When producing the first heartbeat, BuildDescription::getClassDescriptions instantiates every single class of each loader. In the case of AWS, the processors happen to derive from S3Processor, and they contain a data member of type Aws::Client::ClientConfiguration, whose default constructor makes HTTP calls to AWS.
The easy fix is to delay the initialization of this particular member to onSchedule.
The proper fix is to change the class loading and class description generation logic to store more metadata about classes that are collected at registration time, using compile-time introspection, instead of instantiating the classes and using dynamic_cast.
This issue is about the proper fix. For the easy fix, see