feat(sdam_viz): add new tool for visualizing driver sdam changes

test/tools/sdam_viz

@@ -0,0 +1,125 @@
+#!/usr/bin/env node
+'use strict';
+
+const { MongoClient } = require('../..');
+const arrayStrictEqual = require('../../lib/core/utils').arrayStrictEqual;
+const chalk = require('chalk');
+
+function print(msg) {
+  console.log(`${chalk.white(new Date().toISOString())} ${msg}`);
+}
+
+const uri = process.argv[2];
+const client = new MongoClient(uri, {
+  useNewUrlParser: true,
+  useUnifiedTopology: true
+});
+
+async function run() {
+  print(`connecting to: ${uri}`);
+  client.on('serverHeartbeatSucceeded', event =>
+    print(
+      `${chalk.yellow('heartbeat')} ${chalk.green('succeeded')} host: '${
+        event.connectionId
+      }' ${chalk.gray(`(${event.duration} ms)`)}`
+    )
+  );
+
+  client.on('serverHeartbeatFailed', event =>
+    print(
+      `${chalk.yellow('heartbeat')} ${chalk.red('failed')} host: '${
+        event.connectionId
+      }' ${chalk.gray(`(${event.duration} ms)`)}`
+    )
+  );
+
+  // server information
+  client.on('serverOpening', event => {
+    print(`${chalk.cyan('server')} [${event.address}] added to topology#${event.topologyId}`);
+  });
+
+  client.on('serverClosed', event => {
+    print(`${chalk.cyan('server')} [${event.address}] removed from topology#${event.topologyId}`);
+  });
+
+  client.on('serverDescriptionChanged', event => {
+    print(`${chalk.cyan('server')} [${event.address}] changed:`);
+    console.log(serverDescriptionDiff(event.previousDescription, event.newDescription));
+  });
+
+  // topology information
+  client.on('topologyOpening', event => {
+    print(`${chalk.magenta('topology')} adding topology#${event.topologyId}`);
+  });
+
+  client.on('topologyClosed', event => {
+    print(`${chalk.magenta('topology')} removing topology#${event.topologyId}`);
+  });
+
+  client.on('topologyDescriptionChanged', event => {
+    const diff = topologyDescriptionDiff(event.previousDescription, event.newDescription);
+    if (diff !== '') {
+      print(`${chalk.magenta('topology')} [topology#${event.topologyId}] changed:`);
+      console.log(diff);
+    }
+  });
+
+  await client.connect();
+}
+
+function diff(lhs, rhs, fields, comparator) {
+  return fields.reduce((diff, field) => {
+    if (lhs[field] == null || rhs[field] == null) {
+      return diff;
+    }
+
+    if (!comparator(lhs[field], rhs[field])) {
+      diff.push(
+        `  ${field}: ${chalk.green(`[${lhs[field]}]`)} => ${chalk.green(`[${rhs[field]}]`)}`
+      );
+    }
+
+    return diff;
+  }, []);
+}
+
+function serverDescriptionDiff(lhs, rhs) {
+  const objectIdFields = ['electionId'];
+  const arrayFields = ['hosts', 'tags'];
+  const simpleFields = [
+    'type',
+    'minWireVersion',
+    'me',
+    'setName',
+    'setVersion',
+    'electionId',
+    'primary',
+    'logicalSessionTimeoutMinutes'
+  ];
+
+  return diff(lhs, rhs, simpleFields, (x, y) => x === y)
+    .concat(diff(lhs, rhs, arrayFields, (x, y) => arrayStrictEqual(x, y)))
+    .concat(diff(lhs, rhs, objectIdFields, (x, y) => x.equals(y)))
+    .join(',\n');
+}
+
+function topologyDescriptionDiff(lhs, rhs) {
+  const simpleFields = [
+    'type',
+    'setName',
+    'maxSetVersion',
+    'stale',
+    'compatible',
+    'compatibilityError',
+    'logicalSessionTimeoutMinutes',
+    'error',
+    'commonWireVersion'
+  ];
+
+  return diff(lhs, rhs, simpleFields, (x, y) => x === y).join(',\n');
+}
+
+run().catch(error => console.log('Caught', error));
+process.on('SIGINT', async function() {
+  await client.close();
+});