mirror of
https://github.com/therootcompany/golib.git
synced 2026-11-04 15:05:00 +00:00
48 lines
1.7 KiB
Markdown
48 lines
1.7 KiB
Markdown
# [httpcache](https://github.com/therootcompany/golib/tree/main/net/httpcache)
|
|
|
|
Conditional HTTP GET to a local file. ETag / Last-Modified are persisted to a
|
|
`<path>.meta` sidecar so 304s survive process restarts.
|
|
|
|
- skips HTTP when the local file is newer than `MaxAge`
|
|
- backs off failed fetches for `FailureBackoff` (defaults to `MaxAge`)
|
|
- honors a valid server `Retry-After` response over local backoff
|
|
- skips HTTP when the last attempt was within `MinInterval` (in-memory)
|
|
- caps response bodies via `MaxBytes` (defends against fill-disk)
|
|
- `O_EXCL` reservation on `<path>.tmp` for cross-process exclusion;
|
|
`singleflight` coalesces in-process callers
|
|
- safe to call `Fetch` concurrently — peers see `ErrPeerFetching`
|
|
|
|
## Example
|
|
|
|
Fetch a blocklist; re-check periodically:
|
|
|
|
```go
|
|
c := httpcache.New(
|
|
"https://example.com/blocklist.txt",
|
|
"/srv/data/blocklist.txt",
|
|
)
|
|
c.MaxAge = time.Hour // skip HTTP if file is < 1h old
|
|
// c.FailureBackoff = 30 * time.Minute // defaults to MaxAge
|
|
c.MaxBytes = 50 << 20 // 50 MiB cap
|
|
|
|
updated, err := c.Fetch(ctx)
|
|
switch {
|
|
case errors.Is(err, httpcache.ErrPeerFetching):
|
|
// another process is downloading; reload from disk if updated==true
|
|
case err != nil:
|
|
log.Fatalf("fetch: %v", err)
|
|
case updated:
|
|
log.Printf("blocklist refreshed")
|
|
}
|
|
```
|
|
|
|
Pair with `*http.Client` if you need custom timeouts, transport, or a
|
|
`CheckRedirect` that strips non-standard credential headers (the stdlib
|
|
already strips `Authorization` / `Cookie` / `WWW-Authenticate` on
|
|
cross-host redirects):
|
|
|
|
```go
|
|
c := httpcache.NewWith(url, path, &http.Client{Timeout: 30 * time.Second})
|
|
c.Header = http.Header{"Authorization": []string{"Bearer " + token}}
|
|
```
|