Pivotal Greenplum® Command Center 4.1.0 Release Notes

About This Release

This document contains pertinent release information about Pivotal Greenplum Command Center 4.1.0. Greenplum Command Center 4.1.0 is a minor release that adds features and resolves some issues.

See Enhancements and Changes in Greenplum Command Center 4.1.0 for information about new features and changes in this Command Center release.

If your Greenplum Database system has a standby master, you must start Greenplum Command Center on the standby master. When you have finished installing Command Center, see Starting and Stopping the Web Server for steps to start the Command Center web server.

Supported Platforms

Greenplum Command Center 4.1.0 is compatible with the following platforms.

  • Pivotal Greenplum Database 5.8.0 and higher
  • Red Hat Enterprise Linux 6.x and 7.x
  • CentOS 6.x and 7.x

If you use resource groups and workload management on Red Hat or CentOS 6.x, upgrade your kernel to 2.6.32-696 or higher to benefit from improvements in the Linux cgroups service.

Enhancements and Changes in Greenplum Command Center 4.1.0

Greenplum Command Center 4.1.0 contains the following enhancements.

  • Command Center administrators can set permission levels for Command Center users. Permissions are enforced as described in the documentation.
  • On the Query Detail view, clicking Copy in the query text or query plan panel copies the text in the panel to the clipboard.

  • A help icon and in-app help have been added on the Query Monitor and Query Detail views.

The following workload management features, improvements, and bug fixes have been added in the workload management extension included with Greenplum Database 5.8.0.

  • On the Admin>Workload Mgmt view, you can add idle session kill rules for each resource group. When you add these rules, the Greenplum Database workload management extension kills a session after it has been idle for the number of seconds you specify.See Defining Workload Management Rules for syntax and examples.

  • Optimizations have been implemented to reduce the impact on Greenplum Database when the workload management extension is disabled.

  • The workload management extension takes advantage of resource group name-to-id caching added in Greenplum Database.

  • Fixed a bug in the workload management extension that caused errors to print to the psql prompt, even when the extension was disabled.

Greenplum Command Center 4.1.0 contains the following bug fixes.

  • In the History Detail view, when either of the Disk R or Disk W metrics is 0, both are reported to be 0. This is fixed.

  • When using the Kerberos gpmon-only authentication mode, generating an explain plan failed. This is fixed.

  • The Command Center agent failed with the message “Error: can’t find gpcc.query_metrics_port, metrics_collector is not correctly installed.” This occurs when running Command Center on a Greenplum Database system that was upgraded from an earlier Greenplum Database 5.x release. The metrics_collector and gp_wlm extensions are installed with the upgrade, but the upgrade process does not perform the required configuration changes in the postgresql.conf configuration file. The Command Center installation instructions now include steps to manually configure and restart an upgraded Greenplum Database system.

  • When Command Center starts, an error message is written in the Greenplum Database log file: “function gpcc_schema.read_pghba(unknown) does not exist.” This is fixed.

  • A change to time zone handling in Greenplum Database 5.7 can cause Greenplum Command Center 4.0.0 to display an incorrect time if the master host operating system time and Greenplum Database use different time zones. Now Command Center times are displayed using the time zone of the Greenplum Database master host operating system. The current time, last sync time, and timestamps in alert logs, cluster metrics, and query history are all displayed using the master host’s system time zone.

  • On the Admin> Authorization view, when the authorization method is gss and the options field contains text, changing the method to trust does not clear the options field and it is not possible to save changes to the pg_hba.conf file.

  • The Command Center web server, gpccws, spawns ssh processes but does not reap them in a timely manner, leading to many zombie processes. This is fixed.

  • On the Admin> Authentication view, if the number of users listed in the user column is longer than can be displayed, Command Center truncates the list and adds ellipsis (...) to the end. Only administrators can view the complete value, by editing the field. Now any user with access to the view can see the full list of users by hovering over the field.

Enhancements and Changes in Greenplum Command Center 4.0.0

Command Center Installation Changes

Greenplum Command Center 4.x software, unlike previous releases, is installed on every host in the Greenplum Database cluster. The Command Center web server and backend run on the standby master, if your Greenplum Database cluster has a standby master. If there is no standby master, Command Center runs on the master host instead.

To modify the Command Center installation—for example to enable or disable SSL or install Command Center on new or replaced hosts—just re-execute the installer and restart Command Center. It is not necessary to uninstall Command Center before reinstalling.

There is one Command Center installation per Greenplum Database cluster. It is no longer necessary to create Command Center instances after installing the software.

The gpcmdr command-line utility is replaced with the new gpcc utility. Use the gpcc utility to start and stop Command Center and metrics collection agents, check Command Center status, and enable or disable Kerberos authentication.

In previous releases, the gpmon role required only local connections to databases on the Greenplum master host. In Greenplum Command Center 4.x, the gpmon user must be able to connect to databases from the host running the Command Center web server and backend, which requires adding a host entry to the pg_hba.conf authentication configuration file.

Real-time Query Metrics

Greenplum Command Center 4.0 introduces real-time query metrics for Pivotal Greenplum Database 5.7 and above. This new feature combines the following new features in Greenplum Database and Greenplum Command Center:

  • Greenplum Database saves query execution metrics in shared memory while queries execute.
  • A new Greenplum Database metrics collection extension, included with Pivotal Greenplum Database, emits the saved metrics as UDP datagrams.
  • A new Greenplum Command Center metrics collection agent running on each Greenplum Database host receives the datagrams and posts metrics to the Greenplum Command Center backend. The Command Center backend starts and manages the metrics collection agents.

The Command Center Query monitor view updates in real time so you can see queries that are waiting to execute and the current status and resource usage for queries that are running.

Metrics collection now includes lock and spill file information. On the Query Monitor, you can see which queries are blocked and which queries hold the locks blocking them. The Query Monitor shows the total size of spill files created on all segments for each query.

Installing the gpperfmon database remains a prerequisite for Command Center. The gpperfmon database is the source for query history displayed in the Command Center user interface. The new real-time metrics are not persisted and are not directly related to the metrics collected and persisted in the gpperfmon database.

Workload Management

Workload management is now an integrated Command Center feature rather than a separate product. Workload management is available in Command Center only after resource groups have been enabled in Greenplum Database by changing the gp_resource_manager server configuration parameter from 'queue' to 'group' and enabling Linux control groups (cgroups).

In Command Center 4.0, workload management allows you to assign transactions to Greenplum Database resource groups at execution time by evaluating the current database role and query tags against workload assignment filters you define in Command Center. Query tags are user-defined name=value parameters that you define in the gpcc.query_tags database session parameter. You can define multiple query tags separated by semicolons. Set query tags in a Greenplum Database session either as a parameter in the database connection URL or by executing SET gpcc.query_tags TO '<tag1>=<val1>;<tag2>=<val2>;...' in the database session.

When a transaction is about to execute, the current database role and query tags are compared to the workload assignment filters that you have created in Command Center. If a match is found, the transaction is assigned to a resource group according to the workload management filter. Otherwise, the transaction is assigned to the database user’s resource group, which is the default behavior when Command Center workload management is not enabled.

Workload management uses the gp_wlm database extension included with Pivotal Greenplum Database.

Unimplemented Features

Some features available in previous Greenplum Command Center releases have been removed or are not yet implemented in Command Center 4.0.0.

  • The Basic, Operator Basic, and Operator permission levels are not yet implemented. You can only change a role’s permission level between Self Only and Admin. This feature has been restored in Command Center 4.1.0.
  • The ability for a Command Center admin to post a message to the Query Monitor view is not yet implemented.
  • The multi-cluster view has been removed.