tests: new helper to get pid of a particular subdaemon.

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

tests/test_lightningd.py

@@ -4250,16 +4250,13 @@ class LightningDTests(BaseLightningDTests):
         # Fundchannel manually so we get channeld pid.
         self.give_funds(l1, 10**6 + 1000000)
         l1.rpc.fundchannel(l2.info['id'], 10**6)['tx']
-        # Get pid of channeld, eg 'lightning_channeld(...): pid 13933, msgfd 12'
+        pid1 = l1.subd_pid('channeld')
-        pidline = l1.daemon.wait_for_log(r'lightning_channeld.*: pid [0-9]*,')
-        pid1 = re.search(r'pid ([0-9]*),', pidline).group(1)
 
         l1.daemon.wait_for_log('sendrawtx exit 0')
         l1.bitcoin.generate_block(1)
         l1.daemon.wait_for_log(' to CHANNELD_NORMAL')
 
-        pidline = l2.daemon.wait_for_log(r'lightning_channeld.*: pid [0-9]*,')
+        pid2 = l2.subd_pid('channeld')
-        pid2 = re.search(r'pid ([0-9]*),', pidline).group(1)
         l2.daemon.wait_for_log(' to CHANNELD_NORMAL')
 
         # Send it sigusr1: should turn on logging.

tests/utils.py

@@ -470,6 +470,11 @@ class LightningNode(object):
         decoded2 = self.bitcoin.rpc.decoderawtransaction(tx)
         raise ValueError("Can't find {} payment in {} (1={} 2={})".format(amount, tx, decoded, decoded2))
 
+    def subd_pid(self, subd):
+        """Get the process id of the given subdaemon, eg channeld or gossipd"""
+        pidline = self.daemon.is_in_log('lightning_{}.*: pid [0-9]*,'.format(subd))
+        return re.search(r'pid ([0-9]*),', pidline).group(1)
+
     def is_channel_active(self, chanid):
         channels = self.rpc.listchannels()['channels']
         active = [(c['short_channel_id'], c['flags']) for c in channels if c['active']]