Method of creating path signatures to facilitate the recovery from network link failures

Abstract

At any instant, a channel's path signature reflects the last successful path used to access file data. During the course of processing a request from an upstream site currently not connected to the target file, the downstream site will establish a connection to the upstream site and then include in its request response a path signature constructed by adding its signature to the channel's path signature.

What is claimed is: 
     
         1 . In a 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 an upstream file access request for a file from an upstream site;   acquiring a channel for the file identified in the request;   determining if it is possible to service the request without communicating with a downstream node;   if communication with the downstream node is required:
 dispatching a downstream file access request to a downstream site; 
 receiving a response from the downstream site; and 
   if the downstream response contained an indication that the downstream site just established a file connection to this site:
 copying the path signature from the response to the channel; 
   servicing the upstream file access request; 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 a file system. 
     
     
         6 . The system of  claim 1 , wherein the channel includes the number of file service proxy cache node hops to the file system. 
     
     
         7 . The system of  claim 1 , wherein the channel includes a node identifier for each node. 
     
     
         8 . The system of  claim 1 , wherein the servicing the upstream file access request includes:
 receiving file data from the downstream site; and   sending the file data to the upstream site in the upstream response.   
     
     
         9 . The system of  claim 1  further comprising:
 if the connection to the downstream site is interrupted:
 determining an alternate route to the origin file system node; 
 establishing a connection to the file using the alternate route by performing the following steps:
 sending the downstream file access request to a second downstream site; and 
 receiving a response from the second downstream site; and 
 
 copying the path signature from the response to the channel. 
 
 
     
     
         10 . In a 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 an upstream file access request for a file from an upstream site;   acquiring a channel for the file identified in the request;   determining if it is possible to service the request without communicating with a downstream node;   if communication with the downstream node is required:
 dispatching a downstream file access request to a downstream site; 
 receiving a response from the downstream site; and 
   if the downstream response contained an indication that the downstream site just established a file connection to this site:
 copying the path signature from the response to the channel; 
 incrementing the number of hops in the path signature; 
   servicing the upstream file access request; and   dispatching a response to the upstream site.   
     
     
         11 . The system of  claim 10 , further comprising the file service proxy cache node fastpinging the downstream site. 
     
     
         12 . The system of  claim 10 , wherein servicing the upstream file access request includes:
 determining if the upstream site is establishing an initial file connection.   
     
     
         13 . The system of  claim 12 , further comprising:
 if the upstream site is establishing an initial file connection:
 copying the path signature from the channel to the response to the upstream file access request. 
   
     
     
         14 . The system of  claim 13 , further comprising:
 if the upstream site is establishing an initial file connection:
 adding a signature of the file service proxy cache node to the path signature in the response to the upstream file access request. 
   
     
     
         15 . The system of  claim 14 , further comprising:
 if the upstream site is establishing an initial file connection:
 adding an indication that the file service proxy cache node just established a file connection to this site to the response to the upstream file access request.