uncacheability
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Authored by BBlack on Mar 27 2018, 3:16 PM.

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	F16235451: uncacheability
	Mar 27 2018, 3:17 PM

	F16235415: uncacheability
	Mar 27 2018, 3:16 PM

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	Current:
	/* Don't cache private, no-cache, no-store objects */
	if (beresp.http.Cache-Control ~ "(private\|no-cache\|no-store)") {
	set beresp.ttl = 0s;
	// translated to hit-for-pass below
	}
	[...]
	// set a 601s hit-for-pass object based on response conditions in vcl_backend_response:
	// Calculated TTL <= 0 + Status < 500 + No underlying cache hit:
	// These are generally uncacheable responses. The 5xx exception
	// avoids us accidentally replacing a good stale/grace object with
	// an hfp (and then repeatedly passing on potentially-cacheable
	// content) due to an isolated 5xx response, and the exception for
	// underlying cache hits (detected from X-Cache-Int) is to avoid
	// creating a persist HFP object when a lower-level varnish
	// returned an expired object under grace-mode rules.
	if (
	beresp.ttl <= 0s
	&& beresp.status < 500
	&& (!beresp.http.X-Cache-Int \|\| beresp.http.X-Cache-Int !~ " hit")
	) {
	set beresp.grace = 31s;
	set beresp.keep = 0s;
	set beresp.http.X-CDIS = "pass";
	// XXX: HFP for now, but this requires further work: T180712
	<%- if @varnish_version == 5 -%>
	return(pass(601s));
	<%- else -%>
	set beresp.ttl = 601s;
	set beresp.uncacheable = true;
	return (deliver);
	<%- end -%>
	}

	Straw-person replacement:
	if (beresp.status >= 500) {
	// XXX decide how we handle 5xx, probably single-miss + coalesce as now?
	} else if (beresp.http.Cache-Control ~ "(private\|no-cache\|no-store\|max-age=0\|s-maxage=0)") {
	// Don't cache private, no-cache, no-store, zero-maxage objects
	set beresp.grace = 31s;
	set beresp.keep = 0s;
	set beresp.http.X-CDIS = "pass";
	if (beresp.http.ETag \|\| beresp.http.Last-Modified) {
	return(pass(90s)); // HFP
	} else {
	set beresp.ttl = 90s;
	set beresp.uncacheable = true;
	return(deliver); // HFM
	}
	}
	// note if CC doesn't indicate uncacheability but ttl happens to be <= 0 (e.g. expiring age, underlying grace hit), we do nothing here and let default miss->coalesce behaviors take over, as it should be.

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BBlack created this paste.Mar 27 2018, 3:16 PM

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uncacheability
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