Files
moby/client/plugin_install.go
Sebastiaan van Stijn 72c91e378d client: remove serverResponse and use http.Response directly
Looking in history to learn why this struct existed, shows that this type
was mostly the result of tech-debt accumulating over time;

- originally ([moby@1aa7f13]) most of the request handling was internal;
  the [`call()` function][1] would make a request, read the `response.Body`,
  and return it as a `[]byte` (or an error if one happened).
- some features needed the statuscode, so [moby@a4bcf7e] added an extra
  output variable to return the `response.StatusCode`.
- some new features required streaming, so [moby@fdd8d4b] changed the
  function to return the `response.Body` as a `io.ReadCloser`, instead
  of a `[]byte`.
- some features needed access to the content-type header, so a new
  `clientRequest` method was introduced in [moby@6b2eeaf] to read the
  `Content-Type` header from `response.Headers` and return it as a string.
- of course, `Content-Type` may not be the only header needed, so [moby@0cdc3b7]
  changed the signature to return `response.Headers` as a whole as a
  `http.Header`
- things became a bit unwieldy now, with the function having four (4) output
  variables, so [moby@126529c] chose to refactor this code, introducing a
  `serverResponse` struct to wrap them all, not realizing that all these
  values were effectively deconstructed from the `url.Response`, so now
  re-assembling them into our own "URL response", only preserving a subset
  of the information available.
- now that we had a custom struct, it was possible to add more information
  to it without changing the signature. When there was a need to know the
  URL of the request that initiated the response, [moby@27ef09a] introduced
  a `reqURL` field to hold the `request.URL` which notably also is available
  in `response.Request.URL`.

In short;

- The original implementation tried to (pre-maturely) abstract the underlying
  response to provide a simplified interface.
- While initially not needed, abstracting caused relevant information from
  the response (and request) to be unavailable to callers.
- As a result, we ended up in a situation where we are deconstructing the
  original `url.Response`, only to re-assemble it into our own, custom struct
  (`serverResponsee`) with only a subset of the information preserved.

This patch removes the `serverResponse` struct, instead returning the
`url.Response` as-is, so that all information is preserved, allowing callers
to use the information they need.

There is one follow-up change to consider; commit [moby@589df17] introduced
a `ensureReaderClosed` utility. Before that commit, the response body would
be closed in a more idiomatic way through a [`defer serverResp.body.Close()`][2].
A later change in [docker/engine-api@5dd6452] added an optimization to that
utility, draining the response to allow connections to be reused. While
skipping that utility (and not draining the response) would not be a critical
issue, it may be easy to overlook that utility, and to close the response
body in the "idiomatic" way, resulting in a possible performance regression.

We need to check if that optimization is still relevant or if later changes
in Go itself already take care of this; we should also look if context
cancellation is handled correctly for these. If it's still relevant, we could

- Wrap the the `url.Response` in a custom struct ("drainCloser") to provide
  a `Close()` function handling the draining and closing; this would re-
  introduce a custom type to be returned, so perhaps not what we want.
- Wrap the `url.Response.Body` in the response returned (so, calling)
  `response.Body.Close()` would call the wrapped closer.
- Change the signature of `Client.sendRequest()` (and related) to return
  a `close()` func to handle this; doing so would more strongly encourage
  callers to close the response body.

[1]: 1aa7f1392d/commands.go (L1008-L1027)
[2]: 589df17a1a/api/client/ps.go (L84-L89)
[moby@1aa7f13]: 1aa7f1392d
[moby@a4bcf7e]: a4bcf7e1ac
[moby@fdd8d4b]: fdd8d4b7d9
[moby@6b2eeaf]: 6b2eeaf896
[moby@0cdc3b7]: 0cdc3b7539
[moby@126529c]: 126529c6d0
[moby@27ef09a]: 27ef09a46f
[moby@589df17]: 589df17a1a
[docker/engine-api@5dd6452]: 5dd6452d4d

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
2025-02-11 13:20:27 +01:00

118 lines
3.4 KiB
Go

package client // import "github.com/docker/docker/client"
import (
"context"
"encoding/json"
"io"
"net/http"
"net/url"
"github.com/distribution/reference"
"github.com/docker/docker/api/types"
"github.com/docker/docker/api/types/registry"
"github.com/docker/docker/errdefs"
"github.com/pkg/errors"
)
// PluginInstall installs a plugin
func (cli *Client) PluginInstall(ctx context.Context, name string, options types.PluginInstallOptions) (rc io.ReadCloser, err error) {
query := url.Values{}
if _, err := reference.ParseNormalizedNamed(options.RemoteRef); err != nil {
return nil, errors.Wrap(err, "invalid remote reference")
}
query.Set("remote", options.RemoteRef)
privileges, err := cli.checkPluginPermissions(ctx, query, options)
if err != nil {
return nil, err
}
// set name for plugin pull, if empty should default to remote reference
query.Set("name", name)
resp, err := cli.tryPluginPull(ctx, query, privileges, options.RegistryAuth)
if err != nil {
return nil, err
}
name = resp.Header.Get("Docker-Plugin-Name")
pr, pw := io.Pipe()
go func() { // todo: the client should probably be designed more around the actual api
_, err := io.Copy(pw, resp.Body)
if err != nil {
_ = pw.CloseWithError(err)
return
}
defer func() {
if err != nil {
delResp, _ := cli.delete(ctx, "/plugins/"+name, nil, nil)
ensureReaderClosed(delResp)
}
}()
if len(options.Args) > 0 {
if err := cli.PluginSet(ctx, name, options.Args); err != nil {
_ = pw.CloseWithError(err)
return
}
}
if options.Disabled {
_ = pw.Close()
return
}
enableErr := cli.PluginEnable(ctx, name, types.PluginEnableOptions{Timeout: 0})
_ = pw.CloseWithError(enableErr)
}()
return pr, nil
}
func (cli *Client) tryPluginPrivileges(ctx context.Context, query url.Values, registryAuth string) (*http.Response, error) {
return cli.get(ctx, "/plugins/privileges", query, http.Header{
registry.AuthHeader: {registryAuth},
})
}
func (cli *Client) tryPluginPull(ctx context.Context, query url.Values, privileges types.PluginPrivileges, registryAuth string) (*http.Response, error) {
return cli.post(ctx, "/plugins/pull", query, privileges, http.Header{
registry.AuthHeader: {registryAuth},
})
}
func (cli *Client) checkPluginPermissions(ctx context.Context, query url.Values, options types.PluginInstallOptions) (types.PluginPrivileges, error) {
resp, err := cli.tryPluginPrivileges(ctx, query, options.RegistryAuth)
if errdefs.IsUnauthorized(err) && options.PrivilegeFunc != nil {
// todo: do inspect before to check existing name before checking privileges
newAuthHeader, privilegeErr := options.PrivilegeFunc(ctx)
if privilegeErr != nil {
ensureReaderClosed(resp)
return nil, privilegeErr
}
options.RegistryAuth = newAuthHeader
resp, err = cli.tryPluginPrivileges(ctx, query, options.RegistryAuth)
}
if err != nil {
ensureReaderClosed(resp)
return nil, err
}
var privileges types.PluginPrivileges
if err := json.NewDecoder(resp.Body).Decode(&privileges); err != nil {
ensureReaderClosed(resp)
return nil, err
}
ensureReaderClosed(resp)
if !options.AcceptAllPermissions && options.AcceptPermissionsFunc != nil && len(privileges) > 0 {
accept, err := options.AcceptPermissionsFunc(ctx, privileges)
if err != nil {
return nil, err
}
if !accept {
return nil, errors.Errorf("permission denied while installing plugin %s", options.RemoteRef)
}
}
return privileges, nil
}