@Override
    public void addDocument(final IndexShardKey indexShardKey, final IndexDocument document) {
        if (document != null) {
            activeShardsCache.get(indexShardKey).addDocument(document);
        }
    }
Pool API into open index shards.
stroom-index/stroom-index-impl/src/main/java/stroom/index/impl/IndexerImpl.java