error UnexpectedWriteType("CAS")) with multiple tokio tasks

[devrandom]

I am getting error UnexpectedWriteType("CAS")) when doing batch inserts from multiple tasks in the same Session object.

It fails intermittently on a three node cluster with Cassandra version [cqlsh 6.0.0 | Cassandra 4.0.5 | CQL spec 3.4.5 | Native protocol v5]. It works consistently with a single task.

On a local Cassandra instance in docker, it work consistently with multiple tasks - version 4.0.6.

[krojew]

Can you check with protocol v4?

[devrandom]

Do you mean downgrade to an old Cassandra? or is there a way to make it fall back to the older protocol?

[krojew]

You can specify the protocol version when building connection configuration: https://docs.rs/cdrs-tokio/7.0.0/cdrs_tokio/cluster/struct.NodeTcpConfigBuilder.html#method.with_version

[devrandom]

It happens with V3, V4 and V5. Less often in the older protocol versions.

[devrandom]

Also, wanted to mention that this is an LWT batch. The code in question is here: https://gitlab.com/lightning-signer/validating-lightning-signer/-/merge_requests/312/diffs#144ee5d06667bb53830287a66cd0bda0b514e40c_0_319 (look for async fn put if I push again and invalidate the line locator)

[devrandom]

The scylla driver gives me a more detailed error: Scylla(QueryError(DbError(WriteTimeout { consistency: Serial(LocalSerial), received: 1, required: 2, write_type: Cas }, "Operation timed out - received only 1 responses.")))'

So cdrs is probably getting confused by the write_type on this error.

Well, I'm confused by this error myself...

[krojew]

If you're getting it on a two different drivers, it means a problem in your cluster.

[devrandom]

agreed. however, the cdrs driver does eat part of the error - would be good to fix.

[krojew]

Sure, I'll take a look.

[krojew]

This turns out to be a braking change and will be included in the next major version.

• Add remaining options from https://github.com/apache/cassandra/blob/trunk/doc/native_protocol_v5.spec#L1289
• Remove Copy from WriteType
• Add UnknownWriteType(String) variant
• Add non_exhaustive