Enabling the Data Collection Agents

This section describes how to create the Command Center database and enable the Command Center data collection agents. When the data collection agents are enabled, their processes are started and stopped along with the Greenplum Database server processes (using gpstart and gpstop).

Greenplum provides a gpperfmon_install utility that performs the following tasks:

Creates the Command Center database (gpperfmon).
Creates the Command Center superuser role (gpmon).
Configures Greenplum Database server to accept connections from the Command Center superuser role (edits the pg_hba.conf and .pgpass files).
Sets the Command Center server configuration parameters in the Greenplum Database server postgresql.conf files.

To enable the Collection Agents

Log in to the Greenplum master host as the gpadmin user.
```
$ su - gpadmin
```
Source the path file from your master host's Greenplum Database installation directory:
```
# source /usr/local/greenplum-db/greenplum_path.sh
```
Run the gpperfmon_install utility with the --enable option. You must supply the connection port of the Greenplum Database master server process, and set the password for the gpmon superuser that will be created. For example:
```
$ gpperfmon_install --enable --password changeme --port 5432
```
Note:
The gperfmon_install utility adds the gpmon user to the pg_hba.conf authorization configuration file with an entry that permits local connections to any database. Since the gpmon role is a Greenplum Database superuser, you may wish to restrict the role to just the gpperfmon database after you run gpperfmon_install. Edit the $MASTER_DATA_DIRECTORY/pg_hba.conf file and change this line:
```
host     all         gpmon         127.0.0.1/28    md5
```
to the following:
```
host     gpperfmon   gpmon         127.0.0.1/28    md5
```
When the utility completes, restart Greenplum Database server. The data collection agents will not start until the database is restarted.
```
$ gpstop -r
```
Using the ps command, verify that the data collection process is running on the Greenplum master. For example:
```
$ ps -ef | grep gpmmon
```
Run the following command to verify that the data collection processes are writing to the Command Center database. If all of the segment data collection agents are running, you should see one row per segment host.
```
$ psql gpperfmon -c 'SELECT * FROM system_now;'
```

The data collection agents are now running, and your Greenplum system now has a gpperfmon database installed. This is the database where Command Center data is stored. You can connect to it as follows:

$ psql gpperfmon

To configure a standby master host (if enabled)

Copy the $MASTER_DATA_DIRECTORY/pg_hba.conf file from your primary master host to your standby master host. This ensures that the required connection options are also set on the standby master.
Copy your ~/.pgpass file from your primary master host to your standby master host. This file usually resides in the gpadmin user’s home directory. Note that the permissions on .pgpass must be set to 600 (for example: chmod 0600 ~/.pgpass).