Merge bitcoin/bitcoin#21056: rpc: Add a `-rpcwaittimeout` parameter to limit time spent waiting

b9e76f1bf08c52fcd402b2314e00db4ad247ebc8 rpc: Add test for -rpcwaittimeout (Christian Decker)
f76cb10d7dc9a7b0c55d28011161606399417664 rpc: Prefix rpcwaittimeout error with details on its nature (Christian Decker)
c490e17ef698a1695050f82ef6567b3b87a21861 doc: Add release notes for the `-rpcwaittimeout` cli parameter (Christian Decker)
a7fcc8eb59fe51473571661316214156fbdbdcae rpc: Add a `-rpcwaittimeout` parameter to limit time spent waiting (Christian Decker)

Pull request description:

  Adds a new numeric `-rpcwaittimeout` that can be used to limit the
  time we spend waiting on the RPC server to appear. This is used by
  downstream projects to provide a bit of slack when `bitcoind`s RPC
  interface is not available right away.

  This makes the `-rpcwait` argument more useful, since we can now limit
  how long we'll ultimately wait, before potentially giving up and reporting
  an error to the caller. It was discussed in the context of the BTCPayServer
  wanting to have c-lightning wait for the RPC interface to become available
  but still have the option of giving up eventually ([4355]).

  I checked with laanwj whether this is already possible ([comment]), and
  whether this would be a welcome change. Initially I intended to repurpose
  the (optional) argument to `-rpcwait`, however I decided against it since it
  would potentially break existing configurations, using things like `rpcwait=1`,
  or `rpcwait=true` (the former would have an unintended short timeout, when
  old behavior was to wait indefinitely).

  ~Due to its simplicity I didn't implement a test for it yet, but if that's desired I
  can provide one.~ Test was added during reviews.

  [4355]: https://github.com/ElementsProject/lightning/issues/4355
  [comment]: https://github.com/ElementsProject/lightning/issues/4355#issuecomment-768288261

ACKs for top commit:
  laanwj:
    Code review ACK b9e76f1bf08c52fcd402b2314e00db4ad247ebc8
  promag:
    ACK b9e76f1bf08c52fcd402b2314e00db4ad247ebc8.

Tree-SHA512: 3cd6728038ec7ca7c35c2e7ccb213bfbe963f99a49bb48bbc1e511c4dd23d9957c04f9af1f8ec57120e47b26eaf580b46817b099d5fc5083c98da7aa92db8638

1 files changed, 8 insertions, 0 deletions

diff --git a/test/functional/interface_bitcoin_cli.py b/test/functional/interface_bitcoin_cli.py
index 30cd499b3f..22eec59600 100755
--- a/test/functional/interface_bitcoin_cli.py
+++ b/test/functional/interface_bitcoin_cli.py
@@ -10,10 +10,12 @@ from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
+    assert_greater_than_or_equal,
     assert_raises_process_error,
     assert_raises_rpc_error,
     get_auth_cookie,
 )
+import time
 
 # The block reward of coinbaseoutput.nValue (50) BTC/block matures after
 # COINBASE_MATURITY (100) blocks. Therefore, after mining 101 blocks we expect
@@ -248,6 +250,12 @@ class TestBitcoinCli(BitcoinTestFramework):
         self.nodes[0].wait_for_rpc_connection()
         assert_equal(blocks, BLOCKS + 25)
 
+        self.log.info("Test -rpcwait option waits at most -rpcwaittimeout seconds for startup")
+        self.stop_node(0)  # stop the node so we time out
+        start_time = time.time()
+        assert_raises_process_error(1, "Could not connect to the server", self.nodes[0].cli('-rpcwait', '-rpcwaittimeout=5').echo)
+        assert_greater_than_or_equal(time.time(), start_time + 5)
+
 
 if __name__ == '__main__':
     TestBitcoinCli().main()