pytest: make wait_for do exponential backoff, start at 0.25 seconds.

This doesn't alter runtime very much, but does reduce log spam.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_connection.py

@@ -764,10 +764,10 @@ def test_channel_persistence(node_factory, bitcoind, executor):
     wait_for(lambda: len(l2.rpc.listpeers()['peers']) == 1)
 
     # Wait for the restored HTLC to finish
-    wait_for(lambda: only_one(l1.rpc.listpeers()['peers'][0]['channels'])['msatoshi_to_us'] == 99990000, interval=1)
+    wait_for(lambda: only_one(l1.rpc.listpeers()['peers'][0]['channels'])['msatoshi_to_us'] == 99990000)
 
-    wait_for(lambda: len([p for p in l1.rpc.listpeers()['peers'] if p['connected']]), interval=1)
+    wait_for(lambda: len([p for p in l1.rpc.listpeers()['peers'] if p['connected']]))
-    wait_for(lambda: len([p for p in l2.rpc.listpeers()['peers'] if p['connected']]), interval=1)
+    wait_for(lambda: len([p for p in l2.rpc.listpeers()['peers'] if p['connected']]))
 
     # Now make sure this is really functional by sending a payment
     l1.pay(l2, 10000)

tests/test_gossip.py

@@ -543,7 +543,7 @@ def test_routing_gossip(node_factory, bitcoind):
         return len(missing) == 0
 
     for n in nodes:
-        wait_for(lambda: check_gossip(n), interval=1)
+        wait_for(lambda: check_gossip(n))
 
 
 @unittest.skipIf(not DEVELOPER, "needs DEVELOPER=1")

tests/utils.py

@@ -39,10 +39,14 @@ TIMEOUT = int(os.getenv("TIMEOUT", "60"))
 VALGRIND = os.getenv("VALGRIND", config['VALGRIND']) == "1"
 
 
-def wait_for(success, timeout=TIMEOUT, interval=0.1):
+def wait_for(success, timeout=TIMEOUT):
     start_time = time.time()
+    interval = 0.25
     while not success() and time.time() < start_time + timeout:
         time.sleep(interval)
+        interval *= 2
+        if interval > 5:
+            interval = 5
     if time.time() > start_time + timeout:
         raise ValueError("Error waiting for {}", success)
 
@@ -570,7 +574,7 @@ class LightningNode(object):
         wait_for(lambda: txid in self.bitcoin.rpc.getrawmempool())
 
     def wait_channel_active(self, chanid):
-        wait_for(lambda: self.is_channel_active(chanid), interval=1)
+        wait_for(lambda: self.is_channel_active(chanid))
 
     # This waits until gossipd sees channel_update in both directions
     # (or for local channels, at least a local announcement)