aeron-cluster/src/main/java/io/aeron/cluster/service/ServiceHeartbeat.java
public static int findCounterId(final CountersReader counters, final int serviceId)
    {
        final DirectBuffer buffer = counters.metaDataBuffer();

        for (int i = 0, size = counters.maxCounterId(); i < size; i++)
        {
            if (counters.getCounterState(i) == RECORD_ALLOCATED)
            {
                final int recordOffset = CountersReader.metaDataOffset(i);

                if (buffer.getInt(recordOffset + TYPE_ID_OFFSET) == SERVICE_HEARTBEAT_TYPE_ID &&
                    buffer.getInt(recordOffset + KEY_OFFSET + SERVICE_ID_OFFSET) == serviceId)
                {
                    return i;
                }
            }
        }

        return NULL_COUNTER_ID;
    }
public static int findCounterId(final CountersReader counters, final int serviceId)
    {
        final DirectBuffer buffer = counters.metaDataBuffer();

        for (int i = 0, size = counters.maxCounterId(); i < size; i++)
        {
            if (counters.getCounterState(i) == RECORD_ALLOCATED)
            {
                final int recordOffset = CountersReader.metaDataOffset(i);

                if (buffer.getInt(recordOffset + TYPE_ID_OFFSET) == SERVICE_HEARTBEAT_TYPE_ID &&
                    buffer.getInt(recordOffset + KEY_OFFSET + SERVICE_ID_OFFSET) == serviceId)
                {
                    return i;
                }
            }
        }

        return NULL_COUNTER_ID;
    }
Find the active counter id for heartbeat of a given service id.

@param counters  to search within.
@param serviceId to search for.
@return the counter id if found otherwise {@link CountersReader#NULL_COUNTER_ID}.