VMware Cloud Director 維護節點之間的同步串流複寫。如果待命節點變成未連結狀態，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，其中一個未連結的待命節點的狀態為執行中，並且在待命節點之上游節點的名稱前面有一個驚嘆號 (!)。
PostgreSQL 記錄顯示主要節點刪除了 WAL 區段。
2020-10-08 04:10:50.064 UTC [13390] LOG: started streaming WAL from primary at 21/80000000 on timeline 17 2020-10-08 04:10:50.064 UTC [13390] FATAL: could not receive data from WAL stream: ERROR: requested WAL segment 000000110000002100000080 has already been removed 2020-10-08 04:10:55.047 UTC [13432] LOG: started streaming WAL from primary at 21/80000000 on timeline 17 2020-10-08 04:10:55.047 UTC [13432] FATAL: could not receive data from WAL stream: ERROR: requested WAL segment 000000110000002100000080 has already been removed
/nodes API 傳回的資訊指出 localClusterHealth 為 DEGRADED，節點 status 為執行中，nodeHealth 為 HEALTHY。在待命節點之上游節點的名稱前面有一個驚嘆號 (!)，並且 /nodes API 傳回的警告指出待命節點未連結至其上游節點。
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=unattached_standby_host_IP user=repmgr dbname=repmgr connect_timeout=2",
"failover": {
"details": "failover = manual",
"mode": "MANUAL",
"repmgrd": {
"details": "On node unattached_standby_node_ID (unattached_standby_host_name): repmgrd = not applicable",
"status": "NOT APPLICABLE"
}
},
"id": unattached_standby_node_ID,
"location": "default",
"name": "unattached_standby_host_name",
"nodeHealth": "HEALTHY",
"nodeRole": "STANDBY",
"role": "standby",
"status": "running",
"upstream": "! upstream_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_name): 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": "upstream_host_name"
}
],
"warnings": [
"node \"unattached_standby_host_name\" (ID: unattached_standby_node_ID) is not attached to its upstream node \"upstream_host_name\" (ID: upstream_node_id)"
]
}
如果待命節點變成未連結狀態，您必須盡快重新連結。如果節點處於未連結狀態的時間過長，則可能會在處理主要節點持續串流 WAL 記錄方面落後，以至於無法恢復複寫。
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。如果待命節點變成未連結狀態，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
- 部署新的待命節點。
- 解除登錄未連結的待命節點。
