Close owned WebSocket clients after reconnects

src/commonMain/kotlin/net/sergeych/kiloparsec/adapter/websocketClient.kt

@@ -53,16 +53,18 @@ fun <S> websocketClient(
 /**
  * Create kilopaarsec transport over websocket (ws or wss).
  * @param path websocket path (must start with ws:// or wss:// and contain a path part)
- * @client use default [HttpClient], it installs [WebSockets] plugin
+ * @param client optional caller-owned client. When omitted, a client with the
+ * [WebSockets] plugin is created for this device and closed with it.
  */
 fun websocketTransportDevice(
     path: String,
     useTextFrames: Boolean = false,
-    client: HttpClient = HttpClient {
-        install(WebSockets)
-    },
+    client: HttpClient? = null,
 ): Transport.Device {
 
+    val ownsClient = client == null
+    val actualClient = client ?: HttpClient { install(WebSockets) }
+
     val log = LogTag("WSTD")
     var u = Url(path)
     log.debug { "Creating websocket transport device at $u" }
@@ -82,7 +84,7 @@ fun websocketTransportDevice(
     globalLaunch {
         val log = LogTag("KC:${counter.incrementAndGet()}")
         try {
-            client.webSocket({
+            actualClient.webSocket({
                 url.protocol = u.protocol
                 url.host = u.host
                 url.port = u.port
@@ -148,6 +150,8 @@ fun websocketTransportDevice(
             else log.warning { "unexpected IO error $x" }
             runCatching { output.close() }
             runCatching { input.close() }
+        } finally {
+            if (ownsClient) actualClient.close()
         }
         log.info { "closing connection" }
     }
@@ -162,4 +166,3 @@ fun websocketTransportDevice(
     })
     return device
 }
-

src/jvmTest/kotlin/net/sergeych/kiloparsec/adapter/WebsocketClientResourceTest.kt

@@ -0,0 +1,29 @@
+package net.sergeych.kiloparsec.adapter
+
+import java.nio.file.Files
+import java.nio.file.Path
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.runBlocking
+import kotlin.test.Test
+import kotlin.test.assertTrue
+
+class WebsocketClientResourceTest {
+    @Test
+    fun failedReconnectsDoNotLeakFileDescriptors() = runBlocking {
+        val descriptors = Path.of("/proc/self/fd")
+        if (!Files.isDirectory(descriptors)) return@runBlocking
+
+        val client = websocketClient<Unit>("ws://127.0.0.1:1/kp")
+        try {
+            delay(2_500)
+            val before = descriptorCount(descriptors)
+            delay(7_000)
+            val after = descriptorCount(descriptors)
+            assertTrue(after <= before + 3, "file descriptors grew from $before to $after")
+        } finally {
+            client.close()
+        }
+    }
+
+    private fun descriptorCount(path: Path): Long = Files.list(path).use { it.count() }
+}