fix: hyperswarm-mediator limit msg size (#428)

* Export batches in chunks

* Refactored shareDb

* Fixed mergeBatch

services/mediators/hyperswarm/src/hyperswarm-mediator.js

@@ -84,16 +84,6 @@ function shortName(name) {
     return name.slice(0, 4) + '-' + name.slice(-4);
 }
 
-async function createBatch() {
-    console.time('exportBatch');
-    const allEvents = await gatekeeper.exportBatch();
-    console.timeEnd('exportBatch');
-    console.log(`${allEvents.length} events fetched`);
-
-    // hyperswarm distributes only operations
-    return allEvents.map(event => event.operation);
-}
-
 function logBatch(batch, name) {
     const debugFolder = 'data/debug';
 
@@ -111,19 +101,65 @@ function logBatch(batch, name) {
     fs.writeFileSync(batchfile, batchJSON);
 }
 
+function sendBatch(conn, batch) {
+    const limit = 8 * 1024 * 1014; // 8 MB limit
+
+    const msg = {
+        type: 'batch',
+        data: batch,
+        relays: [],
+        node: config.nodeName,
+    };
+
+    const json = JSON.stringify(msg);
+
+    if (json.length < limit) {
+        conn.write(json);
+        console.log(` * sent ${batch.length} ops in ${json.length} bytes`);
+        return batch.length;
+    }
+    else {
+        if (batch.length < 2) {
+            console.error(`Error: Single operation exceeds the limit of ${limit} bytes. Unable to send.`);
+            return 0;
+        }
+
+        // split batch into 2 halves
+        const midIndex = Math.floor(batch.length / 2);
+        const batch1 = batch.slice(0, midIndex);
+        const batch2 = batch.slice(midIndex);
+
+        return sendBatch(conn, batch1) + sendBatch(conn, batch2);
+    }
+}
+
 async function shareDb(conn) {
     try {
-        const batch = await createBatch();
+        console.time('exportBatch in chunks');
+        const batchSize = 1000; // export DIDs in batches of 1000 for scalability
+        const dids = await gatekeeper.getDIDs();
+        let allEvents = [];
+
+        for (let i = 0; i < dids.length; i += batchSize) {
+            const didBatch = dids.slice(i, i + batchSize);
+            const exports = await gatekeeper.exportBatch(didBatch);
+            allEvents = allEvents.concat(exports);
+        }
+        console.timeEnd('exportBatch in chunks');
 
-        const msg = {
-            type: 'batch',
-            data: batch,
-            relays: [],
-            node: config.nodeName,
-        };
+        // hyperswarm distributes only operations
+        const batch = allEvents.map(event => event.operation);
+        console.log(`${batch.length} operations fetched`);
 
-        const json = JSON.stringify(msg);
-        conn.write(json);
+        if (!batch || batch.length === 0) {
+            return;
+        }
+
+        const opsCount = batch.length;
+        console.time('sendBatch');
+        const opsSent = sendBatch(conn, batch);
+        console.timeEnd('sendBatch');
+        console.log(` * sent ${opsSent}/${opsCount} operations`);
     }
     catch (error) {
         console.log(error);
@@ -205,7 +241,10 @@ async function mergeBatch(batch) {
         }
     }
 
-    await importBatch(chunk);
+    if (chunk.length > 0) {
+        await importBatch(chunk);
+    }
+
     console.time('processEvents');
     const response = await gatekeeper.processEvents();
     console.timeEnd('processEvents');