diff --git a/docs/ha_loop_diagram.dot b/docs/ha_loop_diagram.dot new file mode 100644 index 00000000..3e161a3a --- /dev/null +++ b/docs/ha_loop_diagram.dot @@ -0,0 +1,148 @@ +// Graphviz source for ha_loop_diagram.png +// recompile with: +// dot -Tpng ha_loop_diagram.dot -o ha_loop_diagram.png + +digraph G { + rankdir=TB; + fontname="sans-serif"; + penwidth="0.3"; + layout="dot"; + newrank=true; + edge [fontname="sans-serif", + fontsize=12, + color=black, + fontcolor=black]; + node [fontname=serif, + fontsize=12, + fillcolor=white, + color=black, + fontcolor=black, + style=filled]; + "start" [label=Start, shape="rectangle", fillcolor="green"] + "start" -> "load_cluster_from_dcs"; + "update_member" [label="Persist node state in DCS"] + "update_member" -> "start" + + subgraph cluster_run_cycle { + label="run_cycle" + "load_cluster_from_dcs" [label="Load cluster from DCS"]; + "touch_member" [label="Persist node in DCS"]; + "cluster.has_member" [shape="diamond", label="Is node registered on DCS?"] + "cluster.has_member" -> "touch_member" [label="no" color="red"] + "long_action_in_progress?" [shape="diamond" label="Is the PostgreSQL currently being\nstopping/starting/restarting/reinitializing?"] + "load_cluster_from_dcs" -> "cluster.has_member"; + "touch_member" -> "long_action_in_progress?"; + "cluster.has_member" -> "long_action_in_progress?" [label="yes" color="green"]; + "long_action_in_progress?" -> "recovering?" [label="no" color="red"] + "recovering?" [label="Was cluster recovering and failed?", shape="diamond"]; + "recovering?" -> "post_recover" [label="yes" color="green"]; + "recovering?" -> "data_directory_empty" [label="no" color="red"]; + "post_recover" [label="Remove leader key (if I was the leader)"]; + "data_directory_empty" [label="Is data folder empty?", shape="diamond"]; + "data_directory_empty" -> "cluster_initialize" [label="no" color="red"]; + "data_belongs_to_cluster" [label="Does data dir belong to cluster?", shape="diamond"]; + "data_belongs_to_cluster" -> "exit" [label="no" color="red"]; + "data_belongs_to_cluster" -> "is_healthy" [label="yes" color="green"] + "exit" [label="Fail and exit", fillcolor=red]; + "cluster_initialize" [label="Is cluster initialized on DCS?" shape="diamond"] + "cluster_initialize" -> "cluster.has_leader" [label="no" color="red"] + "cluster.has_leader" [label="Does the cluster has leader?", shape="diamond"] + "cluster.has_leader" -> "dcs.initialize" [label="no", color="red"] + "cluster.has_leader" -> "is_healthy" [label="yes", color="green"] + "cluster_initialize" -> "data_belongs_to_cluster" [label="yes" color="green"] + "dcs.initialize" [label="Initialize new cluster"]; + "dcs.initialize" -> "is_healthy" + "is_healthy" [label="Is node healthy?\n(running Postgres)", shape="diamond"]; + "recover" [label="Start as read-only\nand set Recover flag"] + "is_healthy" -> "recover" [label="no" color="red"]; + "is_healthy" -> "cluster.is_unlocked" [label="yes" color="green"]; + "cluster.is_unlocked" [label="Does the cluster has a leader?", shape="diamond"] + } + + "post_recover" -> "update_member" + "recover" -> "update_member" + "long_action_in_progress?" -> "async_has_lock?" [label="yes" color="green"]; + "cluster.is_unlocked" -> "unhealthy_is_healthiest" [label="no" color="red"] + "cluster.is_unlocked" -> "healthy_has_lock" [label="yes" color="green"] + "data_directory_empty" -> "bootstrap.is_unlocked" [label="yes" color="green"] + + subgraph cluster_async { + label = "Long action in progress\n(Start/Stop/Restart/Reinitialize)" + "async_has_lock?" [label="Do I have the leader lock?", shape="diamond"] + "async_update_lock" [label="Renew leader lock"] + "async_has_lock?" -> "async_update_lock" [label="yes" color="green"] + } + "async_update_lock" -> "update_member" + "async_has_lock?" -> "update_member" [label="no" color="red"] + + subgraph cluster_bootstrap { + label = "Node bootstrap"; + "bootstrap.is_unlocked" [label="Does the cluster has a leader?", shape="diamond"] + "bootstrap.is_initialized" [label="Does the cluster has an initialize key?", shape="diamond"] + "bootstrap.is_unlocked" -> "bootstrap.is_initialized" [label="no" color="red"] + "bootstrap.is_unlocked" -> "bootstrap.select_node" [label="yes" color="green"] + "bootstrap.select_node" [label="Select a node to take a backup from"] + "bootstrap.do_bootstrap" [label="Run pg_basebackup\n(async)"] + "bootstrap.select_node" -> "bootstrap.do_bootstrap" + "bootstrap.is_initialized" -> "bootstrap.initialization_race" [label="no" color="red"] + "bootstrap.is_initialized" -> "bootstrap.wait_for_leader" [label="yes" color="green"] + "bootstrap.initialization_race" [label="Race for initialize key"] + "bootstrap.initialization_race" -> "bootstrap.won_initialize_race?" + "bootstrap.won_initialize_race?" [label="Do I won initialize race?", shape="diamond"] + "bootstrap.won_initialize_race?" -> "bootstrap.initdb_and_start" [label="yes" color="green"] + "bootstrap.won_initialize_race?" -> "bootstrap.wait_for_leader" [label="no" color="red"] + "bootstrap.wait_for_leader" [label="Need to wait for leader key"] + "bootstrap.initdb_and_start" [label="Run initdb, start postgres and create roles"] + "bootstrap.initdb_and_start" -> "bootstrap.success?" + "bootstrap.success?" [label="Success", shape="diamond"] + "bootstrap.success?" -> "bootstrap.take_leader_key" [label="yes" color="green"] + "bootstrap.success?" -> "bootstrap.clean" [label="no" color="red"] + "bootstrap.clean" [label="Remove initialize key from DCS\nand data directory from filesystem"] + "bootstrap.take_leader_key" [label="Take a leader key in DCS"] + } + + "bootstrap.do_bootstrap" -> "update_member" + "bootstrap.wait_for_leader" -> "update_member" + "bootstrap.clean" -> "update_member" + "bootstrap.take_leader_key" -> "update_member" + + subgraph cluster_process_healthy_cluster { + label = "process_healthy_cluster" + "healthy_has_lock" [label="Am I the owner of the leader lock?", shape=diamond] + "healthy_is_leader" [label="Is Postgres running as master?", shape=diamond] + "healthy_no_lock" [label="Follow the leader (async,\ncreate/update recovery.conf and restart if necessary)"] + "healthy_has_lock" -> "healthy_no_lock" [label="no" color="red"] + "healthy_has_lock" -> "healthy_update_leader_lock" [label="yes" color="green"] + "healthy_update_leader_lock" [label="Try to update leader lock"] + "healthy_update_leader_lock" -> "healthy_update_success" + "healthy_update_success" [label="Success?", shape=diamond] + "healthy_update_success" -> "healthy_is_leader" [label="yes" color="green"] + "healthy_update_success" -> "healthy_demote" [label="no" color="red"] + "healthy_demote" [label="Demote (async,\nrestart in read-only)"] + "healthy_failover" [label="Promote Postgres to master"] + "healthy_is_leader" -> "healthy_failover" [label="no" color="red"] + } + "healthy_demote" -> "update_member" + "healthy_is_leader" -> "update_member" [label="yes" color="green"] + "healthy_failover" -> "update_member" + "healthy_no_lock" -> "update_member" + + subgraph cluster_process_unhealthy_cluster { + label = "process_unhealthy_cluster" + "unhealthy_is_healthiest" [label="Am I the healthiest node?", shape="diamond"] + "unhealthy_is_healthiest" -> "unhealthy_leader_race" [label="yes", color="green"] + "unhealthy_leader_race" [label="Try to create leader key"] + "unhealthy_leader_race" -> "unhealthy_acquire_lock" + "unhealthy_acquire_lock" [label="Was I able to get the lock?", shape="diamond"] + "unhealthy_is_leader" [label="Is Postgres running as master?", shape=diamond] + "unhealthy_acquire_lock" -> "unhealthy_is_leader" [label="yes" color="green"] + "unhealthy_is_leader" -> "unhealthy_promote" [label="no" color="red"] + "unhealthy_promote" [label="Promote to master"] + "unhealthy_is_healthiest" -> "unhealthy_follow" [label="no" color="red"] + "unhealthy_follow" [label="try to follow somebody else()"] + "unhealthy_acquire_lock" -> "unhealthy_follow" [label="no" color="red"] + } + "unhealthy_follow" -> "update_member" + "unhealthy_promote" -> "update_member" + "unhealthy_is_leader" -> "update_member" [label="yes" color="green"] +} diff --git a/docs/ha_loop_diagram.png b/docs/ha_loop_diagram.png new file mode 100644 index 00000000..fc3ccc9e Binary files /dev/null and b/docs/ha_loop_diagram.png differ