implement timeout option with SIGKILL

fixes #1

README.md

@@ -36,7 +36,7 @@ IsoLatte.fork(
 
 ### Options
 
-* `:stderr` - A path to write the subprocess' stderr stream into. Defaults to '/dev/null',
+* `stderr` - A path to write the subprocess' stderr stream into. Defaults to '/dev/null',
               supplying `nil` lets the subprocess continue writing to the parent's stderr stream.
 * `success` - a callable to execute if the subprocess completes successfully.
 * `fault`   - a callable to execute if the subprocess receives a SIGABRT (segfault).
@@ -45,6 +45,8 @@ IsoLatte.fork(
               Receives the exit status value as its argument.
 * `finish`  - a callable to execute when the subprocess terminates in any way. It receives
                a boolean 'success' value and an exit status as its arguments.
+* `timeout` - a number of seconds to wait - if the process has not terminated by then,
+              the parent will kill it by issuing a SIGKILL signal (triggering the kill callback)
 
 ## Roadmap
 

lib/iso_latte.rb

@@ -1,4 +1,5 @@
 require "ostruct"
+require "timeout"
 
 module IsoLatte
   NO_EXIT = 122
@@ -16,6 +17,7 @@ module IsoLatte
   #   fault:    a callable to execute if the subprocess segfaults, core dumps, etc.
   #   exit:     a callable to execute if the subprocess voluntarily exits with nonzero.
   #             receives the exit status value as its argument.
+  #   timeout:  after this many seconds, the parent should send a SIGKILL to the child.
   #
   # It is allowable to Isolatte.fork from inside an IsoLatte.fork block (reentrant)
   #
@@ -59,7 +61,17 @@ def self.fork(options = nil, &block)
 
     write_ex.close
 
-    pid, rc = Process.wait2(child_pid)
+    pid, rc =
+      begin
+        if opts.timeout
+          Timeout.timeout(opts.timeout) { Process.wait2(child_pid) }
+        else
+          Process.wait2(child_pid)
+        end
+      rescue Timeout::Error
+        kill_child(child_pid)
+      end
+
     fail(Error, "Wrong child's exit received!") unless pid == child_pid
 
     if rc.exited? && rc.exitstatus == EXCEPTION_RAISED
@@ -91,5 +103,12 @@ def self.fork(options = nil, &block)
     rc
   end
 
+  def self.kill_child(pid)
+    Process.kill("KILL", pid)
+    Process.wait2(pid)
+  rescue Errno::ESRCH
+    # Save us from the race condition where it exited just as we decided to kill it.
+  end
+
   class Error < StandardError; end
 end