ZooKeeper in ASAB Maestro

ZooKeeper is the consensus technology for ASAB Maestro. All other services need to communicate with ZooKeeper to access cluster-level data. Thus, ZooKeeper Server string is provided as parameter to all services and ASAB services get [zoookeeper] configuration section from the ZooKeeper Tech.

Parameters

ZOOKEEPER_SERVERS

Comma separated addresses to all ZooKeeper instances. In a three-node cluste (with nodes named lm1, lm2, lm3) the ZOOKEEPER_SERVERS parameter would be replaced with lm1:2181,lm2:2181,lm3:2181 string.

Example

define:
type: rc/descriptor
name: Web-based ZooKeeper UI
url: https://zoonavigator.elkozmon.com/

descriptor:
image: elkozmon/zoonavigator

volumes:
    - "{{SLOW_STORAGE}}/{{INSTANCE_ID}}/logs:/app/logs"

environment:
    HTTP_PORT: "9001"
    CONNECTION_ZK_NAME: Local ZooKeeper
    CONNECTION_ZK_CONN: "{{ZOOKEEPER_SERVERS}}"
    AUTO_CONNECT_CONNECTION_ID: ZK
    BASE_HREF: /zoonavigator

Configuration of ASAB Services

Every ASAB Service obtains zookeeper configuration section.

[zookeeper]
servers=lmc01:2181,lmc02:2181,lmc03:2181

Environment variables

Available for the respective ZooKeeper instance only.

ZOO_MY_ID

Instance number of each ZooKeeper instance becomes ZOO_MY_ID environment variable of the ZooKeeper (Docker) container. That's why renaming of the ZooKeeper instances in the model could be problematic.