a4fadc596b
Now that we have most of the services required for use with containerd, it was found that common patterns were used throughout services. By defining a central `errdefs` package, we ensure that services will map errors to and from grpc consistently and cleanly. One can decorate an error with as much context as necessary, using `pkg/errors` and still have the error mapped correctly via grpc. We make a few sacrifices. At this point, the common errors we use across the repository all map directly to grpc error codes. While this seems positively crazy, it actually works out quite well. The error conditions that were specific weren't super necessary and the ones that were necessary now simply have better context information. We lose the ability to add new codes, but this constraint may not be a bad thing. Effectively, as long as one uses the errors defined in `errdefs`, the error class will be mapped correctly across the grpc boundary and everything will be good. If you don't use those definitions, the error maps to "unknown" and the error message is preserved. Signed-off-by: Stephen J Day <stephen.day@docker.com>
55 lines
1.9 KiB
Go
55 lines
1.9 KiB
Go
// Package errdefs defines the common errors used throughout containerd
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// packages.
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//
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// Use with errors.Wrap and error.Wrapf to add context to an error.
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//
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// To detect an error class, use the IsXXX functions to tell whether an error
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// is of a certain type.
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//
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// The functions ToGRPC and FromGRPC can be used to map server-side and
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// client-side errors to the correct types.
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package errdefs
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import "github.com/pkg/errors"
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// Definitions of common error types used throughout containerd. All containerd
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// errors returned by most packages will map into one of these errors classes.
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// Packages should return errors of these types when they want to instruct a
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// client to take a particular action.
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//
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// For the most part, we just try to provide local grpc errors. Most conditions
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// map very well to those defined by grpc.
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var (
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ErrUnknown = errors.New("unknown") // used internally to represent a missed mapping.
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ErrInvalidArgument = errors.New("invalid")
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ErrNotFound = errors.New("not found")
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ErrAlreadyExists = errors.New("already exists")
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ErrFailedPrecondition = errors.New("failed precondition")
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ErrUnavailable = errors.New("unavailable")
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)
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func IsInvalidArgument(err error) bool {
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return errors.Cause(err) == ErrInvalidArgument
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}
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// IsNotFound returns true if the error is due to a missing object
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func IsNotFound(err error) bool {
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return errors.Cause(err) == ErrNotFound
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}
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// IsAlreadyExists returns true if the error is due to an already existing
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// metadata item
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func IsAlreadyExists(err error) bool {
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return errors.Cause(err) == ErrAlreadyExists
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}
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// IsFailedPrecondition returns true if an operation could not proceed to the
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// lack of a particular condition.
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func IsFailedPrecondition(err error) bool {
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return errors.Cause(err) == ErrFailedPrecondition
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}
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func IsUnavailable(err error) bool {
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return errors.Cause(err) == ErrUnavailable
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}
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