http2: interface to support pluggable schedulers
This adds an interface to support pluggable schedulers. The interface
is defined in writesched.go. The only type needed by this interface is
FrameWriteRequest, which describes a request to write a frame (this used
to be called frameWriteMsg). The scheduler can be configured with a new
field in http2.Server. Two schedulers are implemented:
1) A random scheduler that is essentially equivalent to the existing
scheduler. This is currently the default scheduler if none is
configured. The implementation is in writesched_random.go.
2) A scheduler that uses H2 weights and priorities. The H2 priority tree
is maintained as a tree of priorityNodes. The next frame is chosen by
walking this tree in topological order, where sibling nodes are ordered
by their bandwidth usage relative to their H2 weight. Two optional
features are added to improve performance -- these are configured with
PriorityWriteSchedulerConfig.
Fixes golang/go#16168
Change-Id: I97ec93e5c58c2efec35455ba2f3c31e849f706af
Reviewed-on: https://go-review.googlesource.com/25366
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
8 files changed
