Add test app for experimenting with multi-worker OPFS concurrency. Tweak OPFS VFS to significantly improve the otherwise "unfortunate" concurrency situation.

FossilOrigin-Name: 96f76e7616f8157a342b9e1c42f7b1feab200d182268871a2b25f67d4ee2564c

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

@@ -0,0 +1,97 @@
+(async function(self){
+
+  const logClass = (function(){
+    const mapToString = (v)=>{
+      switch(typeof v){
+          case 'number': case 'string': case 'boolean':
+          case 'undefined': case 'bigint':
+            return ''+v;
+          default: break;
+      }
+      if(null===v) return 'null';
+      if(v instanceof Error){
+        v = {
+          message: v.message,
+          stack: v.stack,
+          errorClass: v.name
+        };
+      }
+      return JSON.stringify(v,undefined,2);
+    };
+    const normalizeArgs = (args)=>args.map(mapToString);
+    const logTarget = document.querySelector('#test-output');
+    const logClass = function(cssClass,...args){
+      const ln = document.createElement('div');
+      if(cssClass){
+        for(const c of (Array.isArray(cssClass) ? cssClass : [cssClass])){
+          ln.classList.add(c);
+        }
+      }
+      ln.append(document.createTextNode(normalizeArgs(args).join(' ')));
+      logTarget.append(ln);
+    };
+    const cbReverse = document.querySelector('#cb-log-reverse');
+    const cbReverseKey = 'tester1:cb-log-reverse';
+    const cbReverseIt = ()=>{
+      logTarget.classList[cbReverse.checked ? 'add' : 'remove']('reverse');
+      localStorage.setItem(cbReverseKey, cbReverse.checked ? 1 : 0);
+    };
+    cbReverse.addEventListener('change', cbReverseIt, true);
+    if(localStorage.getItem(cbReverseKey)){
+      cbReverse.checked = !!(+localStorage.getItem(cbReverseKey));
+    }
+    cbReverseIt();
+    return logClass;
+  })();
+  const stdout = (...args)=>logClass('',...args);
+  const stderr = (...args)=>logClass('error',...args);
+
+  const wait = async (ms)=>{
+    return new Promise((resolve)=>setTimeout(resolve,ms));
+  };
+
+  const urlArgsJs = new URL(document.currentScript.src).searchParams;
+  const urlArgsHtml = new URL(self.location.href).searchParams;
+  const options = Object.create(null);
+  options.sqlite3Dir = urlArgsJs.get('sqlite3.dir');
+  options.workerCount = (
+    urlArgsHtml.has('workers') ? +urlArgsHtml.get('workers') : 3
+  ) || 3;
+  const workers = [];
+  workers.post = (type,...args)=>{
+    for(const w of workers) w.postMessage({type, payload:args});
+  };
+  workers.loadedCount = 0;
+  workers.onmessage = function(msg){
+    msg = msg.data;
+    const wName =  msg.worker;
+    const prefix = 'Worker ['+wName+']:';
+    switch(msg.type){
+        case 'stdout': stdout(prefix,...msg.payload); break;
+        case 'stderr': stderr(prefix,...msg.payload); break;
+        case 'error': stderr(prefix,"ERROR:",...msg.payload); break;
+        case 'loaded':
+          stdout(prefix,"loaded");
+          if(++workers.loadedCount === workers.length){
+            stdout("All workers loaded. Telling them to run...");
+            workers.post('run');
+          }
+          break;
+        default: logClass('error',"Unhandled message type:",msg); break;
+    }
+  };
+
+  stdout("Launching",options.workerCount,"workers...");
+  workers.uri = (
+    'worker.js?'
+      + 'sqlite3.dir='+options.sqlite3Dir
+      + '&opfs-verbose=2'
+  );
+  for(let i = 0; i < options.workerCount; ++i){
+    stdout("Launching worker...");
+    workers.push(new Worker(workers.uri+(i ? '' : '&unlink-db')));
+  }
+  // Have to delay onmessage assignment until after the loop
+  // to avoid that early workers get an undue head start.
+  workers.forEach((w)=>w.onmessage = workers.onmessage);
+})(self);