Describe fork, spawn and exec.
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child_process.exec(): exec spawns a shell and runs a command, then buffers the entire output before passing it to a callback function.
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child_process.spawn(): spawn launches a new process and returns a ChildProcess object that provides a streaming interface for communication.
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child_process.fork(): This method is a special case of spawn() method to create child processes. It creates a new instance of the V8 engine and the Node.js runtime to execute a specific JavaScript module.
Scenario Questions
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You need to run a simple shell command from a Node.js script to list files. Which child_process method would you choose and why?
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If you call child_process.fork to start a worker script and then immediately call process.exit in the parent, what happens to the child?
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Our service spawns a child process to run a Python script for image processing. Occasionally the child hangs and never returns. Walk me through how you'd debug this using spawn vs exec.
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We switched from child_process.spawn to child_process.exec for a data‑import job and saw memory usage spike. Explain why that happened and what trade‑offs you’d consider.
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Design a Node.js microservice that needs to process thousands of concurrent video transcoding tasks using child processes. How would you decide between fork, spawn, and a worker‑thread pool, and what limits would you enforce?
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Explain how you’d handle graceful shutdown of a Node.js server that has multiple long‑running child processes started via fork, ensuring no orphan processes remain.
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Our platform currently uses child_process.fork for each user request, leading to resource exhaustion at scale. Propose a migration strategy to a more scalable architecture, considering monitoring, deployment, and backward compatibility.
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Discuss the security implications of using exec to run user‑provided commands in a SaaS product, and outline policies or sandboxing techniques you’d put in place.
Follow-up Questions
- ❓What are the main differences in stdio handling between spawn and exec?
- ❓How does fork provide IPC compared to spawn?
- ❓When would you prefer spawn over fork for a CPU‑bound task?