Bug 1064258 - Allow caching channels only store metadata, r=jduell

netwerk/base/public/nsICachingChannel.idl

@@ -17,7 +17,7 @@ interface nsIFile;
  *   3) Support for uniquely identifying cached data in cases when the URL
  *      is insufficient (e.g., HTTP form submission).
  */
-[scriptable, uuid(a77b664e-e707-4017-9c03-47bcedcb5b05)]
+[scriptable, uuid(3d46b469-7405-416e-ba42-84899963b403)]
 interface nsICachingChannel : nsICacheInfoChannel
 {
     /**
@@ -64,6 +64,14 @@ interface nsICachingChannel : nsICacheInfoChannel
      */
     attribute nsISupports cacheKey;
 
+    /**
+     * Instructs the channel to only store the metadata of the entry, and not
+     * the content. When reading an existing entry, this automatically sets
+     * LOAD_ONLY_IF_MODIFIED flag.
+     * Must be called before asyncOpen().
+     */
+    attribute boolean cacheOnlyMetadata;
+
     /**************************************************************************
      * Caching channel specific load flags:
      */

netwerk/protocol/http/nsHttpChannel.cpp

@@ -208,6 +208,7 @@ nsHttpChannel::nsHttpChannel()
     , mOfflineCacheLastModifiedTime(0)
     , mCachedContentIsValid(false)
     , mCachedContentIsPartial(false)
+    , mCacheOnlyMetadata(false)
     , mTransactionReplaced(false)
     , mAuthRetryPending(false)
     , mProxyAuthPending(false)
@@ -2826,8 +2827,16 @@ nsHttpChannel::OnCacheEntryCheck(nsICacheEntry* entry, nsIApplicationCache* appC
             if (mCachedContentIsPartial) {
                 rv = OpenCacheInputStream(entry, false, !!appCache);
                 *aResult = ENTRY_NEEDS_REVALIDATION;
+                return rv;
+            } else if (size == 0 && mCacheOnlyMetadata) {
+                // Don't break cache entry load when the entry's data size
+                // is 0 and mCacheOnlyMetadata flag is set. In that case we
+                // want to proceed since the LOAD_ONLY_IF_MODIFIED flag is
+                // also set.
+                MOZ_ASSERT(mLoadFlags & LOAD_ONLY_IF_MODIFIED);
+            } else {
+                return rv;
             }
-            return rv;
         }
     }
 
@@ -4003,14 +4012,24 @@ nsHttpChannel::InstallCacheListener(int64_t offset)
     nsCOMPtr<nsIOutputStream> out;
     rv = mCacheEntry->OpenOutputStream(offset, getter_AddRefs(out));
     if (rv == NS_ERROR_NOT_AVAILABLE) {
-      LOG(("  entry doomed, not writing it [channel=%p]", this));
-      // Entry is already doomed.
-      // This may happen when expiration time is set to past and the entry
-      // has been removed by the background eviction logic.
-      return NS_OK;
+        LOG(("  entry doomed, not writing it [channel=%p]", this));
+        // Entry is already doomed.
+        // This may happen when expiration time is set to past and the entry
+        // has been removed by the background eviction logic.
+        return NS_OK;
     }
     if (NS_FAILED(rv)) return rv;
 
+    if (mCacheOnlyMetadata) {
+        LOG(("Not storing content, cacheOnlyMetadata set"));
+        // We must open and then close the output stream of the cache entry.
+        // This way we indicate the content has been written (despite with zero
+        // length) and the entry is now in the ready state with "having data".
+
+        out->Close();
+        return NS_OK;
+    }
+
     // XXX disk cache does not support overlapped i/o yet
 #if 0
     // Mark entry valid inorder to allow simultaneous reading...
@@ -5716,6 +5735,30 @@ nsHttpChannel::SetCacheKey(nsISupports *key)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsHttpChannel::GetCacheOnlyMetadata(bool *aOnlyMetadata)
+{
+    NS_ENSURE_ARG(aOnlyMetadata);
+    *aOnlyMetadata = mCacheOnlyMetadata;
+    return NS_OK;
+}
+
+NS_IMETHODIMP
+nsHttpChannel::SetCacheOnlyMetadata(bool aOnlyMetadata)
+{
+    LOG(("nsHttpChannel::SetCacheOnlyMetadata [this=%p only-metadata=%d]\n",
+        this, aOnlyMetadata));
+
+    ENSURE_CALLED_BEFORE_ASYNC_OPEN();
+
+    mCacheOnlyMetadata = aOnlyMetadata;
+    if (aOnlyMetadata) {
+        mLoadFlags |= LOAD_ONLY_IF_MODIFIED;
+    }
+
+    return NS_OK;
+}
+
 //-----------------------------------------------------------------------------
 // nsHttpChannel::nsIResumableChannel
 //-----------------------------------------------------------------------------

netwerk/protocol/http/nsHttpChannel.h

@@ -385,6 +385,7 @@ private:
     // state flags
     uint32_t                          mCachedContentIsValid     : 1;
     uint32_t                          mCachedContentIsPartial   : 1;
+    uint32_t                          mCacheOnlyMetadata        : 1;
     uint32_t                          mTransactionReplaced      : 1;
     uint32_t                          mAuthRetryPending         : 1;
     uint32_t                          mProxyAuthPending         : 1;

netwerk/test/unit/test_bug1064258.js

@@ -0,0 +1,154 @@
+/**
+ * Check how nsICachingChannel.cacheOnlyMetadata works.
+ * - all channels involved in this test are set cacheOnlyMetadata = true
+ * - do a previously uncached request for a long living content
+ * - check we have downloaded the content from the server (channel provides it)
+ * - check the entry has metadata, but zero-length content
+ * - load the same URL again, now cached
+ * - check the channel is giving no content (no call to OnDataAvailable) but succeeds
+ * - repeat again, but for a different URL that is not cached (immediately expires)
+ * - only difference is that we get a newer version of the content from the server during the second request
+ */
+
+Cu.import("resource://testing-common/httpd.js");
+
+XPCOMUtils.defineLazyGetter(this, "URL", function() {
+  return "http://localhost:" + httpServer.identity.primaryPort;
+});
+
+var httpServer = null;
+
+function make_channel(url, callback, ctx) {
+  var ios = Cc["@mozilla.org/network/io-service;1"].
+            getService(Ci.nsIIOService);
+  return ios.newChannel(url, "", null);
+}
+
+const responseBody1 = "response body 1";
+const responseBody2a = "response body 2a";
+const responseBody2b = "response body 2b";
+
+function contentHandler1(metadata, response)
+{
+  response.setHeader("Content-Type", "text/plain");
+  response.setHeader("Cache-control", "max-age=999999");
+  response.bodyOutputStream.write(responseBody1, responseBody1.length);
+}
+
+var content2passCount = 0;
+
+function contentHandler2(metadata, response)
+{
+  response.setHeader("Content-Type", "text/plain");
+  response.setHeader("Cache-control", "no-cache");
+  switch (content2passCount++) {
+    case 0:
+      response.setHeader("ETag", "testetag");
+      response.bodyOutputStream.write(responseBody2a, responseBody2a.length);
+      break;
+    case 1:
+      do_check_true(metadata.hasHeader("If-None-Match"));
+      do_check_eq(metadata.getHeader("If-None-Match"), "testetag");
+      response.bodyOutputStream.write(responseBody2b, responseBody2b.length);
+      break;
+    default:
+      throw "Unexpected request in the test";
+  }
+}
+
+
+function run_test()
+{
+  httpServer = new HttpServer();
+  httpServer.registerPathHandler("/content1", contentHandler1);
+  httpServer.registerPathHandler("/content2", contentHandler2);
+  httpServer.start(-1);
+
+  run_test_content1a();
+  do_test_pending();
+}
+
+function run_test_content1a()
+{
+  var chan = make_channel(URL + "/content1");
+  caching = chan.QueryInterface(Ci.nsICachingChannel);
+  caching.cacheOnlyMetadata = true;
+  chan.asyncOpen(new ChannelListener(contentListener1a, null), null);
+}
+
+function contentListener1a(request, buffer)
+{
+  do_check_eq(buffer, responseBody1);
+
+  asyncOpenCacheEntry(URL + "/content1", "disk", 0, null, cacheCheck1)
+}
+
+function cacheCheck1(status, entry)
+{
+  do_check_eq(status, 0);
+  do_check_eq(entry.dataSize, 0);
+  try {
+    do_check_neq(entry.getMetaDataElement("response-head"), null);
+  }
+  catch (ex) {
+    do_throw("Missing response head");
+  }
+
+  var chan = make_channel(URL + "/content1");
+  caching = chan.QueryInterface(Ci.nsICachingChannel);
+  caching.cacheOnlyMetadata = true;
+  chan.asyncOpen(new ChannelListener(contentListener1b, null, CL_IGNORE_CL), null);
+}
+
+function contentListener1b(request, buffer)
+{
+  request.QueryInterface(Ci.nsIHttpChannel);
+  do_check_eq(request.requestMethod, "GET");
+  do_check_eq(request.responseStatus, 200);
+  do_check_eq(request.getResponseHeader("Cache-control"), "max-age=999999");
+
+  do_check_eq(buffer, "");
+  run_test_content2a();
+}
+
+// Now same set of steps but this time for an immediately expiring content.
+
+function run_test_content2a()
+{
+  var chan = make_channel(URL + "/content2");
+  caching = chan.QueryInterface(Ci.nsICachingChannel);
+  caching.cacheOnlyMetadata = true;
+  chan.asyncOpen(new ChannelListener(contentListener2a, null), null);
+}
+
+function contentListener2a(request, buffer)
+{
+  do_check_eq(buffer, responseBody2a);
+
+  asyncOpenCacheEntry(URL + "/content2", "disk", 0, null, cacheCheck2)
+}
+
+function cacheCheck2(status, entry)
+{
+  do_check_eq(status, 0);
+  do_check_eq(entry.dataSize, 0);
+  try {
+    do_check_neq(entry.getMetaDataElement("response-head"), null);
+    do_check_true(entry.getMetaDataElement("response-head").match('Etag: testetag'));
+  }
+  catch (ex) {
+    do_throw("Missing response head");
+  }
+
+  var chan = make_channel(URL + "/content2");
+  caching = chan.QueryInterface(Ci.nsICachingChannel);
+  caching.cacheOnlyMetadata = true;
+  chan.asyncOpen(new ChannelListener(contentListener2b, null), null);
+}
+
+function contentListener2b(request, buffer)
+{
+  do_check_eq(buffer, responseBody2b);
+
+  httpServer.stop(do_test_finished);
+}

netwerk/test/unit/xpcshell.ini

@@ -158,6 +158,7 @@ skip-if = os == "android"
 # Allocating 4GB might actually succeed on 64 bit machines
 skip-if = bits != 32
 [test_bug935499.js]
+[test_bug1064258.js]
 [test_udpsocket.js]
 [test_doomentry.js]
 [test_cacheflags.js]