Twilio class has a lot of multithreading issues.

[bohnman]

Version:

7.22.0

Steps to Reproduce

The Twilio class has a bunch of multithreading issues. I fundamentally disagree with using singletons that are mutable, but if you're going to do it, it needs to be thread safe.

Here's what I recommend:

• add synchronized to all set* and init* methods . These methods are called infrequently so the synchronization penalty will be minimal
• Make the restClient and executorService fields volatile
• For getRestClient and getExecutorService we can minimize the synchronization by doing the double null check trick. Here is an example pattern on how to use it:

public static TwilioRestClient getRestClient() {
   if (restClient == null) {
      synchronized(Twilio.class) {
          if (restClient == null) {
              restClient = buildRestClient()
          }
      }
   }

  return restClient
}

[thinkingserious]

Related to: #428

[childish-sambino]

Makes sense to me. Working on a fix ...