If a 400 error is returned due to an API version mismatch, no
version and server-identification headers were returned by the API.
All information in these headers is "static", so there is no
reason to omit the information in case of an error being
returned.
This patch updates the version middleware to always
return the headers.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Commit e98e4a7111 implemented API version
negotiation using the `/_ping` endpoint. In that change, URL validation for the
maximum supported API version was removed from the API server (validation for
the _minimum_ version was kept in place).
With this feature, clients that support version negotiation would negotiate the
maximum version supported by the daemon, and downgrade to an older API version
if the client's default API version is not supported.
However, clients that do _not_ support version negotiation can call API versions
that are higher than the maximum supported version. Due to the missing version
check, this is silently ignored, and the daemon's default API version is used.
This is a problem, because the actual API version in use is non-deterministic;
for example, calling `/v9999.9999/version` on a daemon that runs API v1.34 will
use API v1.34, but calling the same URL on an older daemon may use API version
v1.24.
This patch reverts the removal of the API check for maximum supported versions.
The documentation has been updated accordingly
Before this patch is applied, the daemon returns a 200 (success):
$ curl -v --unix-socket /var/run/docker.sock http://localhost/v9999.9999/version
* Trying /var/run/docker.sock...
* Connected to localhost (/Users/sebastiaan/Library/Containers/com.dock) port 80 (#0)
> GET /v9999.9999/version HTTP/1.1
> Host: localhost
> User-Agent: curl/7.54.0
> Accept: */*
>
< HTTP/1.1 200 OK
< Api-Version: 1.32
< Content-Length: 240
< Content-Type: application/json
< Date: Tue, 10 Oct 2017 09:11:29 GMT
< Docker-Experimental: true
< Ostype: linux
< Server: Docker/17.09.0-ce (linux)
<
{"Version":"17.09.0-ce","ApiVersion":"1.32","MinAPIVersion":"1.12","GitCommit":"afdb6d4","GoVersion":"go1.8.3","Os":"linux","Arch":"amd64","KernelVersion":"4.9.49-moby","Experimental":true,"BuildTime":"2017-09-26T22:45:38.000000000+00:00"}
* Connection #0 to host localhost left intact
After this patch is applied, a 400 (Bad Request) is returned:
$ curl -v --unix-socket /var/run/docker.sock http://localhost/v9999.9999/version
* Trying /var/run/docker.sock...
* Connected to localhost (/var/run/docker.sock) port 80 (#0)
> GET /v9999.9999/info HTTP/1.1
> Host: localhost
> User-Agent: curl/7.52.1
> Accept: */*
>
< HTTP/1.1 400 Bad Request
< Content-Type: application/json
< Date: Tue, 10 Oct 2017 08:08:34 GMT
< Content-Length: 89
<
{"message":"client version 9999.9999 is too new. Maximim supported API version is 1.34"}
* Curl_http_done: called premature == 0
* Connection #0 to host localhost left intact
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Use strongly typed errors to set HTTP status codes.
Error interfaces are defined in the api/errors package and errors
returned from controllers are checked against these interfaces.
Errors can be wraeped in a pkg/errors.Causer, as long as somewhere in the
line of causes one of the interfaces is implemented. The special error
interfaces take precedence over Causer, meaning if both Causer and one
of the new error interfaces are implemented, the Causer is not
traversed.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Signed-off-by: Victor Vieux <vieux@docker.com>
update cobra and use Tags
Signed-off-by: Victor Vieux <vieux@docker.com>
allow client to talk to an older server
Signed-off-by: Victor Vieux <vieux@docker.com>
This makes separating middlewares from the core api easier.
As an example, the authorization middleware is moved to
it's own package.
Initialize all static middlewares when the server is created, reducing
allocations every time a route is wrapper with the middlewares.
Signed-off-by: David Calavera <david.calavera@gmail.com>
Moving all strings to the errors package wasn't a good idea after all.
Our custom implementation of Go errors predates everything that's nice
and good about working with errors in Go. Take as an example what we
have to do to get an error message:
```go
func GetErrorMessage(err error) string {
switch err.(type) {
case errcode.Error:
e, _ := err.(errcode.Error)
return e.Message
case errcode.ErrorCode:
ec, _ := err.(errcode.ErrorCode)
return ec.Message()
default:
return err.Error()
}
}
```
This goes against every good practice for Go development. The language already provides a simple, intuitive and standard way to get error messages, that is calling the `Error()` method from an error. Reinventing the error interface is a mistake.
Our custom implementation also makes very hard to reason about errors, another nice thing about Go. I found several (>10) error declarations that we don't use anywhere. This is a clear sign about how little we know about the errors we return. I also found several error usages where the number of arguments was different than the parameters declared in the error, another clear example of how difficult is to reason about errors.
Moreover, our custom implementation didn't really make easier for people to return custom HTTP status code depending on the errors. Again, it's hard to reason about when to set custom codes and how. Take an example what we have to do to extract the message and status code from an error before returning a response from the API:
```go
switch err.(type) {
case errcode.ErrorCode:
daError, _ := err.(errcode.ErrorCode)
statusCode = daError.Descriptor().HTTPStatusCode
errMsg = daError.Message()
case errcode.Error:
// For reference, if you're looking for a particular error
// then you can do something like :
// import ( derr "github.com/docker/docker/errors" )
// if daError.ErrorCode() == derr.ErrorCodeNoSuchContainer { ... }
daError, _ := err.(errcode.Error)
statusCode = daError.ErrorCode().Descriptor().HTTPStatusCode
errMsg = daError.Message
default:
// This part of will be removed once we've
// converted everything over to use the errcode package
// FIXME: this is brittle and should not be necessary.
// If we need to differentiate between different possible error types,
// we should create appropriate error types with clearly defined meaning
errStr := strings.ToLower(err.Error())
for keyword, status := range map[string]int{
"not found": http.StatusNotFound,
"no such": http.StatusNotFound,
"bad parameter": http.StatusBadRequest,
"conflict": http.StatusConflict,
"impossible": http.StatusNotAcceptable,
"wrong login/password": http.StatusUnauthorized,
"hasn't been activated": http.StatusForbidden,
} {
if strings.Contains(errStr, keyword) {
statusCode = status
break
}
}
}
```
You can notice two things in that code:
1. We have to explain how errors work, because our implementation goes against how easy to use Go errors are.
2. At no moment we arrived to remove that `switch` statement that was the original reason to use our custom implementation.
This change removes all our status errors from the errors package and puts them back in their specific contexts.
IT puts the messages back with their contexts. That way, we know right away when errors used and how to generate their messages.
It uses custom interfaces to reason about errors. Errors that need to response with a custom status code MUST implementent this simple interface:
```go
type errorWithStatus interface {
HTTPErrorStatusCode() int
}
```
This interface is very straightforward to implement. It also preserves Go errors real behavior, getting the message is as simple as using the `Error()` method.
I included helper functions to generate errors that use custom status code in `errors/errors.go`.
By doing this, we remove the hard dependency we have eeverywhere to our custom errors package. Yes, you can use it as a helper to generate error, but it's still very easy to generate errors without it.
Please, read this fantastic blog post about errors in Go: http://dave.cheney.net/2014/12/24/inspecting-errors
Signed-off-by: David Calavera <david.calavera@gmail.com>
Daniel Nephin