// Called when the tap feed receives an updated channel-log document.
func (c *channelLogWriter) channelLogUpdated(rawLog []byte) {
if c == nil {
return
}
c.cacheMutex.Lock()
defer c.cacheMutex.Unlock()
lastCachedSequence := c.cachedLog.LastSequence()
log := channels.DecodeChangeLog(bytes.NewReader(rawLog), lastCachedSequence, &c.cachedLog)
if log == nil {
return
}
log.TruncateTo(CachedChangeLogLength)
c.cachedLog = *log
}
// Loads a channel's log from the database and returns it.
func (c *changesWriter) getChangeLog(channelName string, afterSeq uint64) (*channels.ChangeLog, error) {
raw, err := c.bucket.GetRaw(channelLogDocID(channelName))
if err != nil {
if base.IsDocNotFoundError(err) {
err = nil
}
return nil, err
}
log := channels.DecodeChangeLog(bytes.NewReader(raw), afterSeq)
if log == nil {
// Log is corrupt, so delete it; caller will regenerate it.
c.bucket.Delete(channelLogDocID(channelName))
return nil, fmt.Errorf("Corrupt log")
}
base.LogTo("ChannelLog", "Read %q -- %d bytes, %d entries (since=%d) after #%d",
channelName, len(raw), len(log.Entries), log.Since, afterSeq)
return log, nil
}
// Loads a channel's log from the database and returns it.
func (c *channelLogWriter) getChangeLog(afterSeq uint64) (*channels.ChangeLog, error) {
c.cacheMutex.RLock()
cachedLog := c.cachedLog
c.cacheMutex.RUnlock()
// Read from cache if available:
entries := cachedLog.EntriesAfter(afterSeq)
if entries == nil && afterSeq > cachedLog.Since {
entries = cachedLog.Entries
}
if entries != nil {
log := &channels.ChangeLog{Since: afterSeq, Entries: entries}
if log.HasEmptyEntries() {
log = log.CopyRemovingEmptyEntries()
}
base.LogTo("Changes", "Using cached entries for afterSeq=%d (returning %d)",
afterSeq, len(log.Entries))
dbExpvars.Add("channelLogCacheHits", 1)
return log, nil
}
raw, err := c.bucket.GetRaw(channelLogDocID(c.channelName))
if err != nil {
if base.IsDocNotFoundError(err) {
err = nil
}
return nil, err
}
dbExpvars.Add("channelLogCacheMisses", 1)
log := channels.DecodeChangeLog(bytes.NewReader(raw), afterSeq, nil)
if log == nil {
// Log is corrupt, so delete it; caller will regenerate it.
c.bucket.Delete(channelLogDocID(c.channelName))
return nil, fmt.Errorf("Corrupt log")
}
log = log.CopyRemovingEmptyEntries()
base.LogTo("ChannelLog", "Read %q -- %d bytes, %d entries (since=%d) after #%d",
c.channelName, len(raw), len(log.Entries), log.Since, afterSeq)
return log, nil
}
func decodeChannelLog(raw []byte) (*channels.ChangeLog, error) {
if raw == nil {
return nil, nil
}
return channels.DecodeChangeLog(bytes.NewReader(raw)), nil
}