_writeTestPipeBsonFileSync() will be a synchronous version of the existing _writeTestPipeBsonFile() function, which is async, that was delivered by SERVER-71564.

This is needed for PERF-3313 Evergreen benchmarks to allow it to be invoked in a background mongo shell on the mongod machine without that shell exiting until the pipe is consumed, because if the shell exits (as would be the case with the current async version), its detached pipe writer thread also exits, leaving the pipe file system entry in place but no writer thread, so when the reader attaches to the pipe it will wait forever for data or EOF, neither of which will ever arrive.

FYI yoonsoo.kim@mongodb.com arun.banala@mongodb.com