Secondary Indexs / Materialized Views maybe be built in the background - please provide some indication of that

[slivne]

There maybe metrics reflecting that as well - @psarna / @nyh - do we have any info of backgroundbuilding of MV/SI and how far are we from completion ?

We have an internal system table providing the status

cassandra@cqlsh:ks> select * from system_distributed.view_build_status ;

 keyspace_name | view_name          | host_id                              | status
---------------+--------------------+--------------------------------------+---------
            ks | testme_v_idx_index | 5bc2500d-9d2c-4edb-97fd-8ba05e55f445 | SUCCESS

In my view - we only need an indication this is being done in the background

[amnonh]

relates to #1227

[amnonh]

@nyh @psarna do we have such metrics?

[psarna]

void view_builder::setup_metrics() {
    namespace sm = seastar::metrics;

    _metrics.add_group("view_builder", {
        sm::make_gauge("pending_bookkeeping_ops",
                sm::description("Number of tasks waiting to perform bookkeeping operations"),
                [this] { return _sem.waiters(); }),

        sm::make_derive("steps_performed",
                sm::description("Number of performed build steps."),
                _stats.steps_performed),

        sm::make_derive("steps_failed",
                sm::description("Number of failed build steps."),
                _stats.steps_failed),

        sm::make_gauge("builds_in_progress",
                sm::description("Number of currently active view builds."),
                [this] { return _base_to_build_step.size(); })
    });
}

builds_in_progress will indicate if there are active background processes, from steps_performed you can estimate how fast the process is going (or if it's stuck for some reason), and steps_failed will indicate if the process generally succeeds or fails.

[amnonh]

@psarna what scylla versions (os/enterprise) this metrics are available?

[psarna]

OS 4.3

[amnonh]

@slivne I'm assigning it to you for the decision, is annotations are applicable