Mirrors the same refactor previously applied to SubscriberFunc:
- Publisher[T]: a thin user-facing facade. Holds a pointer to a
non-generic publisherCore and exposes Publish/Close/ShouldPublish.
- publisherCore: a non-generic struct that owns the *Client back-
pointer, stop flag, and cached reflect.Type. It implements the
package-private publisher interface (publishType, Close).
The bus's per-Client publisher set is set.Set[publisher] keyed
on this single non-generic type.
The publisher interface only exists to support diagnostic
introspection (Debugger.PublishTypes returning the list of types a
client publishes). Previously, satisfying that diagnostic-only
interface forced *Publisher[T] to be the implementor and cost a
per-T itab, generic dictionary, and equality function on every
event type ever passed through Publish[T]. Moving the
implementation to a non-generic core lets the diagnostic surface
work unchanged while charging zero per-T cost for the
diagnostic-driven generic interface.
Publisher[T].Publish is also slimmed: the channel/select/stopFlag
loop is now a non-generic publish() helper that takes the value as
'any'. The per-T body is reduced to forwarding the boxed value to
the helper.
Measured impact (util/eventbus/sizetest):
total per-flow binary cost:
linux/amd64: 2252.8 B/flow -> 1900.5 B/flow (-352.3 B / -15.6%)
linux/arm64: 2228.2 B/flow -> 1835.0 B/flow (-393.2 B / -17.6%)
Publisher per-receiver attribution:
linux/amd64: 635.2 B/flow -> 369.6 B/flow (-265.6 B / -41.8%)
linux/arm64: 751.7 B/flow -> 373.2 B/flow (-378.5 B / -50.4%)
Cumulative reduction from the original baseline (5167ff412):
linux/amd64: 3096.6 B/flow -> 1900.5 B/flow (-1196.1 B / -38.6%)
linux/arm64: 3145.7 B/flow -> 1835.0 B/flow (-1310.7 B / -41.7%)
Dropped per-T symbols (200-flow eventbus binary):
- .dict.Publisher[T] was 14,400 B (72 B/T)
- type:.eq.Publisher[T] was 11,832 B (58 B/T)
- go:itab.*Publisher[T],publisher was 8,000 B (40 B/T)
- (*Publisher[T]).Close shape stencils collapsed to 1
Behavior is unchanged: BenchmarkBasicThroughput is within noise
(2018 -> 2038 ns/op at -benchtime=2s) and all eventbus tests pass.
Updates #12614
Change-Id: I61979c2bf95d2a711c2321e6e0b4b7d15980e9f5
Signed-off-by: James Tucker <james@tailscale.com>
This file was never truly necessary and has never actually been used in
the history of Tailscale's open source releases.
A Brief History of AUTHORS files
---
The AUTHORS file was a pattern developed at Google, originally for
Chromium, then adopted by Go and a bunch of other projects. The problem
was that Chromium originally had a copyright line only recognizing
Google as the copyright holder. Because Google (and most open source
projects) do not require copyright assignemnt for contributions, each
contributor maintains their copyright. Some large corporate contributors
then tried to add their own name to the copyright line in the LICENSE
file or in file headers. This quickly becomes unwieldy, and puts a
tremendous burden on anyone building on top of Chromium, since the
license requires that they keep all copyright lines intact.
The compromise was to create an AUTHORS file that would list all of the
copyright holders. The LICENSE file and source file headers would then
include that list by reference, listing the copyright holder as "The
Chromium Authors".
This also become cumbersome to simply keep the file up to date with a
high rate of new contributors. Plus it's not always obvious who the
copyright holder is. Sometimes it is the individual making the
contribution, but many times it may be their employer. There is no way
for the proejct maintainer to know.
Eventually, Google changed their policy to no longer recommend trying to
keep the AUTHORS file up to date proactively, and instead to only add to
it when requested: https://opensource.google/docs/releasing/authors.
They are also clear that:
> Adding contributors to the AUTHORS file is entirely within the
> project's discretion and has no implications for copyright ownership.
It was primarily added to appease a small number of large contributors
that insisted that they be recognized as copyright holders (which was
entirely their right to do). But it's not truly necessary, and not even
the most accurate way of identifying contributors and/or copyright
holders.
In practice, we've never added anyone to our AUTHORS file. It only lists
Tailscale, so it's not really serving any purpose. It also causes
confusion because Tailscalars put the "Tailscale Inc & AUTHORS" header
in other open source repos which don't actually have an AUTHORS file, so
it's ambiguous what that means.
Instead, we just acknowledge that the contributors to Tailscale (whoever
they are) are copyright holders for their individual contributions. We
also have the benefit of using the DCO (developercertificate.org) which
provides some additional certification of their right to make the
contribution.
The source file changes were purely mechanical with:
git ls-files | xargs sed -i -e 's/\(Tailscale Inc &\) AUTHORS/\1 contributors/g'
Updates #cleanup
Change-Id: Ia101a4a3005adb9118051b3416f5a64a4a45987d
Signed-off-by: Will Norris <will@tailscale.com>
eventbus.Publish() calls newPublisher(), which in turn invokes (*Client).addPublisher().
That method adds the new publisher to c.pub, so we don’t need to add it again in eventbus.Publish.
Updates #cleanup
Signed-off-by: Nick Khyl <nickk@tailscale.com>
Enables monitoring events as they flow, listing bus clients, and
snapshotting internal queues to troubleshoot stalls.
Updates #15160
Signed-off-by: David Anderson <dave@tailscale.com>
This makes the helpers closer in behavior to cancelable contexts
and taskgroup.Single, and makes the worker code use a more normal
and easier to reason about context.Context for shutdown.
Updates #15160
Signed-off-by: David Anderson <dave@tailscale.com>
The Client carries both publishers and subscribers for a single
actor. This makes the APIs for publish and subscribe look more
similar, and this structure is a better fit for upcoming debug
facilities.
Updates #15160
Signed-off-by: David Anderson <dave@tailscale.com>
James Tucker
Will Norris
Brad Fitzpatrick
Nick Khyl
David Anderson