Remove stale-while-revalidate from net

net/http/http_cache_transaction.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/http/http_cache_transaction.h"
 
 #include "build/build_config.h"  // For OS_POSIX
 
 #if defined(OS_POSIX)
 #include <unistd.h>
 #endif
 
 #include <algorithm>
 #include <string>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/compiler_specific.h"
-#include "base/format_macros.h"
 #include "base/location.h"
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"  // For HexEncode.
-#include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"  // For LowerCaseEqualsASCII.
-#include "base/strings/stringprintf.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/time/clock.h"
 #include "base/trace_event/trace_event.h"
 #include "base/values.h"

[mmenke, 2017/03/23 21:39:35]

Tiny nit:  Is this still used in this file?  It was added for SWR, don't see any
current usages (Even before this CL, actually)

[scottmg, 2017/03/24 22:46:00]

Done.

 #include "net/base/auth.h"
 #include "net/base/load_flags.h"
 #include "net/base/load_timing_info.h"
 #include "net/base/trace_constants.h"
 #include "net/base/upload_data_stream.h"
 #include "net/cert/cert_status_flags.h"
 #include "net/cert/x509_certificate.h"
 #include "net/disk_cache/disk_cache.h"
 #include "net/http/http_network_session.h"
 #include "net/http/http_request_info.h"
 #include "net/http/http_util.h"
 #include "net/log/net_log_event_type.h"
 #include "net/ssl/ssl_cert_request_info.h"
 #include "net/ssl/ssl_config_service.h"
 
 using base::Time;
 using base::TimeDelta;
 using base::TimeTicks;
 
 namespace net {
 
 using CacheEntryStatus = HttpResponseInfo::CacheEntryStatus;
 
 namespace {
 
-// TODO(ricea): Move this to HttpResponseHeaders once it is standardised.
-static const char kFreshnessHeader[] = "Resource-Freshness";
-
 // From http://tools.ietf.org/html/draft-ietf-httpbis-p6-cache-21#section-6
 //      a "non-error response" is one with a 2xx (Successful) or 3xx
 //      (Redirection) status code.
 bool NonErrorResponse(int status_code) {
   int status_code_range = status_code / 100;
   return status_code_range == 2 || status_code_range == 3;
 }
 
 void RecordNoStoreHeaderHistogram(int load_flags,
                                   const HttpResponseInfo* response) {
   if (load_flags & LOAD_MAIN_FRAME_DEPRECATED) {
     UMA_HISTOGRAM_BOOLEAN(
         "Net.MainFrameNoStore",
         response->headers->HasHeaderValue("cache-control", "no-store"));
   }
 }
 
 enum ExternallyConditionalizedType {
   EXTERNALLY_CONDITIONALIZED_CACHE_REQUIRES_VALIDATION,
   EXTERNALLY_CONDITIONALIZED_CACHE_USABLE,
   EXTERNALLY_CONDITIONALIZED_MISMATCHED_VALIDATORS,
   EXTERNALLY_CONDITIONALIZED_MAX
 };

[mmenke, 2017/03/23 21:39:35]

This enum (And the related histogram) look to have been added as part of the SWR
experiment.

[scottmg, 2017/03/24 22:45:59]

Aha, good catch. Done.

 
 }  // namespace
 
 #define CACHE_STATUS_HISTOGRAMS(type)                                        \
   do {                                                                       \
     UMA_HISTOGRAM_ENUMERATION("HttpCache.Pattern" type, cache_entry_status_, \
                               CacheEntryStatus::ENTRY_MAX);                  \
     if (validation_request) {                                                \
       UMA_HISTOGRAM_ENUMERATION("HttpCache.ValidationCause" type,            \
                                 validation_cause_, VALIDATION_CAUSE_MAX);    \
@@ skipping 2000 matching lines @@
     next_state_ = STATE_NONE;
     return ERR_CACHE_MISS;
   }
 
   // We don't have the whole resource.
   if (truncated_) {
     next_state_ = STATE_NONE;
     return ERR_CACHE_MISS;
   }
 
-  if (RequiresValidation() != VALIDATION_NONE) {
+  if (RequiresValidation()) {
     next_state_ = STATE_NONE;
     return ERR_CACHE_MISS;
   }
 
   if (request_->method == "HEAD")
     FixHeadersForHead();
 
   if (entry_->disk_entry->GetDataSize(kMetadataIndex))
     next_state_ = STATE_CACHE_READ_METADATA;
   else
     next_state_ = STATE_NONE;
 
   return OK;
 }
 
 int HttpCache::Transaction::BeginCacheValidation() {
   DCHECK_EQ(mode_, READ_WRITE);
 
-  ValidationType required_validation = RequiresValidation();
-
-  bool skip_validation = (required_validation == VALIDATION_NONE);
-
-  if ((effective_load_flags_ & LOAD_SUPPORT_ASYNC_REVALIDATION) &&
-      required_validation == VALIDATION_ASYNCHRONOUS) {
-    DCHECK_EQ(request_->method, "GET");
-    skip_validation = true;
-    response_.async_revalidation_required = true;
-  }
+  bool skip_validation = !RequiresValidation();
 
   if (request_->method == "HEAD" &&
       (truncated_ || response_.headers->response_code() == 206)) {
     DCHECK(!partial_);
     if (skip_validation)
       return SetupEntryForRead();
 
     // Bail out!
     next_state_ = STATE_SEND_REQUEST;
     mode_ = NONE;
@@ skipping 108 matching lines @@
     }
   }
 
   // TODO(ricea): This calculation is expensive to perform just to collect
   // statistics. Either remove it or use the result, depending on the result of
   // the experiment.
   ExternallyConditionalizedType type =
       EXTERNALLY_CONDITIONALIZED_CACHE_USABLE;
   if (mode_ == NONE)
     type = EXTERNALLY_CONDITIONALIZED_MISMATCHED_VALIDATORS;
-  else if (RequiresValidation() != VALIDATION_NONE)
+  else if (RequiresValidation())
     type = EXTERNALLY_CONDITIONALIZED_CACHE_REQUIRES_VALIDATION;
 
-  // TODO(ricea): Add CACHE_USABLE_STALE once stale-while-revalidate CL landed.
   // TODO(ricea): Either remove this histogram or make it permanent by M40.
   UMA_HISTOGRAM_ENUMERATION("HttpCache.ExternallyConditionalized",
                             type,
                             EXTERNALLY_CONDITIONALIZED_MAX);
 
   next_state_ = STATE_SEND_REQUEST;
   return OK;
 }
 
 int HttpCache::Transaction::RestartNetworkRequest() {
@@ skipping 29 matching lines @@
   DCHECK(network_trans_.get());
   DCHECK_EQ(STATE_NONE, next_state_);
 
   next_state_ = STATE_SEND_REQUEST_COMPLETE;
   int rv = network_trans_->RestartWithAuth(credentials, io_callback_);
   if (rv != ERR_IO_PENDING)
     return DoLoop(rv);
   return rv;
 }
 
-ValidationType HttpCache::Transaction::RequiresValidation() {
+bool HttpCache::Transaction::RequiresValidation() {
   // TODO(darin): need to do more work here:
   //  - make sure we have a matching request method
   //  - watch out for cached responses that depend on authentication
 
   if (!(effective_load_flags_ & LOAD_SKIP_VARY_CHECK) &&
       response_.vary_data.is_valid() &&
       !response_.vary_data.MatchesRequest(*request_,
                                           *response_.headers.get())) {
     vary_mismatch_ = true;
     validation_cause_ = VALIDATION_CAUSE_VARY_MISMATCH;
-    return VALIDATION_SYNCHRONOUS;
+    return true;
   }
 
   if (effective_load_flags_ & LOAD_SKIP_CACHE_VALIDATION)
-    return VALIDATION_NONE;
+    return false;
 
   if (response_.unused_since_prefetch &&
       !(effective_load_flags_ & LOAD_PREFETCH) &&
       response_.headers->GetCurrentAge(
           response_.request_time, response_.response_time,
           cache_->clock_->Now()) < TimeDelta::FromMinutes(kPrefetchReuseMins)) {
     // The first use of a resource after prefetch within a short window skips
     // validation.
-    return VALIDATION_NONE;
+    return false;
   }
 
   if (effective_load_flags_ & LOAD_VALIDATE_CACHE) {
     validation_cause_ = VALIDATION_CAUSE_VALIDATE_FLAG;
-    return VALIDATION_SYNCHRONOUS;
+    return true;
   }
 
   if (request_->method == "PUT" || request_->method == "DELETE")
-    return VALIDATION_SYNCHRONOUS;
+    return true;
 
-  ValidationType validation_required_by_headers =
-      response_.headers->RequiresValidation(response_.request_time,
-                                            response_.response_time,
-                                            cache_->clock_->Now());
+  bool validation_required_by_headers = response_.headers->RequiresValidation(
+      response_.request_time, response_.response_time, cache_->clock_->Now());
 
-  if (validation_required_by_headers != VALIDATION_NONE) {
+  if (validation_required_by_headers) {
     HttpResponseHeaders::FreshnessLifetimes lifetimes =
         response_.headers->GetFreshnessLifetimes(response_.response_time);
     if (lifetimes.freshness == base::TimeDelta()) {
       validation_cause_ = VALIDATION_CAUSE_ZERO_FRESHNESS;
     } else {
       validation_cause_ = VALIDATION_CAUSE_STALE;
       stale_entry_freshness_ = lifetimes.freshness;
       stale_entry_age_ = response_.headers->GetCurrentAge(
           response_.request_time, response_.response_time,
           cache_->clock_->Now());
     }
   }
 
-  if (validation_required_by_headers == VALIDATION_ASYNCHRONOUS) {
-    // Asynchronous revalidation is only supported for GET methods.
-    if (request_->method != "GET")
-      return VALIDATION_SYNCHRONOUS;
-  }
-
   return validation_required_by_headers;
 }
 
 bool HttpCache::Transaction::ConditionalizeRequest() {
   DCHECK(response_.headers.get());
 
   if (request_->method == "PUT" || request_->method == "DELETE")
     return false;
 
   // This only makes sense for cached 200 or 206 responses.
@@ skipping 27 matching lines @@
   if (!partial_) {
     // Need to customize the request, so this forces us to allocate :(
     custom_request_.reset(new HttpRequestInfo(*request_));
     request_ = custom_request_.get();
   }
   DCHECK(custom_request_.get());
 
   bool use_if_range =
       partial_ && !partial_->IsCurrentRangeCached() && !invalid_range_;
 
-  if (!use_if_range) {
-    // stale-while-revalidate is not useful when we only have a partial response
-    // cached, so don't set the header in that case.
-    HttpResponseHeaders::FreshnessLifetimes lifetimes =
-        response_.headers->GetFreshnessLifetimes(response_.response_time);
-    if (lifetimes.staleness > TimeDelta()) {
-      TimeDelta current_age = response_.headers->GetCurrentAge(
-          response_.request_time, response_.response_time,
-          cache_->clock_->Now());
-
-      custom_request_->extra_headers.SetHeader(
-          kFreshnessHeader,
-          base::StringPrintf("max-age=%" PRId64
-                             ",stale-while-revalidate=%" PRId64 ",age=%" PRId64,
-                             lifetimes.freshness.InSeconds(),
-                             lifetimes.staleness.InSeconds(),
-                             current_age.InSeconds()));
-    }
-  }
-
   if (!etag_value.empty()) {
     if (use_if_range) {
       // We don't want to switch to WRITE mode if we don't have this block of a
       // byte-range request because we may have other parts cached.
       custom_request_->extra_headers.SetHeader(
           HttpRequestHeaders::kIfRange, etag_value);
     } else {
       custom_request_->extra_headers.SetHeader(
           HttpRequestHeaders::kIfNoneMatch, etag_value);
     }
@@ skipping 616 matching lines @@
     default:
       NOTREACHED();
   }
 }
 
 void HttpCache::Transaction::OnIOComplete(int result) {
   DoLoop(result);
 }
 
 }  // namespace net