http: dynamic responses for empty cache entries #603
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If the cache entry for any given url was cleared, this would be indicated by a null entry for that url, and vere would serve a 404 for those cases, instead of falling back to the normal, dynamic behavior of injecting the request into eyre. Here, we make eyre serve from the cache only if there is a full cache entry for the url, and have it proceed into normal request injection logic otherwise. This way, setting a cached response for some url no longer means giving up dynamic responses on that url for the rest of time. Recent versions of eyre exhibit the same behavior. As such, in practice, this code won't change the observed behavior without a similarly-patched version of eyre.
This was referenced Feb 8, 2024
Fang-
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Feb 15, 2024
Globs contain big, static blobs of data, that only get updated periodically. Eyre has an affordance for caching responses at specified urls. Here we update docket to, whenever a glob gets added, updated or removed, manage the eyre response cache to match. We call +new-cache in every place where either +new-docket or +new-chad gets called, making sure to pass in the old charge so that we can clear potentially-stale entries from the cache. Note that docket's dynamic request serving behavior would respond to both /path.ext and /path/ext with the glob entry for the (clay-style) path /path/ext. However, we only add a response for the '/path.ext' url into the cache. This is the common case, and doing so avoids adding twice the amount of cache pressure. For the %groups desk, whose initial pageload requests 32 files, this takes initial load time down from ~0.5s to ~0.1s (on localhost, so no "real networking" overhead). About half of that remaining time is spent on the initial page request, which usually dynamically falls back to serving /index.html. About a fifth is spent on loading desk.js and session.js, which are served by docket independent of glob contents. Adding those into the cache could bring additional performance gains. This should be considered soft-blocked on urbit/urbit#6909 and urbit/vere#603. Without those changes, docket may make /apps/* urls permanently unusable for dynamic binding.
pkova
approved these changes
Mar 6, 2024
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If the cache entry for any given url was cleared, this would be indicated by a null entry for that url, and vere would serve a 404 for those cases, instead of falling back to the normal, dynamic behavior of injecting the request into eyre.
Here, we make eyre serve from the cache only if there is a full cache entry for the url, and have it proceed into normal request injection logic otherwise.
This way, setting a cached response for some url no longer means giving up dynamic responses on that url for the rest of time.
Recent versions of eyre exhibit the same behavior. As such, in practice, this code won't change the observed behavior without a similarly-patched version of eyre. For that, see the sister PR, urbit/urbit#6909.
The bulk of the updated logic in
_http_cache_respond()comes from_http_rec_accept(), but due to differences in cache checking behavior it isn't a 1:1 match, so it seemed simplest for now to just duplicate the logic, rather than introduce another intermediary request handling function.Resolves urbit/urbit#6702.