Module: HotCell::Filesystem

Defined in:
lib/hot_cell/filesystem.rb

Overview

What the cell does to trees it owns and did not write: a request's home after the request, the slot directory at boot, the scratch at boot.

Class Method Summary collapse

Class Method Details

.remove_tree(path) ⇒ Object

A mode is the only thing a tool needs to make its own tree unremovable, and a mode on a tree this uid owns is ours to put back. chmod 0500 on a directory a conversion wrote is enough to fail the recursive delete underneath it, and the delete failing used to be the end of it: one tree per request stayed on the tmpfs until the container ended. The repair is not a permission the process gains, it is one it never lost.

Repair only after a failure, never before, so the common request pays for a walk of its own tree once rather than twice. force: on the chmod because a partial repair that removes most of the tree is better than none, and the remove that follows is what reports the outcome either way.

Dir.exist? is not the guard, because it follows symlinks and answers false for a dangling one, and an entry a tool left in a directory's place is exactly what this has to remove.

A tree that is gone by the time the removal fails is the outcome this wants, however it went. Two sweepers can meet on one discarded tree — the worker that answered on the slot and the supervisor's own — and the loser's walk fails on an entry the winner unlinked first.



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# File 'lib/hot_cell/filesystem.rb', line 25

def self.remove_tree(path)
  return true if gone?(path)

  FileUtils.remove_entry path
  true
rescue SystemCallError
  repair_and_remove path
end