fix issues when checking EdenFS status on windows

Summary:
- Catch the Windows-specific exceptions types thrown when attempting to open
  the socket if EdenFS is not running, and convert this to an EdenNotRunning
  exception.
- Update EdenFS to write its pid to a separate file, in addition to the normal
  lock file, and have `edenfsctl` read this file instead of the lock file on
  Windows.  Other processes cannot read the lock file while EdenFS is running
  and holding the lock, so it is nice to have the pid written in an alternate
  location.

Reviewed By: pkaush

Differential Revision: D20854615

fbshipit-source-id: 1c8e8f402eb17dd012d03e11fbb662f493d9362d

eden/fs/cli/util.py

@@ -30,6 +30,7 @@ if sys.platform != "win32":
 
 # These paths are relative to the user's client directory.
 LOCK_FILE = "lock"
+PID_FILE = "pid"
 
 
 class EdenStartError(Exception):
@@ -102,7 +103,16 @@ def poll_until(
 def get_pid_using_lockfile(config_dir: Path) -> int:
     """Read the pid from the Eden lockfile, throwing an exception upon failure.
     """
-    lockfile = config_dir / LOCK_FILE
+    if sys.platform == "win32":
+        # On Windows read the separate pid file.  We will not be able to read the
+        # lock file if EdenFS is running and holding the lock.
+        lockfile = config_dir / PID_FILE
+    else:
+        # On other platforms we still prefer reading the pid from the lock file,
+        # just to support older instances of EdenFS that only wrote the pid to the lock
+        # file.
+        lockfile = config_dir / LOCK_FILE
+
     with lockfile.open("r") as f:
         lockfile_contents = f.read()
     return int(lockfile_contents.rstrip())

eden/fs/py/eden/thrift/client.py

@@ -18,10 +18,13 @@ from thrift.transport.TTransport import TTransportException
 
 
 if sys.platform == "win32":
-    from eden.thrift.windows_thrift import WinTSocket  # @manual
+    from eden.thrift.windows_thrift import WinTSocket, WindowsSocketException  # @manual
 else:
     from thrift.transport.TSocket import TSocket
 
+    class WindowsSocketException(Exception):
+        pass
+
 
 SOCKET_PATH = "socket"
 
@@ -91,15 +94,18 @@ class EdenClient(EdenService.Client):
 
     def open(self):
         # type: () -> None
+        transport = self._transport
+        assert transport is not None
         try:
-            assert self._transport is not None
-            # pyre-fixme[16]: `Optional` has no attribute `open`.
-            self._transport.open()
+            transport.open()
         except TTransportException as ex:
             self.close()
             if ex.type == TTransportException.NOT_OPEN:
                 raise EdenNotRunningError(self._socket_path)
             raise
+        except WindowsSocketException:
+            self.close()
+            raise EdenNotRunningError(self._socket_path)
 
     def close(self):
         # type: () -> None

eden/fs/service/EdenStateDir.cpp

@@ -14,6 +14,7 @@ using folly::StringPiece;
 
 namespace {
 constexpr StringPiece kLockFileName{"lock"};
+constexpr StringPiece kPidFileName{"pid"};
 constexpr StringPiece kTakeoverSocketName{"takeover"};
 constexpr StringPiece kThriftSocketName{"socket"};
 } // namespace
@@ -42,6 +43,13 @@ void EdenStateDir::takeoverLock(folly::File lockFile) {
   int rc = fstat(lockFile.fd(), &lockFileStat_);
   folly::checkUnixError(rc, "error getting lock file attributes");
   lockFile_ = std::move(lockFile);
+
+  // On Windows, also write the pid to a separate file.
+  // Other processes cannot read the lock file while we are holding the lock,
+  // so we store it in a separate file too.
+  auto pidFilePath = path_ + PathComponentPiece(kPidFileName);
+  folly::File pidFile(pidFilePath.c_str(), O_WRONLY | O_CREAT, 0644);
+  writePidToLockFile(pidFile);
 }
 
 folly::File EdenStateDir::extractLock() {