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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // FieldTrial is a class for handling details of statistical experiments | 5 // FieldTrial is a class for handling details of statistical experiments |
6 // performed by actual users in the field (i.e., in a shipped or beta product). | 6 // performed by actual users in the field (i.e., in a shipped or beta product). |
7 // All code is called exclusively on the UI thread currently. | 7 // All code is called exclusively on the UI thread currently. |
8 // | 8 // |
9 // The simplest example is an experiment to see whether one of two options | 9 // The simplest example is an experiment to see whether one of two options |
10 // produces "better" results across our user population. In that scenario, UMA | 10 // produces "better" results across our user population. In that scenario, UMA |
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62 #include <set> | 62 #include <set> |
63 #include <string> | 63 #include <string> |
64 #include <vector> | 64 #include <vector> |
65 | 65 |
66 #include "base/base_export.h" | 66 #include "base/base_export.h" |
67 #include "base/command_line.h" | 67 #include "base/command_line.h" |
68 #include "base/gtest_prod_util.h" | 68 #include "base/gtest_prod_util.h" |
69 #include "base/macros.h" | 69 #include "base/macros.h" |
70 #include "base/memory/ref_counted.h" | 70 #include "base/memory/ref_counted.h" |
71 #include "base/memory/shared_memory.h" | 71 #include "base/memory/shared_memory.h" |
72 #include "base/metrics/persistent_memory_allocator.h" | |
72 #include "base/observer_list_threadsafe.h" | 73 #include "base/observer_list_threadsafe.h" |
73 #include "base/strings/string_piece.h" | 74 #include "base/strings/string_piece.h" |
74 #include "base/synchronization/lock.h" | 75 #include "base/synchronization/lock.h" |
75 #include "base/time/time.h" | 76 #include "base/time/time.h" |
76 | 77 |
77 namespace base { | 78 namespace base { |
78 | 79 |
79 class FieldTrialList; | 80 class FieldTrialList; |
80 | 81 |
81 class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> { | 82 class BASE_EXPORT FieldTrial : public RefCounted<FieldTrial> { |
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317 | 318 |
318 DISALLOW_COPY_AND_ASSIGN(FieldTrial); | 319 DISALLOW_COPY_AND_ASSIGN(FieldTrial); |
319 }; | 320 }; |
320 | 321 |
321 //------------------------------------------------------------------------------ | 322 //------------------------------------------------------------------------------ |
322 // Class with a list of all active field trials. A trial is active if it has | 323 // Class with a list of all active field trials. A trial is active if it has |
323 // been registered, which includes evaluating its state based on its probaility. | 324 // been registered, which includes evaluating its state based on its probaility. |
324 // Only one instance of this class exists. | 325 // Only one instance of this class exists. |
325 class BASE_EXPORT FieldTrialList { | 326 class BASE_EXPORT FieldTrialList { |
326 public: | 327 public: |
328 // Allocator used instantiate field trial in child processes. | |
329 static base::SharedPersistentMemoryAllocator* field_trial_allocator; | |
bcwhite
2016/10/13 14:28:02
I don't suppose there is a more generic place to h
lawrencewu
2016/10/14 04:54:10
While that would be nice, I'm reluctant to do that
bcwhite
2016/10/14 13:56:56
That's fine. Add a comment saying that such _coul
lawrencewu
2016/10/19 16:21:28
Done.
| |
330 | |
327 // Year that is guaranteed to not be expired when instantiating a field trial | 331 // Year that is guaranteed to not be expired when instantiating a field trial |
328 // via |FactoryGetFieldTrial()|. Set to two years from the build date. | 332 // via |FactoryGetFieldTrial()|. Set to two years from the build date. |
329 static int kNoExpirationYear; | 333 static int kNoExpirationYear; |
330 | 334 |
331 // Observer is notified when a FieldTrial's group is selected. | 335 // Observer is notified when a FieldTrial's group is selected. |
332 class BASE_EXPORT Observer { | 336 class BASE_EXPORT Observer { |
333 public: | 337 public: |
334 // Notify observers when FieldTrials's group is selected. | 338 // Notify observers when FieldTrials's group is selected. |
335 virtual void OnFieldTrialGroupFinalized(const std::string& trial_name, | 339 virtual void OnFieldTrialGroupFinalized(const std::string& trial_name, |
336 const std::string& group_name) = 0; | 340 const std::string& group_name) = 0; |
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472 // If using shared memory to pass around the list of field trials, then | 476 // If using shared memory to pass around the list of field trials, then |
473 // expects |field_trial_handle_switch| command line argument to | 477 // expects |field_trial_handle_switch| command line argument to |
474 // contain the shared memory handle. | 478 // contain the shared memory handle. |
475 // If not, then create the trials as before (using the kForceFieldTrials | 479 // If not, then create the trials as before (using the kForceFieldTrials |
476 // switch). Needs the |field_trial_handle_switch| argument to be passed in | 480 // switch). Needs the |field_trial_handle_switch| argument to be passed in |
477 // since base/ can't depend on content/. | 481 // since base/ can't depend on content/. |
478 static void CreateTrialsFromCommandLine( | 482 static void CreateTrialsFromCommandLine( |
479 const base::CommandLine& cmd_line, | 483 const base::CommandLine& cmd_line, |
480 const char* field_trial_handle_switch); | 484 const char* field_trial_handle_switch); |
481 | 485 |
486 // Expects a mapped piece of shared memory |shm| that was created from the | |
487 // browser process's field_trial_allocator and shared via the command line. | |
488 // This function recreates the allocator, iterates through all the field | |
489 // trials in it, and creates them via CreateFieldTrial(). | |
490 static void CreateTrialsFromSharedMemory( | |
491 std::unique_ptr<base::SharedMemory> shm); | |
Alexei Svitkine (slow)
2016/10/12 20:41:00
If you're only calling this from the .cc file, it
lawrencewu
2016/10/14 04:54:09
It needs to reference regstration_ when creating t
| |
492 | |
482 // Adds a switch to the command line containing the field trial state as a | 493 // Adds a switch to the command line containing the field trial state as a |
483 // string (if not using shared memory to share field trial state), or the | 494 // string (if not using shared memory to share field trial state), or the |
484 // shared memory handle + length. | 495 // shared memory handle + length. |
485 // Needs the |field_trial_handle_switch| argument to be passed in since base/ | 496 // Needs the |field_trial_handle_switch| argument to be passed in since base/ |
486 // can't depend on content/. | 497 // can't depend on content/. |
487 static std::unique_ptr<base::SharedMemory> CopyFieldTrialStateToFlags( | 498 static void CopyFieldTrialStateToFlags(const char* field_trial_handle_switch, |
488 const char* field_trial_handle_switch, | 499 base::CommandLine* cmd_line); |
489 base::CommandLine* cmd_line); | |
490 | 500 |
491 // Create a FieldTrial with the given |name| and using 100% probability for | 501 // Create a FieldTrial with the given |name| and using 100% probability for |
492 // the FieldTrial, force FieldTrial to have the same group string as | 502 // the FieldTrial, force FieldTrial to have the same group string as |
493 // |group_name|. This is commonly used in a non-browser process, to carry | 503 // |group_name|. This is commonly used in a non-browser process, to carry |
494 // randomly selected state in a browser process into this non-browser process. | 504 // randomly selected state in a browser process into this non-browser process. |
495 // It returns NULL if there is a FieldTrial that is already registered with | 505 // It returns NULL if there is a FieldTrial that is already registered with |
496 // the same |name| but has different finalized group string (|group_name|). | 506 // the same |name| but has different finalized group string (|group_name|). |
497 static FieldTrial* CreateFieldTrial(const std::string& name, | 507 static FieldTrial* CreateFieldTrial(const std::string& name, |
498 const std::string& group_name); | 508 const std::string& group_name); |
499 | 509 |
500 // Add an observer to be notified when a field trial is irrevocably committed | 510 // Add an observer to be notified when a field trial is irrevocably committed |
501 // to being part of some specific field_group (and hence the group_name is | 511 // to being part of some specific field_group (and hence the group_name is |
502 // also finalized for that field_trial). | 512 // also finalized for that field_trial). |
503 static void AddObserver(Observer* observer); | 513 static void AddObserver(Observer* observer); |
504 | 514 |
505 // Remove an observer. | 515 // Remove an observer. |
506 static void RemoveObserver(Observer* observer); | 516 static void RemoveObserver(Observer* observer); |
507 | 517 |
508 // Notify all observers that a group has been finalized for |field_trial|. | 518 // Notify all observers that a group has been finalized for |field_trial|. |
509 static void NotifyFieldTrialGroupSelection(FieldTrial* field_trial); | 519 static void NotifyFieldTrialGroupSelection(FieldTrial* field_trial); |
510 | 520 |
521 // Called in NotifyFieldTrialGroupSelection(). Adds a new entry to | |
522 // field_trial_allocator containing the newly-selected field trial and group. | |
523 static void UpdateFieldTrialAllocator(FieldTrial* field_trial); | |
bcwhite
2016/10/13 14:28:02
Your comment says "adds" but the name says "update
lawrencewu
2016/10/14 04:54:09
It is kind of an "update the list of field trials
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524 | |
511 // Return the number of active field trials. | 525 // Return the number of active field trials. |
512 static size_t GetFieldTrialCount(); | 526 static size_t GetFieldTrialCount(); |
513 | 527 |
514 private: | 528 private: |
515 // A map from FieldTrial names to the actual instances. | 529 // A map from FieldTrial names to the actual instances. |
516 typedef std::map<std::string, FieldTrial*> RegistrationMap; | 530 typedef std::map<std::string, FieldTrial*> RegistrationMap; |
517 | 531 |
518 // If one-time randomization is enabled, returns a weak pointer to the | 532 // If one-time randomization is enabled, returns a weak pointer to the |
519 // corresponding EntropyProvider. Otherwise, returns NULL. | 533 // corresponding EntropyProvider. Otherwise, returns NULL. |
520 static const FieldTrial::EntropyProvider* | 534 static const FieldTrial::EntropyProvider* |
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548 | 562 |
549 // List of observers to be notified when a group is selected for a FieldTrial. | 563 // List of observers to be notified when a group is selected for a FieldTrial. |
550 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; | 564 scoped_refptr<ObserverListThreadSafe<Observer> > observer_list_; |
551 | 565 |
552 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); | 566 DISALLOW_COPY_AND_ASSIGN(FieldTrialList); |
553 }; | 567 }; |
554 | 568 |
555 } // namespace base | 569 } // namespace base |
556 | 570 |
557 #endif // BASE_METRICS_FIELD_TRIAL_H_ | 571 #endif // BASE_METRICS_FIELD_TRIAL_H_ |
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