If the server's CPU usage is at 100% and the cause is related to Apache2, there could be a few different reasons:
High traffic: Apache2 is a web server that serves web pages to clients. If the server is receiving a high amount of traffic, it can cause Apache2 to consume a lot of CPU resources, resulting in high CPU usage.
Misconfiguration: Apache2 is a complex software that requires careful configuration to ensure optimal performance. A misconfigured Apache2 server can cause high CPU usage, for example, if the number of concurrent connections or the size of server processes are set too high.
Resource-intensive requests: If the Apache2 server is receiving requests that require a lot of resources, such as heavy database queries or large file transfers, it can cause high CPU usage.
Malicious traffic: If the server is receiving a high volume of malicious traffic, such as DDoS attacks or other types of attacks, it can cause high CPU usage as Apache2 tries to handle the requests.
To diagnose and resolve high CPU usage related to Apache2, it may be necessary to analyze server logs, adjust server configurations, optimize server code, or implement security measures to prevent malicious traffic.