To monitor memory usage in an application running on Compute Engine, which tool should be installed?

The installation of the Stackdriver Monitoring Agent is essential for monitoring memory usage in applications running on Compute Engine. The Stackdriver Monitoring Agent collects system and application metrics, which include memory usage statistics. It runs on the virtual machine instances and provides a more detailed set of metrics compared to what is available by default.

By using the Monitoring Agent, developers can track not only memory usage but also other important system metrics like CPU utilization, disk I/O, and network traffic. This information is crucial in identifying potential performance issues and ensuring the application runs efficiently.

The other options do serve their purposes in different contexts. The Stackdriver Client Library is primarily used for integrating Stackdriver monitoring within applications but does not itself gather system metrics. The Stackdriver Metrics Explorer is a tool for visualizing and analyzing metrics gathered from various agents and services; it relies on existing data rather than collecting new memory statistics. Accessing the Google Cloud Platform Console allows users to view metrics and dashboards but does not actively monitor memory usage without the agent in place. Thus, for comprehensive memory monitoring, installing the Stackdriver Monitoring Agent is the correct approach.