test: ensure output is large enough to pay for its fees #29283

1. 
   stickies-v commented at 2:22 pm on January 19, 2024: contributor

   Fixes a (rare) intermittency issue in wallet_import_rescan.py

   Since we use subtract_fee_from_outputs=[0] in the send command, the output amount must at least be as large as the fee we’re paying.

   Example in CI: https://api.cirrus-ci.com/v1/task/6107972259020800/logs/ci.log

    02024-01-18T22:16:12.383000Z TestFramework (INFO): Test that the mempool is rescanned as well if the rescan parameter is set to true
    12024-01-18T22:16:20.187000Z TestFramework (ERROR): JSONRPC error
    2Traceback (most recent call last):
    3  File "/ci_container_base/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/test_framework/test_framework.py", line 131, in main
    4    self.run_test()
    5  File "/ci_container_base/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/wallet_import_rescan.py", line 292, in run_test
    6    child = self.nodes[1].send(
    7  File "/ci_container_base/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/test_framework/coverage.py", line 50, in __call__
    8    return_val = self.auth_service_proxy_instance.__call__(*args, **kwargs)
    9  File "/ci_container_base/ci/scratch/build/bitcoin-x86_64-pc-linux-gnu/test/functional/test_framework/authproxy.py", line 129, in __call__
   10    raise JSONRPCException(response['error'], status)
   11test_framework.authproxy.JSONRPCException: The transaction amount is too small to pay the fee (-4)
   

   Can be reproduced locally by forcing usage of the lowest possible value produced by get_rand_amount() (thanks furszy):

    0diff --git a/test/functional/wallet_import_rescan.py b/test/functional/wallet_import_rescan.py
    1index 7f01d23941..925849d5c0 100755
    2--- a/test/functional/wallet_import_rescan.py
    3+++ b/test/functional/wallet_import_rescan.py
    4@@ -270,7 +270,7 @@ class ImportRescanTest(BitcoinTestFramework):
    5                 address_type=variant.address_type.value,
    6             ))
    7             variant.key = self.nodes[1].dumpprivkey(variant.address["address"])
    8-            variant.initial_amount = get_rand_amount() * 2
    9+            variant.initial_amount = Decimal(str(round(AMOUNT_DUST, 8))) * 2
   10             variant.initial_txid = self.nodes[0].sendtoaddress(variant.address["address"], variant.initial_amount)
   11             variant.confirmation_height = 0
   12             variant.timestamp = timestamp
   

2. test: ensure output is large enough to pay for its fees

   Fixes a (rare) intermittency issue in wallet_import_rescan.
   
   Since we use `subtract_fee_from_outputs=[0]` in the `send` command,
   the output amount must at least be as large as the fee we're paying.

   3bfc5bd36e
3. 
   DrahtBot commented at 2:22 pm on January 19, 2024: contributor

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   Type	Reviewers
   ACK	glozow, furszy, achow101

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4. DrahtBot added the label Tests on Jan 19, 2024
5. 
   glozow commented at 2:32 pm on January 19, 2024: member

   utACK 3bfc5bd36e38ca07306a41a3f56ea102ffe02b67, didn’t experience this issue but in theory a minimum of AMOUNT_DUST could be too low to pay the fees
6. 
   furszy commented at 3:03 pm on January 19, 2024: member

   Can be replicated locally by changing line 273 to use the get_rand_amount() floor.

   0variant.initial_amount = Decimal(str(round(AMOUNT_DUST, 8))) * 2
   

7. in test/functional/wallet_import_rescan.py:274 in 3bfc5bd36e

   270@@ -270,7 +271,9 @@ def run_test(self):
   271                 address_type=variant.address_type.value,
   272             ))
   273             variant.key = self.nodes[1].dumpprivkey(variant.address["address"])
   274-            variant.initial_amount = get_rand_amount() * 2
   275+            # Ensure output is large enough to pay for fees: conservatively assuming txsize of
   

   ---

   ---

   

   furszy commented at 2:09 pm on January 25, 2024:

   Maybe:

   0            # Ensure output is large enough to pay for its fees. Following transactions will contain one input and one unspendable output. Conservatively assuming...
   

   Also, just as an extra note (no need to do it): could calculate the floor in a more dynamic manner if you want. The input type is known here, and the future tx is always fixed to be a 1 input, 1 bech32 output tx.

   ---

   

   stickies-v commented at 2:23 pm on January 25, 2024:

   Thx, will consider if I need to retouch!
8. 
   furszy commented at 2:09 pm on January 25, 2024: member

   utACK 3bfc5bd36
9. 
   achow101 commented at 11:30 pm on January 26, 2024: member

   ACK 3bfc5bd36e38ca07306a41a3f56ea102ffe02b67
10. achow101 merged this on Jan 26, 2024
11. achow101 closed this on Jan 26, 2024

    ---

12. stickies-v deleted the branch on Jan 26, 2024

Contributors
stickies-v DrahtBot glozow furszy achow101 maflcko

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