[CRIU] [PATCH v4 5/6] p.haul: handle older criu RPC interfaces

[Adrian Reber]

From: Adrian Reber <areber at redhat.com>

Wrap the calls to the new feature-check RPC interface into try: except:
to continue gracefully without stack traces. If the installed criu
supports feature-check it will be used to detect if memory tracking
should be enabled. If the installed criu is too old to support
feature-check no pre-dumping will be performed. Pre-dumps can still be
manually enabled via p.haul's command-line.

v2: rebased

v3: rebased

v4: avoid code duplication using Nikita Spiridonov's example

Signed-off-by: Adrian Reber <areber at redhat.com>
---
 phaul/criu_req.py     | 25 +++++++++++++++++--------
 phaul/p_haul_iters.py | 40 ++++++++++++++++++++++++++++------------
 2 files changed, 45 insertions(+), 20 deletions(-)

diff --git a/phaul/criu_req.py b/phaul/criu_req.py
index d97d4cf..3cc1721 100644
--- a/phaul/criu_req.py
+++ b/phaul/criu_req.py
@@ -4,16 +4,25 @@
 
 import pycriu.rpc
 
-_names = {
-	pycriu.rpc.DUMP: "dump",
-	pycriu.rpc.PRE_DUMP: "pre_dump",
-	pycriu.rpc.PAGE_SERVER: "page_server",
-	pycriu.rpc.RESTORE: "restore",
-	pycriu.rpc.CPUINFO_DUMP: "cpuinfo-dump",
-	pycriu.rpc.CPUINFO_CHECK: "cpuinfo-check",
-	pycriu.rpc.FEATURE_CHECK: "feature-check",
+def _build_names(name_strings):
+	names = {}
+	for key, value in name_strings.items():
+		if hasattr(pycriu.rpc, key):
+			names[getattr(pycriu.rpc, key)] = value
+	return names
+
+_name_strings = {
+	"DUMP": "dump",
+	"PRE_DUMP": "pre_dump",
+	"PAGE_SERVER": "page_server",
+	"RESTORE": "restore",
+	"CPUINFO_DUMP": "cpuinfo-dump",
+	"CPUINFO_CHECK": "cpuinfo-check",
+	"FEATURE_CHECK": "feature-check",
 }
 
+_names = _build_names(_name_strings)
+
 def get_name(req_type):
 	"""Return printable request name"""
 	return _names[req_type]
diff --git a/phaul/p_haul_iters.py b/phaul/p_haul_iters.py
index 971a68e..91d4392 100644
--- a/phaul/p_haul_iters.py
+++ b/phaul/p_haul_iters.py
@@ -94,25 +94,41 @@ class phaul_iter_worker:
 		self.fs.set_work_dir(self.img.work_dir())
 		self.fs.start_migration()
 
+		logging.info("Checking for Dirty Tracking")
 		if self.pre_dump == PRE_DUMP_AUTO_DETECT:
 			# pre-dump auto-detection
-			logging.info("Checking for Dirty Tracking")
-			req = criu_req.make_dirty_tracking_req(self.htype, self.img)
-			resp = self.criu_connection.send_req(req)
-			self.pre_dump = resp.success
+			try:
+				req = criu_req.make_dirty_tracking_req(
+						self.htype, self.img)
+				resp = self.criu_connection.send_req(req)
+				self.pre_dump = False
+				if not resp.success:
+					# Not able to do auto-detection, disable memory tracking
+					raise Exception()
+				if resp.HasField('features'):
+					if resp.features.HasField('mem_track'):
+						if resp.features.mem_track:
+							logging.info("\t`- Auto Enabled")
+							self.pre_dump = True
+				else:
+					logging.info("\t`- Auto Disabled")
+
+			except:
+				# The available criu seems to not
+				# support memory tracking auto detection.
+				self.pre_dump = False
+				logging.info("\t`- Auto detection not possible "
+						"- Disabled")
+
 		elif self.pre_dump == PRE_DUMP_DISABLE:
 			self.pre_dump = False
+			logging.info("\t`- Command-line disabled")
 		else:
 			self.pre_dump = True
+			logging.info("\t`- Command-line enabled")
 
-		if resp.success:
-			if resp.HasField('features'):
-				if resp.features.HasField('mem_track'):
-					if resp.features.mem_track:
-						logging.info("Starting iterations")
-						self.pre_dump = True
-			else:
-				self.criu_connection.memory_tracking(False)
+		if self.pre_dump:
+			logging.info("Starting iterations")
 		else:
 			self.criu_connection.memory_tracking(False)
 
-- 
1.8.3.1