Category: Software

Clickhouse multi master replication

EnglishSoftwareTutorials

File for reproductible environment :

Nothing is stored on the VM instances : see volumes configuration out of the docker-compose file.

Sharding and replica is straightforward and defined in these files :

  • ch_configs/config.d/remote_server.xml
  • ch-configs/macros_chX.xml (replace X with server’s instance number)

Starting clickhouse servers :

$ docker-compose up -d ch1 ch2 ch3 ch4

$ docker ps -a

To use it either use any client you prefer (Tabix, …) or connect with the client (already defined in docker-compose file):

$ docker-compose run –rm client –host ch1 –user quid –password quid

3d8fccb51750 🙂 SELECT * FROM system.clusters

Database and tables creation

CREATE DATABASE todos_cluster on cluster todos;

SHOW DATABASES;

show tables from todos_cluster

This database has been replicated on all the shards/replicas, no tables are yet existing

The name of the cluster can be found in this file : ch_configs/config.d/remote_server.xml with the tag <todos>

Local table

To create tables where content will only be replicated with its replica :

You can check on each server (ch1, ch2, ch3, ch4) if the tatble is created

Now let’s insert data

INSERT INTO todos_cluster.events_local VALUES(1, ‘2020-03-28 00:00:00’, 3, ‘Hit the road Jack’, ‘2020-04-15 00:00:00’);

select * from todos_cluster.events_local;

Distributed tables

To create tables where content will be replicated in all shards :

Use show tables on all instances to see it has been created.

Now we insert data inside this table

INSERT INTO todos_cluster.events_distributed VALUES(2, ‘2020-03-28 00:00:00’, 4, ‘Sweig – Le joueur d\’échec’, ‘2020-05-05 00:00:00’);

INSERT INTO todos_cluster.events_distributed VALUES(3, ‘2020-03-28 00:00:00’, 1, ‘Kitchen’, ‘2020-03-30 00:00:00’);

INSERT INTO todos_cluster.events_distributed VALUES(4, ‘2020-03-28 00:00:00’, 3, ‘Muse Hysteria’, ‘2020-04-25 00:00:00’);

select * from todos_cluster.events_distributed

Roadbouc – Création de roadbook facile sous android

FrançaisSoftware

Voici un petit logiciel bien pratique afin de créer des roadbook (des carnet de voyages si vous préférez).
Le principe de cette application est de permettre de créer très rapidement des trajets que vous pouvez ensuite exporter aux formats KML (google), ITN (tomtom), GPX (standart), ou RBK (format interne) afin de le charger dans votre GPS. Keep reading