Repeatedly probe the litepages service to keep a hot connection

Bug: 971918
Change-Id: Icb952b211e066f7c70f283f6156ed4e279b4013b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1738676Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Christian Dullweber <dullweber@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688551}

chrome/browser/previews/previews_lite_page_decider.cc

@@ -190,8 +190,9 @@ PreviewsLitePageDecider::PreviewsLitePageDecider(
             "Requests a small resource to test network connectivity to a "
             "Google domain."
           trigger:
-            "Requested when Lite mode and Previews are enabled on startup and "
-            "on every network change."
+            "Requested when Lite mode and Previews are enabled at any of the "
+            "following events: on startup, on every network change, and every "
+            "30 seconds (experiment configurable) to maintain a hot connection."
           data: "None."
           destination: GOOGLE_OWNED_SERVICE
         }
@@ -218,7 +219,9 @@ PreviewsLitePageDecider::PreviewsLitePageDecider(
       retry_policy, timeout_policy, traffic_annotation,
       10 /* max_cache_entries */,
       base::TimeDelta::FromHours(24) /* revalidate_cache_after */);
-  litepages_service_prober_->SendNowIfInactive(
+  // Note: probing will only occur when |ShouldSendNextProbe| return true.
+  litepages_service_prober_->RepeatedlyProbe(
+      previews::params::LitePageRedirectPreviewProbeInterval(),
       true /* send_only_in_foreground */);
 }
 
@@ -485,7 +488,9 @@ bool PreviewsLitePageDecider::ShouldSendNextProbe() {
   return data_reduction_proxy::DataReductionProxySettings::
              IsDataSaverEnabledByUser(pref_service_) &&
          previews::params::ArePreviewsAllowed() &&
-         previews::params::IsLitePageServerPreviewsEnabled();
+         previews::params::IsLitePageServerPreviewsEnabled() &&
+         // Only probe if we rely on it for triggering.
+         previews::params::LitePageRedirectOnlyTriggerOnSuccessfulProbe();
 }
 
 bool PreviewsLitePageDecider::IsResponseSuccess(

components/previews/core/previews_experiments.cc

@@ -239,6 +239,11 @@ base::TimeDelta LitePageRedirectPreviewPresolveInterval() {
       features::kLitePageServerPreviews, "preresolve_interval_in_seconds", 60));
 }
 
+base::TimeDelta LitePageRedirectPreviewProbeInterval() {
+  return base::TimeDelta::FromSeconds(base::GetFieldTrialParamByFeatureAsInt(
+      features::kLitePageServerPreviews, "probe_interval_in_seconds", 30));
+}
+
 net::EffectiveConnectionType GetECTThresholdForPreview(
     previews::PreviewsType type) {
   switch (type) {

components/previews/core/previews_experiments.h

@@ -145,6 +145,9 @@ GURL LitePageRedirectProbeURL();
 // The duration in between preresolving the lite page redirect server.
 base::TimeDelta LitePageRedirectPreviewPresolveInterval();
 
+// The duration in between probes to the lite page redirect server.
+base::TimeDelta LitePageRedirectPreviewProbeInterval();
+
 // The maximum number of seconds to loadshed the Previews server for.
 int PreviewServerLoadshedMaxSeconds();
 

tools/traffic_annotation/summary/annotations.xml

@@ -200,7 +200,7 @@ Refer to README.md for content description and update process.
  <item id="ppapi_download_request" hash_code="135967426" type="0" content_hash_code="110461402" os_list="linux,windows" file_path="chrome/browser/safe_browsing/download_protection/ppapi_download_request.cc"/>
  <item id="prefetch_download" hash_code="44583172" type="0" content_hash_code="21424542" os_list="linux,windows" file_path="components/offline_pages/core/prefetch/prefetch_downloader_impl.cc"/>
  <item id="prefetch_visuals" hash_code="91068704" type="0" content_hash_code="90439946" os_list="linux,windows" file_path="components/offline_pages/core/prefetch/visuals_fetch_by_url.cc"/>
- <item id="previews_litepage_prober" hash_code="33813109" type="0" content_hash_code="123476142" os_list="linux,windows" file_path="chrome/browser/previews/previews_lite_page_decider.cc"/>
+ <item id="previews_litepage_prober" hash_code="33813109" type="0" content_hash_code="52572789" os_list="linux,windows" file_path="chrome/browser/previews/previews_lite_page_decider.cc"/>
  <item id="previews_prober" hash_code="41010697" type="0" deprecated="2019-07-24" content_hash_code="51581107" file_path=""/>
  <item id="printer_job_handler" hash_code="67638271" type="1" second_id="111712433" content_hash_code="75712693" os_list="linux,windows" semantics_fields="2,3,4" file_path="chrome/service/cloud_print/printer_job_handler.cc"/>
  <item id="privet_http_impl" hash_code="71251498" type="0" content_hash_code="107348604" os_list="linux,windows" file_path="chrome/browser/printing/cloud_print/privet_http_impl.cc"/>