src: keep track of open requests

Workers cannot shut down while requests are open, so keep a counter
that is increased whenever libuv requests are made and decreased
whenever their callback is called.

This also applies to other embedders, who may want to shut down
an `Environment` instance early.

Many thanks for Stephen Belanger for reviewing the original version of
this commit in the Ayo.js project.

Fixes: https://github.com/nodejs/node/issues/20517
Refs: https://github.com/ayojs/ayo/pull/85
PR-URL: https://github.com/nodejs/node/pull/19377
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/src/node_zlib.cc b/src/node_zlib.cc
index ec447638e2..3249905dfb 100644
--- a/src/node_zlib.cc
+++ b/src/node_zlib.cc
@@ -214,6 +214,7 @@ class ZCtx : public AsyncWrap {
     }
 
     // async version
+    env->IncreaseWaitingRequestCounter();
     uv_queue_work(env->event_loop(), work_req, ZCtx::Process, ZCtx::After);
   }
 
@@ -361,10 +362,17 @@ class ZCtx : public AsyncWrap {
 
   // v8 land!
   static void After(uv_work_t* work_req, int status) {
-    CHECK_EQ(status, 0);
-
     ZCtx* ctx = ContainerOf(&ZCtx::work_req_, work_req);
     Environment* env = ctx->env();
+    ctx->write_in_progress_ = false;
+
+    env->DecreaseWaitingRequestCounter();
+    if (status == UV_ECANCELED) {
+      ctx->Close();
+      return;
+    }
+
+    CHECK_EQ(status, 0);
 
     HandleScope handle_scope(env->isolate());
     Context::Scope context_scope(env->context());
@@ -374,7 +382,6 @@ class ZCtx : public AsyncWrap {
 
     ctx->write_result_[0] = ctx->strm_.avail_out;
     ctx->write_result_[1] = ctx->strm_.avail_in;
-    ctx->write_in_progress_ = false;
 
     // call the write() cb
     Local<Function> cb = PersistentToLocal(env->isolate(),