Historically, the client would downgrade to API v1.24 when failing
to negotiate as this was the API version from before API-version
negotiation was introduced.
Given that those daemons are EOL and those API versions no longer
supported, we should not fall back to an older API version, and
just continue using the latest / current version.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
When manually setting the API version to use, automatic API version
negotiation should no longer be performed. Instead of keeping track
of these options individually, we can mark negotiation to have happend
if either the version was set manually, or if API version negotiation
took place.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
While a manual overridden version shouldn't perform automatic version
negotiation, the "ForceNegotiate" option could still be used to (re)
negotiate a version. This allows a client to be configured with an
initial API version, then triggered to perform API-version negotiation.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Environment-variables are expected to override config / defaults, so
make sure that the DOCKER_API_VERSION env-var always takes priority.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Add WithAPIVersion and WithAPIVersionFromEnv to be more clear on
the intent, and to align with other related options and fields.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The API does not produce these as a response; the fields in the Ping
struct, including the Swarm status are propagated from headers returned
by the /_ping endpoint.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
The Ping function first tries to do a HEAD request, but the parsePingResponse
was written with the assumption that a Body could be present in the response
that may include errors returned by the API server.
HEAD responses don't include a body, so there's no response to handle, and
no errors to return by the API, other than a HTTP status code.
This patch:
- Rewrites `parsePingResponse` to a `newPingResponse`, removing the error-
handling for the response-body. It's also simplified, because a non-nil
response is guaranteed to have a non-nil Header (but it may not have
any of the headers set that are used for the Ping).
- Rewrites the `Client.Ping` to only return a Ping-response from the HEAD
request if no error was returned (i.e., we connected with the API) and
a successful status-code, otherwise it will fallback to a GET request,
which allows (for non "OK" (200) status-codes) returning errors from
the daemon (for example, if the daemon is in an unhealthy state).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
It was implemented as a method on Client, but the receiver was not used;
make it a regular function to prevent passing around the Client where
not needed.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
These comments were added to enforce using the correct import path for
our packages ("github.com/docker/docker", not "github.com/moby/moby").
However, when working in go module mode (not GOPATH / vendor), they have
no effect, so their impact is limited.
Remove these imports in preparation of migrating our code to become an
actual go module.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
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>
Go automatically canonicalises HTTP headers, meaning the string `API-Version` passed as a header has always been returned as `Api-Version`. Similarly, `OSType` is returned as `Ostype`.
This commit updates the documentation to reflect this behaviour and modifies the codebase to ensure that input strings are aligned with their canonical output values.
Signed-off-by: maggie44 <64841595+maggie44@users.noreply.github.com>
NegotiateAPIVersion was ignoring errors returned by Ping. The intent here
was to handle API responses from a daemon that may be in an unhealthy state,
however this case is already handled by Ping itself.
Ping only returns an error when either failing to connect to the API (daemon
not running or permissions errors), or when failing to parse the API response.
Neither of those should be ignored in this code, or considered a successful
"ping", so update the code to return
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Attach the context to the request while we're creating it, instead of
creating the context first, and adding the context later.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Re-use the request, and change the method to GET instead of building
a new request "from scratch".
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
When we see an `ECONNREFUSED` (or equivalent) from an attempted `HEAD` on the
`/_ping` endpoint there is no point in trying again with `GET` since the server
is not responding/available at all.
Once vendored into the cli this will partially mitigate https://github.com/docker/cli/issues/1739
("Docker commands take 1 minute to timeout if context endpoint is unreachable")
by cutting the effective timeout in half.
Signed-off-by: Ian Campbell <ijc@docker.com>
Unlike a plain `net/http/client.Do()`, requests made through client/request
use the `sendRequest` function, which parses the server response, and may
convert non-transport errors into errors (through `cli.checkResponseErr()`).
This means that we cannot assume that no reader was opened if an error is
returned.
This patch changes various locations where `ensureReaderClosed` was only
called in the non-error situation, and uses a `defer` to make sure it's
always called.
`ensureReaderClosed` itself already checks if the response's body was set,
so in situations where the error was due to a transport error, calling
`ensureReaderClosed` should be a no-op.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Monitoring systems and load balancers are usually configured to use HEAD
requests for health monitoring. The /_ping endpoint currently does not
support this type of request, which means that those systems have fallback
to GET requests.
This patch adds support for HEAD requests on the /_ping endpoint.
Although optional, this patch also returns `Content-Type` and `Content-Length`
headers in case of a HEAD request; Refering to RFC 7231, section 4.3.2:
The HEAD method is identical to GET except that the server MUST NOT
send a message body in the response (i.e., the response terminates at
the end of the header section). The server SHOULD send the same
header fields in response to a HEAD request as it would have sent if
the request had been a GET, except that the payload header fields
(Section 3.3) MAY be omitted. This method can be used for obtaining
metadata about the selected representation without transferring the
representation data and is often used for testing hypertext links for
validity, accessibility, and recent modification.
A payload within a HEAD request message has no defined semantics;
sending a payload body on a HEAD request might cause some existing
implementations to reject the request.
The response to a HEAD request is cacheable; a cache MAY use it to
satisfy subsequent HEAD requests unless otherwise indicated by the
Cache-Control header field (Section 5.2 of [RFC7234]). A HEAD
response might also have an effect on previously cached responses to
GET; see Section 4.3.5 of [RFC7234].
With this patch applied, either `GET` or `HEAD` requests work; the only
difference is that the body is empty in case of a `HEAD` request;
curl -i --unix-socket /var/run/docker.sock http://localhost/_ping
HTTP/1.1 200 OK
Api-Version: 1.40
Cache-Control: no-cache, no-store, must-revalidate
Docker-Experimental: false
Ostype: linux
Pragma: no-cache
Server: Docker/dev (linux)
Date: Mon, 14 Jan 2019 12:35:16 GMT
Content-Length: 2
Content-Type: text/plain; charset=utf-8
OK
curl --head -i --unix-socket /var/run/docker.sock http://localhost/_ping
HTTP/1.1 200 OK
Api-Version: 1.40
Cache-Control: no-cache, no-store, must-revalidate
Content-Length: 0
Content-Type: text/plain; charset=utf-8
Docker-Experimental: false
Ostype: linux
Pragma: no-cache
Server: Docker/dev (linux)
Date: Mon, 14 Jan 2019 12:34:15 GMT
The client is also updated to use `HEAD` by default, but fallback to `GET`
if the daemon does not support this method.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
Since Go 1.7, context is a standard package. Since Go 1.9, everything
that is provided by "x/net/context" is a couple of type aliases to
types in "context".
Many vendored packages still use x/net/context, so vendor entry remains
for now.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
In some cases a server may return an error on the ping response but
still provide version details. The client should use these values when
available.
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>
