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[bugfix] Tidy up rss feed serving; don't error on empty feed (#1970)

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* [bugfix] Tidy up rss feed serving; don't error on empty feed

* fall back to account creation time as rss feed update time

* return feed early when account has no eligible statuses
This commit is contained in:
tobi
2023-07-10 17:05:59 +02:00
committed by GitHub
parent a29b5affc8
commit ca5492b65f
3 changed files with 267 additions and 126 deletions
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198
internal/web/rss.go
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@ -19,8 +19,6 @@ package web
import (
"bytes"
"errors"
"fmt"
"net/http"
"strings"
"time"
@ -31,86 +29,50 @@ import (
"github.com/superseriousbusiness/gotosocial/internal/log"
)
const appRSSUTF8 = string(apiutil.AppRSSXML + "; charset=utf-8")
func (m *Module) GetRSSETag(urlPath string, lastModified time.Time, getRSSFeed func() (string, gtserror.WithCode)) (string, error) {
if cachedETag, ok := m.eTagCache.Get(urlPath); ok && !lastModified.After(cachedETag.lastModified) {
// only return our cached etag if the file wasn't
// modified since last time, otherwise generate a
// new one; eat fresh!
return cachedETag.eTag, nil
}
rssFeed, errWithCode := getRSSFeed()
if errWithCode != nil {
return "", fmt.Errorf("error getting rss feed: %s", errWithCode)
}
eTag, err := generateEtag(bytes.NewReader([]byte(rssFeed)))
if err != nil {
return "", fmt.Errorf("error generating etag: %s", err)
}
// put new entry in cache before we return
m.eTagCache.Set(urlPath, eTagCacheEntry{
eTag: eTag,
lastModified: lastModified,
})
return eTag, nil
}
func extractIfModifiedSince(r *http.Request) time.Time {
hdr := r.Header.Get(ifModifiedSinceHeader)
if hdr == "" {
return time.Time{}
}
t, err := http.ParseTime(hdr)
if err != nil {
log.Errorf(r.Context(), "couldn't parse if-modified-since %s: %s", hdr, err)
return time.Time{}
}
return t
}
const appRSSUTF8 = string(apiutil.AppRSSXML) + "; charset=utf-8"
func (m *Module) rssFeedGETHandler(c *gin.Context) {
// set this Cache-Control header to instruct clients to validate the response with us
// before each reuse (https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control)
c.Header(cacheControlHeader, cacheControlNoCache)
ctx := c.Request.Context()
if _, err := apiutil.NegotiateAccept(c, apiutil.AppRSSXML); err != nil {
apiutil.WebErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGetV1)
return
}
// usernames on our instance will always be lowercase
username := strings.ToLower(c.Param(usernameKey))
if username == "" {
err := errors.New("no account username specified")
apiutil.WebErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGetV1)
return
}
ifNoneMatch := c.Request.Header.Get(ifNoneMatchHeader)
ifModifiedSince := extractIfModifiedSince(c.Request)
getRssFeed, accountLastPostedPublic, errWithCode := m.processor.Account().GetRSSFeedForUsername(ctx, username)
// Fetch + normalize username from URL.
username, errWithCode := apiutil.ParseWebUsername(c.Param(apiutil.WebUsernameKey))
if errWithCode != nil {
apiutil.WebErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
return
}
var rssFeed string
cacheKey := c.Request.URL.Path
cacheEntry, ok := m.eTagCache.Get(cacheKey)
// Usernames on our instance will always be lowercase.
//
// todo: https://github.com/superseriousbusiness/gotosocial/issues/1813
username = strings.ToLower(username)
if !ok || cacheEntry.lastModified.Before(accountLastPostedPublic) {
// we either have no cache entry for this, or we have an expired cache entry; generate a new one
rssFeed, errWithCode = getRssFeed()
// Retrieve the getRSSFeed function from the processor.
// We'll only call the function if we need to, to save db calls.
// lastPostAt may be a zero time if account has never posted.
getRSSFeed, lastPostAt, errWithCode := m.processor.Account().GetRSSFeedForUsername(c.Request.Context(), username)
if errWithCode != nil {
apiutil.WebErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
return
}
var (
rssFeed string // Stringified rss feed.
cacheKey = c.Request.URL.Path
cacheEntry, wasCached = m.eTagCache.Get(cacheKey)
)
if !wasCached || unixAfter(lastPostAt, cacheEntry.lastModified) {
// We either have no ETag cache entry for this account's feed,
// or we have an expired cache entry (account has posted since
// the cache entry was last generated).
//
// As such, we need to generate a new ETag, and for that we need
// the string representation of the RSS feed.
rssFeed, errWithCode = getRSSFeed()
if errWithCode != nil {
apiutil.WebErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
return
@ -122,29 +84,73 @@ func (m *Module) rssFeedGETHandler(c *gin.Context) {
return
}
cacheEntry.lastModified = accountLastPostedPublic
cacheEntry.eTag = eTag
// We never want lastModified to be zero, so if account
// has never actually posted anything, just use Now as
// the lastModified time instead for cache control.
var lastModified time.Time
if lastPostAt.IsZero() {
lastModified = time.Now()
} else {
lastModified = lastPostAt
}
// Store the new cache entry.
cacheEntry = eTagCacheEntry{
eTag: eTag,
lastModified: lastModified,
}
m.eTagCache.Set(cacheKey, cacheEntry)
}
// Set 'ETag' and 'Last-Modified' headers no matter what;
// even if we return 304 in the next checks, caller may
// want to cache these header values.
c.Header(eTagHeader, cacheEntry.eTag)
c.Header(lastModifiedHeader, accountLastPostedPublic.Format(http.TimeFormat))
c.Header(lastModifiedHeader, cacheEntry.lastModified.Format(http.TimeFormat))
// Instruct caller to validate the response with us before
// each reuse, so that the 'ETag' and 'Last-Modified' headers
// actually take effect.
//
// "The no-cache response directive indicates that the response
// can be stored in caches, but the response must be validated
// with the origin server before each reuse, even when the cache
// is disconnected from the origin server."
//
// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control
c.Header(cacheControlHeader, cacheControlNoCache)
// Check if caller submitted an ETag via 'If-None-Match'.
// If they did + it matches what we have, that means they've
// already seen the latest version of this feed, so just bail.
ifNoneMatch := c.Request.Header.Get(ifNoneMatchHeader)
if ifNoneMatch == cacheEntry.eTag {
c.AbortWithStatus(http.StatusNotModified)
return
}
lmUnix := cacheEntry.lastModified.Unix()
imsUnix := ifModifiedSince.Unix()
if lmUnix <= imsUnix {
// Check if the caller submitted a time via 'If-Modified-Since'.
// If they did, and our cached ETag entry is not newer than the
// given time, this means the caller has already seen the latest
// version of this feed, so just bail.
ifModifiedSince := extractIfModifiedSince(c.Request)
if !ifModifiedSince.IsZero() &&
!unixAfter(cacheEntry.lastModified, ifModifiedSince) {
c.AbortWithStatus(http.StatusNotModified)
return
}
// At this point we know that the client wants the newest
// representation of the RSS feed, either because they didn't
// submit any 'If-None-Match' / 'If-Modified-Since' cache headers,
// or because they did but the account has posted more recently
// than the values of the submitted headers would suggest.
//
// If we had a cache hit earlier, we may not have called the
// getRSSFeed function yet; if that's the case then do call it
// now because we definitely need it.
if rssFeed == "" {
// we had a cache entry already so we didn't call to get the rss feed yet
rssFeed, errWithCode = getRssFeed()
rssFeed, errWithCode = getRSSFeed()
if errWithCode != nil {
apiutil.WebErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
return
@ -153,3 +159,41 @@ func (m *Module) rssFeedGETHandler(c *gin.Context) {
c.Data(http.StatusOK, appRSSUTF8, []byte(rssFeed))
}
// unixAfter returns true if the unix value of t1
// is greater than (ie., after) the unix value of t2.
func unixAfter(t1 time.Time, t2 time.Time) bool {
if t1.IsZero() {
// if t1 is zero then it cannot
// possibly be greater than t2.
return false
}
if t2.IsZero() {
// t1 is not zero but t2 is,
// so t1 is necessarily greater.
return true
}
return t1.Unix() > t2.Unix()
}
// extractIfModifiedSince parses a time.Time from the
// 'If-Modified-Since' header of the given request.
//
// If no time was provided, or the provided time was
// not parseable, it will return a zero time.
func extractIfModifiedSince(r *http.Request) time.Time {
imsStr := r.Header.Get(ifModifiedSinceHeader)
if imsStr == "" {
return time.Time{} // Nothing set.
}
ifModifiedSince, err := http.ParseTime(imsStr)
if err != nil {
log.Errorf(r.Context(), "couldn't parse %s value '%s' as time: %q", ifModifiedSinceHeader, imsStr, err)
return time.Time{}
}
return ifModifiedSince
}