[PATCH] tcp_listener_stats: always eagerly close sockets

[Jean Boussier <jean.boussier@gmail.com>]

Hello,

Once again apologies for not submitting the patch in an usable format. It can be downloaded with curl/wget from https://github.com/casperisfine/raindrops/commit/1c92b440ad7b11a1708a1d5ed75b0767f213b40a.patch

I just debugged an issue with our system, I was witnessing the
number of file descriptor in our process grow at an alarming rate
which I mapped to our use of raindrops to report utilisation.

For various reasons we don’t call raindrops from a Rack middleware
but have one process that monitor the socket continuously, and
share that data with the workers.

Since we call tcp_listener_stats every seconds in a process
that doesn't do much else, GC very rarely triggers if at all
 which cause `InetDiagSocket` instances to accumulate very
quickly.

Each of those instances holds a file descriptor.

Looking at the raindrops implementation it seems to assume
the GC will take care of regularly closing these sockets, but
I think it’s a bit too bold of an assumption.

Regards.

---
 ext/raindrops/linux_inet_diag.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/ext/raindrops/linux_inet_diag.c b/ext/raindrops/linux_inet_diag.c
index 2a2360c..b3d9a51 100644
--- a/ext/raindrops/linux_inet_diag.c
+++ b/ext/raindrops/linux_inet_diag.c
@@ -634,7 +634,7 @@ static VALUE tcp_listener_stats(int argc, VALUE *argv, VALUE self)
 	switch (TYPE(addrs)) {
 	case T_STRING:
 		rb_hash_aset(rv, addrs, tcp_stats(&args, addrs));
-		return rv;
+		goto out;
 	case T_ARRAY: {
 		long i;
 		long len = RARRAY_LEN(addrs);
@@ -643,7 +643,7 @@ static VALUE tcp_listener_stats(int argc, VALUE *argv, VALUE self)
 			VALUE cur = rb_ary_entry(addrs, 0);
 
 			rb_hash_aset(rv, cur, tcp_stats(&args, cur));
-			return rv;
+			goto out;
 		}
 		for (i = 0; i < len; i++) {
 			union any_addr check;
@@ -659,6 +659,7 @@ static VALUE tcp_listener_stats(int argc, VALUE *argv, VALUE self)
 		gen_bytecode_all(&args.iov[2]);
 		break;
 	default:
+        rb_io_close(sock);
 		rb_raise(rb_eArgError,
 		         "addr must be an array of strings, a string, or nil");
 	}
@@ -671,6 +672,7 @@ static VALUE tcp_listener_stats(int argc, VALUE *argv, VALUE self)
 	if (RHASH_SIZE(rv) > 1)
 		rb_hash_foreach(rv, drop_placeholders, Qfalse);
 
+out:
 	/* let GC deal with corner cases */
 	if (argc < 2) rb_io_close(sock);
 	return rv;