When we request the HTTP cookie for a SWR request, we were providing the
cookie to the standard request corresponding to the SWR request's ID.
This had two effects:
1. The SWR request would never finish.
2. If the corresponding standard request happened to be a connect-only
request, this would result in a crash as we were expecting it to have
gone through the normal fetch process.
This was seen on some articles on news.google.com.
Our HTTP test server supports a limited amount of byte range request
formats. The format we were using was incorrect, causing the server to
fail an assertion. We now ensure the response body is piped as expected
to catch issues like this in the future.
The caching RFC is quite strict about the format of date strings. If we
received a revalidation attribute with an invalid date string, we would
previously fail a runtime assertion. This was because to start a
revalidation request, we would simply check for the presence of any
revalidation header; but then when we issued the request, we would fail
to parse the header, and end up with all attributes being null.
We now don't parse the revalidation attributes at all. Whatever we
receive in the Last-Modified response header is what we will send in the
If-Modified-Since request header, verbatim. For better or worse, this is
how other browsers behave. So if the server sends us an invalid date
string, it can receive its own date format for revalidation.
We now partition the HTTP disk cache based on the Vary response header.
If a cached response contains a Vary header, we look for each of the
header names in the outgoing HTTP request. The outgoing request must
match every header value in the original request for the cache entry
to be used; otherwise, a new request will be issued, and a separate
cache entry will be created.
Note that we must now defer creating the disk cache file itself until we
have received the response headers. The Vary key is computed from these
headers, and affects the partitioned disk cache file name.
There are further optimizations we can make here. If we have a Vary
mismatch, we could find the best candidate cached response and issue a
conditional HTTP request. The content server may then respond with an
HTTP 304 if the mismatched request headers are actually okay. But for
now, if we have a Vary mismatch, we issue an unconditional request as
a purely correctness-oriented patch.
If the cache mode is no-store, we must not interact with the cache at
all.
If the cache mode is reload, we must not use any cached response.
If the cache-mode is only-if-cached or force-cache, we are permitted
to respond with stale cache responses.
Note that we currently cannot test only-if-cached in test-web. Setting
this mode also requires setting the cors mode to same-origin, but our
http-test-server infra requires setting the cors mode to cors.
If we have the response for a non-Range request in the memory cache, we
would previously use it in reply to Range requests. Similar to commit
878b00ae61f998a26aad7f50fae66cf969878ad6, we are just punting on Range
requests in the HTTP caches for now.
We currently do not handle responses for range requests at all in our
HTTP caches. This means if we issue a request for a range of bytes=1-10,
that response will be served to a subsequent request for a range of
bytes=10-20. This is obviously invalid - so until we handle these
requests, just don't cache them for now.
If the cURL request completes with anything other than CURLE_OK, we must
not keep the cache entry. For example, if the server's connection closes
while transferring data, we receive CURLE_PARTIAL_FILE. We don't want
this cache entry to be treated as valid in a subsequent request.
This directive allows our disk cache to serve stale responses for a time
indicated by the directive itself, while we revalidate the response in
the background.
Issuing requests that weren't initiated by a client is a new thing for
RequestServer. In this implementation, we associate the request with
the client that initiated the request to the stale cache entry. This
adds a "background request" mode to the Request object, to prevent us
from trying to send any of the revalidation response over IPC.
This wouldn't actually result in false positives. If a test failed, the
expectation error message above this line would print, and then we would
fail the test. The point of this flag is just to avoid printing "PASS!"
as well, to avoid confusion.
Our HTTP disk cache is currently manually tested against various sites.
This patch adds some tests to cover various scenarios, including non-
cacheable responses, expired responses, and revalidation.
In order to ensure we hit the disk cache in RequestServer, we must
disable the in-memory cache in WebContent.
