close: add notification for slow closes.

For compatibility, we only do this if `allow-deprecated-apis` is false
for now.  Otherwise scripts parsing should use `grep -v '^# '` or
start using `-N none`.

Changelog-Added: JSON-RPC: `close` now sends notifications for slow closes (if `allow-deprecated-apis`=false)
Changelog-Deprecated: cli: scripts should filter out '^# ' or use `-N none`, as commands will start returning notifications soon
Fixes: #3925
Signed-off-by: Rusty Russell <[email protected]>

doc/lightning-close.7.md

@@ -57,6 +57,12 @@ Prior to 0.7.2, **close** took two parameters: *force* and *timeout*.
 an RPC error (default). Even after the timeout, the channel would be
 closed if the peer reconnected.
 
+NOTIFICATIONS
+-------------
+If `allow-deprecated-apis` is false, notifications may be returned
+indicating what is going on, especially if the peer is offline and we
+are waiting.  This will be enabled by default in future!
+
 RETURN VALUE
 ------------
 

lightningd/peer_control.c

@@ -284,6 +284,9 @@ close_command_timeout(struct close_command *cc)
 	/* This will trigger drop_to_chain, which will trigger
 	 * resolution of the command and destruction of the
 	 * close_command. */
+	if (!deprecated_apis)
+		json_notify_fmt(cc->cmd, LOG_INFORM,
+				"Timed out, forcing close.");
 	channel_fail_permanent(cc->channel,
 			       "Forcibly closed by 'close' command timeout");
 }
@@ -306,6 +309,14 @@ register_close_command(struct lightningd *ld,
 	tal_add_destructor2(channel,
 			    &destroy_close_command_on_channel_destroy,
 			    cc);
+
+	if (!deprecated_apis && !channel->owner) {
+		char *msg = tal_strdup(tmpctx, "peer is offline, will negotiate once they reconnect");
+		if (timeout)
+			tal_append_fmt(&msg, " (%u seconds before unilateral close)",
+				       timeout);
+		json_notify_fmt(cmd, LOG_INFORM, "%s.", msg);
+	}
 	log_debug(ld->log, "close_command: timeout = %u", timeout);
 	if (timeout)
 		new_reltimer(ld->timers, cc, time_from_sec(timeout),

lightningd/test/run-invoice-select-inchan.c

@@ -277,6 +277,12 @@ void json_array_start(struct json_stream *js UNNEEDED, const char *fieldname UNN
 char *json_member_direct(struct json_stream *js UNNEEDED,
 			 const char *fieldname UNNEEDED, size_t extra UNNEEDED)
 { fprintf(stderr, "json_member_direct called!\n"); abort(); }
+/* Generated stub for json_notify_fmt */
+void json_notify_fmt(struct command *cmd UNNEEDED,
+		     enum log_level level UNNEEDED,
+		     const char *fmt UNNEEDED, ...)
+
+{ fprintf(stderr, "json_notify_fmt called!\n"); abort(); }
 /* Generated stub for json_object_end */
 void json_object_end(struct json_stream *js UNNEEDED)
 { fprintf(stderr, "json_object_end called!\n"); abort(); }

tests/test_closing.py

@@ -4,13 +4,14 @@
 from shutil import copyfile
 from utils import (
     only_one, sync_blockheight, wait_for, DEVELOPER, TIMEOUT,
-    account_balance, first_channel_id, basic_fee
+    account_balance, first_channel_id, basic_fee, TEST_NETWORK,
 )
 
 import os
 import queue
 import pytest
 import re
+import subprocess
 import threading
 import unittest
 
@@ -126,6 +127,25 @@ def test_closing_while_disconnected(node_factory, bitcoind, executor):
     wait_for(lambda: len(l2.rpc.listchannels()['channels']) == 0)
 
 
+def test_closing_disconnected_notify(node_factory, bitcoind, executor):
+    l1, l2 = node_factory.line_graph(2)
+
+    l1.pay(l2, 200000000)
+    l2.stop()
+    wait_for(lambda: not only_one(l1.rpc.listpeers(l2.info['id'])['peers'])['connected'])
+
+    out = subprocess.check_output(['cli/lightning-cli',
+                                   '--network={}'.format(TEST_NETWORK),
+                                   '--lightning-dir={}'
+                                   .format(l1.daemon.lightning_dir),
+                                   'close',
+                                   l2.info['id'],
+                                   '5']).decode('utf-8').splitlines()
+    assert out[0] == '# peer is offline, will negotiate once they reconnect (5 seconds before unilateral close).'
+    assert out[1] == '# Timed out, forcing close.'
+    assert not any([line.startswith('#') for line in out[2:]])
+
+
 def test_closing_id(node_factory):
     """Test closing using peer ID and full channel ID
     """

wallet/test/run-wallet.c

@@ -347,6 +347,12 @@ void json_array_start(struct json_stream *js UNNEEDED, const char *fieldname UNN
 const jsmntok_t *json_get_member(const char *buffer UNNEEDED, const jsmntok_t tok[] UNNEEDED,
 				 const char *label UNNEEDED)
 { fprintf(stderr, "json_get_member called!\n"); abort(); }
+/* Generated stub for json_notify_fmt */
+void json_notify_fmt(struct command *cmd UNNEEDED,
+		     enum log_level level UNNEEDED,
+		     const char *fmt UNNEEDED, ...)
+
+{ fprintf(stderr, "json_notify_fmt called!\n"); abort(); }
 /* Generated stub for json_object_end */
 void json_object_end(struct json_stream *js UNNEEDED)
 { fprintf(stderr, "json_object_end called!\n"); abort(); }