Transaction exec sometimes returns null response

Expected behavior

When running the following code:

            jedis.watch(key);
            Transaction t = jedis.multi();
            t.incr(key);
            List<Object> response = t.exec();
            jedis.unwatch();
            if (response != null && response.size() == 1) {
                jedis.expire(key, expiry);
                return (Long)response.get(0);
            } else {
                LOGGER.error(String.format("Unexpected response size. The response was %s for key %s and expiry %d",
                response, key, expiry));

                return null;
            }

That logger statement should never occur, because if there was no exception until that point then there should always be exactly one item in the list of responses.

Actual behavior

On rare occasion, the response object is null.

This logging statement is available: “Unexpected response size. The response was null for key my_key and expiry 31536000”

Steps to reproduce:

Unknown. Cannot reproduce consistency.

Redis / Jedis Configuration

Jedis version: 2.8.0

Redis version: 6.2.4

Java version: 1.8

[sazzad16]

@spmason In short, could be.

[spmason]

Thanks. It’s good to have confirmation.

So then this issue could be explained by an overlapping transaction on the watched key?