Merge #295: add getzmqnotifications rpc

a9be191 add getzmqnotifications integration test (Antoni Spaanderman)
b8fa99d add getzmqnotifications rpc (Antoni Spaanderman)

Pull request description:

  this rpc gives information about the active zmq publishers of bitcoin core

  currently `get_zmq_notifications` returns a Vec directly from bitcoind, but a structure like getindexinfo could also be used because the possible values of the "type" field are known

ACKs for top commit:
  apoelstra:
    ACK a9be191
  tcharding:
    ACK a9be191

Tree-SHA512: b9c617de9c8f356e259eaf685be63f14b2608a6433d54ed28450c48c740b07af913a217802e8aec49b92c56be559e4b3c7be23a83163c0f8e4bc300c2107c047

client/src/client.rs

@@ -1261,6 +1261,11 @@ pub trait RpcApi: Sized {
     ) -> Result<json::ScanTxOutResult> {
         self.call("scantxoutset", &["start".into(), into_json(descriptors)?])
     }
+
+    /// Returns information about the active ZeroMQ notifications
+    fn get_zmq_notifications(&self) -> Result<Vec<json::GetZmqNotificationsResult>> {
+        self.call("getzmqnotifications", &[])
+    }
 }
 
 /// Client implements a JSON-RPC client for the Bitcoin Core daemon or compatible APIs.

integration_test/run.sh

@@ -34,7 +34,9 @@ bitcoind -regtest $BLOCKFILTERARG $FALLBACKFEEARG \
     -rpcport=12349 \
     -server=1 \
     -txindex=1 \
-    -printtoconsole=0 &
+    -printtoconsole=0 \
+    -zmqpubrawblock=tcp://0.0.0.0:28332 \
+    -zmqpubrawtx=tcp://0.0.0.0:28333 &
 PID2=$!
 
 # Let it connect to the other node.

integration_test/src/main.rs

@@ -32,7 +32,7 @@ use bitcoin::{
     Transaction, TxIn, TxOut, Txid, Witness,
 };
 use bitcoincore_rpc::bitcoincore_rpc_json::{
-    GetBlockTemplateModes, GetBlockTemplateRules, ScanTxOutRequest,
+    GetBlockTemplateModes, GetBlockTemplateRules, GetZmqNotificationsResult, ScanTxOutRequest,
 };
 
 lazy_static! {
@@ -226,6 +226,7 @@ fn main() {
     test_add_ban(&cl);
     test_set_network_active(&cl);
     test_get_index_info(&cl);
+    test_get_zmq_notifications(&cl);
     test_stop(cl);
 }
 
@@ -1426,6 +1427,36 @@ fn test_get_index_info(cl: &Client) {
     }
 }
 
+fn test_get_zmq_notifications(cl: &Client) {
+    let mut zmq_info = cl.get_zmq_notifications().unwrap();
+
+    // it doesn't matter in which order Bitcoin Core returns the result,
+    // but checking it is easier if it has a known order
+
+    // sort_by_key does not allow returning references to parameters of the compare function
+    // (removing the lifetime from the return type mimics this behavior, but we don't want it)
+    fn compare_fn(result: &GetZmqNotificationsResult) -> impl Ord + '_ {
+        (&result.address, &result.notification_type, result.hwm)
+    }
+    zmq_info.sort_by(|a, b| compare_fn(a).cmp(&compare_fn(b)));
+
+    assert!(
+        zmq_info
+            == [
+                GetZmqNotificationsResult {
+                    notification_type: "pubrawblock".to_owned(),
+                    address: "tcp://0.0.0.0:28332".to_owned(),
+                    hwm: 1000
+                },
+                GetZmqNotificationsResult {
+                    notification_type: "pubrawtx".to_owned(),
+                    address: "tcp://0.0.0.0:28333".to_owned(),
+                    hwm: 1000
+                },
+            ]
+    );
+}
+
 fn test_stop(cl: Client) {
     println!("Stopping: '{}'", cl.stop().unwrap());
 }

json/src/lib.rs

@@ -2140,6 +2140,14 @@ pub struct GetIndexInfoResult {
     pub basic_block_filter_index: Option<IndexStatus>,
 }
 
+#[derive(Clone, PartialEq, Eq, Debug, Deserialize, Serialize)]
+pub struct GetZmqNotificationsResult {
+    #[serde(rename = "type")]
+    pub notification_type: String,
+    pub address: String,
+    pub hwm: u64,
+}
+
 impl<'a> serde::Serialize for PubKeyOrAddress<'a> {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where