commit 45995e6892720fce476f1c9df53941ed870d1a04
author Michael Smith <michael.smith@cloudera.com> Wed Dec 06 13:39:41 2023 -0800
committer Michael Smith <michael.smith@cloudera.com> Thu Mar 28 16:34:48 2024 +0000
tree b1303c9a2caecbe3cdd6978f8b2c192f5ad0671b
parent b03cfcf2ade6dea7fed10f4a3db5c58ddf2c6bd2

IMPALA-12540: Query Live Table

Defines SystemTable which are in-memory tables that can provide access
to Impala state. Adds the 'impala_query_live' to the database 'sys',
which already exists for 'sys.impala_query_log'.

Implements the 'impala_query_live' table to view active queries across
all coordinators sharing the same statestore. SystemTables create new
SystemTableScanNodes for their scan node implementation. When computing
scan range locations, SystemTableScanNodes creates a scan range for each
in the cluster (identified via ClusterMembershipMgr). This produces a
plan that looks like:

Query: explain select * from sys.impala_query_live
+------------------------------------------------------------+
| Explain String                                             |
+------------------------------------------------------------+
| Max Per-Host Resource Reservation: Memory=4.00MB Threads=2 |
| Per-Host Resource Estimates: Memory=11MB                   |
| WARNING: The following tables are missing relevant table   |
| and/or column statistics.                                  |
| sys.impala_query_live                                      |
|                                                            |
| PLAN-ROOT SINK                                             |
| |                                                          |
| 01:EXCHANGE [UNPARTITIONED]                                |
| |                                                          |
| 00:SCAN SYSTEM_TABLE [sys.impala_query_live]               |
|    row-size=72B cardinality=20                             |
+------------------------------------------------------------+

Impala's scheduler checks for whether the query contains fragments that
can be scheduled on coordinators, and if present includes an
ExecutorGroup containing all coordinators. These are used to schedule
scan ranges that are flagged as 'use_coordinator', allowing
SystemTableScanNodes to be scheduled on dedicated coordinators and
outside the selected executor group.

Execution will pull data from ImpalaServer on the backend via a
SystemTableScanner implementation based on table name.

In the query profile, SYSTEM_TABLE_SCAN_NODE includes
ActiveQueryCollectionTime and PendingQueryCollectionTime to track time
spent collecting QueryState from ImpalaServer.

Grants QueryScanner private access to ImpalaServer, identical to how
ImpalaHttpHandler access internal server state.

Adds custom cluster tests for impala_query_live, and unit tests for
changes to planner and scheduler.

Change-Id: Ie2f9a449f0e5502078931e7f1c5df6e0b762c743
Reviewed-on: http://gerrit.cloudera.org:8080/20762
Reviewed-by: Jason Fehr <jfehr@cloudera.com>
Reviewed-by: Riza Suminto <riza.suminto@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>