Merge bitcoin#14812: qa: fix p2p_invalid_messages on macOS

5a1f576 qa: clean up assert_memory_usage_stable utility (James O'Beirne)
0cf1632 qa: fix p2p_invalid_messages on macOS (James O'Beirne)

Pull request description:

  Infinite mea culpa for the number of problems with this test.

  This change bumps the acceptable RSS increase threshold from 3% to 50% when spamming the test node with junk 4MB messages. On [@MarcoFalke's macOS test build](https://travis-ci.org/MarcoFalke/btc_nightly) we see RSS grow ~14% from ~71MB to 81MB, so a 50% increase threshold should be more than sufficient to avoid spurious failures.

Tree-SHA512: 150a7b88080fd883c7a5d0b9ffa470f61a97c4885fccc1a06fde6260aaef15640a7c1de7e89c581b245df7807d617ec3d86775330386ec5149ad567492fc5d31

test/functional/p2p_invalid_messages.py

@@ -66,7 +66,7 @@ def run_test(self):
         msg_at_size = msg_unrecognized("b" * valid_data_limit)
         assert len(msg_at_size.serialize()) == msg_limit
 
-        with node.assert_memory_usage_stable(perc_increase_allowed=0.03):
+        with node.assert_memory_usage_stable(increase_allowed=0.5):
             self.log.info(
                 "Sending a bunch of large, junk messages to test "
                 "memory exhaustion. May take a bit...")

test/functional/test_framework/test_node.py

@@ -115,7 +115,7 @@ def get_deterministic_priv_key(self):
         ]
         return PRIV_KEYS[self.index]
 
-    def get_mem_rss(self):
+    def get_mem_rss_kilobytes(self):
         """Get the memory usage (RSS) per `ps`.
 
         Returns None if `ps` is unavailable.
@@ -291,26 +291,30 @@ def assert_debug_log(self, expected_msgs):
                     self._raise_assertion_error('Expected message "{}" does not partially match log:\n\n{}\n\n'.format(expected_msg, print_log))
 
     @contextlib.contextmanager
-    def assert_memory_usage_stable(self, perc_increase_allowed=0.03):
+    def assert_memory_usage_stable(self, *, increase_allowed=0.03):
         """Context manager that allows the user to assert that a node's memory usage (RSS)
         hasn't increased beyond some threshold percentage.
+
+        Args:
+            increase_allowed (float): the fractional increase in memory allowed until failure;
+                e.g. `0.12` for up to 12% increase allowed.
         """
-        before_memory_usage = self.get_mem_rss()
+        before_memory_usage = self.get_mem_rss_kilobytes()
 
         yield
 
-        after_memory_usage = self.get_mem_rss()
+        after_memory_usage = self.get_mem_rss_kilobytes()
 
         if not (before_memory_usage and after_memory_usage):
             self.log.warning("Unable to detect memory usage (RSS) - skipping memory check.")
             return
 
         perc_increase_memory_usage = (after_memory_usage / before_memory_usage) - 1
 
-        if perc_increase_memory_usage > perc_increase_allowed:
+        if perc_increase_memory_usage > increase_allowed:
             self._raise_assertion_error(
                 "Memory usage increased over threshold of {:.3f}% from {} to {} ({:.3f}%)".format(
-                    perc_increase_allowed * 100, before_memory_usage, after_memory_usage,
+                    increase_allowed * 100, before_memory_usage, after_memory_usage,
                     perc_increase_memory_usage * 100))
 
     def assert_start_raises_init_error(self, extra_args=None, expected_msg=None, match=ErrorMatch.FULL_TEXT, *args, **kwargs):