Document pre/post upgrade and reload scripts

[dveeden]

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• Other reference link(s):

https://github.com/pingcap/tiup/pull/2130

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[dveeden]

The option is set here: https://github.com/pingcap/tiup/blob/e543145831d44a863366ff8c379d25980730bbd1/components/cluster/command/reload.go#L58-L59

And here: https://github.com/pingcap/tiup/blob/e543145831d44a863366ff8c379d25980730bbd1/components/cluster/command/upgrade.go#L76-L77

And executed/used here: https://github.com/pingcap/tiup/blob/e543145831d44a863366ff8c379d25980730bbd1/pkg/cluster/operation/upgrade.go#L245

And here: https://github.com/pingcap/tiup/blob/e543145831d44a863366ff8c379d25980730bbd1/pkg/cluster/operation/upgrade.go#L268

[dveeden]

From the help info:

$ tiup cluster reload --help
Checking updates for component cluster... Timedout (after 2s)
Reload a TiDB cluster's config and restart if needed

Usage:
  tiup cluster reload <cluster-name> [flags]

Flags:
      --force                        Force reload without transferring PD leader and ignore remote error
  -h, --help                         help for reload
      --ignore-config-check          Ignore the config check result
  -N, --node strings                 Only reload specified nodes
      --post-restart-script string   (EXPERIMENTAL) Custom script to be executed on each server after the service is restarted, does not take effect when --skip-restart is set to true
      --pre-restart-script string    (EXPERIMENTAL) Custom script to be executed on each server before the service is restarted, does not take effect when --skip-restart is set to true
  -R, --role strings                 Only reload specified roles
      --skip-restart                 Only refresh configuration to remote and do not restart services
      --transfer-timeout uint        Timeout in seconds when transferring PD and TiKV store leaders, also for TiCDC drain one capture (default 600)

Global Flags:
  -c, --concurrency int     max number of parallel tasks allowed (default 5)
      --format string       (EXPERIMENTAL) The format of output, available values are [default, json] (default "default")
      --ssh string          (EXPERIMENTAL) The executor type: 'builtin', 'system', 'none'.
      --ssh-timeout uint    Timeout in seconds to connect host via SSH, ignored for operations that don't need an SSH connection. (default 5)
      --wait-timeout uint   Timeout in seconds to wait for an operation to complete, ignored for operations that don't fit. (default 120)
  -y, --yes                 Skip all confirmations and assumes 'yes'

--post-restart-script string: "(EXPERIMENTAL) Custom script to be executed on each server after the service is restarted, does not take effect when --skip-restart is set to true"

--pre-restart-script string: "(EXPERIMENTAL) Custom script to be executed on each server before the service is restarted, does not take effect when --skip-restart is set to true"

[ti-chi-bot[bot]]

[LGTM Timeline notifier]

Timeline:

• 2024-06-17 08:22:52.201851011 +0000 UTC m=+16698.687339843: :ballot_box_with_check: agreed by qiancai.
• 2024-07-16 11:14:01.108037501 +0000 UTC m=+352463.098978974: :ballot_box_with_check: agreed by hfxsd.

[qiancai]

/approve

[ti-chi-bot[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.1: #18336.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.2: #18337.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.0: #18338.