fix(getport): randomize first port using crypto.randomInt (#844)

* fix(getport): Randomize first port using crypto

The current implementation of `getPort()` relies on using `Date.now()`
to get the first port to try to launch mongo on, even when the
`EXP_NET0LISTEN` flag is set. This causes a couple issues:
- If the `Date` module is mocked, it can result in `getFreePort()`
  returning the same first port every time.
- If multiple mongos are being started at once in parallel, it's
  possible for the same first port to be picked leading to port
  conflicts
In order to better randomize the initial port selection so that port
conflicts can be avoided, instead of using `Date.now()` for an initial
seed, use `crypto.randomInt()` which should provide more randomness and
hopefully avoid some of these race conditions.

re #827

* fix(getport): change crypto.randomInt "max" to be inclusive

---------

Co-authored-by: hasezoey <[email protected]>

Author: noseworthy

packages/mongodb-memory-server-core/src/util/getport/index.ts

@@ -1,4 +1,5 @@
 import resolveConfig, { ResolveConfigVariables, envToBool } from '../resolveConfig';
+import * as crypto from 'node:crypto';
 import * as net from 'node:net';
 import debug from 'debug';
 
@@ -48,10 +49,10 @@ export async function getFreePort(
   firstPort?: number,
   max_tries: number = MAX_DEFAULT_TRIES
 ): Promise<number> {
-  // use "Date" as a semi-random value to lessen conflicts between simultaneous tests
-  firstPort = firstPort || validPort(Date.now());
+  // Get a random value from crypto to use as first port if none is given
+  firstPort = firstPort || validPort(crypto.randomInt(MIN_PORT, MAX_PORT + 1));
 
-  // clear ports cache after some time, but not on a interval
+  // clear ports cache after some time, but not on an interval
   if (PORTS_CACHE.timeSet && Date.now() - PORTS_CACHE.timeSet > PORTS_CACHE_CLEAN_TIME) {
     PORTS_CACHE.ports.clear();
     PORTS_CACHE.timeSet = Date.now();