Serial consistency issue

[Silviu Butnariu]

Hi guys,

Having the following configuration: 3 nodes, RF=2, when executing a LWT query with CL=one (no serial consistency manually set) if one of the nodes is down (basically have 2 out of 3 nodes up) I get this error: SERIAL is not supported as conditional update commit consistency. Use ANY if you mean \"make sure it is accepted but I don't care how many replicas commit it for non-SERIAL reads\

It's similar to what error you'd get when setting serial consistency values to the consistency field - but i do set consistency one, not serial.

Some code, for context:

$clusterBuilder = new Builder();
$clusterBuilder
->withDefaultConsistency(\Cassandra::CONSISTENCY_ONE)
->withDefaultPageSize(1000)
->withContactPoints('node1, node2, node3')//node3 is down
->withPort(6666)
->withTokenAwareRouting(true)
->withConnectTimeout(5)
->withRequestTimeout(5)
->withPersistentSessions(true)
->withRoundRobinLoadBalancingPolicy()
->withCredentials('test', 'test');
$cluster = $clusterBuilder->build();
$session = $cluster->connect('mykeyspace');
$statement = new \Cassandra\SimpleStatement(
"UPDATE mykeyspace.my_table SET field1 = true WHERE field2 = false IF EXISTS");
$future = $session->executeAsync($statement);
$result = $future->get();
//this code(under the given conditions - 1 node down) gives the error above.

Even if i manually set consistency and serial_consistency via execution options, the same error appears.

$options = new \Cassandra\ExecutionOptions(array(
'consistency' => \Cassandra::CONSISTENCY_ONE,
'serial_consistency' => \Cassandra::CONSISTENCY_SERIAL
));
$future = $session->executeAsync($statement, $options);
$result = $future->get();

If all nodes are up, everything works as expected.
The issue seems similar to the one described here: https://issues.apache.org/jira/browse/CASSANDRA-10785
Could it be a driver problem, or am I missing something?

Thanks,
Silviu

[Michael Penick]

Before we dig into this. What versions of the php-driver and cpp-driver are you using?

Mike

The issue seems similar to the one described here: https://urldefense.proofpoint.com/v2/url?u=https-3A__issues.apache.org_jira_browse_CASSANDRA-2D10785&d=DwIFaQ&c=adz96Xi0w1RHqtPMowiL2g&r=Rf6Q4KBOgazA7AqLjbPEhmTMX0gM5i3vnlC-YCIo38g&m=qy0nBC53KL-L0hM6WxtiWfrx0YOZc87TmWw7yIBHE4w&s=BGLiGs_g0CPSh2zPL2vwmuXy3XrEbKek6-uqt32gTII&e=

Could it be a driver problem, or am I missing something?

Thanks,
Silviu

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[Michael Penick]

SERIAL and LOCAL_SERIAL are not supported by writes. Those consistencies should only be used for reads.

https://docs.datastax.com/en/cql/3.3/cql/cql_reference/cqlshConsistency.html

I was able to reproduce the "SERIAL is not supported as conditional update commit consistency..." error using cqlsh on a 3 node cluster:

cqlsh> CREATE KEYSPACE IF NOT EXISTS cycling  WITH REPLICATION = {    'class' : 'NetworkTopologyStrategy',    'dc1' : 2};

cqlsh> CREATE TYPE cycling.fullname ( firstname text, lastname text );

cqlsh> CREATE TABLE cycling.race_winners (race_name text, race_position int, cyclist_name FROZEN<fullname>, PRIMARY KEY (race_name, race_position));

cqlsh> INSERT INTO cycling.race_winners (race_name, race_position, cyclist_name) VALUES ('a', 1, {firstname:'mike',lastname:'p'});

cqlsh> CONSISTENCY SERIAL ;

cqlsh> UPDATE cycling.race_winners SET cyclist_name = {firstname:'mike',lastname:'q'} WHERE race_name = 'a' AND race_position = 1 IF EXISTS;

InvalidRequest: Error from server: code=2200 [Invalid query] message="SERIAL is not supported as conditional update commit consistency. Use ANY if you mean "make sure it is accepted but I don't care how many replicas commit it for non-SERIAL reads""

Note: All 3 nodes are up.

Mike

[Silviu Butnariu]

Hi Michael,

datastax/php-driver version is 1.2.2.

Yes, from cqlsh it all makes sense: if one sets CL=SERIAL and runs update query, it crashes. Thing is, I'm NOT setting CL to SERIAL, as highlighted in my snippet(I set CL to ONE), and I still get this error.

Thanks,
Silviu

[regis le bretonnic]

Hi Mickael

Thank for the answer. I work with Silviu and we think to have an explaination. It is globally a misunderstanding of how serial consistency works. To be honest, it is not very well explained.

The issue occured on our dev cluster that is a small one (3 nodes and RF=2). The serial CL seems to operate not on all nodes but on nodes that own data.

With RF=2 and 1 node down, we can not reach SERIAL on 66% of our LWT. Increasing RF to 3 solves everything.

What I learnt with our tests is that SERIAL CL operates on surviving servers that owns data and not on just surviving data.

Thread can be closed.

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