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Timescale is Postgresql based open source time series DB. Unlike Influx, Timescale does not store all the indexes in RAM, therefore it can be used to store large amount of metric values. In this case, the same Postgresql DB can be used to store metric values, stream history and data acquisition settings.

Postgresql and Timescale DB installation

A specific Postgresql version (9.6, 10 or 11) must be installed during setup process. If earlier Postgresql version is installed (for example, Centos 7 default repository contains Posgresql 9.2), it shoud be fully removed including /usr/bin executables.

To setup Postgresql 9.6+Timescale DB on CentOS 7, do the following:

1. Install Postgresql repository

yum install -y https://download.postgresql.org/pub/repos/yum/11/redhat/rhel-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm

2. Create /etc/yum.repos.d/timescale_timescaledb.repo file

[timescale_timescaledb]
name=timescale_timescaledb
baseurl=https://packagecloud.io/timescale/timescaledb/el/7/$basearch
repo_gpgcheck=1
gpgcheck=0
enabled=1
gpgkey=https://packagecloud.io/timescale/timescaledb/gpgkey
sslverify=1
sslcacert=/etc/pki/tls/certs/ca-bundle.crt
metadata_expire=300

3. Install Postgresql

yum install -y postgresql96-server

4. Install TimescaleDB

yum install -y timescaledb-postgresql-9.6

5. Initialize Postgresql DB

/usr/pgsql-9.6/bin/postgresql96-setup initdb

6. Configure Postgresql to work with Timescale DB

timescaledb-tune --yes --pg-config=/usr/pgsql-9.6/bin/pg_config

7. Configure access to Postgresql tables in /var/lib/pgsql/9.6/data/pg_hba.conf file

# IPv4 local connections:
host    all             all             127.0.0.1/32            md5
# IPv6 local connections:
host    all             all             ::1/128                 md5

8. Launch Postgresql

su - postgres
/usr/pgsql-9.6/bin/postgresql &

9. Enter Postgresql console

/usr/pgsql-9.6/bin/psql

10. Create user and DB

CREATE USER wcsoam WITH PASSWORD 'wcsoam';
CREATE DATABASE wcsstat;

11. Grant DB privileges to user

\с wcsstat
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO "wcsoam";

12. Initialize Timescale extension

CREATE EXTENSION IF NOT EXISTS timescaledb CASCADE;

13. Create DB to store stream history and data acquisition settings

CREATE DATABASE wcsoam;
\c wcsoam
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO "wcsoam";

14. Exit Postgresql console

\q
exit

Timescale DB setup

To configure Timescale DB for metric storage, do the following:

1. Set the following parameter in wcsoam.properties file

metric_store=timescale

2. Set metrics storage chunk interval in init_tsdb.properties file

timescale_chunk_interval=2 days

By default, metrics are stored in 2 days chunks.

3. Launch DB setup script

./init_tsdb.sh

Data retention setup using cron

To save disk space, data retention can be set using cron utility. For example, set crontab as follows to check conditions table every 5 minutes and delete metrics data older than 5 days:

*/5 * * * * PGPASSWORD="wcsoam" /usr/pgsql-9.6/bin/psql -h localhost -p 5432 -U wcsoam -d wcsstat -w -c "SELECT drop_chunks(interval '5 days', 'conditions');"

DB structure

The following table shoul be in Postgresql to store metrics data

FieldTypeNote
CONDITIONS
timetimestamptzNOT NULL
node_idbigintNOT NULL
media_idcharacter varying(255)
video_heightbigint
video_widthbigint
video_ratebigint


video_syncbigint
video_fpsbigint
video_nackbigint
video_plibigint
video_codecbigint
audio_syncbigint
audio_ratebigint
audio_lostbigint
audio_codecbigint

Metrics data are fragmented to chunks and are stored to subtables, each subtable volume is defined by chunk duration. To limit subtables amount, it is recommeded to setup data retention using cron with maximum data storage interval.

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