probe: Poll for probe completion instead of waiting

This just polls pending probes and calls a callback upon completion.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

probe/probe.py

@@ -112,10 +112,16 @@ def probe(request, plugin, node_id=None, **kwargs):
 
     s.commit()
     plugin.rpc.sendpay(route, p.payment_hash)
-    complete_probe(plugin, request, p.id)
+    plugin.pending_probes.append({
+        'request': request,
+        'probe_id': p.id,
+        'payment_hash': p.payment_hash,
+        'callback': complete_probe,
+        'plugin': plugin,
+    })
 
 
-def complete_probe(plugin, request, probe_id):
+def complete_probe(plugin, request, probe_id, payment_hash):
     s = plugin.Session()
     p = s.query(Probe).get(probe_id)
     try:
@@ -148,6 +154,19 @@ def complete_probe(plugin, request, probe_id):
     request.set_result(res)
 
 
+def poll_payments(plugin):
+    """Iterate through all probes and complete the finalized ones.
+    """
+    for probe in plugin.pending_probes:
+        p = plugin.rpc.listpayments(None, payment_hash=probe['payment_hash'])
+        if p['payments'][0]['status'] == 'pending':
+            continue
+
+        plugin.pending_probes.remove(probe)
+        cb = probe['callback']
+        del probe['callback']
+        cb(**probe)
+
 def clear_temporary_exclusion(plugin):
     timed_out = [k for k, v in temporary_exclusions.items() if v < time()]
     for k in timed_out:
@@ -162,7 +181,8 @@ def schedule(plugin):
     # List of scheduled calls with next runtime, function and interval
     next_runs = [
         (time() + 300, clear_temporary_exclusion, 300),
-        (time() + plugin.probe_interval, start_probe, plugin.probe_interval)
+        (time() + plugin.probe_interval, start_probe, plugin.probe_interval),
+        (time() + 1, poll_payments, 1),
     ]
     heapq.heapify(next_runs)
 
@@ -196,6 +216,9 @@ def init(configuration, options, plugin):
     t.daemon = True
     t.start()
 
+    # Probes that are still pending and need to be checked against.
+    plugin.pending_probes = []
+
 
 plugin.add_option(
     'probe-interval',