OPFS VFS: translate createSyncAccessHandle() exceptions which appear to be locking violations to SQLITE_BUSY. This seems to improve concurrency considerably even with a reduced retry count of 5 (was 6).

FossilOrigin-Name: 0d36021d107d3afca190ad61c3380536ad0cc2d493d345d48f9f9c1191741128

ext/wasm/api/sqlite3-opfs-async-proxy.js

@@ -263,21 +263,18 @@ const installAsyncProxy = function(self){
     }
   };
   GetSyncHandleError.convertRc = (e,rc)=>{
-    if(0){
+    if(1){
-      /* This approach makes the very wild assumption that such a
+      return (
-         failure _is_ a locking error. In practice that appears to be
+        e instanceof GetSyncHandleError
-         the most common error, by far, but we cannot unambiguously
+          && ((e.cause.name==='NoModificationAllowedError')
-         distinguish that from other errors.
+              /* Inconsistent exception.name from Chrome/ium with the
-
+                 same exception.message text: */
-         This approach is highly questionable.
+              || (e.cause.name==='DOMException'
-
+                  && 0===e.cause.message.indexOf('Access Handles cannot')))
-         Note that even if we return SQLITE_IOERR_LOCK from here,
+      ) ? (
-         it bubbles up to the client as a plain I/O error.
+        /*console.warn("SQLITE_BUSY",e),*/
-      */
+        state.sq3Codes.SQLITE_BUSY
-      return (e instanceof GetSyncHandleError
+      ) : rc;
-              && e.cause.name==='NoModificationAllowedError')
-        ? state.sq3Codes.SQLITE_IOERR_LOCK
-        : rc;
     }else{
       return rc;
     }
@@ -298,7 +295,7 @@ const installAsyncProxy = function(self){
     if(!fh.syncHandle){
       const t = performance.now();
       log("Acquiring sync handle for",fh.filenameAbs);
-      const maxTries = 6, msBase = state.asyncIdleWaitTime * 3;
+      const maxTries = 5, msBase = state.asyncIdleWaitTime * 2;
       let i = 1, ms = msBase;
       for(; true; ms = msBase * ++i){
         try {

ext/wasm/api/sqlite3-vfs-opfs.c-pp.js

@@ -277,7 +277,7 @@ const installOpfsVfs = function callee(options){
        of this value is also used for determining how long to wait on
        lock contention to free up.
     */
-    state.asyncIdleWaitTime = 100;
+    state.asyncIdleWaitTime = 150;
     /**
        Whether the async counterpart should log exceptions to
        the serialization channel. That produces a great deal of
@@ -636,6 +636,12 @@ const installOpfsVfs = function callee(options){
         a[i] = f._chars[ndx];
       }
       return a.join("");
+      /*
+        An alternative impl. with an unpredictable length
+        but much simpler:
+
+        Math.floor(Math.random() * Number.MAX_SAFE_INTEGER).toString(36)
+      */
     };
 
     /**
@@ -1159,7 +1165,7 @@ const installOpfsVfs = function callee(options){
           "pragma journal_mode=persist;",
           /* Set a default busy-timeout handler to help OPFS dbs
              deal with multi-tab/multi-worker contention. */
-          "pragma busy_timeout=3000;",
+          "pragma busy_timeout=5000;",
           /*
             This vfs benefits hugely from cache on moderate/large
             speedtest1 --size 50 and --size 100 workloads. We currently

ext/wasm/tests/opfs/concurrency/test.js

@@ -69,6 +69,7 @@
   options.unlockAsap = (
     urlArgsHtml.has('unlock-asap') ? +urlArgsHtml.get('unlock-asap') : 0
   ) || 0;
+  options.noUnlink = !!urlArgsHtml.has('no-unlink');
   const workers = [];
   workers.post = (type,...args)=>{
     for(const w of workers) w.postMessage({type, payload:args});
@@ -124,7 +125,9 @@
   for(let i = 0; i < options.workerCount; ++i){
     stdout("Launching worker...");
     workers.push(new Worker(
-      workers.uri+'&workerId='+(i+1)+(i ? '' : '&unlink-db')
+      workers.uri+'&workerId='+(i+1)+(
+        (i || options.noUnlink) ? '' : '&unlink-db'
+      )
     ));
   }
   // Have to delay onmessage assignment until after the loop

manifest

@@ -1,5 +1,5 @@
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+C OPFS\sVFS:\stranslate\screateSyncAccessHandle()\sexceptions\swhich\sappear\sto\sbe\slocking\sviolations\sto\sSQLITE_BUSY.\sThis\sseems\sto\simprove\sconcurrency\sconsiderably\seven\swith\sa\sreduced\sretry\scount\sof\s5\s(was\s6).
-D 2022-12-02T17:52:52.611
+D 2022-12-02T18:06:26.286
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
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 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -508,9 +508,9 @@ F ext/wasm/api/sqlite3-api-oo1.js c8b6c9ccb64cf93ca990ac689e98963735110aec21f98e
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-F ext/wasm/api/sqlite3-opfs-async-proxy.js 9963c78bf6e5ccb5ba28e8597851bd9d980e86803b6d341cc985e586aef10c82
+F ext/wasm/api/sqlite3-opfs-async-proxy.js 132e27f2172411020bb3a35ce5897c6437a960b4d744e7b8bdf3c6e3e32369dd
 F ext/wasm/api/sqlite3-vfs-helper.js 4ad4faf02e1524bf0296be8452c00b5708dce6faf649468d0377e26a0b299263
-F ext/wasm/api/sqlite3-vfs-opfs.c-pp.js 654f37fd6312d3bb0d067b21ad42f9dcfd629fd34ace892e67e06143a65dc6d0
+F ext/wasm/api/sqlite3-vfs-opfs.c-pp.js 146fbdac3c2ffa006ad4e95430396496caca0584c70623ae64e6c452a82c0e7f
 F ext/wasm/api/sqlite3-wasi.h 25356084cfe0d40458a902afb465df8c21fc4152c1d0a59b563a3fba59a068f9
 F ext/wasm/api/sqlite3-wasm.c 733bc939f93caef0df0b3ebfea14cbd528da580fdef1a35b1f69c2b3e044c7b7
 F ext/wasm/api/sqlite3-worker1-promiser.js 0c7a9826dbf82a5ed4e4f7bf7816e825a52aff253afbf3350431f5773faf0e4b
@@ -557,7 +557,7 @@ F ext/wasm/tester1-worker.html ead6bdcc6cca221deb0dc9855a56f376351dbf2294fd7978c
 F ext/wasm/tester1.c-pp.html 74aa9b31c75f12490653f814b53c3dd39f40cd3f70d6a53a716f4e8587107399
 F ext/wasm/tester1.c-pp.js e73a91eba4b59aaadd98f383c00a5101dbbbc52d937fff3162fc4761986f4a88
 F ext/wasm/tests/opfs/concurrency/index.html 86d8ac435074d1e7007b91105f4897f368c165e8cecb6a9aa3d81f5cf5dcbe70
-F ext/wasm/tests/opfs/concurrency/test.js bfc3d7e27b207f0827f12568986b8d516a744529550b449314f5c21c9e9faf4a
+F ext/wasm/tests/opfs/concurrency/test.js 9315339ed27849e65890eda924a516562936525a4f3f162fa71aeb489b9dc707
 F ext/wasm/tests/opfs/concurrency/worker.js 0a8c1a3e6ebb38aabbee24f122693f1fb29d599948915c76906681bb7da1d3d2
 F ext/wasm/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd72273503ae7d5
 F ext/wasm/wasmfs.make 7ab655788bf0b52dce4538acbd5b11cdbe77edd36a14af5dec6dfe1ec4ab25fc
@@ -2065,8 +2065,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 5652154a8c93cf3b1ff6c2e55e94abbe995b0bb625f733461df20e006c2f13f8
+P b57e3c3db00a6bc6db20c82530479f9eba7e37b731f0da6fe81682e84c7ac916
-R abeafb6b0b2c2a0d499e07055ea2ac86
+R 8232ca838233bb862b578dd17ef993c2
-U drh
+U stephan
-Z 85652852cafea1303e4df55e9d9dc80a
+Z a512e857bd2ba2b089c64ccfca3b82d0
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-b57e3c3db00a6bc6db20c82530479f9eba7e37b731f0da6fe81682e84c7ac916
+0d36021d107d3afca190ad61c3380536ad0cc2d493d345d48f9f9c1191741128