From 8666033630eeaf851ec69e018bb53eb23093f4b9 Mon Sep 17 00:00:00 2001
From: Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
Date: Sat, 23 Jan 2021 22:33:48 +0100
Subject: [PATCH] zmq test: accept arbitrary sequence start number in
 ZMQSubscriber

The ZMQSubscriber reception methods currently assert that the first
received publisher message has a sequence number of zero. In order to
fix the current test flakiness via "syncing up" to nodes in the setup
phase, we have to cope with the situation that messages get lost and the
first actual received message has a sequence number larger than zero.
---
 test/functional/interface_zmq.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/test/functional/interface_zmq.py b/test/functional/interface_zmq.py
index 4c23c4d30c1..527126fac38 100755
--- a/test/functional/interface_zmq.py
+++ b/test/functional/interface_zmq.py
@@ -27,7 +27,7 @@ def hash256_reversed(byte_str):
 
 class ZMQSubscriber:
     def __init__(self, socket, topic):
-        self.sequence = 0
+        self.sequence = None  # no sequence number received yet
         self.socket = socket
         self.topic = topic
 
@@ -39,7 +39,11 @@ class ZMQSubscriber:
         # Topic should match the subscriber topic.
         assert_equal(topic, self.topic)
         # Sequence should be incremental.
-        assert_equal(struct.unpack('<I', seq)[-1], self.sequence)
+        received_seq = struct.unpack('<I', seq)[-1]
+        if self.sequence is None:
+            self.sequence = received_seq
+        else:
+            assert_equal(received_seq, self.sequence)
         self.sequence += 1
         return body