Function resolveConflicts

ring/model.go:392–454

This function resolves token conflicts, if there are any. We deal with two possibilities: 1) if one node is LEAVING or LEFT and the other node is not, LEVING/LEFT one loses the token 2) otherwise node names are compared, and node with "lower" name wins the token Modifies ingesters map with updated

(normalizedIngesters map[string]InstanceDesc)

//
// Modifies ingesters map with updated tokens.
func resolveConflicts(normalizedIngesters map[string]InstanceDesc) {
	size := 0
	for _, ing := range normalizedIngesters {
		size += len(ing.Tokens)
	}
	tokens := make([]uint32, 0, size)
	tokenToIngester := make(map[uint32]string, size)

	for ingKey, ing := range normalizedIngesters {
		if ing.State == LEFT {
			// LEFT ingesters don't use tokens anymore
			continue
		}

		for _, token := range ing.Tokens {
			prevKey, found := tokenToIngester[token]
			if !found {
				tokens = append(tokens, token)
				tokenToIngester[token] = ingKey
			} else {
				// there is already ingester for this token, let's do conflict resolution
				prevIng := normalizedIngesters[prevKey]

				winnerKey := ingKey
				switch {
				case ing.State == LEAVING && prevIng.State != LEAVING:
					winnerKey = prevKey
				case prevIng.State == LEAVING && ing.State != LEAVING:
					winnerKey = ingKey
				case ingKey < prevKey:
					winnerKey = ingKey
				case prevKey < ingKey:
					winnerKey = prevKey
				}

				tokenToIngester[token] = winnerKey
			}
		}
	}

	sort.Sort(Tokens(tokens))

	// let's store the resolved result back
	newTokenLists := map[string][]uint32{}
	for key := range normalizedIngesters {
		// make sure that all ingesters start with empty list
		// especially ones that will no longer have any tokens
		newTokenLists[key] = nil
	}

	// build list of tokens for each ingester
	for _, token := range tokens {
		key := tokenToIngester[token]
		newTokenLists[key] = append(newTokenLists[key], token)
	}

	// write tokens back
	for key, tokens := range newTokenLists {