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// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "content/browser/field_trial_synchronizer.h"
#include "base/check_op.h"
#include "base/functional/bind.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/field_trial_list_including_low_anonymity.h"
#include "base/strings/strcat.h"
#include "base/threading/thread.h"
#include "components/metrics/persistent_system_profile.h"
#include "components/variations/active_field_trials.h"
#include "components/variations/variations_client.h"
#include "content/common/renderer_variations_configuration.mojom.h"
#include "content/public/browser/browser_context.h"
#include "content/public/browser/browser_task_traits.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/render_process_host.h"
#include "ipc/ipc_channel_proxy.h"
#include "mojo/public/cpp/bindings/associated_remote.h"
namespace content {
namespace {
FieldTrialSynchronizer* g_instance = nullptr;
// Notifies all renderer processes about the |group_name| that is finalized for
// the given field trail (|field_trial_name|). This is called on UI thread.
void NotifyAllRenderersOfFieldTrial(const std::string& field_trial_name,
const std::string& group_name,
bool is_low_anonymity,
bool is_overridden) {
// To iterate over RenderProcessHosts, or to send messages to the hosts, we
// need to be on the UI thread.
DCHECK_CURRENTLY_ON(BrowserThread::UI);
// Low anonymity or overridden field trials must not be written to persistent
// data, otherwise they might end up being logged in metrics.
//
// TODO(crbug.com/40263398): split this out into a separate class that
// registers using |FieldTrialList::AddObserver()| (and so doesn't get told
// about low anonymity trials at all).
if (!is_low_anonymity) {
// Note this in the persistent profile as it will take a while for a new
// "complete" profile to be generated.
metrics::GlobalPersistentSystemProfile::GetInstance()->AddFieldTrial(
field_trial_name,
is_overridden ? base::StrCat({group_name, variations::kOverrideSuffix})
: group_name);
}
for (RenderProcessHost::iterator it(RenderProcessHost::AllHostsIterator());
!it.IsAtEnd(); it.Advance()) {
auto* host = it.GetCurrentValue();
IPC::ChannelProxy* channel = host->GetChannel();
// channel might be null in tests.
if (host->IsInitializedAndNotDead() && channel) {
mojo::AssociatedRemote<mojom::RendererVariationsConfiguration>
renderer_variations_configuration;
channel->GetRemoteAssociatedInterface(&renderer_variations_configuration);
renderer_variations_configuration->SetFieldTrialGroup(field_trial_name,
group_name);
}
}
}
} // namespace
// static
void FieldTrialSynchronizer::CreateInstance() {
// Only 1 instance is allowed per process.
DCHECK(!g_instance);
g_instance = new FieldTrialSynchronizer();
}
FieldTrialSynchronizer::FieldTrialSynchronizer() {
// TODO(crbug.com/40263398): consider whether there is a need to exclude low
// anonymity field trials from non-browser processes (or to plumb through the
// anonymity property for more fine-grained access).
bool success = base::FieldTrialListIncludingLowAnonymity::AddObserver(this);
// Ensure the observer was actually registered.
DCHECK(success);
variations::VariationsIdsProvider::GetInstance()->AddObserver(this);
NotifyAllRenderersOfVariationsHeader();
}
void FieldTrialSynchronizer::OnFieldTrialGroupFinalized(
const base::FieldTrial& trial,
const std::string& group_name) {
if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
NotifyAllRenderersOfFieldTrial(trial.trial_name(), group_name,
trial.is_low_anonymity(),
trial.IsOverridden());
} else {
// Note that in some tests, `trial` may not be alive when the posted task is
// called.
GetUIThreadTaskRunner({})->PostTask(
FROM_HERE,
base::BindOnce(&NotifyAllRenderersOfFieldTrial, trial.trial_name(),
group_name, trial.is_low_anonymity(),
trial.IsOverridden()));
}
}
// static
void FieldTrialSynchronizer::NotifyAllRenderersOfVariationsHeader() {
// To iterate over RenderProcessHosts, or to send messages to the hosts, we
// need to be on the UI thread.
DCHECK_CURRENTLY_ON(BrowserThread::UI);
for (RenderProcessHost::iterator it(RenderProcessHost::AllHostsIterator());
!it.IsAtEnd(); it.Advance()) {
UpdateRendererVariationsHeader(it.GetCurrentValue());
}
}
// static
void FieldTrialSynchronizer::UpdateRendererVariationsHeader(
RenderProcessHost* host) {
if (!host->IsInitializedAndNotDead())
return;
IPC::ChannelProxy* channel = host->GetChannel();
// |channel| might be null in tests.
if (!channel)
return;
variations::VariationsClient* client =
host->GetBrowserContext()->GetVariationsClient();
// |client| might be null in tests.
if (!client || client->IsOffTheRecord())
return;
mojo::AssociatedRemote<mojom::RendererVariationsConfiguration>
renderer_variations_configuration;
channel->GetRemoteAssociatedInterface(&renderer_variations_configuration);
renderer_variations_configuration->SetVariationsHeaders(
client->GetVariationsHeaders());
}
void FieldTrialSynchronizer::VariationIdsHeaderUpdated() {
// PostTask to avoid recursive lock.
GetUIThreadTaskRunner({})->PostTask(
FROM_HERE,
base::BindOnce(
&FieldTrialSynchronizer::NotifyAllRenderersOfVariationsHeader));
}
FieldTrialSynchronizer::~FieldTrialSynchronizer() {
NOTREACHED();
}
} // namespace content
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