language the for_each argument can also accept a set.
// It's the caller's responsibility to convert that into an identity map before
// calling this method.
func (e *Expander) SetModuleForEach(parentAddr addrs.ModuleInstance, callAddr addrs.ModuleCall, mapping map[string]cty.Value) {
e.setModuleExpansion(parentAddr, callAddr, expansionForEach(mapping))
}
// SetResourceSingle records that the given resource inside the given module
// does not use any repetition arguments and is therefore a singleton.
func (e *Expander) SetResourceSingle(moduleAddr addrs.ModuleInstance, resourceAddr addrs.Resource) {
e.setResourceExpansion(moduleAddr, resourceAddr, expansionSingleVal)
}
// SetResourceCount records that the given resource inside the given module
// uses the "count" repetition argument, with the given value.
func (e *Expander) SetResourceCount(moduleAddr addrs.ModuleInstance, resourceAddr addrs.Resource, count int) {
e.setResourceExpansion(moduleAddr, resourceAddr, expansionCount(count))
}
// SetResourceForEach records that the given resource inside the given module
// uses the "for_each" repetition argument, with the given map value.
//
// In the configuration language the for_each argument can also accept a set.
// It's the caller's responsibility to convert that into an identity map before
// calling this method.
func (e *Expander) SetResourceForEach(moduleAddr addrs.ModuleInstance, resourceAddr addrs.Resource, mapping map[string]cty.Value) {
e.setResourceExpansion(moduleAddr, resourceAddr, expansionForEach(mapping))
}
// ExpandModule finds the exhaustive set of module instances resulting from
// the expansion of the given module and all of its ancestor modules.
//
// All of the modules on the path to the identified module must already have
// had their expansion registered using one of the SetModule* methods before
// calling, or this method will panic.
func (e *Expander) ExpandModule(addr addrs.Module) []addrs.ModuleInstance {
if len(addr) == 0 {
// Root module is always a singleton.
return singletonRootModule
}
e.mu.RLock()
defer e.mu.RUnlock()
// We're going to be dynamically growing ModuleInstance addresses, so
// we'll preallocate some space to do it so that for typical shallow
// module trees we won't need to reallocate this.
// (moduleInstances does plenty of allocations itself, so the benefit of
// pre-allocating this is marginal but it's not hard to do.)
parentAddr := make(addrs.ModuleInstance, 0, 4)
ret := e.exps.moduleInstances(addr, parentAddr)
sort.SliceStable(ret, func(i, j int) bool {
return ret[i].Less(ret[j])
})
return ret
}
// ExpandModuleResource finds the exhaustive set of resource instances resulting from
// the expansion of the given resource and all of its containing modules.
//
// All of the modules on the path to the identified resource and the resource
// itself must already have had their expansion registered using one of the
// SetModule*/SetResource* methods before calling, or this method will panic.
func (e *Expander) ExpandModuleResource(moduleAddr addrs.Module, resourceAddr addrs.Resource) []addrs.AbsResourceInstance {
e.mu.RLock()
defer e.mu.RUnlock()
// We're going to be dynamically growing ModuleInstance addresses, so
// we'll preallocate some space to do it so that for typical shallow
// module trees we won't need to reallocate this.
// (moduleInstances does plenty of allocations itself, so the benefit of
// pre-allocating this is marginal but it's not hard to do.)
moduleInstanceAddr := make(addrs.ModuleInstance, 0, 4)
ret := e.exps.resourceInstances(moduleAddr, resourceAddr, moduleInstanceAddr)
sort.SliceStable(ret, func(i, j int) bool {
return ret[i].Less(ret[j])
})
return ret
}
// ExpandResource finds the set of resource instances resulting from
// the expansion of the given resource within its module instance.
//
// All of the modules on the path to the identified resource and the resource
// itself must already have had their expansion registered using one of the
// SetModule*/SetResource* methods before calling, or this method will panic.
func (e *Expander) ExpandResource(resourceAddr addrs.AbsResource) []addrs.AbsResourceInstance {
var ret []addrs.AbsResourceInstance
// Take the full set of expanded resource instances and filter for only
// those within our module instance.
for _, r := range e.ExpandModuleResource(resourceAddr.Module.Module(), resourceAddr.Resource) {
if !r.Module.Equal(resourceAddr.Module) {
continue
}
ret = append(ret, r)
}
return ret
}
// GetModuleInstanceRepetitionData returns an object describing the values
// that should be available for each.key, each.value, and count.index within
// the call block for the given module instance.
func (e *Expander) GetModuleInstanceRepetitionData(addr addrs.ModuleInstance) RepetitionData {
if len(addr) == 0 {
// The root module is always a singleton, so it has no repetition data.
return RepetitionData{}
}
e.mu.RLock()
defer e.mu.RUnlock()
parentMod := e.findModule(addr[:len(addr)-1])
lastStep := addr[len(addr)-1]
exp, ok := parentMod.moduleCalls[addrs.ModuleCall{Name: lastStep.Name}]
if !ok {
panic(fmt.Sprintf("no expansion has been registered for %s", addr))
}
return exp.repetitionData(lastStep.InstanceKey)
}
// GetResourceInstanceRepetitionData returns an object describing the values
// that should be available for each.key, each.value, and count.index within
// the definition block for the given resource instance.
func (e *Expander) GetResourceInstanceRepetitionData(addr addrs.AbsResourceInstance) RepetitionData {
e.mu.RLock()
defer e.mu.RUnlock()
parentMod := e.findModule(addr.Module)
exp, ok := parentMod.resources[addr.Resource.Resource]
if !ok {
panic(fmt.Sprintf("no expansion has been registered for %s", addr.ContainingResource()))
}
return exp.repetitionData(addr.Resource.Key)
}
func (e *Expander) findModule(moduleInstAddr addrs.ModuleInstance) *expanderModule {
// We expect that all of the modules on the path to our module instance
// should already have expansions registered.
mod := e.exps
for i, step := range moduleInstAddr {
next, ok := mod.childInstances[step]
if !ok {
// Top-down ordering of registration is part of the contract of
// Expander, so this is always indicative of a bug in the caller.
panic(fmt.Sprintf("no expansion has been registered for ancestor module %s", moduleInstAddr[:i+1]))
}
mod = next
}
return mod
}
func (e *Expander) setModuleExpansion(parentAddr addrs.ModuleInstance, callAddr addrs.ModuleCall, exp expansion) {
e.mu.Lock()
defer e.mu.Unlock()
mod := e.findModule(parentAddr)
if _, exists := mod.moduleCalls[callAddr]; exists {
panic(fmt.Sprintf("expansion already registered for %s", parentAddr.Child(callAddr.Name, addrs.NoKey)))
}
// We'll also pre-register the child instances so that later calls can
// populate them as the caller traverses the configuration tree.
for _, key := range exp.instanceKeys() {
step := addrs.ModuleInstanceStep{Name: callAddr.Name, InstanceKey: key}
mod.childInstances[step] = newExpanderModule()
}
mod.moduleCalls[callAddr] = exp
}
func (e *Expander) setResourceExpansion(parentAddr addrs.ModuleInstance, resourceAddr addrs.Resource, exp expansion) {
e.mu.Lock()
defer e.mu.Unlock()
mod := e.findModule(parentAddr)
if _, exists := mod.resources[resourceAddr]; exists {
panic(fmt.Sprintf("expansion already registered for %s", resourceAddr.Absolute(parentAddr)))
}
mod.resources[resourceAddr] = exp
}
type expanderModule struct {
moduleCalls map[addrs.ModuleCall]expansion
resources map[addrs.Resource]expansion
childInstances map[addrs.ModuleInstanceStep]*expanderModule
}
func newExpanderModule() *expanderModule {
return &expanderModule{
moduleCalls: make(map[addrs.ModuleCall]expansion),
resources: make(map[addrs.Resource]expansion),
childInstances: make(map[addrs.ModuleInstanceStep]*expanderModule),
}
}
var singletonRootModule = []addrs.ModuleInstance{addrs.RootModuleInstance}
func (m *expanderModule) moduleInstances(addr addrs.Module, parentAddr addrs.ModuleInstance) []addrs.ModuleInstance {
callName := addr[0]
exp, ok := m.moduleCalls[addrs.ModuleCall{Name: callName}]
if !ok {
// This is a bug in the caller, because it should always register
// expansions for an object and all of its ancestors before requesting
// expansion of it.
panic(fmt.Sprintf("no expansion has been registered for %s", parentAddr.Child(callName, addrs.NoKey)))
}
var ret []addrs.ModuleInstance
// If there's more than one step remaining then we need to traverse deeper.
if len(addr) > 1 {
for step, inst := range m.childInstances {
if step.Name != callName {
continue
}
instAddr := append(parentAddr, step)
ret = append(ret, inst.moduleInstances(addr[1:], instAddr)...)
}
return ret
}
// Otherwise, we'll use the expansion from the final step to produce
// a sequence of addresses under this prefix.
for _, k := range exp.instanceKeys() {
// We're reusing the buffer under parentAddr as we recurse through
// the structure, so we need to copy it here to produce a final
// immutable slice to return.
full := make(addrs.ModuleInstance, 0, len(parentAddr)+1)
full = append(full, parentAddr...)
full = full.Child(callName, k)
ret = append(ret, full)
}
return ret
}
func (m *expanderModule) resourceInstances(moduleAddr addrs.Module, resourceAddr addrs.Resource, parentAddr addrs.ModuleInstance) []addrs.AbsResourceInstance {
var ret []addrs.AbsResourceInstance
if len(moduleAddr) > 0 {
// We need to traverse through the module levels first, so we can
// then iterate resource expansions in the context of each module
// path leading to them.
callName := moduleAddr[0]
if _, ok := m.moduleCalls[addrs.ModuleCall{Name: callName}]; !ok {
// This is a bug in the caller, because it should always register
// expansions for an object and all of its ancestors before requesting
// expansion of it.
panic(fmt.Sprintf("no expansion has been registered for %s", parentAddr.Child(callName, addrs.NoKey)))
}
for step, inst := range m.childInstances {
if step.Name != callName {
continue
}
moduleInstAddr := append(parentAddr, step)
ret = append(ret, inst.resourceInstances(moduleAddr[1:], resourceAddr, moduleInstAddr)...)
}
return ret
}
exp, ok := m.resources[resourceAddr]
if !ok {
panic(fmt.Sprintf("no expansion has been registered for %s", resourceAddr.Absolute(parentAddr)))
}
for _, k := range exp.instanceKeys() {
// We're reusing the buffer under parentAddr as we recurse through
// the structure, so we need to copy it here to produce a final
// immutable slice to return.
moduleAddr := make(addrs.ModuleInstance, len(parentAddr))
copy(moduleAddr, parentAddr)
ret = append(ret, resourceAddr.Instance(k).Absolute(moduleAddr))
}
return ret
}