Changeset 31956

Timestamp:

2017-09-08T19:08:40+12:00 (7 years ago)

Author:

ak19

Message:

Dr Bainbridge read up on why the Sockets to our wget child process' iostreams were being forcibly closed on Windows when we've finished successfully downloading, resulting unexpectedly in the $len bytes that we sysread() being undefined (usually denoting an error) rather than 0. It turns out that by using Sockets on Windows as filehandles to a child process' iostreams is merely implemented in this manner on success.

File:

• main/trunk/greenstone2/perllib/downloaders/WgetDownload.pm (modified) (4 diffs)

main/trunk/greenstone2/perllib/downloaders/WgetDownload.pm

@@ -295 +295 @@
     local (*TO_CHLD_R,     *TO_CHLD_W);
     local (*FR_CHLD_R,     *FR_CHLD_W);
-    local (*FR_CHLD_ERR_R, *FR_CHLD_ERR_W);
+    #local (*FR_CHLD_ERR_R, *FR_CHLD_ERR_W);
 
     if ($^O =~ /Win32/) {
@@ -311 +311 @@
                                                                       # see http://blog.0x1fff.com/2009/09/howto-execute-system-commands-in-perl.html
     
-    return ( $pid, *TO_CHLD_W, *FR_CHLD_R, *FR_CHLD_ERR_R );
+    #return ( $pid, *TO_CHLD_W, *FR_CHLD_R, *FR_CHLD_ERR_R );
+    return ( $pid, *TO_CHLD_W, *FR_CHLD_R);
 }
 
@@ -457 +458 @@
         else { # error or EOF: (!defined $len || $len == 0)         
             
-            if(!defined $len) { # error reading         
-            print STDERR "WgetDownload: Error reading from child stream: $!\n";
-            # SHOULD THIS 'die "errmsg";' instead? - no, sockets may need closing
-            $error = 1;
-            }
-            elsif ($len == 0) { # EOF           
-            # Finished reading from this filehand $fh because we read 0 bytes.
+            if(!defined $len) { # could be an error reading 
+              # On Windows, the socket ends up forcibly closed on the "other" side. It's just the way it's implemented 
+              # on Windows when using sockets to our child process' iostreams. So $len not being defined is not an error in that case. Refer to
+              # https://stackoverflow.com/questions/16675950/perl-select-returning-undef-on-sysread-when-using-windows-ipcopen3-and-ios/16676271
+              if(!$!{ECONNRESET}) { # anything other ECONNRESET error means it's a real case of undefined $len being an error
+                print STDERR "WgetDownload: Error reading from child stream: $!\n";
+                # SHOULD THIS 'die "errmsg";' instead? - no, sockets may need closing
+                $error = 1;
+              } else { # $! contains message "An existing connection was forcibly closed by remote host" where "remote" is a reference to the sockets to our wget child process,
+                    # NOT to the remote web server we're downloading from. In such a case, the error code is ECONNRESET, and it's not an error, despite $len being undefined.
+                print STDERR "WgetDownload: wget finished\n";
+              }
+            }
+            elsif ($len == 0) { # EOF
+            # Finished reading from this filehandle $fh because we read 0 bytes.
             # wget finished, terminate naturally
             print STDERR "WgetDownload: wget finished\n";
@@ -694 +703 @@
             $error = 1;
             }
+             if(!defined $len) {
+              if(!$!{ECONNRESET}) { # anything other ECONNRESET error means it's a real case of undefined $len being an error
+                #print STDERR "WgetDownload: Error reading from child stream: $!\n";                
+                $error = 1;
+              } else { # the error code is ECONNRESET, and it's not an error, despite $len being undefined. 
+                       # Happens on Windows when using sockets to a child process' iostreams
+                #print STDERR "WgetDownload: wget finished\n";
+              }
+            }
             elsif ($len == 0) { # EOF, finished with this filehandle because 0 bytes read
             #print STDERR "WgetDownload: wget finished\n"; # wget terminated naturally