Not all clients and systems can support SPDY protocols. This commit adds
support for two new websocket protocols, one to handle streaming of pod
logs from a pod, and the other to allow exec to be tunneled over
websocket.
Browser support for chunked encoding is still poor, and web consoles
that wish to show pod logs may need to make compromises to display the
output. The /pods/<name>/log endpoint now supports websocket upgrade to
the 'binary.k8s.io' subprotocol, which sends chunks of logs as binary to
the client. Messages are written as logs are streamed from the container
daemon, so flushing should be unaffected.
Browser support for raw communication over SDPY is not possible, and
some languages lack libraries for it and HTTP/2. The Kubelet supports
upgrade to WebSocket instead of SPDY, and will multiplex STDOUT/IN/ERR
over websockets by prepending each binary message with a single byte
representing the channel (0 for IN, 1 for OUT, and 2 for ERR). Because
framing on WebSockets suffers from head-of-line blocking, clients and
other server code should ensure that no particular stream blocks. An
alternative subprotocol 'base64.channel.k8s.io' base64 encodes the body
and uses '0'-'9' to represent the channel for ease of use in browsers.
kubelet sends up status updates to flip the ready condition of a pod after the
pod is already in the running state. RunRC should wait until the pod condition
is ready to make sure there is no pending status update which may affect the
follow-up performance test.
In many cases clients may wish to view not ready addresses for endpoints
in order to do set membership prior to a pod being ready. For instance,
a pod that uses the service endpoints to connect to other pods under
the same service, but does not want to signal ready before it has
contacted at least a minimal number of other pods.
This is backwards compatible with old servers and clients. There is
an additional cost in size of endpoints before services ramp up, which
will add minor CPU and memory use for services that have a significant
number of pods which have not become ready.
A lot of packages use StringSet, but they don't use anything else from
the util package. Moving StringSet into another package will shrink
their dependency trees significantly.
If stdin is noninteractive, the io.Copy from stdin to remoteStdin will
unblock when it finishes reading from stdin. In this case, make sure to
close remoteStdin so the server knows the client won't be sending any
more data. This ensures that the remote process terminates. For example:
echo foo | kubectl exec -i <pod> -- cat
Without this change, the `cat` process never terminates and `kubectl
exec` hangs.
Fix interactive exec sessions hanging after you type 'exit'.
Add e2e test to cover noninteractive stdin: `echo a | kubectl exec -i <pod>
cat`
Add e2e test to cover psuedo-interactive stdin: `kubectl exec -i <pod> bash`
Prep for sending multiple data frames over multiple streams in remote command
test, which is more likely to find flakes (requires bump of spdystream
once an issue with the frame worker queues not being fully drained when
a goaway frame is received).
Andy Goldstein