Setting up Exporters

The exporters below can be set up on any Linux-based system, but the instructions below use RHEL/CentOS 6 or 7. Version 7 or higher is recommended if possible.

• Installation
• Setup
  • RHEL / CentOS 7
  • RHEL / CentOS 6

Installation

Upgrading

• See CHANGELOG in documentation for full details on both major & minor version upgrades.

Installation on RHEL/CentOS 7

With RPM Packages

There are RPM packages available to Crunchy Data customers through the Crunchy Customer Portal.

If you install the below available packages with RPM, you can continue reading at the Setup section.

Available Packages

Without Packages

For non-package installations, the exporters & pg_bloat_check can be downloaded from their respective repositories:

User and Configuration Directory Installation

You will need to create a user named ccp_monitoring which you can do with the following command:

sudo useradd -m -d /var/lib/ccp_monitoring ccp_monitoring

Configuration File Installation

All executables are expected to be in the /usr/bin directory. A base node_exporter systemd file is expected to be in place already. An example one can be found here:

https://github.com/lest/prometheus-rpm/tree/master/node_exporter

The files contained in this repository are assumed to be installed in the following locations with the following names. In the instructions below, you should replace a double-hash (##) with the two-digit major version of PostgreSQL you are running (ex: 95, 96, 10, etc.).

node_exporter

The node_exporter data directory should be /var/lib/ccp_monitoring/node_exporter and owned by the ccp_monitoring user. You can set it up with:

sudo mkdir /var/lib/ccp_monitoring/node_exporter
sudo chmod 0700 /var/lib/ccp_monitoring/node_exporter
sudo chown ccp_monitoring /var/lib/ccp_monitoring/node_exporter

The following pgmonitor configuration files should be placed according to the following mapping:

postgres_exporter

The following pgmonitor configuration files should be placed according to the following mapping:

Setup

Setup on RHEL/CentOS 7

Service Configuration

The following files contain defaults that should enable the exporters to run effectively on your system for the purposes of using pgmonitor. You should take some time to review them.

If you need to modify them, see the notes in the files for more details and recommendations: - /etc/systemd/system/node_exporter.service.d/crunchy-node-exporter-service-el7.conf - /etc/sysconfig/node_exporter - /etc/sysconfig/postgres_exporter_pg##

Note that /etc/sysconfig/postgres_exporter_pg## is the default sysconfig file for monitoring the database running on the default port 5432 and connects to the “postgres” database. If you’ve installed the pgmonitor setup to a different database, modify this file accordingly or make a new one. If you make a new one, ensure the service name you enable references this file (see the Enable Services section below ).

Database Configuration

General Configuration

First, make sure you have installed the PostgreSQL contrib modules. You can install them with the following command:

sudo yum install postgresql##-contrib

Where ## corresponds to your current PostgreSQL version. For PostgreSQL 11 this would be:

sudo yum install postgresql11-contrib

You will need to modify your postgresql.conf configuration file to tell PostgreSQL to load shared libraries. In the default setup, this file can be found at /var/lib/pgsql/11/data/postgresql.conf.

Modify your postgresql.conf configuration file to add the following shared libraries

shared_preload_libraries = 'pg_stat_statements,auto_explain'

You will need to restart your PostgreSQL instance for the change to take effect. Neither of the above extensions are used outside of the postgres database itself, but we find they are extremely useful to have loaded and available in the database when further diagnosis of issues is required.

For each database you are planning to monitor, you will need to run the following command as a PostgreSQL superuser:

CREATE EXTENSION pg_stat_statements;

If you want the pg_stat_statements extension to be available in all newly created databases, you can run the following command as a PostgreSQL superuser:

psql -d template1 -c "CREATE EXTENSION pg_stat_statements;"

Monitoring Setup

Install the setup_pg##.sql script on the primary to main database you will be monitoring. If you have multiple databases in your cluster, it is best to just run this setup on the default “postgres” database and have the exporter service connect to it. For monitoring database specific metrics, see the section below for running multiple postgres exporters.

The common queries to all postgres versions are contained in queries_common.yml. Major version specific queries are contained in a relevantly named file. Queries for more specialized monitoring are contained in additional files.

postgres_exporter only takes a single yaml file as an argument for custom queries, so this requires concatinating the relevant files together. The sysconfig file for the service helps with this concatination task. The sysconfig config file /etc/sysconfig/postgres_exporter_pg## defines the variable QUERY_FILE_LIST=. Set this variable to a space delimited list of the full path names to all files that contain queries you want to be in the single file that postgres_exporter uses.

For example, to use just the common queries for PostgreSQL 9.6 modify relevant /etc/sysconfig/ file and update QUERY_FILE_LIST.

QUERY_FILE_LIST="/etc/postgres_exporter/96/queries_common.yml /etc/postgres_exporter/96/queries_per_db.yml /etc/postgres_exporter/96/queries_pg96.yml"

As an another example, to include queries for PostgreSQL 10 as well as pgbackrest and bloat modify the relevant /etc/sysconfig/ file and update QUERY_FILE_LIST:

QUERY_FILE_LIST="/etc/postgres_exporter/10/queries_common.yml /etc/postgres_exporter/10/queries_per_db.yml /etc/postgres_exporter/10/queries_pg10.yml /etc/postgres_exporter/10/queries_bloat.yml /etc/postgres_exporter/10/queries_backrest.yml"

For replica servers, the setup is the same except that the setup_pg##.sql file does not need to be run since writes cannot be done there and it was already run on the primary.

Access Control: GRANT statements

The ccp_monitoring database role (created by running the “setup_pg##.sql” file above) must be allowed to connect to all databases in the cluster. To do this, run the following command to generate the necessary GRANT statements:

SELECT 'GRANT CONNECT ON DATABASE "' || datname || '" TO ccp_monitoring;'
FROM pg_database
WHERE datallowconn = true;

This should generate one or more statements similar to the following:

GRANT CONNECT ON DATABASE "postgres" TO ccp_monitoring;

Bloat setup

Run the script on the specific database(s) you will be for monitoring bloat in the cluster. See special note in crontab.txt concerning a superuser requirement for using this script

psql -d postgres -c "CREATE EXTENSION pgstattuple;"
/usr/bin/pg_bloat_check.py -c "host=localhost dbname=postgres user=postgres" --create_stats_table
psql -d postgres -c "GRANT SELECT,INSERT,UPDATE,DELETE,TRUNCATE ON bloat_indexes, bloat_stats, bloat_tables TO ccp_monitoring;"

The /etc/postgres_exporter/##/crontab.txt file is meant to be a guide for how you setup the ccp_monitoring crontab. You should modify crontab entries to schedule your bloat check for off-peak hours. This script is meant to be run at most, once a week. Once a month is usually good enough for most databases as long as the results are acted upon quickly.

The script requires being run by a database superuser by default since it must be able to run a scan on every table. If you’d like to not run it as a superuser, you will have to create a new role that has read permissions on all tables in all schemas that are to be monitored for bloat. You can then change the user in the connection string option to the script.

Enable Services

sudo systemctl enable node_exporter
sudo systemctl start node_exporter
sudo systemctl status node_exporter

To most easily allow the possibility of multiple postgres exporters, running multiple major versions of PostgreSQL, and to avoid maintaining many similar service files, a systemd template service file is used. The name of the sysconfig EnvironmentFile to be used by the service is passed as the value after the “@” and before “.service” in the service name. The default exporter’s EnvironmentFile is named “postgres_exporter_pg##” and tied to the major version of postgres that it was installed for. Be sure to replace the ## in the below commands first!

sudo systemctl enable crunchy-postgres-exporter@postgres_exporter_pg##.service
sudo systemctl start crunchy-postgres-exporter@postgres_exporter_pg##
sudo systemctl status crunchy-postgres-exporter@postgres_exporter_pg##

Running multiple postgres exporters (RHEL / CentOS 7)

Certain metrics are not cluster-wide, so in that case multiple exporters must be run to collect all relevant metrics. The queries_perdb.yml file contains these queries and the secondary exporter(s) can use this file to collect those metrics and avoid duplicating cluster-wide metrics. Note that some other metrics are per database as well (bloat). You can then define multiple targets for that job in Prometheus so that all the metrics are collected together. Note that the “setup*.sql” file does not need to be run on these additional databases.

cd /etc/postgres_exporter/96
cat queries_per_db.yml queries_bloat.yml > queries_mydb.yml

You’ll need to create a new sysconfig environment file for the second exporter service. You can just copy the existing ones and modify the relevant lines, mainly being the port, database name, and query file

cp /etc/sysconfig/postgres_exporter_pg## /etc/sysconfig/postgres_exporter_mydb

OPT="--web.listen-address=0.0.0.0:9188 --extend.query-path=/etc/postgres_exporter/96/queries_mydb.yml"
DATA_SOURCE_NAME="postgresql://ccp_monitoring@localhost:5432/mydb?sslmode=disable"
QUERY_FILE_LIST="/etc/postgres_exporter/96/queries_common.yml /etc/postgres_exporter/96/queries_per_db.yml /etc/postgres_exporter/96/queries_pg96.yml"

Since a systemd template is used for the postgres_exporter services, all you need to do is pass the sysconfig file name as part of the new service name.

sudo systemctl enable crunchy-postgres-exporter@postgres_exporter_mydb.service
sudo systemctl start cruncy-postgres-exporter@postgres_exporter_mydb
sudo systemctl status crunchy-postgres-exporter@postgres_exporter_mydb

Lastly, update the Prometheus auto.d target file to include the new exporter in the same one you already had running for this system

Note for packaging (RHEL/CENTOS 7)

The service override file(s) must be placed in the relevant drop-in folder to override the default service files.

/etc/systemd/system/node_exporter.service.d/\*.conf

After a daemon-reload, systemd should automatically find these files and the crunchy services should work as intended.

Installation / Setup on RHEL/CentOS 6

The node_exporter and postgres_exporter services on RHEL6 require the “daemonize” package that is part of the EPEL repository. This can be turned on by running:

sudo yum install epel-release

All setup for the exporters is the same on RHEL6 as it was for 7 with the exception of the base service files. Whereas RHEL7 uses systemd, RHEL6 uses init.d. The Crunchy RHEL6 packages will create the base service files for you

/etc/init.d/crunchy-node-exporter
/etc/init.d/crunchy-postgres-exporter

Note that these service files are managed by the package and any changes you make to them could be overwritten by future updates. If you need to customize the service files for RHEL6, it’s recommended making a copy and editing/using those.

Or if you are setting this up manually, the repository file locations and expected directories are:

node/crunchy-node-exporter-el6.service -> /etc/init.d/crunchy-postgres-exporter
postgres/crunchy-postgres-exporter-el6.service -> /etc/init.d/crunchy-postgres-exporter

/var/run/postgres_exporter/
/var/log/postgres_exporter/ (owned by postgres_exporter service user)

/var/run/node_exporter/
/var/log/node_exporter/ (owned by node_exporter service user)

The same /etc/sysconfig files that are used in RHEL7 above are also used in RHEL6, so follow guidance above concerning them and the notes that are contained in the files themselves.

Once the files are in place, set the service to start on boot, then manually start it

sudo chkconfig crunchy-node-exporter on
sudo service crunchy-node-exporter start
sudo service crunchy-node-exporter status

sudo chkconfig crunchy-postgres-exporter on
sudo service crunchy-postgres-exporter start
sudo service crunchy-postgres-exporter status

Running multiple postgres exporters (RHEL / CentOS 6)

If you need to run multiple postgres_exporter services, follow the same instructions as RHEL / CentOS 7 for making a new queries_XX.yml file to only gather database specific metrics. Then follow the steps below:

- Make a copy of the /etc/sysconfig file with a new name
- Update --web.listen-address in the new sysconfig file to use a new port number
- Update --extend.query-path in the new sysconfig file to point to the new query file generated
- Update the DATA_SOURCE_NAME in the new sysconfig file to point to the name of the database to be monitored
- Update the QUERY_FILE_LIST in the new sysconfig file to list all the name of yaml files used for metric collection
- Make a copy of the /etc/init.d/crunchy-postgres-exporter with a new name
- Update the SYSCONFIG variable in the new init.d file to match the new sysconfig file
- Update the Prometheus auto.d target file to include the new exporter in the same one you already had running for this system

Remaining steps to initialize service at boot and start it up should be the same as above for the default service.