VMware Cloud Director 維護節點之間的同步串流複寫。如果待命節點變得無法連線，您必須確定原因並解決問題。
問題
VMware Cloud Director 應用裝置管理使用者介面將叢集健全狀況顯示為 DEGRADED，其中一個待命節點的狀態為 ? 無法連線。
/nodes API 傳回的資訊指出 localClusterHealth 為 DEGRADED，節點 status 為 ? 無法連線，且 nodeHealth 為 UNHEALTHY。
例如，
/nodes API 可能會針對節點傳回下列資訊。
{
"localClusterFailover": "MANUAL",
"localClusterHealth": "DEGRADED",
"localClusterState": [
{
"connectionString": "host=primary_host_IP user=repmgr dbname=repmgr connect_timeout=2",
"failover": {
"details": "failover = manual",
"mode": "MANUAL",
"repmgrd": {
"details": "On node primary_node_ID (primary_host_name): repmgrd = not applicable",
"status": "NOT APPLICABLE"
}
},
"id": primary_node_ID,
"location": "default",
"name": "primary_host_name",
"nodeHealth": "HEALTHY",
"nodeRole": "PRIMARY",
"role": "primary",
"status": "* running",
"upstream": ""
},
{
"connectionString": "host=unreachable_standby_host_IP user=repmgr dbname=repmgr connect_timeout=2",
"failover": {
"details": "failover state unknown - unable to ssh to failed or unreachable node",
"mode": "UNKNOWN",
"repmgrd": {
"details": "On node unreachable_standby_node_ID (unreachable_standby_host_name): repmgrd = n/a",
"status": "UNKNOWN"
}
},
"id": unreachable_standby_node_ID,
"location": "default",
"name": "unreachable_standby_host_name",
"nodeHealth": "UNHEALTHY",
"nodeRole": "STANDBY",
"role": "standby",
"status": "? unreachable",
"upstream": "primary_host_name"
},
{
"connectionString": "host=running_standby_host_IP user=repmgr dbname=repmgr connect_timeout=2",
"failover": {
"details": "failover = manual",
"mode": "MANUAL",
"repmgrd": {
"details": "On node running_standby_node_ID (running_standby_host_IP): repmgrd = not applicable",
"status": "NOT APPLICABLE"
}
},
"id": running_standby_node_ID,
"location": "default",
"name": "running_standby_host_name",
"nodeHealth": "HEALTHY",
"nodeRole": "STANDBY",
"role": "standby",
"status": "running",
"upstream": "primary_host_name"
}
],
"warnings": [
"unable to connect to node \"unreachable_standby_host_name\" (ID: unreachable_standby_node_ID)",
"node \"unreachable_standby_host_name\" (ID: unreachable_standby_node_ID) is registered as an active standby but is unreachable"
]
}
原因
為確保資料完整性，PostgreSQL 資料庫使用預寫式記錄 (WAL)。主要節點持續將 WAL 串流至作用中的待命節點，以進行複寫和復原。待命節點會在收到 WAL 後對其進行處理。如果待命節點無法連線，它會停止接收 WAL，且無法成為升階為新主要節點的候選節點。
解決方案
- 確認無法連線的待命節點的虛擬機器是否正在執行。
- 確認與待命節點的網路連線是否運作正常。
- 確認沒有可能會阻止待命節點與其他節點通訊的 SSH 問題。
- 確認待命節點上的 vpostgres 服務是否正在執行。
