Max emitters test and fix

index.js

@@ -319,7 +319,10 @@ class Corestore extends Nanoresource {
     this._isNamespaced = !!opts.name
     this._openedCores = new Map()
 
-    const onfeed = feed => this.emit('feed', feed)
+    const onfeed = feed => {
+      this.emit('feed', feed)
+      this._unlisten()
+    }
     const onerror = err => this.emit('error', err)
     this.inner.on('feed', onfeed)
     this.inner.on('error', onerror)

test/stress.js

@@ -0,0 +1,56 @@
+/**
+ * Makes a couple dozen namespaced corestores
+ *
+ * For example, kappa-mulitfeed makes a new corestore for each new multifeed
+ *
+ * When more than 11 corestores are made, a MaxListenersExceededWarning happens
+ * due to too many listeners, see:
+ *
+ * https://github.com/andrewosh/corestore/issues/20
+ *
+ */
+const ram = require('random-access-memory')
+const test = require('tape')
+const Corestore = require('..')
+const { once } = require('events')
+
+test('make a couple dozen namespaced corestores (without MaxListener warning)', async t => {
+  const store = await create(ram)
+  let spaces = []
+  let cores = []
+
+  let index = 0
+  while (index < 24) {
+    try {
+      spaces[index] = store.namespace('namespace-' + index)
+      cores[index] = spaces[index].default()
+      await cores[index].ready()
+
+      // feed and event never passes 3 listeners
+      t.ok(store.inner._events.feed.length < 3, '## feed event listener length before is only 1 or 2')
+      t.ok(spaces[index].inner._events.feed.length < 3, '## feed event listener length before is only 1 or 2')
+      t.ok(store.inner._events.error.length < 3, '## feed event listener length before is only 1 or 2')
+      t.ok(spaces[index].inner._events.error.length < 3, '## feed event listener length before is only 1 or 2')
+
+      await once(store.inner, 'feed')
+
+      // feed and event never passes 0 listeners
+      t.ok(store.inner._events.feed === undefined, '## feed event listener length after is zero')
+      t.ok(spaces[index].inner._events.feed === undefined, '## feed event listener length after is zero')
+      t.ok(store.inner._events.error === undefined, '## feed event listener length after is zero')
+      t.ok(spaces[index].inner._events.error === undefined, '## feed event listener length after is zero')
+    } catch (err) {
+      console.error('error happened', err)
+    }
+    t.ok(store.inner._events.feed === undefined, 'no event listner memory leak')
+    index++
+  }
+
+  t.end()
+})
+
+async function create (storage, opts) {
+  const store = new Corestore(storage, opts)
+  await store.ready()
+  return store
+}