HDDS-14327. [Website v2][Docs][Administrator Guide] Reorganize Decommissioning and Maintenance Modes for Datanodes

[sarvekshayr]

What changes were proposed in this pull request?

#181 (comment) - Introduced an overview page with decommission and maintenance introduction and then created sub pages for these topics.

What is the link to the Apache Jira?

HDDS-14327

How was this patch tested?

Check off which of the following tests were done on this change. If additional testing was done, please elaborate here as well.

• The CI checks on my fork are passing
• I verified the rendered content using a local preview
• I manually verified the steps provided in this change work as described

[Gargi-jais11]

Thanks @sarvekshayr for the patch.
Just some minor comments.

[Gargi-jais11]

@sarvekshayr
The NodeDecommissionMetrics class tracks both decommissioning and maintenance workflows. The documentation currently lists only 2 metrics, but there are more that are useful for monitoring decommissioning maintenance mode.
Could you please double check the above class and verify if more metrics we need to include in documentation?

[Gargi-jais11]

Below are the metrics I am talking about. Please double check if we need these as well to be documented.
NodeDecommissionMetrics (entire section missing)
This metrics class is not documented. It tracks decommissioning and maintenance workflows.
Aggregate metrics (cluster-wide):

• DecommissioningMaintenanceNodesTotal (node_decommission_metrics_decommissioning_maintenance_nodes_total): Number of nodes tracked for decommissioning and maintenance
• RecommissionNodesTotal (node_decommission_metrics_recommission_nodes_total): Number of nodes tracked for recommissioning
• PipelinesWaitingToCloseTotal (node_decommission_metrics_pipelines_waiting_to_close_total): Number of nodes tracked with pipelines waiting to close
• ContainersUnderReplicatedTotal (node_decommission_metrics_containers_under_replicated_total): Number of containers under replicated in tracked nodes
• ContainersUnClosedTotal (node_decommission_metrics_containers_un_closed_total): Number of containers not fully closed in tracked nodes
• ContainersSufficientlyReplicatedTotal (node_decommission_metrics_containers_sufficiently_replicated_total): Number of containers sufficiently replicated in tracked nodes

Per-host metrics (tagged by datanode hostname):

• UnderReplicatedDN (node_decommission_metrics_under_replicated_dn): Number of under-replicated containers for the specific host
• PipelinesWaitingToCloseDN (node_decommission_metrics_pipelines_waiting_to_close_dn): Number of pipelines waiting to close for the specific host
• SufficientlyReplicatedDN (node_decommission_metrics_sufficiently_replicated_dn): Number of sufficiently replicated containers for the specific host
• UnclosedContainersDN (node_decommission_metrics_unclosed_containers_dn): Number of containers not fully closed for the specific host
• StartTimeDN (node_decommission_metrics_start_time_dn): Timestamp when decommissioning was started for the specific host

[jojochuang]

That looks like sizeable update. Can we merge it as is, and I can open a follow-up jira to address those issues.

[Gargi-jais11]

That looks like sizeable update. Can we merge it as is, and I can open a follow-up jira to address those issues.

That makes sense

[sarvekshayr]

Sorry for the delay, I've addressed the comments.

[sarvekshayr]

Thanks @jojochuang and @Gargi-jais11 for the review.