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.
Correct port-forward data copying logic so that the server closes its
half of the data stream when socat exits, and the client closes its half
of the data stream when it finishes writing.
Modify the client to wait for both copies (client->server,
server->client) to finish before it unblocks.
Fix race condition in the Kubelet's handling of incoming port forward
streams. Have the client generate a connectionID header to be used to
associate the error and data streams for a single connection, instead of
assuming that streams n and n+1 go together. Attempt to generate a
pseudo connectionID in the server in the event the connectionID header
isn't present (older clients); this is a best-effort approach that only
really works with 1 connection at a time, whereas multiple concurrent
connections will only work reliably with a newer client that is
generating connectionID.
Have poller() send to the channel once, immediately, before the ticker
starts. This way, Poll, PollInfinite, and WaitFor will check the
condition immediately, instead of waiting for the poller's interval to
elapse once before doing the initial condition check.
k8s-merge-robot