Bug: Non-Paged CQL Reads Gauge isn't working.

[Daniel Reis]

Installation details
Dashboard Name: Scylla CQL
Scylla-Monitoring Version: 4.6, 4.7 (tested)
Scylla-Version: Any

Problem

I was testing the Optimization Tab and saw that the "Non-Paged CQL Reads" gauge isn't working. After a couple hours debugging, I found out that the query is crashing due a [[by]] inside the statement that isn't present in any other gauge.

To make sure I replicated it into other versions and also at Scylla Cloud and we still have the same problem. Maybe it is affecting other versions, but it would be really good to check it out.

Here's the current query:

100 * (
    (
        sum(rate(
            scylla_cql_unpaged_select_queries{
                instance=~"[[node]]",
                cluster="$cluster", 
                dc=~"$dc", 
                shard=~"[[shard]]"
            }[1m]
        )) 
        - 
        sum(rate(
            scylla_cql_unpaged_select_queries_per_ks{
                ks="system", 
                instance=~"[[node]]", 
                cluster="$cluster", 
                dc=~"$dc", 
                shard=~"[[shard]]"
            }[1m]
        )) by ([[by]])
    )
    /
    sum(rate(
        scylla_cql_reads{
            instance=~"[[node]]",
            cluster="$cluster", 
            dc=~"$dc", 
            shard=~"[[shard]]"
        }[1m]
    ))
) OR vector(0)

The new query with the fix:

100 * (
    (
        sum(rate(
            scylla_cql_unpaged_select_queries{
                instance=~"[[node]]",
                cluster="$cluster", 
                dc=~"$dc", 
                shard=~"[[shard]]"
            }[1m]
        )) 
        - 
        sum(rate(
            scylla_cql_unpaged_select_queries_per_ks{
                ks="system", 
                instance=~"[[node]]", 
                cluster="$cluster", 
                dc=~"$dc", 
                shard=~"[[shard]]"
            }[1m]
        )) // by removed
    )
    /
    sum(rate(
        scylla_cql_reads{
            instance=~"[[node]]",
            cluster="$cluster", 
            dc=~"$dc", 
            shard=~"[[shard]]"
        }[1m]
    ))
) OR vector(0)

Hope that it helps somehow.

[Daniel Reis]

Hey @amnonh! I'm running the LTS 4.7 and still having this issue. Can you verify if it was merged in the other versions?

[Yaniv Kaul]

Hey @amnonh! I'm running the LTS 4.7 and still having this issue. Can you verify if it was merged in the other versions?

4.7 isn't LTS (AFAIK) and the bug is fixed in 4.8 (not released yet).