feat: Add queue in enc/dec group message (#191)

WASignalGroup/queue_job.js

@@ -0,0 +1,69 @@
+// vim: ts=4:sw=4:expandtab
+
+/*
+ * jobQueue manages multiple queues indexed by device to serialize
+ * session io ops on the database.
+ */
+'use strict';
+
+
+const _queueAsyncBuckets = new Map();
+const _gcLimit = 10000;
+
+async function _asyncQueueExecutor(queue, cleanup) {
+    let offt = 0;
+    while (true) {
+        let limit = Math.min(queue.length, _gcLimit); // Break up thundering hurds for GC duty.
+        for (let i = offt; i < limit; i++) {
+            const job = queue[i];
+            try {
+                job.resolve(await job.awaitable());
+            } catch (e) {
+                job.reject(e);
+            }
+        }
+        if (limit < queue.length) {
+            /* Perform lazy GC of queue for faster iteration. */
+            if (limit >= _gcLimit) {
+                queue.splice(0, limit);
+                offt = 0;
+            } else {
+                offt = limit;
+            }
+        } else {
+            break;
+        }
+    }
+    cleanup();
+}
+
+module.exports = function (bucket, awaitable) {
+    /* Run the async awaitable only when all other async calls registered
+     * here have completed (or thrown).  The bucket argument is a hashable
+     * key representing the task queue to use. */
+    if (!awaitable.name) {
+        // Make debuging easier by adding a name to this function.
+        Object.defineProperty(awaitable, 'name', { writable: true });
+        if (typeof bucket === 'string') {
+            awaitable.name = bucket;
+        } else {
+            console.warn("Unhandled bucket type (for naming):", typeof bucket, bucket);
+        }
+    }
+    let inactive;
+    if (!_queueAsyncBuckets.has(bucket)) {
+        _queueAsyncBuckets.set(bucket, []);
+        inactive = true;
+    }
+    const queue = _queueAsyncBuckets.get(bucket);
+    const job = new Promise((resolve, reject) => queue.push({
+        awaitable,
+        resolve,
+        reject
+    }));
+    if (inactive) {
+        /* An executor is not currently active; Start one now. */
+        _asyncQueueExecutor(queue, () => _queueAsyncBuckets.delete(bucket));
+    }
+    return job;
+};