Allow specifying a bitcoin wallet with an empty name (#2737)

We make the distinction between _not_ defining a bitcoin wallet name, and using an bitcoin wallet with an _empty_ name.

This remains mostly backward compatible, as:
- by default `eclair.bitcoind.wallet` is undefined so we keep using the default loaded wallet as before
- if user already set `eclair.bitcoind.wallet`, then eclair will use that wallet.
- only in the case where the user left `eclair.bitcoind.wallet` undefined, and if bitcoin had only one wallet with a non-empty name, then eclair will fail right at startup with an explicit error

---------

Co-authored-by: Bastien Teinturier <31281497+t-bast@users.noreply.github.com>

eclair-core/src/main/resources/reference.conf

@@ -25,8 +25,8 @@ eclair {
     rpcpassword = "bar"
     // Name of the bitcoind wallet that should be used to fund channels.
     // Once set you should NOT change it if your node has channels open, otherwise you may lose funds.
-    // NB: leave empty to automatically select the default loaded wallet.
-    wallet = ""
+    // NB: leave this field commented to automatically select the default loaded wallet.
+    // wallet = ""
     zmqblock = "tcp://127.0.0.1:29000"
     zmqtx = "tcp://127.0.0.1:29000"
     // Batching requests saves bandwidth but may slightly degrade latency and reliability. It is useful for the watcher,

eclair-core/src/main/scala/fr/acinq/eclair/Setup.scala

@@ -125,10 +125,7 @@ class Setup(val datadir: File,
   val onChainKeyManager_opt = LocalOnChainKeyManager.load(datadir, NodeParams.hashFromChain(chain))
 
   val (bitcoin, bitcoinChainHash) = {
-    val wallet = {
-      val name = config.getString("bitcoind.wallet")
-      if (!name.isBlank) Some(name) else None
-    }
+    val wallet = if (config.hasPath("bitcoind.wallet")) Some(config.getString("bitcoind.wallet")) else None
     val rpcAuthMethod = config.getString("bitcoind.auth") match {
       case "safecookie" => BitcoinJsonRPCAuthMethod.readCookie(config.getString("bitcoind.cookie")) match {
         case Success(safeCookie) => safeCookie

eclair-core/src/main/scala/fr/acinq/eclair/blockchain/Monitoring.scala

@@ -32,6 +32,7 @@ object Monitoring {
 
   object Tags {
     val Method = "method"
+    val Wallet = "wallet"
     val Priority = "priority"
 
     object Priorities {

eclair-core/src/main/scala/fr/acinq/eclair/blockchain/bitcoind/rpc/BasicBitcoinJsonRPCClient.scala

@@ -54,10 +54,10 @@ class BasicBitcoinJsonRPCClient(rpcAuthMethod: BitcoinJsonRPCAuthMethod, host: S
 
   private def send(requests: Seq[JsonRPCRequest], user: String, password: String)(implicit ec: ExecutionContext): Future[Response[Either[ResponseException[String, Exception], Seq[JsonRPCResponse]]]] = {
     requests.groupBy(_.method).foreach {
-      case (method, calls) => Metrics.RpcBasicInvokeCount.withTag(Tags.Method, method).increment(calls.size)
+      case (method, calls) => Metrics.RpcBasicInvokeCount.withTag(Tags.Method, method).withTag(Tags.Wallet, wallet.getOrElse("default")).increment(calls.size)
     }
     // for the duration metric, we use a "mixed" method for batched requests
-    KamonExt.timeFuture(Metrics.RpcBasicInvokeDuration.withTag(Tags.Method, if (requests.size == 1) requests.head.method else "mixed")) {
+    KamonExt.timeFuture(Metrics.RpcBasicInvokeDuration.withTag(Tags.Method, if (requests.size == 1) requests.head.method else "mixed").withTag(Tags.Wallet, wallet.getOrElse("default"))) {
       for {
         response <- basicRequest
           .post(serviceUri)

eclair-core/src/test/scala/fr/acinq/eclair/integration/StartupIntegrationSpec.scala

@@ -31,15 +31,15 @@ import scala.jdk.CollectionConverters._
 class StartupIntegrationSpec extends IntegrationSpec {
 
   test("no bitcoind wallet configured and one wallet loaded") {
-    instantiateEclairNode("A", ConfigFactory.parseMap(Map("eclair.bitcoind.wallet" -> "", "eclair.server.port" -> TestUtils.availablePort).asJava).withFallback(withDefaultCommitment).withFallback(commonConfig))
+    instantiateEclairNode("A", ConfigFactory.parseMap(Map("eclair.server.port" -> TestUtils.availablePort).asJava).withFallback(withDefaultCommitment).withFallback(commonConfig).withoutPath("eclair.bitcoind.wallet"))
   }
 
   test("no bitcoind wallet configured and two wallets loaded") {
     val sender = TestProbe()
     sender.send(bitcoincli, BitcoinReq("createwallet", ""))
     sender.expectMsgType[Any]
     val thrown = intercept[BitcoinDefaultWalletException] {
-      instantiateEclairNode("C", ConfigFactory.parseMap(Map("eclair.bitcoind.wallet" -> "", "eclair.server.port" -> TestUtils.availablePort).asJava).withFallback(withDefaultCommitment).withFallback(commonConfig))
+      instantiateEclairNode("C", ConfigFactory.parseMap(Map("eclair.server.port" -> TestUtils.availablePort).asJava).withFallback(withDefaultCommitment).withFallback(commonConfig).withoutPath("eclair.bitcoind.wallet"))
     }
     assert(thrown == BitcoinDefaultWalletException(List(defaultWallet, "")))
   }