Make the prefork mode more robust (#755)
Make the prefork mode more robust (#755)

* Make the prefork mode more robust

The main process will exit if one of the prefork child processes doesn't complete successfully under the current prefork mode, so it ought to make sure that all child processes run independently and the main process will only exit after all child processes are finished.

* Start over those failed child processes automatically

* Kill all child processes before main process exits

* Remove redundant code

* Add configurable threshold of starting over child processes

* Return a error of RecoverThreshold

* Resolved requested changes

* Add logs

* Resolve requested changes
valyala/fasthttp