docker: When running as effective init inside container, wait on zombies.

Propellor/Property/Docker.hs

@@ -17,6 +17,7 @@ import Utility.Path
 
 import Control.Concurrent.Async
 import System.Posix.Directory
+import System.Posix.Process
 import Data.List
 
 -- | Configures docker with an authentication file, so that images can be
@@ -272,6 +273,9 @@ runningContainer cid@(ContainerId hn cn) image containerprops = containerDesc ci
 -- | Called when propellor is running inside a docker container.
 -- The string should be the container's ContainerId.
 --
+-- This process is effectively init inside the container.
+-- It even needs to wait on zombie processes!
+--
 -- Fork a thread to run the SimpleSh server in the background.
 -- In the foreground, run an interactive bash (or sh) shell,
 -- so that the user can interact with it when attached to the container.
@@ -291,19 +295,23 @@ chain s = case toContainerId s of
 	Just cid -> do
 		changeWorkingDirectory localdir
 		writeFile propellorIdent . show =<< readIdentFile cid
+		gogo reapzombies
 		-- Run boot provisioning before starting simpleSh,
 		-- to avoid ever provisioning twice at the same time.
 		whenM (checkProvisionedFlag cid) $ do
 			let shim = Shim.file (localdir </> "propellor") (localdir </> shimdir cid)
 			unlessM (boolSystem shim [Param "--continue", Param $ show $ Chain $ fromContainerId cid]) $
 				warningMessage "Boot provision failed!"
-		void $ async $ simpleSh $ namedPipe cid
+		gogo $ simpleSh $ namedPipe cid
 		forever $ do
 			void $ ifM (inPath "bash")
 				( boolSystem "bash" [Param "-l"]
 				, boolSystem "/bin/sh" []
 				)
 			putStrLn "Container is still running. Press ^P^Q to detach."
+  where
+	gogo =  void . async . forever . void . tryIO
+	reapzombies = void $ getAnyProcessStatus True False
 
 -- | Once a container is running, propellor can be run inside
 -- it to provision it.
@@ -335,7 +343,7 @@ provisionContainer cid = containerDesc cid $ Property "provision" $ do
 			hPutStrLn stderr s
 			hFlush stderr
 			go Nothing rest
-		Done _ -> ret lastline
+		Done -> ret lastline
 	go lastline [] = ret lastline
 
 	ret lastline = return $ fromMaybe FailedChange $

Propellor/SimpleSh.hs

@@ -9,7 +9,6 @@ import Network.Socket
 import Control.Concurrent.Chan
 import Control.Concurrent.Async
 import System.Process (std_in, std_out, std_err)
-import System.Exit
 
 import Propellor
 import Utility.FileMode
@@ -18,7 +17,7 @@ import Utility.ThreadScheduler
 data Cmd = Cmd String [String]
 	deriving (Read, Show)
 
-data Resp = StdoutLine String | StderrLine String | Done ExitCode
+data Resp = StdoutLine String | StderrLine String | Done
 	deriving (Read, Show)
 
 simpleSh :: FilePath -> IO ()
@@ -49,7 +48,7 @@ simpleSh namedpipe = do
 			v <- readChan chan
 			hPutStrLn h (show v)
 			case v of
-				Done _ -> noop
+				Done -> noop
 				_ -> runwriter
 		writer <- async runwriter
 
@@ -59,7 +58,9 @@ simpleSh namedpipe = do
 			(mkreader StdoutLine outh)
 			(mkreader StderrLine errh)
 		
-		writeChan chan . Done =<< waitForProcess pid
+		void $ tryIO $ waitForProcess pid
+
+		writeChan chan Done
 
 		wait writer
 

debian/changelog

@@ -3,6 +3,7 @@ propellor (0.2.3) UNRELEASED; urgency=medium
   * docker: Fix laziness bug that caused running containers to be
     unnecessarily stopped and committed.
   * Add locking so only one propellor can run at a time on a host.
+  * docker: When running as effective init inside container, wait on zombies.
 
  -- Joey Hess <joeyh@debian.org>  Fri, 04 Apr 2014 15:58:03 -0400