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2d7a3e7ca8
This new name emphasizes that the field trial keys are only allowed within the current scope. We already have test::ScopedFieldTrials that can be used to ensure that the global field trials string itself is isolated. Bug: webrtc:14705 Change-Id: I8b66bbd9c11d97985292c334d2d3496a047074a1 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/284862 Commit-Queue: Emil Lundmark <lndmrk@webrtc.org> Reviewed-by: Harald Alvestrand <hta@webrtc.org> Cr-Commit-Position: refs/heads/main@{#38796}
116 lines
4.5 KiB
C++
116 lines
4.5 KiB
C++
//
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// Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the LICENSE file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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//
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#ifndef SYSTEM_WRAPPERS_INCLUDE_FIELD_TRIAL_H_
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#define SYSTEM_WRAPPERS_INCLUDE_FIELD_TRIAL_H_
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#include <string>
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#include "absl/strings/string_view.h"
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#include "rtc_base/containers/flat_set.h"
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// Field trials allow webrtc clients (such as Chrome) to turn on feature code
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// in binaries out in the field and gather information with that.
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//
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// By default WebRTC provides an implementation of field trials that can be
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// found in system_wrappers/source/field_trial.cc. If clients want to provide
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// a custom version, they will have to:
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//
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// 1. Compile WebRTC defining the preprocessor macro
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// WEBRTC_EXCLUDE_FIELD_TRIAL_DEFAULT (if GN is used this can be achieved
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// by setting the GN arg rtc_exclude_field_trial_default to true).
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// 2. Provide an implementation of:
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// std::string webrtc::field_trial::FindFullName(absl::string_view trial).
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//
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// They are designed to wire up directly to chrome field trials and to speed up
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// developers by reducing the need to wire APIs to control whether a feature is
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// on/off. E.g. to experiment with a new method that could lead to a different
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// trade-off between CPU/bandwidth:
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//
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// 1 - Develop the feature with default behaviour off:
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//
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// if (FieldTrial::FindFullName("WebRTCExperimentMethod2") == "Enabled")
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// method2();
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// else
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// method1();
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//
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// 2 - Once the changes are rolled to chrome, the new code path can be
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// controlled as normal chrome field trials.
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//
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// 3 - Evaluate the new feature and clean the code paths.
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//
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// Notes:
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// - NOT every feature is a candidate to be controlled by this mechanism as
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// it may require negotiation between involved parties (e.g. SDP).
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//
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// TODO(andresp): since chrome --force-fieldtrials does not marks the trial
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// as active it does not get propagated to the renderer process. For now one
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// needs to push a config with start_active:true or run a local finch
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// server.
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//
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// TODO(andresp): find out how to get bots to run tests with trials enabled.
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namespace webrtc {
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namespace field_trial {
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// Returns the group name chosen for the named trial, or the empty string
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// if the trial does not exists.
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//
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// Note: To keep things tidy append all the trial names with WebRTC.
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std::string FindFullName(absl::string_view name);
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// Convenience method, returns true iff FindFullName(name) return a string that
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// starts with "Enabled".
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// TODO(tommi): Make sure all implementations support this.
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inline bool IsEnabled(absl::string_view name) {
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return FindFullName(name).find("Enabled") == 0;
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}
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// Convenience method, returns true iff FindFullName(name) return a string that
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// starts with "Disabled".
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inline bool IsDisabled(absl::string_view name) {
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return FindFullName(name).find("Disabled") == 0;
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}
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// Optionally initialize field trial from a string.
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// This method can be called at most once before any other call into webrtc.
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// E.g. before the peer connection factory is constructed.
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// Note: trials_string must never be destroyed.
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void InitFieldTrialsFromString(const char* trials_string);
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const char* GetFieldTrialString();
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// Validates the given field trial string.
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bool FieldTrialsStringIsValid(absl::string_view trials_string);
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// Merges two field trial strings.
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//
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// If a key (trial) exists twice with conflicting values (groups), the value
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// in 'second' takes precedence.
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// Shall only be called with valid FieldTrial strings.
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std::string MergeFieldTrialsStrings(absl::string_view first,
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absl::string_view second);
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// This helper allows to temporary "register" a field trial within the current
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// scope. This is only useful for tests that use the global field trial string,
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// otherwise you can use `webrtc::FieldTrialsRegistry`.
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//
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// If you want to isolate changes to the global field trial string itself within
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// the current scope you should use `webrtc::test::ScopedFieldTrials`.
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class FieldTrialsAllowedInScopeForTesting {
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public:
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explicit FieldTrialsAllowedInScopeForTesting(flat_set<std::string> keys);
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~FieldTrialsAllowedInScopeForTesting();
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};
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} // namespace field_trial
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} // namespace webrtc
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#endif // SYSTEM_WRAPPERS_INCLUDE_FIELD_TRIAL_H_
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