Documentation
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Overview ¶
Package sharecache decides how a response served behind a portal share token may be cached.
It is the caching counterpart of shareaccess: that package decides who may open a token, this one keeps the answer from being given again out of a cache. For every mode but public the verdict is a property of the caller's session or guest cookie, not of the URL, so a shared cache keyed on the URL alone would populate on the first authorized fetch and answer every later holder of the token without the gate ever running — the bearer-URL access the mode domain exists to end (#999, #1070).
The decision lives next to the access decision rather than in the handlers for the same reason the access decision does: a per-handler directive leaves a route publicly cacheable by omission.
Index ¶
- Constants
- func Apply(w http.ResponseWriter, mode shareaccess.Mode)
- func MaxAge(expiresAt *time.Time, now time.Time) time.Duration
- func PubliclyCacheable(mode shareaccess.Mode) bool
- func Refuse(w http.ResponseWriter)
- func Thumbnail(w http.ResponseWriter, mode shareaccess.Mode, expiresAt *time.Time, ...)
Constants ¶
const Window = time.Hour
Window is how long a thumbnail behind a share may be reused. It is what makes a collection page of thumbnails cheap to revisit, and it is the ceiling on how long a revoked public share's thumbnail can still be served from a shared cache that already stored it.
Variables ¶
This section is empty.
Functions ¶
func Apply ¶
func Apply(w http.ResponseWriter, mode shareaccess.Mode)
Apply writes the caching floor for a response the share gate is about to produce, admitted or refused.
Vary is unconditional: even on a public share the viewer page differs for a signed-in caller, a guest and an anonymous one. Cache-Control is written only for identity-gated shares, and only as a floor the handler behind the gate may narrow or — on a public share, for the thumbnail a link preview fetches — widen. A public share's other responses are left to blobserve's private default rather than opened up: the bytes are anonymous, but nothing needs a CDN holding a copy of every shared file.
A caller authenticating with a header rather than a cookie is covered by the directive rather than by Vary: a shared cache must not store a `private` response whatever it varies on.
func MaxAge ¶
MaxAge returns how long a thumbnail may be reused: Window, or whatever is left of the share's life when that is shorter, so no cached copy outlives the token that authorized it. The gate refuses an expired share before a thumbnail is served, so the clamp only ever narrows a live window.
Revocation has no equivalent clamp — it is not a time the response can be written against — so a copy already stored is served until it goes stale. That residue is why Window is an hour and not a day.
func PubliclyCacheable ¶
func PubliclyCacheable(mode shareaccess.Mode) bool
PubliclyCacheable reports whether a shared cache may store responses served behind a share in mode. Only a fully public share qualifies: its verdict is the same for every caller, so the URL alone is a complete cache key.
The empty mode — what rows written before the mode column carry — is not public, matching shareaccess.Authorize, which resolves it to its shape's default rather than to public. An unset value can never widen caching any more than it can widen access.
func Refuse ¶
func Refuse(w http.ResponseWriter)
Refuse marks a gate refusal as never storable. A 410 is cacheable by default, and a stored refusal keyed on the URL would answer for the recipient the share was made for, turning a per-caller verdict into a per-URL one in the direction that denies access rather than grants it.
func Thumbnail ¶
func Thumbnail(w http.ResponseWriter, mode shareaccess.Mode, expiresAt *time.Time, now time.Time)
Thumbnail writes the directive for a thumbnail served behind a share that expires at expiresAt (nil for a share that does not expire). Only a fully public share's thumbnail is offered to shared caches; any other mode gets the browser that was authorized and nothing else.
Types ¶
This section is empty.
Source Files