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Node lifecycle

As explained in ScyllaDB in Action

A node lifecycle state describes a node's membership transition or position in a cluster, such as joining, normal, leaving, or moving.

A node lifecycle state identifies where a node is in its cluster membership: joining, normal, leaving, or moving. It is separate from status, which indicates whether the node is up and taking traffic or down and unhealthy. section 2.1.2

The state letters reported by nodetool describe these lifecycle positions:

  • N — Normal: the node has successfully joined the cluster. section 2.1.2
  • J — Joining: the node is in the process of joining the cluster. section 2.1.2
  • L — Leaving: the node is in the process of leaving the cluster. section 2.1.2
  • M — Moving: the node is moving datacenters or racks. section 2.1.2

Reading a node line

In a nodetool status result, the prefix UN means the node is Up and in the Normal state: it is healthy, taking traffic, and has previously joined the cluster. section 2.1.2

Table 2.2 Possible values for the node’s state
State letter
Meaning
Description
N
Normal
Node is in the normal state, having successfully joined the cluster previously
J
Joining
Node is in the process of joining the cluster
L
Leaving
Node is in the process of leaving the cluster
M
Moving
Node is moving datacenters or racks in the cluster

Use the state table to compare lifecycle letters with their operational meanings. section 2.1.2

How ScyllaDB in Action covers it

How deep it goes
Defines four lifecycle states and distinguishes them from Up or Down status without describing transition mechanics.
Examples
Uses nodetool status output where UN identifies an Up, Normal node.
What it assumes
Assumes access to a running node and a shell from which nodetool can be executed.
What you can do after
Diagnose cluster membership and traffic readiness by reading nodetool status state and status letters.
How it connects
Connects node lifecycle state with clusters, nodetool, status, datacenters, and racks.
Cover of ScyllaDB in Action
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Related concepts

This explainer was generated by Manning's knowledge graph from the text of ScyllaDB in Action. The section links point to the parts of the book it draws on.