// mapFP takes a raw fingerprint (as returned by Metrics.FastFingerprint) and
// returns a truly unique fingerprint. The caller must have locked the raw
// fingerprint.
//
// If an error is encountered, it is returned together with the unchanged raw
// fingerprint.
func (m *fpMapper) mapFP(fp model.Fingerprint, metric model.Metric) model.Fingerprint {
// First check if we are in the reserved FP space, in which case this is
// automatically a collision that has to be mapped.
if fp <= maxMappedFP {
return m.maybeAddMapping(fp, metric)
}
// Then check the most likely case: This fp belongs to a series that is
// already in memory.
s, ok := m.fpToSeries.get(fp)
if ok {
// FP exists in memory, but is it for the same metric?
if metric.Equal(s.metric) {
// Yupp. We are done.
return fp
}
// Collision detected!
return m.maybeAddMapping(fp, metric)
}
// Metric is not in memory. Before doing the expensive archive lookup,
// check if we have a mapping for this metric in place already.
m.mtx.RLock()
mappedFPs, fpAlreadyMapped := m.mappings[fp]
m.mtx.RUnlock()
if fpAlreadyMapped {
// We indeed have mapped fp historically.
ms := metricToUniqueString(metric)
// fp is locked by the caller, so no further locking of
// 'collisions' required (it is specific to fp).
mappedFP, ok := mappedFPs[ms]
if ok {
// Historical mapping found, return the mapped FP.
return mappedFP
}
}
// If we are here, FP does not exist in memory and is either not mapped
// at all, or existing mappings for FP are not for m. Check if we have
// something for FP in the archive.
archivedMetric, err := m.p.archivedMetric(fp)
if err != nil || archivedMetric == nil {
// Either the archive lookup has returend an error, or fp does
// not exist in the archive. In the former case, the storage has
// been marked as dirty already. We just carry on for as long as
// it goes, assuming that fp does not exist. In either case,
// since now we know (or assume) now that fp does not exist,
// neither in memory nor in archive, we can safely keep it
// unmapped.
return fp
}
// FP exists in archive, but is it for the same metric?
if metric.Equal(archivedMetric) {
// Yupp. We are done.
return fp
}
// Collision detected!
return m.maybeAddMapping(fp, metric)
}
