Q.In the web-server example (for result declaration), suppose the server receives a request from an Administrator to access the result of a school on an urgent basis, along with other requests from students to check individual results. Can you suggest some strategy to ensure service to all as per their urgency?

This is a plain theory question — it asks you to suggest a scheduling strategy for a real-world scenario involving mixed urgency levels.

---

The Scenario

A web server handles two types of requests during result declaration:

1. Administrator request — high urgency, needs immediate access to a school's result.
2. Student requests — many, lower urgency, each checking an individual result.

The core problem is that the administrator's request is urgent but arrives among many routine student requests. Without a strategy, the server might process requests in arrival order (FCFS), causing the urgent request to wait behind a queue of student requests.

---

Suggested Strategy: Priority Scheduling with Preemption

The most suitable approach is Priority Scheduling, where each request is assigned a priority level. The administrator's request gets a higher priority than student requests.

How it works:

• Every incoming request is tagged with a priority value (e.g., 0 for highest, 1 for normal).
• The CPU scheduler always picks the process with the highest priority from the ready queue.
• If a new high-priority request arrives while a low-priority request is being served, preemption occurs — the low-priority request is paused, and the high-priority request is served immediately.

Why this works here:

• The administrator's request is served almost instantly, regardless of how many student requests are queued.
• Student requests are still served, but they yield the CPU when a higher-priority request arrives.
• This matches the real-world need: urgent tasks should not be blocked by routine ones.

---

Additional Practical Considerations

• Priority inversion can occur if a low-priority process holds a resource needed by a high-priority process. This is avoided here because each request is independent (no shared locked resources). …

This is a plain theory question that asks for a strategy to handle multiple requests with different urgency levels in a web-server scenario. The core idea is to use Priority Scheduling, where each request is assigned a priority level, and the server processes higher-priority requests first.

Why Priority Scheduling?

In a real-world web server handling result declarations, requests come from different users with varying needs. An Administrator's urgent request to access a school's result should be processed before a student's routine request to check their individual result. Without a prioritization mechanism, all requests would be treated equally, leading to delays for urgent tasks.

Priority Scheduling solves this by assigning a priority value to each request. The server then processes requests in order of their priority — highest priority first. This ensures that urgent requests are served promptly while still eventually serving all other requests.

Suggested Strategy

1. Assign Priority Levels

• Administrator requests: Priority 1 (highest)
• Student requests: Priority 2 (normal)
• Other requests (e.g., public information): Priority 3 (lowest)

2. Implement a Priority Queue

The server maintains a priority queue where each request is enqueued with its priority. The scheduler always dequeues the request with the highest priority.

3. Use Preemptive or Non-Preemptive Scheduling

• Non-preemptive: Once a request starts processing, it runs to completion. This is simpler but may cause a high-priority request to wait if a low-priority one is already being served.
• Preemptive: If a higher-priority request arrives while a lower-priority one is being processed, the server pauses the lower-priority request and serves the higher-priority one first. This is more responsive but complex to implement.

For this scenario, non-preemptive priority scheduling is usually sufficient because the requests are short (fetching a result from a database). The Administrator's request will be queued with high priority and served before any pending student requests.

4. Handle Starvation

A risk with priority scheduling is that low-priority requests may never get served if high-priority requests keep arriving. To prevent this, use aging — gradually increase the priority of waiting low-priority requests over time. For example, every 30 seconds, increase the priority of any waiting student request by 1, so it eventually becomes high-priority. …