Method of using path signatures to recover from network link failures

Abstract

At any instant, a channel's path signature reflects the last successful network path used to access file data. Methods whereby a distributed virtual file server, composed of standard file servers and file service proxy caches, uses path signatures to facilitate the re-routing of file system traffic to transparently overcome network link failures.

What is claimed is: 
     
         1 . In a networked computing system where a data request has been passed between an upstream site and a file service proxy cache node, the file service proxy cache node being a network node located between the upstream site and the origin file system node, a non-transitory computer-readable storage medium including instructions that, when executed by the file service proxy cache node, performs the steps:
 receiving a file access request for a file from the upstream site;   acquiring a channel for the file identified in the request;   determining if a reconnect flag is set in the request;   if the reconnect flag is set:
 determining if a path signature within the request contains the node signature of the file service proxy cache node; and 
 if the path signature contains the node signature of the file service proxy cache node:
 sending a recall message to a second upstream site identified in the path signature; 
 
 servicing the file access request from the upstream site; and 
 dispatching a response to the upstream site. 
   
     
     
         2 . The system of  claim 1 , wherein the upstream site includes an intermediate node. 
     
     
         3 . The system of  claim 1 , wherein the upstream site includes a client system. 
     
     
         4 . The system of  claim 1 , wherein the downstream site includes an intermediate node. 
     
     
         5 . The system of  claim 1 , wherein the downstream site includes the origin file system. 
     
     
         6 . The system of  claim 1 , wherein the path signature includes the number of file service proxy cache node hops to the origin file system. 
     
     
         7 . The system of  claim 1 , wherein the path signature includes a node identifier. 
     
     
         8 . In a networked computing system where a data request has been passed between an upstream site and a file service proxy cache node, the file service proxy cache node being a network node located between the upstream site and the origin file system node, a non-transitory computer-readable storage medium including instructions that, when executed by the file service proxy cache node, performs the steps:
 receiving a file access request for a file from the upstream site;   acquiring a channel for the file identified in the request;   determining if a reconnect flag is set in the request;   if the reconnect flag is set:
 determining if a path signature within the request contains the node signature of the file service proxy cache node; 
 if the path signature contains the node signature of the file service proxy cache node:
 sending a recall message to a second upstream site identified in the path signature; and 
 determining if a response is received from the second upstream site; and
 if a response is received from the second upstream site: 
  updating the upstream site structure for the second upstream site; and 
 if a response is not received from the second upstream site: 
  updating the upstream site structure for the second upstream site to indicate the second upstream site is offline; and 
 
 
   servicing the file access request from the upstream site; and   dispatching a response to the upstream site.   
     
     
         9 . In a networked computing system where a data request has been passed between an upstream site and a file service proxy cache node, the file service proxy cache node being a network node located between the upstream site and the origin file system node, a non-transitory computer-readable storage medium including instructions that, when executed by the file service proxy cache node, performs the steps:
 receiving a file access request from the upstream site;   acquiring a channel for the file identified in the request;   determining if a reconnect flag is set in the request;   if the reconnect flag is set:
 determining if a path signature within the request contains the node signature of the file service proxy cache node; 
 if the path signature contains the node signature of the file service proxy cache node:
 sending a recall message to a second upstream site identified in the path signature; and 
 determining if a response is received from the second upstream site; and
 if a response is received from the second upstream site: 
  updating the upstream site structure for the second upstream site; and 
 if a response is not received from the second upstream site: 
  updating the upstream site structure for the second upstream site to indicate the second upstream site is offline; and 
 
 
 if the path signature does not contain the node signature of the file service proxy cache node:
 resetting the channel's attributes valid flag to force the file service proxy cache node to dispatch a downstream request to fetch valid attributes; 
 
   servicing the file access request from the upstream site; and   dispatching a response to the upstream site.   
     
     
         10 . The system of  claim 9 , further comprising the file service proxy cache node fastpinging the downstream site.