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https://issues.apache.org/jira/browse/CASSANDRA-15399?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16980225#comment-16980225
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Stefan Podkowinski commented on CASSANDRA-15399:
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We could also have the coordinator send VALIDATION_REQUEST on reoccurring basis
and receive the latest status from that, instead of sending
VALIDATION_STATUS_REQ explicitly. This would allow us to resume validations, in
case the participant went down during validation and was restarted.
Haven't looked through all the proposed code changes, but impact seems to be
rather big for an observability patch. I think it will be convenient for users
to be able to query repair state, but we should keep a good balance between
value from that and potential regressions.
> Add ability to track state in repair
> ------------------------------------
>
> Key: CASSANDRA-15399
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15399
> Project: Cassandra
> Issue Type: Improvement
> Components: Consistency/Repair
> Reporter: David Capwell
> Assignee: David Capwell
> Priority: Normal
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> To enhance the visibility in repair, we should expose internal state via
> virtual tables; the state should include coordinator as well as participant
> state (validation, sync, etc.)
> I propose the following tables:
> repairs - high level summary of the global state of repair; this should be
> called on the coordinator.
> {code:sql}
> CREATE TABLE repairs (
> id uuid,
> keyspace_name text,
> table_names frozen<list<text>>,
> ranges frozen<list<text>>,
> coordinator text,
> participants frozen<list<text>>,
> state text,
> progress_percentage float,
> last_updated_at_millis bigint,
> duration_micro bigint,
> failure_cause text,
> PRIMARY KEY ( (id) )
> )
> {code}
> repair_tasks - represents RepairJob and participants state. This will show
> if validations are running on participants and the progress they are making;
> this should be called on the coordinator.
> {code:sql}
> CREATE TABLE repair_tasks (
> id uuid,
> session_id uuid,
> keyspace_name text,
> table_name text,
> ranges frozen<list<text>>,
> coordinator text,
> participant text,
> state text,
> state_description text,
> progress_percentage float, -- between 0.0 and 100.0
> last_updated_at_millis bigint,
> duration_micro bigint,
> failure_cause text,
> PRIMARY KEY ( (id), session_id, table_name, participant )
> )
> {code}
> repair_validations - shows the state of the validation task and updated
> periodically while validation is running; this should be called on the
> participants.
> {code:sql}
> CREATE TABLE repair_validations (
> id uuid,
> session_id uuid,
> ranges frozen<list<text>>,
> keyspace_name text,
> table_name text,
> initiator text,
> state text,
> progress_percentage float,
> queue_duration_ms bigint,
> runtime_duration_ms bigint,
> total_duration_ms bigint,
> estimated_partitions bigint,
> partitions_processed bigint,
> estimated_total_bytes bigint,
> failure_cause text,
> PRIMARY KEY ( (id), session_id, table_name )
> )
> {code}
> The main reason for exposing virtual tables rather than exposing through
> durable tables is to make sure what is exposed is accurate. In cases of
> write failures or node failures, the durable tables could become in-accurate
> and could add edge cases where the repair is not running but the tables say
> it is; by relying on repair's internal in-memory bookkeeping, these problems
> go away.
> This jira does not try to solve the following:
> 1) repair resiliency - there are edge cases where repair hits an error and
> runs forever (at least from nodetool's perspective).
> 2) repair stream tracking - I have not learned the streaming side yet and
> what I see is multiple implementations exist, so seems like high scope. My
> hope is to punt from this jira and tackle separately.
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