Add mysql.performance.performance_schema_digest_lost (#19121)

* new metrics from Performance_schema_digest_lost

* fix tests

* add metric to metadata.csv

* changelog

* move to STATUS_VARS

* fix test

mysql/changelog.d/19121.added

@@ -0,0 +1 @@
+Add `mysql.performance.performance_schema_digest_lost`, the number of digest instances that could not be instrumented in the `events_statements_summary_by_digest` table.

mysql/datadog_checks/mysql/const.py

@@ -39,6 +39,8 @@
     # Table Cache Metrics
     'Open_files': ('mysql.performance.open_files', GAUGE),
     'Open_tables': ('mysql.performance.open_tables', GAUGE),
+    # Performance schema metrics
+    'Performance_schema_digest_lost': ('mysql.performance.performance_schema_digest_lost', GAUGE),
     # Network Metrics
     'Bytes_sent': ('mysql.performance.bytes_sent', RATE),
     'Bytes_received': ('mysql.performance.bytes_received', RATE),

mysql/metadata.csv

@@ -170,6 +170,7 @@ mysql.performance.max_prepared_stmt_count,gauge,,,,The maximum allowed prepared
 mysql.performance.open_files,gauge,,file,,The number of open files.,0,mysql,open files,
 mysql.performance.open_tables,gauge,,table,,The number of of tables that are open.,0,mysql,open tables,
 mysql.performance.opened_tables,gauge,,table,second,"The number of tables that have been opened. If `opened_tables` is big, your `table_open_cache` value is probably too small.",0,mysql,mysql performance opened_tables,
+mysql.performance.performance_schema_digest_lost,gauge,,,,The number of digest instances that could not be instrumented in the events_statements_summary_by_digest table. This can be nonzero if the value of performance_schema_digests_size is too small.,0,mysql,mysql performance performance schema digest lost,
 mysql.performance.prepared_stmt_count,gauge,,query,second,The current number of prepared statements.,0,mysql,current prepared statements,
 mysql.performance.qcache.utilization,gauge,,fraction,,Fraction of the query cache memory currently being used.,0,mysql,mysql performance qcache utilization,
 mysql.performance.qcache_free_blocks,gauge,,block,,The number of free memory blocks in the query cache.,0,mysql,mysql performance qcache_free_blocks,

mysql/tests/variables.py

@@ -25,6 +25,8 @@
     # Table Cache Metrics
     'mysql.performance.open_files',
     'mysql.performance.open_tables',
+    # Performance schema metrics
+    'mysql.performance.performance_schema_digest_lost',
     # Network Metrics
     'mysql.performance.bytes_sent',
     'mysql.performance.bytes_received',