There should be a way to check whether ZeroMQ is enabled #13526

1. 
   domob1812 commented at 4:56 pm on June 23, 2018: contributor

   Bitcoin’s ZeroMQ interface is handy for software layered on top of the core daemon, like wallet frontends (or other similar things). It would be useful to have an easy way to query the daemon whether ZeroMQ publications are enabled and if so which address is configured for them. That way, such a frontend application can show a helpful message to the user if the daemon is not configured correctly.

   We could add a new RPC method for this, like getzmqinfo. In the simplest case, it would be called without arguments and just return a JSON object that contains whether each of the possible ZeroMQ endpoints (hashtx, hashblock, rawtx and rawblock) is configured and if so at which address.

2. 
   domob1812 commented at 4:56 pm on June 23, 2018: contributor

   With this issue, I want to get feedback on what everyone thinks about this idea. If it seems useful, I’m happy to implement it and provide a pull request.
3. fanquake added the label RPC/REST/ZMQ on Jun 23, 2018
4. 
   ianwaldrop commented at 7:45 pm on June 25, 2018: none

   Such a method would also enable self-configuration of zmq ports by front-end applications given the simplest case outlined above.
5. 
   sipa commented at 1:06 am on June 26, 2018: member

   It seems reasonable to add a getzmqinfo RPC. Alternatively, we could also have an RPC to inspect the config/cmdline arguments generically.
6. 
   promag commented at 1:25 am on June 26, 2018: member

   we could also have an RPC to inspect the config/cmdline arguments generically

   It wouldn’t work with runtime configuration if implemented.

7. 
   domob1812 commented at 9:01 am on June 26, 2018: contributor

   While I think that an RPC to query for all command-line arguments might be useful as well (and if desired, I’m happy to implement that also), I agree with @promag that having a ZMQ-specific variant solves a somewhat different need and is useful in its own right.

   Is the interface proposed in the OP good? I. e., something like this:

   $ bitcoin-cli getzmqinfo
   {
     "hashtx": "tcp:/tcp://127.0.0.1:28332",
     "hashblock": "ipc:///tmp/bitcoind.tx.raw"
   }
   

   Meaning that hashtx and hashblock are published at the given addresses, while others (rawtx and rawblock) are not enabled at all. Or should the interface be different?

8. 
   promag commented at 12:53 pm on June 26, 2018: member

   I would suggest getzmqnotifications and return:

   0{
   1    "publish": {
   2        "hashtx": "...",
   3    },
   4}
   

   Other examples getzmqconfig, setzmqconfig, addzmqnotification…

9. 
   domob1812 commented at 12:46 pm on June 27, 2018: contributor

   Yes, that makes sense. I’ll create a patch implementing @promag’s getzmqnotifications format as a first step. (I may be interested in adding more things, like addzmqnotification, later on as well.)
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18. 
    domob1812 commented at 8:53 am on July 10, 2018: contributor

    Change merged, this is now implemented.

    I may take a look at addzmqnotification (i.e. making the configuration of notifications dynamic / configurable after start up) later, but that is separate and I’ll open a new issue to discuss the proposal for it when I do.

19. domob1812 closed this on Jul 10, 2018

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Contributors
domob1812 ianwaldrop sipa promag

Labels
RPC/REST/ZMQ