59e2bbf2d3a99e5f18436a756e1e5c8b64308e33 braney Tue Sep 8 09:21:02 2026 -0700 Copy a track collection's hub file when the program that writes it asks for a copy, instead of on every session load. cartCopyLocalHubs ran on every session load, in every CGI and in four more places in hgSession. For each customComposite-<db> cart variable it copied the collection's hub file to a fresh trash name and registered the copy in hgcentral.hubStatus to get a hub id. Nothing removed the old row. 81% of the 3.1 million rows in hubStatus on the RR are these dead registrations, and each load also took the central_hubStatus advisory lock and wrote to a MyISAM table, which serializes every concurrent load of a shared session that carries a collection. The copy itself is needed. A saved session's hub file lives under sessionDataDir and every load of that session names it, so hgCollection must not write it in place. It was just being made for every load, and almost no load is followed by an edit. hgCollection is the only program that writes one of these files, so it now asks for its own copy: main() calls cartRequestLocalHubCopy() before it opens the cart, and cartNew() makes the copy for it. That has to be a property of the program rather than of the request, and the copy has to be made at cart open, above hubConnectLoadHubs. Copying the file gives the hub a new id, the hubs are loaded during cart open, and trackList carries that id in every track name, so a copy made any later leaves printTrackDbListToHub looking for the collection under an id trackList does not have and the hub file comes out with a header and no tracks. A condition that instead tries to work out whether this particular request will write cannot be correct either: "cmd" is not in hgTracks' excludeVars, so it persists in the cart and hgCollection dispatches on the cart rather than on the CGI variable, a settings file can carry it, and a command-line run has no SCRIPT_NAME to test. Three other parts. copyLocalHubs skips a hub the cart already owns, so repeated edits reuse one file and one hub id rather than renumbering the hub on every drag; the test requires a plain file, because saveTrackFile leaves the trash name behind as a symbolic link to the durable copy and writing through that link would rewrite the saved session's own file. copyLocalHubs also screens the path with isServerUserFilePath before opening it, the way getHubName does, and selects on customComposite-<db> with the dash so that the names it acts on are the ones fileNameCartVarPrefixes screens. saveTrackFile copies when the source is a local hub outside trash that is not under this session's own directory, so loading one session and saving it under a new name gives the new session its own file instead of a reference into the first one's directory. pathIsUnderDir is no longer static in trashDir.c. All of it is behind the hg.conf gate collectionHubCopyOnWrite, default off, which reproduces the old behavior exactly. Retiring the gate is not uniform: the body of cartCopyLocalHubsOnSessionLoad is the old behavior and that function and its five callers go away with the gate, while the other three tests lose only the gate term. Measured on hgcentraltest with one binary. With the gate off, five loads of a session carrying a collection add five hubStatus rows and three later edits add none; with it on, the five loads add none and the first edit adds one. Saving a loaded session costs two rows off and one on. The resulting hub file is byte identical either way apart from the hub id, and the file the saved session names is unchanged by md5 and mtime, including after an edit made straight after a save, and including when the cart names a trash symbolic link into session storage. refs #38273 diff --git src/hg/inc/cart.h src/hg/inc/cart.h index 368f5ea09a6..4400a6c77eb 100644 --- src/hg/inc/cart.h +++ src/hg/inc/cart.h @@ -624,32 +624,42 @@ boolean ignoreRemoved,boolean ignoreCreated); /* Returns TRUE if new cart setting has changed from old cart setting */ int cartRemoveFromTdbTree(struct cart *cart,struct trackDb *tdb,char *suffix,boolean skipParent); /* Removes a 'trackName.suffix' from all tdb descendents (but not parent). If suffix NULL then removes 'trackName' which holds visibility */ boolean cartTdbTreeReshapeIfNeeded(struct cart *cart,struct trackDb *tdbComposite); /* When subtrack vis is set via findTracks, and composite has no cart settings, then fashion composite to match found */ boolean cartTdbTreeCleanupOverrides(struct trackDb *tdb,struct cart *newCart,struct hash *oldVars, struct lm *lm); /* When composite/view settings changes, remove subtrack specific settings Returns TRUE if any cart vars are removed */ -void cartCopyLocalHubs(struct cart *cart); -/* Find any custom composite and quickLift hubs and copy them so they can be modified. */ +boolean cartCollectionHubCopyOnWrite(); +/* Return TRUE if a track collection hub file is copied when the program that writes it asks for + * a copy, rather than on every session load. hg.conf gate for #38273. */ + +void cartRequestLocalHubCopy(); +/* Declare that this program rewrites the track collection hub file that the cart names, so that + * cartNew() replaces it with a private copy in trash before the hubs are loaded. Call this + * before opening the cart. hgCollection is the only caller. refs #38273 */ + +void cartCopyLocalHubsOnSessionLoad(struct cart *cart); +/* Copy any custom composite hubs after loading a session. The pre-#38273 behavior; does nothing + * under the collectionHubCopyOnWrite gate. Goes away when the gate does. */ void cartReplaceHubVars(struct cart *cart, char *hubFileVar, char *oldHubUrl, char *newHubUrl); /* Replace all cart variables corresponding to oldHubUrl (and/or its hub ID) with * equivalents for newHubUrl. */ void cgiExitTime(char *cgiName, long enteredMainTime); /* single stderr print out called at end of CGI binaries to record run * time in apache error_log */ void cartHubWarn(char *format, va_list args); /* save up hub related warnings to put out later */ void cartFlushHubWarnings(); /* flush the hub errors (if any) */