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Add Stale While Revalidate Handling #853

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merged 6 commits into from
May 3, 2019
Merged

Add Stale While Revalidate Handling #853

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e8e75dd
Add Async Stale While Revalidate Handling
dtapuska Dec 21, 2018
1847576
formatting nits
annevk Apr 5, 2019
1cef013
Link current age
dtapuska Apr 12, 2019
e90e382
more tidying
annevk Apr 15, 2019
70532d3
Add condition for non-null client
dtapuska Apr 18, 2019
e17297b
nit
annevk May 3, 2019
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119 changes: 91 additions & 28 deletions fetch.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,9 @@ url:https://tools.ietf.org/html/rfc7234#section-1.2.1;text:delta-seconds;type:df
"REFERRER": {
"aliasOf": "referrer-policy"
},
"STALE-WHILE-REVALIDATE": {
"aliasOf": "RFC5861"
},
"SW": {
"aliasOf": "service-workers"
},
Expand Down Expand Up @@ -1378,10 +1381,14 @@ Unless stated otherwise, it is unset.
<div class="note no-backref">
<dl>
<dt>"<code>default</code>"
<dd><a for=/>Fetch</a> will inspect the HTTP cache on the way to the network.
If there is a fresh response it will be used. If there is a stale response a conditional request
will be created, and a normal request otherwise. It then updates the HTTP cache with the response.
[[!HTTP]] [[!HTTP-SEMANTICS]] [[!HTTP-COND]] [[!HTTP-CACHING]] [[!HTTP-AUTH]]
<dd><a for=/>Fetch</a> will inspect the HTTP cache on the way to the network. If the HTTP cache
contains a matching <a>fresh response</a> it will be returned. If the HTTP cache contains a
matching <a>stale-while-revalidate response</a> it will be returned, and a conditional network
fetch will be made to update the entry in the HTTP cache. If the HTTP cache contains a matching
<a>stale response</a>, a conditional network fetch will be returned to update the entry in
the HTTP cache. Otherwise, a non-conditional network fetch will be returned to update the entry
in the HTTP cache. [[!HTTP]] [[!HTTP-SEMANTICS]] [[!HTTP-COND]] [[!HTTP-CACHING]] [[!HTTP-AUTH]]
[[!STALE-WHILE-REVALIDATE]]

<dt>"<code>no-store</code>"
<dd>Fetch behaves as if there is no HTTP cache at all.
Expand Down Expand Up @@ -1495,6 +1502,10 @@ Unless stated otherwise, it is zero.
which is "<code>basic</code>", "<code>cors</code>", or "<code>opaque</code>".
Unless stated otherwise, it is "<code>basic</code>".

<p>A <a for=/>request</a> has an associated
<dfn export for=request id=no-cache-prevent-cache-control>prevent no-cache cache-control header modification flag</dfn>.
Unless stated otherwise, it is unset.

<p>A <a for=/>request</a> has an associated <dfn export for=request id=done-flag>done flag</dfn>.
Unless stated otherwise, it is unset.

Expand Down Expand Up @@ -1870,6 +1881,19 @@ is a <a>filtered response</a> whose
<li><p>Return <var>newResponse</var>.
</ol>

<p>A <dfn id=concept-fresh-response>fresh response</dfn> is a <a for=/>response</a> whose
<a href=https://tools.ietf.org/html/rfc7234#section-4.2.3>current age</a> is within its
<a href=https://tools.ietf.org/html/rfc7234#section-4.2.1>freshness lifetime</a>.

<p>A <dfn id=concept-stale-while-revalidate-response>stale-while-revalidate response</dfn> is a
<a for=/>response</a> that is not a <a>fresh response</a> and whose
<a href=https://tools.ietf.org/html/rfc7234#section-4.2.3>current age</a> is within the
<a href=https://tools.ietf.org/html/rfc5861#section-3>stale-while-revalidate lifetime</a>.

<p>A <dfn export id=concept-stale-response>stale response</dfn> is a <a for=/>response</a> is a
<a for=/>response</a> that is not a <a>fresh response</a> or a
<a>stale-while-revalidate response</a>.
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<h4 id=miscellaneous>Miscellaneous</h4>

Expand Down Expand Up @@ -4065,10 +4089,11 @@ Range Requests</cite>. [[HTTP-RANGE]] However, this is not widely supported by b
`<code>If-Range</code>`, then set <var>httpRequest</var>'s
<a for=request>cache mode</a> to "<code>no-store</code>".

<li><p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is "<code>no-cache</code>" and
<var>httpRequest</var>'s <a for=request>header list</a> <a for="header list">does not contain</a>
`<code>Cache-Control</code>`, then <a for="header list">append</a>
`<code>Cache-Control</code>`/`<code>max-age=0</code>` to
<li><p>If <var>httpRequest</var>'s <a for=request>cache mode</a> is "<code>no-cache</code>",
<var>httpRequest</var>'s <a for=request>prevent no-cache cache-control header modification flag</a>
is unset, and <var>httpRequest</var>'s <a for=request>header list</a>
<a for="header list">does not contain</a> `<code>Cache-Control</code>`, then
<a for="header list">append</a> `<code>Cache-Control</code>`/`<code>max-age=0</code>` to
<var>httpRequest</var>'s <a for=request>header list</a>.

<li>
Expand Down Expand Up @@ -4197,32 +4222,69 @@ Range Requests</cite>. [[HTTP-RANGE]] However, this is not widely supported by b

<!-- cache hit -->
<ol>
<li><p>If <var>storedResponse</var> requires validation (i.e., it is not fresh), then set the
<var>revalidatingFlag</var>.

<li>
<p>If the <var>revalidatingFlag</var> is set and <var>httpRequest</var>'s
<a for=request>cache mode</a> is neither "<code>force-cache</code>" nor
"<code>only-if-cached</code>", then:
<p>If <a for=request>cache mode</a> is "<code>default</code>", <var>storedResponse</var>
is a <a>stale-while-revalidate response</a>, and <var>httpRequest</var>'s
<a for=request>client</a> is not null, then:

<ol>
<li><p>If <var>storedResponse</var>'s <a for=response>header list</a>
<a for="header list">contains</a> `<code>ETag</code>`, then <a for="header list">append</a>
`<code>If-None-Match</code>` with its value to <var>httpRequest</var>'s
<a for=request>header list</a>.

<li><p>If <var>storedResponse</var>'s <a for=response>header list</a>
<a for="header list">contains</a> `<code>Last-Modified</code>`, then
<a for="header list">append</a> `<code>If-Modified-Since</code>` with its value to
<var>httpRequest</var>'s <a for=request>header list</a>.
<li><p>Set <var>response</var> to <var>storedResponse</var>.

<li><p>Set <var>response</var>'s <a for=response>cache state</a> to "<code>local</code>".

<li><p>Let <var>revalidateRequest</var> be a <a for=request>clone</a> of
<var>request</var>.

<li><p>Set <var>revalidateRequest</var>'s <a for=request>cache mode</a> set to
"<code>no-cache</code>".

<li><p>Set <var>revalidateRequest</var>'s
<a for=request>prevent no-cache cache-control header modification flag</a>.

<li><p>Set <var>revalidateRequest</var>'s <a for=request>service-workers mode</a> set to
"<code>none</code>".

<li>
<p><a>In parallel</a>, perform <a for=main>main fetch</a> using
<var>revalidateRequest</var>.

<p class=note>This fetch is only meant to update the state of the HTTP cache and the
response will be unused until another cache access. The stale response will be used as the
response to current request. This fetch is issued in the context of a client so if it goes
away the request will be terminated.
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</ol>

<p class=note>See also the
"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Sending a Validation Request</a>"
chapter of <cite>HTTP Caching</cite> [[!HTTP-CACHING]].
<li>
<p>Otherwise:

<ol>
<li><p>If <var>storedResponse</var> is a <a>stale response</a>, then set the
<var>revalidatingFlag</var>.

<li><p>Otherwise, set <var>response</var> to <var>storedResponse</var> and set
<var>response</var>'s <a for=response>cache state</a> to "<code>local</code>".
<li>
<p>If the <var>revalidatingFlag</var> is set and <var>httpRequest</var>'s
<a for=request>cache mode</a> is neither "<code>force-cache</code>" nor
"<code>only-if-cached</code>", then:

<ol>
<li><p>If <var>storedResponse</var>'s <a for=response>header list</a>
<a for="header list">contains</a> `<code>ETag</code>`, then
<a for="header list">append</a> `<code>If-None-Match</code>` with its value to
<var>httpRequest</var>'s <a for=request>header list</a>.

<li><p>If <var>storedResponse</var>'s <a for=response>header list</a>
<a for="header list">contains</a> `<code>Last-Modified</code>`, then
<a for="header list">append</a> `<code>If-Modified-Since</code>` with its value to
<var>httpRequest</var>'s <a for=request>header list</a>.
</ol>

<p class=note>See also the
"<a href=https://tools.ietf.org/html/rfc7234#section-4.3.4>Sending a Validation Request</a>"
chapter of <cite>HTTP Caching</cite> [[!HTTP-CACHING]].

<li><p>Otherwise, set <var>response</var> to <var>storedResponse</var> and set
<var>response</var>'s <a for=response>cache state</a> to "<code>local</code>".
</ol>
</ol>
</ol>
</ol>
Expand Down Expand Up @@ -6942,6 +7004,7 @@ Clement Pellerin,
Collin Jackson,
Daniel Robertson,
Daniel Veditz,
Dave Tapuska,
David Benjamin,
David Håsäther,
David Orchard,
Expand Down