CODEWITHSUNDEEP
cassandradatastax-java-driver
gioper86
gioper86

Reputation: 90

Cassandra. Not enough replica available - Java driver behaviour different from CQL console

I have a very simple cluster with 2 nodes. I have created a keyspace with SimpleStrategy replication and a replication factor of 2. For reads and writes I always use the default data consistency level of ONE.

If I take down one of the two nodes, by using the datastax java driver, I can still read data but when I try to write I get "Not enough replica available for query at consistency ONE (1 required but only 0 alive)".

Strangely if I execute the exactly same insert statement by using the CQL console it works without any problem. Even when using the CQL console the data consistency level was 1.

Am I missing something?

TIA

Update

I have done some more tests and the problem appears only when I use the BatchStatement. If I execute the prepared statement directly it works. Any idea ?

Here the code

    Cluster cluster = Cluster.builder()
            .addContactPoint("192.168.1.10")
            .addContactPoint("192.168.1.12")
            .build();

    Session session = cluster.connect();
    session.execute("use giotest");

    BatchStatement batch = new BatchStatement();
    PreparedStatement statement = session.prepare("INSERT INTO hourly(series_id, timestamp, value) VALUES (?, ?, ?)");

    for (int i = 0; i < 50; i++) {
        batch.add(statement.bind(new Long(i), new Date(), 2345.5));
    }

    session.execute(batch);
    batch.clear();
    session.close();
    cluster.close();

Upvotes: 2

Views: 1266

Answers (2)

Olivier Michallat
Olivier Michallat

Reputation: 2312

Batches are atomic by default: if the coordinator fails mid-batch, Cassandra will make sure other nodes replay the remaining requests. It uses a distributed batch log for that (see this post for more details).

This batch log must be replicated to at least one replica other than the coordinator, otherwise that would defeat the above mechanism.

In your case, there is no other replica, only the coordinator. So Cassandra is telling you that it cannot provide the guarantees of an atomic batch. See also the discussion on CASSANDRA-7870.

Upvotes: 2

phact
phact

Reputation: 7305

If you haven't already, make sure you have specified both hosts at the driver level.

Upvotes: 0

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