cluster: fix edge cases that throw ERR_INTERNAL_ASSERTION

[oyyd]

Some cases use both cluster and net/cluser will throw
ERR_INTERNAL_ASSERTION when listen/bind to the port of 0, like below:

const cluster = require('cluster')
const dgram = require('dgram')

const kPort = 0;

function child() {
  for (let i = 0; i < 2; i += 1) {
    const socket = new dgram.Socket('udp4')
    socket.bind(kPort)
    setTimeout(() => {
      socket.close()
      const socket2 = new dgram.Socket('udp4')
      socket2.bind(kPort);
    }, 100)
  }
}

if (cluster.isMaster) {
  cluster.fork(__filename)
} else {
  child()
}

would throw:

internal/assert.js:14
    throw new ERR_INTERNAL_ASSERTION(message);
    ^

Error [ERR_INTERNAL_ASSERTION]: This is caused by either a bug in Node.js or incorrect usage of Node.js internals.
Please open an issue with this stack trace at https://github.com/nodejs/node/issues

    at assert (internal/assert.js:14:11)
    at SharedHandle.add (internal/cluster/shared_handle.js:28:3)
    at queryServer (internal/cluster/master.js:309:10)
    at Worker.onmessage (internal/cluster/master.js:249:5)
    at ChildProcess.onInternalMessage (internal/cluster/utils.js:47:8)
    at ChildProcess.emit (events.js:326:22)
    at emit (internal/child_process.js:906:12)
    at processTicksAndRejections (internal/process/task_queues.js:81:21) {
  code: 'ERR_INTERNAL_ASSERTION'
}

After some investigation, I believe it's because we remove the indexesKey when close servers while it might reference more than one index:

node/lib/internal/cluster/child.js

Line 127 in 8b8620d

indexes.delete(indexesKey);

This PR maitains a separate map of the index to fix the issue.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

[aduh95]

Shouldn't we use a SafeSet instead of a SafeMap?

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/35419/

[aduh95]

Benchmark CI: https://ci.nodejs.org/view/Node.js%20benchmark/job/benchmark-node-micro-benchmarks/884/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/35438/

[aduh95]

Benchmark CI didn't show any perf regressions or improvements

                                                                                                   confidence improvement accuracy (*)    (**)   (***)
 cluster/echo.js n=100000 serialization='advanced' sendsPerBroadcast=10 payload='object' workers=1                -2.39 %       ±6.11%  ±8.13% ±10.58%
 cluster/echo.js n=100000 serialization='advanced' sendsPerBroadcast=10 payload='string' workers=1                -1.81 %       ±7.25%  ±9.65% ±12.57%
 cluster/echo.js n=100000 serialization='advanced' sendsPerBroadcast=1 payload='object' workers=1                 -6.29 %      ±16.92% ±22.52% ±29.32%
 cluster/echo.js n=100000 serialization='advanced' sendsPerBroadcast=1 payload='string' workers=1                  0.04 %       ±7.12%  ±9.48% ±12.34%
 cluster/echo.js n=100000 serialization='json' sendsPerBroadcast=10 payload='object' workers=1                    -8.05 %      ±11.64% ±15.52% ±20.29%
 cluster/echo.js n=100000 serialization='json' sendsPerBroadcast=10 payload='string' workers=1                    10.75 %      ±11.97% ±15.99% ±20.92%
 cluster/echo.js n=100000 serialization='json' sendsPerBroadcast=1 payload='object' workers=1                     -9.79 %      ±11.02% ±14.67% ±19.09%
 cluster/echo.js n=100000 serialization='json' sendsPerBroadcast=1 payload='string' workers=1                      4.68 %      ±11.14% ±14.82% ±19.29%

Be aware that when doing many comparisons the risk of a false-positive
result increases. In this case there are 8 comparisons, you can thus
expect the following amount of false-positive results:
  0.40 false positives, when considering a   5% risk acceptance (*, **, ***),
  0.08 false positives, when considering a   1% risk acceptance (**, ***),
  0.01 false positives, when considering a 0.1% risk acceptance (***)

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/35439/

[aduh95]

Landed in 8e3f606