func()

in v1storage/mapper.go [88:144]

• 30 lines of code
• 9 McCabe index (conditional complexity)

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)
}