b7576b9b14
This change adds the capability for a resource provider to indicate that, where an action carried out in response to a diff, a certain set of properties would be "stable"; that is to say, they are guaranteed not to change. As a result, properties may be resolved to their final values during previewing, avoiding erroneous cascading impacts. This avoids the ever-annoying situation I keep running into when demoing: when adding or removing an ingress rule to a security group, we ripple the impact through the instance, and claim it must be replaced, because that instance depends on the security group via its name. Well, the name is a great example of a stable property, in that it will never change, and so this is truly unfortunate and always adds uncertainty into the demos. Particularly since the actual update doesn't need to perform replacements. This resolves pulumi/pulumi#330.
60 lines
3.2 KiB
Go
60 lines
3.2 KiB
Go
// Copyright 2016-2017, Pulumi Corporation. All rights reserved.
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package plugin
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import (
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"io"
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"github.com/pulumi/pulumi/pkg/resource"
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"github.com/pulumi/pulumi/pkg/tokens"
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)
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// Provider presents a simple interface for orchestrating resource create, reead, update, and delete operations. Each
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// provider understands how to handle all of the resource types within a single package.
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//
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// This interface hides some of the messiness of the underlying machinery, since providers are behind an RPC boundary.
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//
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// It is important to note that provider operations are not transactional. (Some providers might decide to offer
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// transactional semantics, but such a provider is a rare treat.) As a result, failures in the operations below can
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// range from benign to catastrophic (possibly leaving behind a corrupt resource). It is up to the provider to make a
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// best effort to ensure catastrophes do not occur. The errors returned from mutating operations indicate both the
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// underlying error condition in addition to a bit indicating whether the operation was successfully rolled back.
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type Provider interface {
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// Closer closes any underlying OS resources associated with this provider (like processes, RPC channels, etc).
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io.Closer
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// Pkg fetches this provider's package.
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Pkg() tokens.Package
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// Configure configures the resource provider with "globals" that control its behavior.
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Configure(vars map[tokens.ModuleMember]string) error
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// Check validates that the given property bag is valid for a resource of the given type.
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Check(urn resource.URN, props resource.PropertyMap) (resource.PropertyMap, []CheckFailure, error)
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// Diff checks what impacts a hypothetical update will have on the resource's properties.
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Diff(urn resource.URN, id resource.ID, olds resource.PropertyMap, news resource.PropertyMap) (DiffResult, error)
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// Create allocates a new instance of the provided resource and returns its unique resource.ID.
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Create(urn resource.URN, props resource.PropertyMap) (resource.ID, resource.PropertyMap, resource.Status, error)
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// Update updates an existing resource with new values.
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Update(urn resource.URN, id resource.ID,
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olds resource.PropertyMap, news resource.PropertyMap) (resource.PropertyMap, resource.Status, error)
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// Delete tears down an existing resource.
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Delete(urn resource.URN, id resource.ID, props resource.PropertyMap) (resource.Status, error)
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// Invoke dynamically executes a built-in function in the provider.
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Invoke(tok tokens.ModuleMember, args resource.PropertyMap) (resource.PropertyMap, []CheckFailure, error)
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}
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// CheckFailure indicates that a call to check failed; it contains the property and reason for the failure.
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type CheckFailure struct {
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Property resource.PropertyKey // the property that failed checking.
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Reason string // the reason the property failed to check.
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}
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// DiffResult indicates whether an operation should replace or update an existing resource.
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type DiffResult struct {
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ReplaceKeys []resource.PropertyKey // an optional list of replacement keys.
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StableKeys []resource.PropertyKey // an optional list of property keys that are stable.
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}
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// Replace returns true if this diff represents a replacement.
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func (r DiffResult) Replace() bool {
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return len(r.ReplaceKeys) > 0
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}
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