More tweaking of OPFS concurrency measures and the related test app.

FossilOrigin-Name: a8d4da1501d411085ec2fd48c4a056c8b1d97ef3c3203c5b403a854ac2864870

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

@@ -220,22 +220,19 @@ class GetSyncHandleError extends Error {
   }
 };
 GetSyncHandleError.convertRc = (e,rc)=>{
-  if(1){
-    /* This approach returns SQLITE_LOCKED to the C API
-       when getSyncHandle() fails but makes the very
-       wild assumption that such a failure _is_ a locking
-       error. In practice that appears to be the most
-       common error, by far, but we cannot unambiguously
+  if(0){
+    /* This approach makes the very wild assumption that such a
+       failure _is_ a locking error. In practice that appears to be
+       the most common error, by far, but we cannot unambiguously
        distinguish that from other errors.
 
-       This approach demonstrably reduces concurrency-related
-       errors but is highly questionable.
+       This approach is highly questionable.
     */
     return (e instanceof GetSyncHandleError)
-      ? state.sq3Codes.SQLITE_LOCKED
+      ? state.sq3Codes.SQLITE_IOERR_LOCK
       : rc;
   }else{
-    return ec;
+    return rc;
   }
 }
 /**
@@ -253,7 +250,7 @@ const getSyncHandle = async (fh)=>{
   if(!fh.syncHandle){
     const t = performance.now();
     log("Acquiring sync handle for",fh.filenameAbs);
-    const maxTries = 4, msBase = 300;
+    const maxTries = 6, msBase = 300;
     let i = 1, ms = msBase;
     for(; true; ms = msBase * ++i){
       try {
@@ -271,7 +268,7 @@ const getSyncHandle = async (fh)=>{
         }
         warn("Error getting sync handle. Waiting",ms,
              "ms and trying again.",fh.filenameAbs,e);
-        //await closeAutoLocks();
+        await closeAutoLocks();
         Atomics.wait(state.sabOPView, state.opIds.retry, 0, ms);
       }
     }

ext/wasm/tests/opfs/concurrency/index.html

@@ -18,7 +18,21 @@
     <h1></h1>
     <p>
       OPFS concurrency tester using multiple independent Workers.
-      This app is incomplete.
+      Disclaimer: concurrency in OPFS is currently a pain point
+      and timing/concurrency mitigation in this environment is
+      highly unpredictable!
+    </p>
+    <p>
+      URL flags: pass a number of workers using
+      the <code>workers=N</code> URL flag and the worker work interval
+      as <code>interval=N</code> (milliseconds).  Enable OPFS VFS
+      verbosity with <code>verbose=1-3</code> (output goes to the
+      dev console).
+    </p>
+    <p>Achtung: if it does not start to do anything within a couple of
+      seconds, check the dev console: Chrome often fails with "cannot allocate
+      WasmMemory" at startup. Closing and re-opening the tab usually resolves
+      it.
     </p>
     <div class='input-wrapper'>
       <input type='checkbox' id='cb-log-reverse'>

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

@@ -57,6 +57,12 @@
   options.workerCount = (
     urlArgsHtml.has('workers') ? +urlArgsHtml.get('workers') : 3
   ) || 3;
+  options.opfsVerbose = (
+    urlArgsHtml.has('verbose') ? +urlArgsHtml.get('verbose') : 1
+  ) || 1;
+  options.interval = (
+    urlArgsHtml.has('interval') ? +urlArgsHtml.get('interval') : 750
+  ) || 750;
   const workers = [];
   workers.post = (type,...args)=>{
     for(const w of workers) w.postMessage({type, payload:args});
@@ -91,7 +97,8 @@
   workers.uri = (
     'worker.js?'
       + 'sqlite3.dir='+options.sqlite3Dir
-      + '&opfs-verbose=2'
+      + '&interval='+options.interval
+      + '&opfs-verbose='+options.opfsVerbose
   );
   for(let i = 0; i < options.workerCount; ++i){
     stdout("Launching worker...");

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

@@ -8,7 +8,6 @@ self.sqlite3InitModule().then(async function(sqlite3){
   };
   const stdout = (...args)=>wPost('stdout',...args);
   const stderr = (...args)=>wPost('stderr',...args);
-  const postErr = (...args)=>wPost('error',...args);
   if(!sqlite3.opfs){
     stderr("OPFS support not detected. Aborting.");
     return;
@@ -19,15 +18,33 @@ self.sqlite3InitModule().then(async function(sqlite3){
   };
 
   const dbName = 'concurrency-tester.db';
-  if((new URL(self.location.href).searchParams).has('unlink-db')){
+  const urlArgs = new URL(self.location.href).searchParams;
+  if(urlArgs.has('unlink-db')){
     await sqlite3.opfs.unlink(dbName);
     stdout("Unlinked",dbName);
   }
   wPost('loaded');
-
+  let db;
+  const interval = Object.assign(Object.create(null),{
+    delay: urlArgs.has('interval') ? (+urlArgs.get('interval') || 750) : 750,
+    handle: undefined,
+    count: 0
+  });
+  const finish = ()=>{
+    if(db){
+      if(!db.pointer) return;
+      db.close();
+    }
+    if(interval.error){
+      wPost('failed',"Ending work after interval #"+interval.count,
+            "due to error:",interval.error);
+    }else{
+      wPost('finished',"Ending work after",interval.count,"intervals.");
+    }
+  };
   const run = async function(){
-    const db = new sqlite3.opfs.OpfsDb(dbName,'c');
-    //sqlite3.capi.sqlite3_busy_timeout(db.pointer, 2000);
+    db = new sqlite3.opfs.OpfsDb(dbName,'c');
+    sqlite3.capi.sqlite3_busy_timeout(db.pointer, 5000);
     db.transaction((db)=>{
       db.exec([
         "create table if not exists t1(w TEXT UNIQUE ON CONFLICT REPLACE,v);",
@@ -36,11 +53,6 @@ self.sqlite3InitModule().then(async function(sqlite3){
     });
 
     const maxIterations = 10;
-    const interval = Object.assign(Object.create(null),{
-      delay: 500,
-      handle: undefined,
-      count: 0
-    });
     stdout("Starting interval-based db updates with delay of",interval.delay,"ms.");
     const doWork = async ()=>{
       const tm = new Date().getTime();
@@ -57,15 +69,6 @@ self.sqlite3InitModule().then(async function(sqlite3){
         interval.error = e;
       }
     };
-    const finish = ()=>{
-      db.close();
-      if(interval.error){
-        wPost('failed',"Ending work after interval #"+interval.count,
-              "due to error:",interval.error);
-      }else{
-        wPost('finished',"Ending work after",interval.count,"intervals.");
-      }
-    };
     if(1){/*use setInterval()*/
       interval.handle = setInterval(async ()=>{
         await doWork();
@@ -89,7 +92,10 @@ self.sqlite3InitModule().then(async function(sqlite3){
 
   self.onmessage = function({data}){
     switch(data.type){
-        case 'run': run().catch((e)=>postErr(e.message));
+        case 'run': run().catch((e)=>{
+          if(!interval.error) interval.error = e;
+          finish();
+        });
           break;
         default:
           stderr("Unhandled message type '"+data.type+"'.");