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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>
103 lines
4.5 KiB
Go
103 lines
4.5 KiB
Go
// Copyright (c) Tailscale Inc & contributors
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// SPDX-License-Identifier: BSD-3-Clause
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// Package eventbus provides an in-process event bus.
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//
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// An event bus connects publishers of typed events with subscribers
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// interested in those events. Typically, there is one global event
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// bus per process.
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//
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// # Usage
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//
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// To send or receive events, first use [Bus.Client] to register with
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// the bus. Clients should register with a human-readable name that
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// identifies the code using the client, to aid in debugging.
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//
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// To publish events, use [Publish] on a Client to get a typed
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// publisher for your event type, then call [Publisher.Publish] as
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// needed. If your event is expensive to construct, you can optionally
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// use [Publisher.ShouldPublish] to skip the work if nobody is
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// listening for the event.
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//
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// To receive events, use [Subscribe] to get a typed subscriber for
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// each event type you're interested in. Receive the events themselves
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// by selecting over all your [Subscriber.Events] channels, as well as
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// [Subscriber.Done] for shutdown notifications.
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//
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// # Concurrency properties
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//
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// The bus serializes all published events across all publishers, and
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// preserves that ordering when delivering to subscribers that are
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// attached to the same Client. In more detail:
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//
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// - An event is published to the bus at some instant between the
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// start and end of the call to [Publisher.Publish].
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// - Two events cannot be published at the same instant, and so are
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// totally ordered by their publication time. Given two events E1
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// and E2, either E1 happens before E2, or E2 happens before E1.
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// - Clients dispatch events to their Subscribers in publication
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// order: if E1 happens before E2, the client always delivers E1
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// before E2.
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// - Clients do not synchronize subscriptions with each other: given
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// clients C1 and C2, both subscribed to events E1 and E2, C1 may
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// deliver both E1 and E2 before C2 delivers E1.
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//
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// Less formally: there is one true timeline of all published events.
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// If you make a Client and subscribe to events, you will receive
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// events one at a time, in the same order as the one true
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// timeline. You will "skip over" events you didn't subscribe to, but
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// your view of the world always moves forward in time, never
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// backwards, and you will observe events in the same order as
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// everyone else.
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//
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// However, you cannot assume that what your client see as "now" is
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// the same as what other clients. They may be further behind you in
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// working through the timeline, or running ahead of you. This means
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// you should be careful about reaching out to another component
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// directly after receiving an event, as its view of the world may not
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// yet (or ever) be exactly consistent with yours.
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//
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// To make your code more testable and understandable, you should try
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// to structure it following the actor model: you have some local
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// state over which you have authority, but your only way to interact
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// with state elsewhere in the program is to receive and process
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// events coming from elsewhere, or to emit events of your own.
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//
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// # Expected subscriber behavior
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//
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// Subscribers are expected to promptly receive their events on
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// [Subscriber.Events]. The bus has a small, fixed amount of internal
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// buffering, meaning that a slow subscriber will eventually cause
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// backpressure and block publication of all further events.
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//
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// In general, you should receive from your subscriber(s) in a loop,
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// and only do fast state updates within that loop. Any heavier work
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// should be offloaded to another goroutine.
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//
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// Causing publishers to block from backpressure is considered a bug
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// in the slow subscriber causing the backpressure, and should be
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// addressed there. Publishers should assume that Publish will not
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// block for extended periods of time, and should not make exceptional
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// effort to behave gracefully if they do get blocked.
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//
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// These blocking semantics are provisional and subject to
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// change. Please speak up if this causes development pain, so that we
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// can adapt the semantics to better suit our needs.
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//
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// # Debugging facilities
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//
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// The [Debugger], obtained through [Bus.Debugger], provides
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// introspection facilities to monitor events flowing through the bus,
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// and inspect publisher and subscriber state.
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//
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// Additionally, a debug command exists for monitoring the eventbus:
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//
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// tailscale debug daemon-bus-events
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//
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// # Testing facilities
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//
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// Helpers for testing code with the eventbus can be found in:
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//
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// eventbus/eventbustest
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package eventbus
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