fix: memory leak introduced in [email protected]

fixes #12

Author: analog-nico

index.js

@@ -1248,6 +1248,23 @@ class Tangerine extends dns.promises.Resolver {
     }
   }
 
+  // #createAbortController and #releaseAbortController manage all AbortController instances created by this resolver
+  // - to support cancel() and
+  // - to avoid keeping references in this.abortControllers after a query is finished (which would create a memory leak)
+  #createAbortController() {
+    const abortController = new AbortController();
+    this.abortControllers.add(abortController);
+    return abortController;
+  }
+
+  #releaseAbortController(abortController) {
+    try {
+      this.abortControllers.delete(abortController);
+    } catch (err) {
+      this.options.logger.debug(err);
+    }
+  }
+
   // Cancel all outstanding DNS queries made by this resolver
   // NOTE: callbacks not currently called with ECANCELLED (prob need to alter got options)
   //       (instead they are called with "ABORT_ERR"; see ABORT_ERROR_CODES)
@@ -1265,26 +1282,22 @@ class Tangerine extends dns.promises.Resolver {
 
   #resolveByType(name, options = {}, parentAbortController) {
     return async (type) => {
-      const abortController = new AbortController();
-      this.abortControllers.add(abortController);
-      abortController.signal.addEventListener(
-        'abort',
-        () => {
-          this.abortControllers.delete(abortController);
-        },
-        { once: true }
-      );
-      parentAbortController.signal.addEventListener(
-        'abort',
-        () => {
-          try {
-            abortController.abort('Parent abort controller aborted');
-          } catch (err) {
-            this.options.logger.debug(err);
-          }
-        },
-        { once: true }
-      );
+      const abortController = this.#createAbortController();
+      try {
+        parentAbortController.signal.addEventListener(
+          'abort',
+          () => {
+            try {
+              abortController.abort('Parent abort controller aborted');
+            } catch (err) {
+              this.options.logger.debug(err);
+            }
+          },
+          { once: true }
+        );
+      } finally {
+        this.#releaseAbortController(abortController);
+      }
       // wrap with try/catch because ENODATA shouldn't cause errors
       try {
         switch (type) {
@@ -1379,6 +1392,8 @@ class Tangerine extends dns.promises.Resolver {
 
         if (err.code === dns.NODATA) return;
         throw err;
+      } finally {
+        this.#releaseAbortController(abortController);
       }
     };
   }
@@ -1394,23 +1409,21 @@ class Tangerine extends dns.promises.Resolver {
     // <https://gist.github.com/andrewcourtice/ef1b8f14935b409cfe94901558ba5594#file-task-ts-L37>
     // <https://github.com/nodejs/undici/blob/0badd390ad5aa531a66aacee54da664468aa1577/lib/api/api-fetch/request.js#L280-L295>
     // <https://github.com/nodejs/node/issues/40849>
+    let mustReleaseAbortController = false;
     if (!abortController) {
-      abortController = new AbortController();
-      this.abortControllers.add(abortController);
-      abortController.signal.addEventListener(
-        'abort',
-        () => {
-          this.abortControllers.delete(abortController);
-        },
-        { once: true }
-      );
+      abortController = this.#createAbortController();
+      mustReleaseAbortController = true;
 
-      // <https://github.com/nodejs/undici/pull/1910/commits/7615308a92d3c8c90081fb99c55ab8bd59212396>
-      setMaxListeners(
-        getEventListeners(abortController.signal, 'abort').length +
-          this.constructor.ANY_TYPES.length,
-        abortController.signal
-      );
+      try {
+        // <https://github.com/nodejs/undici/pull/1910/commits/7615308a92d3c8c90081fb99c55ab8bd59212396>
+        setMaxListeners(
+          getEventListeners(abortController.signal, 'abort').length +
+            this.constructor.ANY_TYPES.length,
+          abortController.signal
+        );
+      } finally {
+        this.#releaseAbortController(abortController);
+      }
     }
 
     try {
@@ -1428,6 +1441,10 @@ class Tangerine extends dns.promises.Resolver {
       err.syscall = 'queryAny';
       err.message = `queryAny ${err.code} ${name}`;
       throw err;
+    } finally {
+      if (mustReleaseAbortController) {
+        this.#releaseAbortController(abortController);
+      }
     }
   }
 
@@ -1674,20 +1691,20 @@ class Tangerine extends dns.promises.Resolver {
     if (this.options.cache && result) {
       debug(`cached result found for "${key}"`);
     } else {
+      let mustReleaseAbortController = false;
       if (!abortController) {
-        abortController = new AbortController();
-        this.abortControllers.add(abortController);
-        abortController.signal.addEventListener(
-          'abort',
-          () => {
-            this.abortControllers.delete(abortController);
-          },
-          { once: true }
-        );
+        abortController = this.#createAbortController();
+        mustReleaseAbortController = true;
       }
 
-      // setImmediate(() => this.cancel());
-      result = await this.#query(name, rrtype, ecsSubnet, abortController);
+      try {
+        // setImmediate(() => this.cancel());
+        result = await this.#query(name, rrtype, ecsSubnet, abortController);
+      } finally {
+        if (mustReleaseAbortController) {
+          this.#releaseAbortController(abortController);
+        }
+      }
     }
 
     // <https://github.com/m13253/dns-over-https/blob/2e36b4ebcdb8a1a102ea86370d7f8b1f1e72380a/json-dns/response.go#L50-L74>