private broadcast: define and use new RPC_LIMIT_EXCEEDED error code ( + other follow-ups) #35678

1. 
   stickies-v commented at 3:32 PM on July 7, 2026: contributor

   The server isn't running out of memory when the private broadcast transaction queue is full. Add and use a new -37 (RPC_LIMIT_EXCEEDED) code that can be used whenever a resource is bound and currently at capacity.

   Addresses #35406 (review)

   Also includes commits to address other outstanding suggestions/nits from #35406:

   • no-op [[nodiscard]]: #35406 (review)
   • use BOOST_CHECK_EQUAL: #35406 (review)
   • improve clarity remove-add test case: #35406 (review)
2. rpc: define and use new RPC_LIMIT_EXCEEDED error code

   The server isn't running out of memory when the private broadcast
   transaction queue is full. Add a new RPC_LIMIT_EXCEEDED code that
   can be used whenever a resource is bound and currently at capacity.

   82a02a2a22
3. test: use BOOST_CHECK_EQUAL for PrivateBroadcast::AddResult

   Makes the failure output more useful.

   7ad311be18
4. test: align test better with described scenario

   Add the tx that was just removed, instead of an earlier one, for
   improved clarity.

   191bdcba26
5. private broadcast: remove no-op [[nodiscard]]

   The header file already properly uses the attribution.

   8ac222484c
6. 
   DrahtBot commented at 3:32 PM on July 7, 2026: contributor

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   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/35678.

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   Conflicts

   Reviewers, this pull request conflicts with the following ones:

   • #35587 (Remove boost as a unit test runner by rustaceanrob)

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7. fanquake added the label Private Broadcast on Jul 7, 2026
8. fanquake requested review from vasild on Jul 7, 2026
9. fanquake requested review from andrewtoth on Jul 7, 2026
10. fanquake requested review from instagibbs on Jul 7, 2026
11. 
    instagibbs commented at 5:06 PM on July 7, 2026: member

    ACK 8ac222484c92f320f56273035bc66dbc14c0b9a1

12. andrewtoth approved
13. 
    andrewtoth commented at 7:25 PM on July 7, 2026: contributor

    ACK 8ac222484c92f320f56273035bc66dbc14c0b9a1

14. sedited approved
15. 
    sedited commented at 7:33 PM on July 7, 2026: contributor

    ACK 8ac222484c92f320f56273035bc66dbc14c0b9a1

16. in src/rpc/util.cpp:399 in 82a02a2a22

     395 | @@ -396,7 +396,7 @@ RPCErrorCode RPCErrorFromTransactionError(TransactionError terr)
     396 |          case TransactionError::ALREADY_IN_UTXO_SET:
     397 |              return RPC_VERIFY_ALREADY_IN_UTXO_SET;
     398 |          case TransactionError::PRIVATE_BROADCAST_FULL:
     399 | -            return RPC_OUT_OF_MEMORY;
     400 | +            return RPC_LIMIT_EXCEEDED;
    

    ---

    ---

    

    furszy commented at 7:33 PM on July 7, 2026:

    it would be nice to use a more descriptive/specific constant name here. RPC_LIMIT_EXCEEDED reads like an http queue capacity error, and not something related to the private broadcast queue.

    extra note: we use HTTP_SERVICE_UNAVAILABLE for the http queue return error code.

    ---

    

    sedited commented at 7:34 PM on July 7, 2026:

    I think that is the idea,no? The description indicates that this can be re-used for other purposes.

    ---

    

    furszy commented at 7:44 PM on July 7, 2026:

    I think that is the idea,no? The description indicates that this can be re-used for other purposes.

    Ups, I jumped straight to the code. Forget what I said.

    I thought this was suggesting to use the introduced RPCErrorCode at the http queue level, but that is not the case. I'm just not fan of the http <--> json-rpc coupling we have.

17. sedited merged this on Jul 8, 2026
18. sedited closed this on Jul 8, 2026

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19. stickies-v deleted the branch on Jul 8, 2026

Contributors

stickies-vDrahtBotinstagibbsandrewtothseditedfurszy

Review Requested
vasildinstagibbs