ZDDC
ed7a7fc9c0
The apps subsystem previously sent Cache-Control: public, max-age=300|3600, must-revalidate but no ETag. With must-revalidate and no validator, the browser cannot return 304 — it has to refetch the full body once max-age expires. For mdedit that's 920 KB on every reload after an hour. Add a content-addressed ETag (sha256 hex prefix, 32 chars) to: - apps/handler.go's serveBody + serveEmbedded (both paths now emit ETag + handle If-None-Match short-circuit to 304) - handler/directory.go's embedded:browse fallback (mirror behavior so the bare-directory landing serves the same way) Drop max-age to 0 with must-revalidate: every page load revalidates, but a matching ETag returns 304 with empty body. Steady-state cost of a reload drops from N KB to a few hundred bytes. When the binary is redeployed, the ETag changes (content hash) and the next request returns 200 with the new bytes. Tests in apps/handler_test.go cover both paths: - TestServer_Embedded_ConditionalGET: full GET, matching INM, stale INM - TestEmbeddedETag_Stable: same bytes → same ETag, different → different Live smoke (curl against zddc-server -root /tmp/empty): GET / → 200, ETag set, body = 80919 bytes (landing.html) GET / + INM:tag → 304 Not Modified, empty body
89 lines
2.5 KiB
Go
89 lines
2.5 KiB
Go
package apps
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import (
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"crypto/sha256"
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"encoding/hex"
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_ "embed"
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"sync"
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)
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// Embedded fallback: the five tool HTMLs from the time the binary was
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// built. Used as a last-resort served-bytes when (cache miss) AND
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// (upstream unreachable) AND (no operator override) — see handler.go.
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//
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// The files are populated by the top-level build.sh, which copies the
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// freshly-built dist/<tool>.html into ./embedded/ before `go build` runs.
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// Empty placeholder files are checked in so the package compiles when no
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// build has been run yet (CI bootstrap, fresh clone, etc.); at runtime an
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// empty embedded body is treated as "no embedded fallback available."
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//go:embed embedded/archive.html
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var embeddedArchive []byte
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//go:embed embedded/transmittal.html
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var embeddedTransmittal []byte
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//go:embed embedded/classifier.html
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var embeddedClassifier []byte
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//go:embed embedded/mdedit.html
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var embeddedMdedit []byte
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//go:embed embedded/index.html
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var embeddedLanding []byte
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//go:embed embedded/browse.html
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var embeddedBrowse []byte
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// EmbeddedBytes returns the embedded HTML for app, or nil if either app is
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// not one of the canonical names or the embedded slot is empty (no build
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// has populated it).
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func EmbeddedBytes(app string) []byte {
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var b []byte
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switch app {
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case "archive":
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b = embeddedArchive
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case "transmittal":
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b = embeddedTransmittal
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case "classifier":
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b = embeddedClassifier
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case "mdedit":
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b = embeddedMdedit
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case "landing":
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b = embeddedLanding
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case "browse":
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b = embeddedBrowse
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default:
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return nil
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}
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if len(b) == 0 {
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return nil
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}
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return b
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}
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// EmbeddedETag returns a strong ETag (sha256-hex prefix, 32 chars) for the
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// app's embedded bytes. Computed lazily on first call per-app and memoized
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// — the embedded slot is fixed for the binary's lifetime, so the ETag
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// changes only when the binary is redeployed. Empty slot returns "".
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//
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// Used by apps.Server.serveEmbedded to issue conditional-GET-friendly
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// responses: with this ETag + Cache-Control: max-age=0, must-revalidate,
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// every page load revalidates and gets a 304 unless the binary has been
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// updated. Saves re-transmitting 50–920 KB tool HTMLs on every reload.
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func EmbeddedETag(app string) string {
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if v, ok := etagCacheByApp.Load(app); ok {
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return v.(string)
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}
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body := EmbeddedBytes(app)
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if body == nil {
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return ""
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}
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sum := sha256.Sum256(body)
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etag := hex.EncodeToString(sum[:])[:32]
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etagCacheByApp.Store(app, etag)
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return etag
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}
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// etagCacheByApp memoizes EmbeddedETag results keyed by app name.
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var etagCacheByApp sync.Map
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