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Michael SnowdenandGitHub
44d5f69cfb
<!-- Describe what has changed in this PR --> **What changed?** I added `quotas.DelayedRateLimiter`, which adds a delay before an input `quotas.RateLimiter` actually takes effect. I also added some utilities to make its implementation easier. The delayed rate limiter depends on the new rate limiter delegator and no-op rate limiter structs. <!-- Tell your future self why have you made these changes --> **Why?** In some cases in the history service, we want to delay rate limiters for a short period after startup. <!-- How have you verified this change? Tested locally? Added a unit test? Checked in staging env? --> **How did you test it?** There is 100% test coverage for the new code. <!-- Assuming the worst case, what can be broken when deploying this change to production? --> **Potential risks** None. These are just additions. <!-- Is this PR a hotfix candidate or require that a notification be sent to the broader community? (Yes/No) --> **Is hotfix candidate?** No.
72 lines
3.0 KiB
Go
72 lines
3.0 KiB
Go
// The MIT License
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//
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// Copyright (c) 2020 Temporal Technologies Inc. All rights reserved.
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//
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// Copyright (c) 2020 Uber Technologies, Inc.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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package quotas
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import (
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"context"
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"sync/atomic"
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"time"
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)
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// RequestRateLimiterDelegator is a request rate limiter that delegates to another rate limiter. The delegate can be
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// changed at runtime by calling SetRateLimiter. This rate limiter is useful for cases where you want to substitute one
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// rate limiter implementation for another at runtime. All methods of this type are thread-safe.
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type RequestRateLimiterDelegator struct {
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// delegate is an atomic.Value so that it can be safely read from and written to concurrently. It stores the rate
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// limiter that this rate limiter delegates to as a monomorphicRequestRateLimiter.
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delegate atomic.Value
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}
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// monomorphicRequestRateLimiter is a workaround for the fact that the value stored in an atomic.Value must always be
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// the same type, but we want to allow the rate limiter delegate to be any type that implements the RequestRateLimiter
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// interface.
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type monomorphicRequestRateLimiter struct {
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RequestRateLimiter
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}
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// SetRateLimiter sets the rate limiter to delegate to.
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func (d *RequestRateLimiterDelegator) SetRateLimiter(rl RequestRateLimiter) {
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d.delegate.Store(monomorphicRequestRateLimiter{rl})
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}
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// loadDelegate returns the rate limiter that this rate limiter delegates to.
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func (d *RequestRateLimiterDelegator) loadDelegate() RequestRateLimiter {
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return d.delegate.Load().(RequestRateLimiter)
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}
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// The following methods just delegate to the underlying rate limiter.
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func (d *RequestRateLimiterDelegator) Allow(now time.Time, request Request) bool {
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return d.loadDelegate().Allow(now, request)
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}
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func (d *RequestRateLimiterDelegator) Reserve(now time.Time, request Request) Reservation {
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return d.loadDelegate().Reserve(now, request)
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}
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func (d *RequestRateLimiterDelegator) Wait(ctx context.Context, request Request) error {
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return d.loadDelegate().Wait(ctx, request)
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}
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