Race condition on `ServiceFactory.setUmask()`

[jamoore]

To set a umask for a particular call, one calls ServiceFactory.setUmask(Permissions). However, between calling SF.setUmask() and service.someMethod() another thread might reset the umask.

• Document the need for synchronization, or
• Change the method to ServiceFactory.setUmask( ServiceInterface, Permissions ) and handle the synchronization internally.

[jmoore]

Another option would be to use a PrincipalHolder rather than a Principal so that the threads don't compete.

It may also be necessary that new ServiceFactory() NOT return a static instance for similar reasons.

[jmoore]

Should also provide a ServiceFactory.getUmask() method so that something of the form:

  Permissions oldPermissions = sf.getUmask();
  try {
      sf.setUmask(newPermissions);
      // do something
  } finally {
      if (sf!=null) sf.setUmask(oldPermissions);
  }

can be done.

[jmoore]

This needs the new session management code: proposals/SessionsAndMessages

[jmoore]

Merged into #864.