@Override
  public Cache getCache() throws CacheClosedException {
    if (cache == null) {
      throw new CacheClosedException("FunctionContext does not have a valid Cache");
    }
    return cache;
  }
Get the identifier of the running function used for logging and administration purposes

@return String uniquely identifying this running instance
@see Function#getId()
geode-core/src/main/java/org/apache/geode/internal/cache/execute/FunctionContextImpl.java