presto-main/src/main/java/io/prestosql/memory/ClusterMemoryManager.java/ClusterMemoryManager/getWorkerMemoryInfo
class ClusterMemoryManager:    public synchronized Map<String, Optional<MemoryInfo>> getWorkerMemoryInfo()
    {
        Map<String, Optional<MemoryInfo>> memoryInfo = new HashMap<>();
        for (Entry<String, RemoteNodeMemory> entry : nodes.entrySet()) {
            // workerId is of the form "node_identifier [node_host]"
            String workerId = entry.getKey() + " [" + entry.getValue().getNode().getHost() + "]";
            memoryInfo.put(workerId, entry.getValue().getInfo());
        }
        return memoryInfo;
    }