6194a59798
This change adds a new Check RPC method on the provider interface, permitting resource providers to perform arbitrary verification on the values of properties. This is useful for validating things that might be difficult to express in the type system, and it runs before *any* modifications are run (so failures can be caight early before it's too late). My favorite motivating example is verifying that an AWS EC2 instance's AMI is available within the target region. This resolves pulumi/coconut#107, although we aren't using this in any resource providers just yet. I'll add a work item now for that...
47 lines
2.7 KiB
Go
47 lines
2.7 KiB
Go
// Copyright 2016 Pulumi, Inc. All rights reserved.
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package resource
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import (
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"io"
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"github.com/pulumi/coconut/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 catastrophies 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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// Check validates that the given property bag is valid for a resource of the given type.
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Check(t tokens.Type, props PropertyMap) ([]CheckFailure, error)
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// Name names a given resource. Sometimes this will be assigned by a developer, and so the provider
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// simply fetches it from the property bag; other times, the provider will assign this based on its own algorithm.
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// In any case, resources with the same name must be safe to use interchangeably with one another.
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Name(t tokens.Type, props PropertyMap) (tokens.QName, error)
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// Create allocates a new instance of the provided resource and returns its unique ID afterwards.
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Create(t tokens.Type, props PropertyMap) (ID, error, ResourceState)
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// Read reads the instance state identified by id/t, and returns a bag of properties.
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Read(id ID, t tokens.Type) (PropertyMap, error)
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// Update updates an existing resource with new values.
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Update(id ID, t tokens.Type, olds PropertyMap, news PropertyMap) (error, ResourceState)
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// UpdateImpact checks what impacts a hypothetical update will have on the resource's properties.
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UpdateImpact(id ID, t tokens.Type, olds PropertyMap, news PropertyMap) ([]string, PropertyMap, error)
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// Delete tears down an existing resource.
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Delete(id ID, t tokens.Type) (error, ResourceState)
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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 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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