Charm flowcharts

The file charm.py is the entrypoint for the charm. It contains functions for its basic operation, including its major hooks and file management. This file can be found at src/charm.py.

Hook Handler Flowcharts

These flowcharts detail the control flow of the hooks in this program. Unless otherwise stated, a hook deferral is always followed by a return.

Leader Elected Hook

Click to navigate the mermaid diagram on GitHub.

flowchart TD
  hook_fired([leader-elected Hook]) --> generate_passwords{Generate password for charm users?}
  generate_passwords --> create_k8s_resources[Create k8s resources\n needed by Patroni]
  create_k8s_resources --> is_part_of_cluster{Is current unit \n part of the cluster?}
  is_part_of_cluster -- no --> add_to_cluster[Add current unit \n to the cluster]
  add_to_cluster --> remove_departed_units
  is_part_of_cluster -- yes --> remove_departed_units[Remove pending departed \n units from the cluster]
  remove_departed_units --> has_cluster_initialised{Has cluster\n initialised?}
  has_cluster_initialised -- no --> rtn([return])
  has_cluster_initialised -- yes --> all_units_on_cluster{Are all the units \n part of the cluster?}
  all_units_on_cluster -- yes --> update_config[Turn on/off PostgreSQL \n synchronous_commit configuration]
  all_units_on_cluster -- no --> are_all_members_ready{Are all cluster \n members ready?}

  %% This defer should have a return after it to stop the execution.
  are_all_members_ready -- no --> defer2>defer]
  defer2 --> update_config

  are_all_members_ready -- yes --> add_unit_to_cluster[Add unit to cluster]
  add_unit_to_cluster --> patch_pod_labels[Patch pod labels of the new cluster member]
  patch_pod_labels --> all_units_on_cluster
  update_config --> rtn2([return])

PostgreSQL Pebble Ready Hook

Click to navigate the mermaid diagram on GitHub.

flowchart TD
  hook_fired([leader-elected Hook]) --> create_pgdata{Create data\n directory}
  create_pgdata --> is_leader_or_has_cluster_initialised{Is current unit\n leader or has the \n cluster initialised?}
  is_leader_or_has_cluster_initialised -- no --> defer>defer]
  is_leader_or_has_cluster_initialised -- yes --> has_pushed_tls_files{Has successfully \n pushed TLS files?}
  has_pushed_tls_files -- no --> defer2>defer]
  has_pushed_tls_files -- yes --> has_services_changed{Have pebble \n services changed?}
  has_services_changed -- no --> has_member_started
  has_services_changed -- yes --> update_and_restart_service[Update and restart \n the PostgreSQL service]
  update_and_restart_service --> has_member_started{Have Patroni and \n PostgreSQL  started in \n the current unit?}
  has_member_started -- no --> defer3>defer]
  has_member_started -- yes --> is_leader{Is current\nunit leader?}
  is_leader -- yes --> has_patched_pod_labels{Has successfully \n patched pod labels of \n the new current unit}
  is_leader -- no --> update_config
  has_patched_pod_labels -- no --> set_blocked[Set Blocked\nstatus]
  set_blocked --> rtn([return])
  has_patched_pod_labels -- yes --> is_service_redirecting_traffic{Is custom k8s service \n redirecting traffic to \n primary pod?}
  is_service_redirecting_traffic -- no --> set_waiting[Set Waiting\nstatus]
  set_waiting --> defer4>defer]
  is_service_redirecting_traffic -- yes --> mark_cluster_as_initialised[Mark cluster as initialised]
  mark_cluster_as_initialised--> update_config[Turn on/off PostgreSQL \n synchronous_commit configuration]
  update_config --> set_active[Set Active\n Status]
  set_active --> rtn2([return])