Synchronous I/O
Blocking the calling thread while I/O completes can reduce performance and affect vertical scalability.
A synchronous I/O operation blocks the calling thread while the I/O completes. The calling thread enters a wait state and is unable to perform useful work during this interval, wasting processing resources.
Common examples of I/O include:
- Retrieving or persisting data to a database or any type of persistent storage.
- Sending a request to a web service.
- Posting a message or retrieving a message from a queue.
- Writing to or reading from a local file.
This antipattern typically occurs because:
It appears to be the most intuitive way to perform an operation.
The application requires a response from a request.
The application uses a library that only provides synchronous methods for I/O.
An external library performs synchronous I/O operations internally. A single synchronous I/O call can block an entire call chain.