Merge lp:~cmiller/desktopcouch/find-port-runtimeerror2 into lp:desktopcouch

[Chad Miller]

A possible fix for a bug I can't reproduce, Bug#465216. It is possible that two calls to find_port will happen near the same time. The steps tostarting up couchdb are 1) start couchdb if not already running, 2) get pid, 3) get port. Two processes can be in that chain at the same time, and only one will win the race of having started the winning couchdb. In that case, each should be willing to restart the entire chain over.

[Tim Cole (tcole)]

Sensible, I think.

review: Approve

[Guillermo Gonzalez (verterok)]

it's possible to add some tests for this?

[Eric Casteleijn (thisfred)]

Looks good tests pass

review: Approve

=== modified file 'desktopcouch/__init__.py'
--- desktopcouch/__init__.py	2010-03-10 22:18:24 +0000
+++ desktopcouch/__init__.py	2010-04-27 18:20:31 +0000
@@ -68,13 +68,16 @@
 ####  ^^
 
 
-def __find_port__linux(pid=None, ctx=local_files.DEFAULT_CONTEXT):
+def __find_port__linux(pid=None, ctx=local_files.DEFAULT_CONTEXT,
+        retries_left=3):
     """This returns a valid port or raises a RuntimeError exception.  It never
     returns anything else."""
     if pid is None:
         pid = find_pid(start_if_not_running=True, ctx=ctx)
 
     if pid is None:
+        if retries_left:
+            return __find_port__linux(pid, ctx, retries_left-1)
         raise RuntimeError("Have no PID to use to look up port.")
 
     proc_dir = "/proc/%d" % (pid,)
@@ -92,6 +95,8 @@
                         (dirent_path,))
                 continue
     except OSError:
+        if retries_left:
+            return __find_port__linux(pid, ctx, retries_left-1)
         logging.exception("Unable to find file descriptors in %s" % proc_dir)
         raise RuntimeError("Unable to find file descriptors in %s" % proc_dir)
 
@@ -129,6 +134,8 @@
                 break
 
     if port is None:
+        if retries_left:
+            return __find_port__linux(pid, ctx, retries_left-1)
         raise RuntimeError("Unable to find listening port")
 
     return port