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I just start reading about zookeeper. And I am getting confused about the data replication and data module.
The ZooKeeper ensemble will contain multiple nodes(Machine) with one leader and others as followers.
The data module is a tree structure with each node as znode.
How does those two structure work together? Is the znode and node refer to the same thing?
I am trying to understand it as each node in ZooKeeper ensemble will have the same data module that contains znode. So the znode is actually, data on nodes. Is that right?
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In the ZooKeeper documentatin, znodes refer to the data nodes. Servers to refer to machines that make up the ZooKeeper service; quorum peers refer to the servers that make up an ensemble; client refers to any host or process which uses a ZooKeeper service. Znodes are the main enitity that a programmer access.
Types of Znodes Persistence znode − Persistence znode is alive even after the client, which created that particular znode, is disconnected. By default, all znodes are persistent unless otherwise specified. Ephemeral znode − Ephemeral znodes are active until the client is alive.
In case of Zookeeper 2 nodes is not enough. Even if one of your nodes went out, the remaining one couldn't tell if it was down or just partitioned. This would cause inconsistency, a split brain scenario, because both of them would continue serving their clients.
== Types of Znodes == There are three types of znodes or nodes: Persistent, Ephemeral and Sequential. == Types of Znodes - Ephemeral == Ephemeral node gets deleted if the session in which the node was created has disconnected.
The two concepts don't really relate to each other in any way. A znode is part of the data model. Essentially, it's a path on a tree-like structure that represents a piece of data stored in ZooKeeper. Conversely, a node is a general systems term you could just replace with server.
Unfortunately, we don't have enough terms in computer science, so terminology can become confusing. But this is simply the difference between a tree node (in the data model) and a cluster node (in the ensemble).
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