From 6504106a9e62b9647ee94065fa5b694e9f073e34 Mon Sep 17 00:00:00 2001
From: Franck Royer <franck@status.im>
Date: Wed, 15 Sep 2021 16:53:55 +1000
Subject: [PATCH] Connects to a limited number of bootstrap nodes, defaults to
 1

---
 CHANGELOG.md                      |  1 +
 src/lib/discovery.browser.spec.ts | 35 +++++++++++++++++++++++++++++++
 src/lib/discovery.ts              | 27 +++++++++++++++++++++---
 3 files changed, 60 insertions(+), 3 deletions(-)
 create mode 100644 src/lib/discovery.browser.spec.ts

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9911fea549..b47709784c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 - Upgrade libp2p libraries: @chainsafe/libp2p-noise@4.1.1, libp2p@0.32.4, libp2p-gossipsub@0.11.1.
+- Connects to a limited number of bootstrap nodes, defaults to 1. 
 
 ## [0.12.0] - 2021-09-2
 
diff --git a/src/lib/discovery.browser.spec.ts b/src/lib/discovery.browser.spec.ts
new file mode 100644
index 0000000000..ff4b7a7fa2
--- /dev/null
+++ b/src/lib/discovery.browser.spec.ts
@@ -0,0 +1,35 @@
+import { expect } from 'chai';
+
+import { getPseudoRandomSubset } from './discovery';
+
+describe('Discovery', () => {
+  it('returns all values when wanted number matches available values', function () {
+    const values = ['a', 'b', 'c'];
+
+    const res = getPseudoRandomSubset(values, 3);
+
+    expect(res.length).to.eq(3);
+    expect(res.includes('a')).to.be.true;
+    expect(res.includes('b')).to.be.true;
+    expect(res.includes('c')).to.be.true;
+  });
+
+  it('returns all values when wanted number is greater than available values', function () {
+    const values = ['a', 'b', 'c'];
+
+    const res = getPseudoRandomSubset(values, 5);
+
+    expect(res.length).to.eq(3);
+    expect(res.includes('a')).to.be.true;
+    expect(res.includes('b')).to.be.true;
+    expect(res.includes('c')).to.be.true;
+  });
+
+  it('returns a subset of values when wanted number is lesser than available values', function () {
+    const values = ['a', 'b', 'c'];
+
+    const res = getPseudoRandomSubset(values, 2);
+
+    expect(res.length).to.eq(2);
+  });
+});
diff --git a/src/lib/discovery.ts b/src/lib/discovery.ts
index 4999bdcb33..327bb236ee 100644
--- a/src/lib/discovery.ts
+++ b/src/lib/discovery.ts
@@ -1,8 +1,11 @@
 import axios from 'axios';
 import debug from 'debug';
+import { shuffle } from 'libp2p-gossipsub/src/utils';
 
 const dbg = debug('waku:discovery');
 
+const DefaultWantedNumber = 1;
+
 /**
  * GET list of nodes from remote HTTP host.
  *
@@ -14,6 +17,7 @@ const dbg = debug('waku:discovery');
  * request returns `{ foo: { bar: [address1, address2] } }` then `path` should be
  * `[ "foo", "bar" ]`.
  * @param url Remote host containing bootstrap peers in JSON format.
+ * @param wantedNumber The number of connections desired. Defaults to [DefaultWantedNumber].
  *
  * @returns An array of multiaddresses.
  * @throws If the remote host is unreachable or the response cannot be parsed
@@ -21,8 +25,13 @@ const dbg = debug('waku:discovery');
  */
 export async function getBootstrapNodes(
   path: string[] = ['fleets', 'wakuv2.prod', 'waku-websocket'],
-  url = 'https://fleets.status.im/'
+  url = 'https://fleets.status.im/',
+  wantedNumber: number = DefaultWantedNumber
 ): Promise<string[]> {
+  if (wantedNumber <= 0) {
+    return [];
+  }
+
   const res = await axios.get(url, {
     headers: { 'Content-Type': 'application/json' },
   });
@@ -43,7 +52,7 @@ export async function getBootstrapNodes(
   }
 
   if (Array.isArray(nodes)) {
-    return nodes;
+    return getPseudoRandomSubset(nodes, wantedNumber);
   }
 
   if (typeof nodes === 'string') {
@@ -51,10 +60,22 @@ export async function getBootstrapNodes(
   }
 
   if (typeof nodes === 'object') {
-    return Object.values(nodes);
+    nodes = Object.values(nodes);
+    getPseudoRandomSubset(nodes, wantedNumber);
   }
 
   throw `Failed to retrieve bootstrap nodes: response format is not supported: ${JSON.stringify(
     nodes
   )}`;
 }
+
+export function getPseudoRandomSubset(
+  values: string[],
+  wantedNumber: number
+): string[] {
+  if (values.length <= wantedNumber) {
+    return values;
+  }
+
+  return shuffle(values).slice(0, wantedNumber);
+}