docs: more pnfs flow diagrams

dCache · Aug 4, 2023 · 5eb4e70 · 5eb4e70
1 parent dbd85ee
commit 5eb4e70
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diff --git a/modules/dcache-nfs/README.md b/modules/dcache-nfs/README.md
@@ -1,6 +1,8 @@
 # NFSv4.1/pNFS Door
 
+## Set of sequence diagrams of pNFS flow
 
+### Positive path
 ```mermaid
 sequenceDiagram
     autonumber
@@ -24,4 +26,125 @@ sequenceDiagram
     poolA-->>Door: Trnaster Finish
     Door->>Door: Invalidate state
     Door-->>Client: OK
+```
+
+### File is offline
+```mermaid
+sequenceDiagram
+    autonumber
+    actor Client
+    participant Door
+    participant PoolManager
+    Client->>Door: OPEN(file), LAYOUTGET 
+    Door->>PoolManager: Select Pool
+    PoolManager-->>Door: 'No Pools'
+    Door-->>Client:  NFS4ERR_LAYOUTTRYLATER
+```
+
+### No disk and tape locations
+```mermaid
+sequenceDiagram
+    autonumber
+    actor Client
+    participant Door
+    participant PoolManager
+    Client->>Door: OPEN(file), LAYOUTGET 
+    Door-->>Client:  NFS4ERR_IO
+```
+
+### PoolManager is offline
+```mermaid
+sequenceDiagram
+    autonumber
+    actor Client
+    participant Door
+    participant PoolManager
+    Client->>Door: OPEN(file), LAYOUTGET 
+    Door--XPoolManager: Select Pool
+    Door-->>Client:  NFS4ERR_DELAY
+```
+
+### Two opens
+```mermaid
+sequenceDiagram
+    autonumber
+    box HostA
+    actor ClientA as App1
+    actor ClientB as App2
+    end
+    participant Door
+    participant poolA
+    participant PoolManager
+    ClientA->>Door: OPEN(file), LAYOUTGET 
+    Door->>PoolManager: Select Pool
+    PoolManager-->>Door: 'poolA'
+    Door->>poolA: Start Mover (state1)
+    poolA-->>Door: Ready(id)
+    Door-->>ClientA: 'open state1', 'layout'
+
+    ClientB->>Door: OPEN(file), LAYOUTGET 
+    Note right of Door: By same open owner stateid and layouts are shared
+    Door-->>ClientB: 'open state1', 'layout'
+
+    loop Application IO
+        ClientA->>poolA: READ(file, state1, offset, len)
+        poolA-->>ClientA: 'bytes'
+    end
+    loop Application IO
+        ClientB->>poolA: READ(file, state1, offset, len)
+        poolA-->>ClientB: 'bytes'
+    end
+    
+    ClientA->>Door: LAYOUT_RETURN, CLOSE
+    Door->>poolA: Kill Mover(id)
+    poolA->>poolA: state invalidated
+    poolA-->>Door: Trnaster Finish
+    Door->>Door: Invalidate state
+    Note right of Door: Single close for all previous opens
+    Door-->>ClientA: OK
+```
+
+### Competing opens (race condition)
+
+(fixed by commit 421e1dc932c73186d52901431ec8b822fdadb508)
+```mermaid
+sequenceDiagram
+    autonumber
+    box HostA
+    actor ClientA as App1
+    actor ClientB as App2
+    end
+    participant Door
+    participant poolA
+    participant PoolManager
+    ClientA->>Door: OPEN(file), LAYOUTGET 
+    Door->>PoolManager: Select Pool
+    PoolManager-->>Door: 'poolA'
+    Door->>poolA: Start Mover (state1)
+    poolA-->>Door: Ready(id)
+    Door-->>ClientA: 'open state1', 'layout'
+
+    loop Application IO
+        ClientA->>poolA: READ(file, state1, offset, len)
+        poolA-->>ClientA: 'bytes'
+    end
+    
+    ClientA->>Door: LAYOUT_RETURN, CLOSE
+    Door->>poolA: Kill Mover(id)
+    
+    ClientB->>Door: OPEN(file), LAYOUTGET  
+    Door-->>ClientB: 'open state1', 'layout'
+    
+    poolA->>poolA: state invalidated
+    poolA-->>Door: Trnaster Finish
+    Door->>Door: Invalidate state
+    Door-->>ClientA: NFS4ERR_BAD_SEQID
+    Note right of Door: older verion stateid is used. File stays open
+    
+    loop Application IO
+        ClientB->>poolA: READ(file, state1, offset, len)
+        poolA-->>ClientB: NFS4ERR_BAD_STATEID
+        Note right of PoolA: Mover is aleady gone
+    end
+    
 ```