finagle-core: Add fixedinet scheme resolution to global Namer

Problem
Name paths with fixed addresses don't need background
DNS updates. But "fixedinet" scheme was not recognized
by global namer and path like "/$/fixedinet/localhost/1234"
was not resolved.

Solution
Add additional checks for "fixedinet" scheme in InetPath
object inside global Namer.

Result
Global namer recognizes both "inet" and "fixedinet" schemes
and uses corresponding Resolver.

Differential Revision: https://phabricator.twitter.biz/D589429

CHANGELOG.rst

@@ -80,6 +80,9 @@ Bug Fixes
   `java.lang.UnsupportedOperationException: tail of empty stream` when a `c.t.f.s.RetryPolicy`
   is converted to a String for showing. ``PHAB_ID=D582199``
 
+* finagle-core: Recognize `fixedinet` name scheme in global `com.twitter.finagle.Namer`.
+  ``PHAB_ID=D589429``
+
 20.10.0
 -------
 

finagle-core/src/main/scala/com/twitter/finagle/Namer.scala

@@ -72,8 +72,8 @@ object Namer {
 
     private[this] object InetPath {
 
-      private[this] def resolve(host: String, port: Int): Var[Addr] =
-        Resolver.eval(s"inet!$host:$port") match {
+      private[this] def resolve(scheme: String, host: String, port: Int): Var[Addr] =
+        Resolver.eval(s"$scheme!$host:$port") match {
           case Name.Bound(va) => va
           case n: Name.Path =>
             Var.value(
@@ -82,11 +82,16 @@ object Namer {
         }
 
       def unapply(path: Path): Option[(Var[Addr], Path)] = path match {
-        case Path.Utf8("$", "inet", host, IntegerString(port), residual @ _*) =>
-          Some((resolve(host, port), Path.Utf8(residual: _*)))
-        case Path.Utf8("$", "inet", IntegerString(port), residual @ _*) =>
+        case Path.Utf8(
+              "$",
+              scheme @ ("inet" | "fixedinet"),
+              host,
+              IntegerString(port),
+              residual @ _*) =>
+          Some((resolve(scheme, host, port), Path.Utf8(residual: _*)))
+        case Path.Utf8("$", scheme @ ("inet" | "fixedinet"), IntegerString(port), residual @ _*) =>
           // no host provided means localhost
-          Some((resolve("", port), Path.Utf8(residual: _*)))
+          Some((resolve(scheme, "", port), Path.Utf8(residual: _*)))
         case _ => None
       }
     }

finagle-core/src/test/scala/com/twitter/finagle/NamerTest.scala

@@ -188,6 +188,39 @@ class NamerTest extends FunSuite with AssertionsForJUnit {
     }
   }
 
+  test("Namer.global: /$/fixedinet") {
+    Namer.global.lookup(Path.read("/$/fixedinet/1234")).sample() match {
+      case NameTree.Leaf(Name.Bound(addr)) =>
+        assert(addr.sample() == Addr.Bound(Set(Address(1234))))
+      case _ => fail()
+    }
+
+    Await.result(
+      Namer.global.lookup(Path.read("/$/fixedinet/127.0.0.1/1234")).values.toFuture(),
+      1.second
+    )() match {
+      case NameTree.Leaf(Name.Bound(addr)) =>
+        assert(
+          Await.result(addr.changes.filter(_ != Addr.Pending).toFuture(), 1.second)
+            == Addr.Bound(Set(Address("127.0.0.1", 1234)))
+        )
+      case _ => fail()
+    }
+
+    intercept[ClassNotFoundException] {
+      Namer.global.lookup(Path.read("/$/fixedinet")).sample()
+    }
+
+    Namer.global.lookup(Path.read("/$/fixedinet/1234/foobar")).sample() match {
+      case NameTree.Leaf(bound: Name.Bound) =>
+        assert(bound.addr.sample() == Addr.Bound(Address(1234)))
+        assert(bound.id == Path.Utf8("$", "fixedinet", "1234"))
+        assert(bound.path == Path.Utf8("foobar"))
+
+      case _ => fail()
+    }
+  }
+
   test("Namer.global: /$/fail") {
     assert(
       Namer.global.lookup(Path.read("/$/fail")).sample()