How do you collect memory usage metrics for an application running on Compute Engine?

To collect detailed system-level metrics like memory utilization from a Compute Engine instance, you need to install the Stackdriver Monitoring Agent (now called Operations Agent). This agent collects a wide range of metrics, including CPU, disk I/O, network, and memory, and sends them to Cloud Monitoring. Installing the Stackdriver Client Library is for instrumenting your application code to send custom metrics or logs, not for collecting host-level metrics like memory usage. The Stackdriver Metrics Explorer is a tool within the Cloud Console used to visualize and analyze collected metrics; it doesn't collect them. The Google Cloud Platform Console is the web-based interface for managing Google Cloud resources; while you can view metrics here, the console itself doesn't collect them from within the VM.