1c52aaa92828b6ecc18dd5800fe6650b91daf696
max
  Fri Sep 18 07:22:10 2026 -0700
hgSession: the new Sessions page also lists the sessions saved on our other servers

#Preview2 week - bugs introduced now will need a build patch to fix
Every geo mirror node keeps its own namedSessionDb, so a session saved on
genome-euro is invisible on genome.ucsc.edu and people do not find it again.
The table now holds the sessions from every node, with a new Server column
saying where each one lives, and the session name links to the server that
holds it.

Two new hgSession actions, both answered in main() before the cart is built,
so that a request from another node leaves no cart, userDb or sessionDb row
behind:

hgS_doSessionListJson  returns this server's sessions for the user named by
the login cookie, as JSON.  This is what the other
nodes call.
hgS_doMirrorSessions   asks every other gbNode for that list and returns
what came back.  It sends all of the requests before
reading any of the answers, so the wait is the
slowest node rather than the sum of them.

The fetch goes through our own server rather than from the browser to the
other nodes, which keeps cross-origin requests out of it: apache handles the
CORS headers differently on every node, and the two mirrors are administered
by Bielefeld and RIKEN, while CGI code reaches them with the release.  The
user's login cookies, and only those, are passed on (wikiLinkLoginCookieHeader),
which works because the nodes share a cookie salt.

The page never waits for any of this: the table is drawn from this server's
own sessions and the rows from the other servers are merged in as they
arrive, keeping the current sort, search and page.  A node that does not
answer, times out, or runs a release without the endpoint is named in a line
under the toolbar instead, and costs nothing else.

Sessions from another server are shown but not managed here: no Share, Edit,
Overwrite or Delete, no bulk-select checkbox, and the Update now shortcut
keeps ignoring them.  Table rows are keyed by a new uid rather than by the
session name, since the same name can now be in the table twice, once per
server.

geoMirrorThisNode() and geoMirrorOtherNodes() read the node list from the
hgcentral gbNode table, so nothing new has to be configured: browser.node
already says which node a server is.

diff --git src/hg/hgSession/hgSession.h src/hg/hgSession/hgSession.h
index 691f0b354b1..3afb807b491 100644
--- src/hg/hgSession/hgSession.h
+++ src/hg/hgSession/hgSession.h
@@ -34,30 +34,36 @@
 // When set to a registered snapshotType (e.g. "blat"), doSaveSessionJson saves a lightweight
 // "snapshot" session holding only that feature's declared cart vars (see lib/snapshotSession.c)
 // instead of the whole cart.  The stored name is forced to the "__" snapshot prefix.
 #define hgsSnapshotType hgSessionPrefix "snapshotType"
 // Rename an existing session (hgsOldSessionName -> hgsNewSessionName) for the "Specify name" step.
 #define hgsDoRenameSessionJson hgSessionPrefix "doRenameSessionJson"
 
 // AJAX endpoints for the experimental client-rendered Sessions page (hgSession.js).  Each acts on
 // the session named by hgsOldSessionName (decoded) under the current user and returns JSON instead
 // of re-rendering the whole page.  All are covered by the hgsDo prefix in cleanHgSessionFromCart.
 #define hgsDoDeleteJson hgSessionPrefix "doDeleteJson"
 #define hgsDoShareJson hgSessionPrefix "doShareJson"
 #define hgsDoGalleryJson hgSessionPrefix "doGalleryJson"
 #define hgsDoOverwriteJson hgSessionPrefix "doOverwriteJson"
 #define hgsDoDescribeJson hgSessionPrefix "doDescribeJson"
+/* Asked for by hgSession.js on another mirror node; answered without a cart, see
+ * doSessionListJson(). */
+#define hgsDoSessionListJson hgSessionPrefix "doSessionListJson"
+/* Asked for by this server's own hgSession.js; fetches the above from every other node, see
+ * doMirrorSessionsJson(). */
+#define hgsDoMirrorSessions hgSessionPrefix "doMirrorSessions"
 
 #define hgsSharePrefix hgSessionPrefix "share_"
 #define hgsGalleryPrefix hgSessionPrefix "gallery_"
 #define hgsEditPrefix hgSessionPrefix "edit_"
 #define hgsLoadPrefix hgSessionPrefix "load_"
 #define hgsDeletePrefix hgSessionPrefix "delete_"
 
 #define hgsShowDownloadPrefix hgSessionPrefix "showDownload_"
 #define hgsMakeDownloadPrefix hgSessionPrefix "makeDownload_"
 #define hgsDoDownloadPrefix hgSessionPrefix "doDownload_"
 
 #define hgsSaveLocalBackupFileName hgSessionPrefix "saveLocalBackupFileName"
 #define hgsSaveLocalFileName hgSessionPrefix "saveLocalFileName"
 #define hgsSaveLocalFileCompress hgSessionPrefix "saveLocalFileCompress"
 #define hgsDoSaveLocal hgSessionPrefix "doSaveLocal"