This PR
* Addresses a concurrency issue in the probabilistic approach of tenant
monitoring by acquiring a shared lock for tenant existence checks.
* Changes `citus.stat_tenants_sample_rate_for_new_tenants` type to
double
* Renames `citus.stat_tenants_sample_rate_for_new_tenants` to
`citus.stat_tenants_untracked_sample_rate`
DESCRIPTION: Enabling citus_stat_tenants to support schema-based
tenants.
This pull request modifies the existing logic to enable tenant
monitoring with schema-based tenants. The changes made are as follows:
- If a query has a partitionKeyValue (which serves as a tenant
key/identifier for distributed tables), Citus annotates the query with
both the partitionKeyValue and colocationId. This allows for accurate
tracking of the query.
- If a query does not have a partitionKeyValue, but its colocationId
belongs to a distributed schema, Citus annotates the query with only the
colocationId. The tenant monitor can then easily look up the schema to
determine if it's a distributed schema and make a decision on whether to
track the query.
---------
Co-authored-by: Jelte Fennema <jelte.fennema@microsoft.com>
citus.tenant_stats_limit was set to 2 when we were adding tests for it.
Then we changed it to 10, making the tests incorrect.
This PR fixes that without breaking other tests.
This PR updates the tenant stats implementation to set partitionKeyValue
and colocationId in ExecuteLocalTaskListExtended, in addition to
LocallyExecuteTaskPlan. This ensures that tenant stats can be properly
gathered regardless of the code path taken. The changes were initially
made while testing stored procedure calls for tenant stats.
Fixes the bug that causes updating the citus_stat_tenants periods
incorrectly.
`TimestampDifferenceExceeds` expects the difference in milliseconds but
it was microseconds, this is fixed.
`tenantStats->lastQueryTime` was updated during monitoring too, now it's
updated only when there are tenant queries.
DESCRIPTION: Adds views that monitor statistics on tenant usages
This PR adds `citus_stats_tenants` view that monitors the tenants on the
cluster.
`citus_stats_tenants` shows the node id, colocation id, tenant
attribute, read count in this period and last period, and query count in
this period and last period of the tenant.
Tenant attribute currently is the tenant's distribution column value,
later when schema based sharding is introduced, this meaning might
change.
A period is a time bucket the queries are counted by. Read and query
counts for this period can increase until the current period ends. After
that those counts are moved to last period's counts, which cannot
change. The period length can be set using 'citus.stats_tenants_period'.
`SELECT` queries are counted as _read_ queries, `INSERT`, `UPDATE` and
`DELETE` queries are counted as _write_ queries. So in the view read
counts are `SELECT` counts and query counts are `SELECT`, `INSERT`,
`UPDATE` and `DELETE` count.
The data is stored in shared memory, in a struct named
`MultiTenantMonitor`.
`citus_stats_tenants` shows the data from local tenants.
`citus_stats_tenants` show up to `citus.stats_tenant_limit` number of
tenants.
The tenants are scored based on the number of queries they run and the
recency of those queries. Every query ran increases the score of tenant
by `ONE_QUERY_SCORE`, and after every period ends the scores are halved.
Halving is done lazily.
To retain information a longer the monitor keeps up to 3 times
`citus.stats_tenant_limit` tenants. When the tenant count hits `3 *
citus.stats_tenant_limit`, last `citus.stats_tenant_limit` tenants are
removed. To see all stored tenants you can use
`citus_stats_tenants(return_all_tenants := true)`
- [x] Create collector view that gets data from all nodes. #6761
- [x] Add monitoring log #6762
- [x] Create enable/disable GUC #6769
- [x] Parse the annotation string correctly #6796
- [x] Add local queries and prepared statements #6797
- [x] Rename to citus_stat_statements #6821
- [x] Run pgbench
- [x] Fix role permissions #6812
---------
Co-authored-by: Gokhan Gulbiz <ggulbiz@gmail.com>
Co-authored-by: Jelte Fennema <github-tech@jeltef.nl>
Gokhan Gulbiz
Ahmet Gedemenli
Halil Ozan Akgül