make database syncing asynchronous

respodns/dns.py

@@ -177,8 +177,12 @@ async def try_ip(db, server_ip, checks, opts: Options):
 
 
 async def sync_database(db, opts: Options):
-    # TODO: handle addresses that were removed from respodns.ips.china.
     from .ips import china, blocks
+
+    if db is None:
+        return
+
+    # TODO: handle addresses that were removed from respodns.ips.china.
     for ips, kw in ((china, "china"), (blocks, "block_target")):
         for ip in ips:
             kwargs = dict()
@@ -193,11 +197,10 @@ async def sync_database(db, opts: Options):
 async def main(db, filepath, checks, opts: Options):
     from .ip_util import read_ips
     from .util import make_pooler
-    from asyncio import sleep
-    from sys import stdin
+    from asyncio import sleep, create_task
+    from sys import stdin, stderr
 
-    if db is not None:
-        await sync_database(db, opts)
+    syncing = create_task(sync_database(db, opts))
 
     def finisher(done, pending):
         for task in done:
@@ -226,3 +229,4 @@ async def main(db, filepath, checks, opts: Options):
         f.close()
 
     await pooler()
+    await syncing