private FetchEmitTuple readFetchEmitTuple() {
        try {
            int length = input.readInt();
            byte[] bytes = new byte[length];
            input.readFully(bytes);
            try (ObjectInputStream objectInputStream = new ObjectInputStream(
                    UnsynchronizedByteArrayInputStream.builder().setByteArray(bytes).get())) {
                return (FetchEmitTuple) objectInputStream.readObject();
            }
        } catch (IOException e) {
            LOG.error("problem reading tuple", e);
            exit(1);
        } catch (ClassNotFoundException e) {
            LOG.error("can't find class?!", e);
            exit(1);
        }
        //unreachable, no?!
        return null;
    }
returns stack trace if there was a container exception or empty string
if there was no stacktrace

@param t
@param metadataList
@return
tika-core/src/main/java/org/apache/tika/pipes/PipesServer.java