// write writes the values to the entry in the partition, creating the entry
// if it does not exist.
// write is safe for use by multiple goroutines.
func (p *partition) write(key string, values Values) error {
p.mu.RLock()
e, ok := p.store[key]
p.mu.RUnlock()
if ok {
// Hot path.
return e.add(values)
}
p.mu.Lock()
defer p.mu.Unlock()
// Check again.
if e, ok = p.store[key]; ok {
return e.add(values)
}
// Create a new entry using a preallocated size if we have a hint available.
hint, _ := p.entrySizeHints[xxhash.Sum64([]byte(key))]
e, err := newEntryValues(values, hint)
if err != nil {
return err
}
p.store[key] = e
return nil
}
// reset resets the partition by reinitialising the store. reset returns hints
// about sizes that the entries within the store could be reallocated with.
func (p *partition) reset() {
p.mu.Lock()
defer p.mu.Unlock()
// Collect the allocated sizes of values for each entry in the store.
p.entrySizeHints = make(map[uint64]int)
for k, entry := range p.store {
// If the capacity is large then there are many values in the entry.
// Store a hint to pre-allocate the next time we see the same entry.
if cap(entry.values) > 128 { // 4 x the default entry capacity size.
p.entrySizeHints[xxhash.Sum64([]byte(k))] = cap(entry.values)
}
}
// Reset the store.
p.store = make(map[string]*entry, len(p.store))
}
// getPartition retrieves the hash ring partition associated with the provided
// key.
func (r *ring) getPartition(key string) *partition {
return r.continuum[int(uint8(xxhash.Sum64([]byte(key))))]
}