// EvictCachedRangeMetadata will evict any cached metadata range descriptors for
// the given key. It is intended that this method be called from a consumer of
// RangeMetadataCache when the returned range metadata is discovered to be
// stale.
func (rmc *RangeMetadataCache) EvictCachedRangeMetadata(key storage.Key) {
for {
k, _ := rmc.getCachedRangeMetadata(key)
if k != nil {
rmc.rangeCacheMu.Lock()
rmc.rangeCache.Del(k)
rmc.rangeCacheMu.Unlock()
}
// Retrieve the metadata range key for the next level of metadata, and
// evict that key as well. This loop ends after the meta1 range, which
// returns KeyMin as its metadata key.
key = storage.RangeMetaKey(key)
if len(key) == 0 {
break
}
}
}
// getCachedRangeMetadata is a helper function to retrieve the metadata
// range which contains the given key, if present in the cache.
func (rmc *RangeMetadataCache) getCachedRangeMetadata(key storage.Key) (
rangeCacheKey, *storage.RangeDescriptor) {
metaKey := storage.RangeMetaKey(key)
rmc.rangeCacheMu.RLock()
defer rmc.rangeCacheMu.RUnlock()
k, v, ok := rmc.rangeCache.Ceil(rangeCacheKey(metaKey))
if !ok {
return nil, nil
}
metaEndKey := k.(rangeCacheKey)
rd := v.(*storage.RangeDescriptor)
// Check that key actually belongs to range
if !rd.ContainsKey(key) {
return nil, nil
}
return metaEndKey, rd
}
// LookupRangeMetadata retrieves the range metadata for the range containing the
// given key. Because range metadata in cockroach is stored using a multi-level
// lookup table, this method may be called recursively to look up higher-level
// ranges. Recursive lookups are dispatched through the metadata range cache.
func (db *DistDB) LookupRangeMetadata(key storage.Key) (storage.Key, *storage.RangeDescriptor, error) {
metadataKey := storage.RangeMetaKey(key)
if len(metadataKey) == 0 {
// Metadata range is the first range, the description of which is always
// gossiped.
infoI, err := db.gossip.GetInfo(gossip.KeyFirstRangeMetadata)
if err != nil {
return nil, nil, firstRangeMissingError{err}
}
info := infoI.(storage.RangeDescriptor)
return storage.KeyMin, &info, nil
}
// Look up the range containing metadataKey in the cache, which will
// recursively call into db.LookupRangeMetadata if it is not cached.
metadataRange, err := db.rangeCache.LookupRangeMetadata(metadataKey)
if err != nil {
return nil, nil, err
}
return db.internalRangeLookup(metadataKey, metadataRange)
}
// LookupRangeMetadata attempts to locate metadata for the range containing the
// given Key. This is done by querying the two-level lookup table of range
// metadata which cockroach maintains.
//
// This method first looks up the specified key in the first level of range
// metadata, which returns the location of the key within the second level of
// range metadata. This second level location is then queried to retrieve
// metadata for the range where the key's value resides. Range metadata
// descriptors retrieved during each search are cached for subsequent lookups.
//
// This method returns the RangeDescriptor for the range containing the key's
// data, or an error if any occurred.
func (rmc *RangeMetadataCache) LookupRangeMetadata(key storage.Key) (*storage.RangeDescriptor, error) {
metadataKey := storage.RangeMetaKey(key)
if len(metadataKey) == 0 {
// The description of the first range is gossiped, and thus does not
// need to be cached. Just ask the underlying db, which will return
// immediately.
_, r, err := rmc.db.LookupRangeMetadata(key)
return r, err
}
_, r := rmc.getCachedRangeMetadata(key)
if r != nil {
return r, nil
}
k, r, err := rmc.db.LookupRangeMetadata(key)
if err != nil {
return nil, err
}
rmc.rangeCacheMu.Lock()
rmc.rangeCache.Add(rangeCacheKey(k), r)
rmc.rangeCacheMu.Unlock()
return r, nil
}
