mirror of
https://github.com/edgelesssys/constellation.git
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106 lines
2.7 KiB
Go
106 lines
2.7 KiB
Go
/*
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Copyright (c) Edgeless Systems GmbH
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SPDX-License-Identifier: AGPL-3.0-only
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*/
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/*
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Package fetcher implements a client for the versions API.
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The fetcher is used to get information from the versions API without having to
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authenticate with AWS, where the API is currently hosted. This package should be
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used in user-facing application code most of the time, like the CLI.
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*/
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package fetcher
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import (
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"context"
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"encoding/json"
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"fmt"
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"net/http"
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)
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// fetcher fetches versions API resources without authentication.
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type fetcher struct {
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httpc HTTPClient
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}
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// NewHTTPClient returns a new http client.
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func NewHTTPClient() HTTPClient {
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return &http.Client{Transport: &http.Transport{DisableKeepAlives: true}} // DisableKeepAlives fixes concurrency issue see https://stackoverflow.com/a/75816347
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}
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func newFetcherWith(client HTTPClient) *fetcher {
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return &fetcher{
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httpc: client,
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}
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}
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func newFetcher() *fetcher {
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return newFetcherWith(NewHTTPClient()) // DisableKeepAlives fixes concurrency issue see https://stackoverflow.com/a/75816347
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}
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type apiObject interface {
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ValidateRequest() error
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Validate() error
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URL() (string, error)
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}
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func fetch[T apiObject](ctx context.Context, c HTTPClient, obj T) (T, error) {
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if err := obj.ValidateRequest(); err != nil {
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return *new(T), fmt.Errorf("validating request for %T: %w", obj, err)
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}
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url, err := obj.URL()
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if err != nil {
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return *new(T), fmt.Errorf("getting URL for %T: %w", obj, err)
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}
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req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, http.NoBody)
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if err != nil {
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return *new(T), fmt.Errorf("creating request for %T: %w", obj, err)
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}
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resp, err := c.Do(req)
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if err != nil {
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return *new(T), fmt.Errorf("sending request for %T: %w", obj, err)
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}
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defer resp.Body.Close()
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switch resp.StatusCode {
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case http.StatusOK:
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case http.StatusNotFound:
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return *new(T), &NotFoundError{fmt.Errorf("requesting resource at %s returned status code 404", url)}
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default:
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return *new(T), fmt.Errorf("unexpected status code %d while requesting resource", resp.StatusCode)
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}
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var newObj T
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if err := json.NewDecoder(resp.Body).Decode(&newObj); err != nil {
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return *new(T), fmt.Errorf("decoding %T: %w", obj, err)
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}
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if newObj.Validate() != nil {
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return *new(T), fmt.Errorf("received invalid %T: %w", newObj, newObj.Validate())
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}
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return newObj, nil
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}
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// NotFoundError is an error that is returned when a resource is not found.
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type NotFoundError struct {
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err error
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}
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func (e *NotFoundError) Error() string {
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return fmt.Sprintf("the requested resource was not found: %s", e.err.Error())
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}
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func (e *NotFoundError) Unwrap() error {
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return e.err
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}
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// HTTPClient is an interface for http clients.
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type HTTPClient interface {
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Do(req *http.Request) (*http.Response, error)
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}
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