a8273be9da3b7a87a8d829d3efb79bce66e22039
angie
  Wed Jan 23 17:42:02 2019 -0800
New hg.conf settings sessionDataDir and sessionDataDbPrefix enable hgSession to move saved session trash files and customTrash tables into safe storage, so trash cleaner can be simpler.  refs #22440

When hgSession saves a session to namedSessionDb:
* If sessionDataDir is set in hg.conf (e.g. /data/apache/userdata on hgwdev), trash paths in cart variable values and in the contents of ctfile_$db and customComposite-$db files are replaced with paths in a directory hierarchy under sessionDataDir.  Files are moved from trash into the new directories and symlinks are made from trash locations to new locations.
* If sessionDataDbPrefix is set in hg.conf (e.g. customData), customTrash tables named in dbTableName settings in ctfile_$db are moved to a <sessionDataDbPrefix><dayOfMonth> database (e.g. customData03 on the third day of the month).  dbTableName settings are updated to point to the new locations.  If sessionDataDir is also set and a table contains a trash path, then the table is updated to contain to the new path under sessionDataDir.

sessionDataDir must be an absolute path to keep the symlinks straightforward.

The new directory hierarchy under sessionDataDir is A/B/C/D where A-D are defined as follows:
* A: the first two characters of the hex string md5sum of namedSessionDb.userName, i.e. the URI-encoded username truncated to varchar(32)
(there can be tens of thousands of userNames; using this mini-hash distributes them across up to 256 subdirectories of sessionDataDir)
* B: the URI-encoded userName
* C: the first 8 characters of the hex string md5sum of namedSessionDb.sessionName, i.e. the URI-encoded session name truncated to varchar(255)
* D: the original path below ../trash/

So, for example, the file ../trash/ct/ct_hgwdev_angie_11fc0_2b5970.maf could be moved to
/data/apache/userdata/fb/AngieHinrichs/cf2a2304/ct/ct_hgwdev_angie_11fc0_2b5970.maf

diff --git src/hg/lib/customFactory.c src/hg/lib/customFactory.c
index 586c9c5..8e8bcec 100644
--- src/hg/lib/customFactory.c
+++ src/hg/lib/customFactory.c
@@ -2558,32 +2558,34 @@
     safef(text, sizeof(text), "%f:%f", sum.minVal, sum.maxVal);
     hashAdd(settings, "viewLimits", cloneString(text));
     }
 }
 
 boolean isValidBigDataUrl(char *url, boolean doAbort)
 /* return True if the URL is a valid bigDataUrl.
  * It can be a local filename if this is allowed by udc.localDir
  */
 {
 if ((startsWith("http://", url)
    || startsWith("https://", url)
    || startsWith("ftp://", url)))
 return TRUE;
 
-// we allow bigDataUrl's to point to trash
-if (startsWith(trashDir(), url))
+// we allow bigDataUrl's to point to trash (or sessionDataDir, if configured)
+char *sessionDataDir = cfgOption("sessionDataDir");
+if (startsWith(trashDir(), url) ||
+    (isNotEmpty(sessionDataDir) && startsWith(sessionDataDir, url)))
     return TRUE;
 
 char *prefix = cfgOption("udc.localDir");
 if (prefix == NULL)
     {
     if (doAbort)
         errAbort("Only network protocols http, https, or ftp allowed in bigDataUrl: '%s'", url);
     return FALSE;
     }
 
 if (!startsWith(prefix, url))
     {
     if (doAbort)
         errAbort("bigDataUrl '%s' on local file system has to start with '%s' (see udc.localDir directive in cgi-bin/hg.conf)", url, prefix);
     return FALSE;