lightningd: add --dev-no-version-checks, use if SLOW_MACHINE and VALGRIND

Reduces VALGRIND=1 node_factory.line_graph(5) time on my laptop from 42s to 36s.

This is simply because forking all the subdaemons just to check the
version is very expensive under valgrind.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

contrib/pyln-testing/pyln/testing/utils.py

@@ -579,6 +579,9 @@ class LightningNode(object):
             self.daemon.opts["dev-disconnect"] = "dev_disconnect"
         if DEVELOPER:
             self.daemon.opts["dev-fail-on-subdaemon-fail"] = None
+            # Don't run --version on every subdaemon if we're valgrinding and slow.
+            if SLOW_MACHINE and VALGRIND:
+                self.daemon.opts["dev-no-version-checks"] = None
             self.daemon.env["LIGHTNINGD_DEV_MEMLEAK"] = "1"
             if os.getenv("DEBUG_SUBD"):
                 self.daemon.opts["dev-debugger"] = os.getenv("DEBUG_SUBD")

lightningd/lightningd.c

@@ -139,6 +139,7 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	ld->dev_force_channel_secrets_shaseed = NULL;
 	ld->dev_force_tmp_channel_id = NULL;
 	ld->dev_no_htlc_timeout = false;
+	ld->dev_no_version_checks = false;
 #endif
 
 	/*~ These are CCAN lists: an embedded double-linked list.  It's not
@@ -820,8 +821,13 @@ int main(int argc, char *argv[])
 	 * daemon running, so we call before doing almost anything else. */
 	pidfile_create(ld);
 
-	/*~ Make sure we can reach the subdaemons, and versions match. */
-	test_subdaemons(ld);
+	/*~ Make sure we can reach the subdaemons, and versions match.
+	 * This can be turned off in DEVELOPER builds with --dev-skip-version-checks,
+	 * but the `dev_no_version_checks` field of `ld` doesn't even exist
+	 * if DEVELOPER isn't defined, so we use IFDEV(devoption,non-devoption):
+	 */
+	if (IFDEV(!ld->dev_no_version_checks, 1))
+		test_subdaemons(ld);
 
 	/*~ Set up the HSM daemon, which knows our node secret key, so tells
 	 *  us who we are.

lightningd/lightningd.h

@@ -240,6 +240,8 @@ struct lightningd {
 	/* For slow tests (eg protocol tests) don't die if HTLC not
 	 * committed in 30 secs */
 	bool dev_no_htlc_timeout;
+
+	bool dev_no_version_checks;
 #endif /* DEVELOPER */
 
 	/* tor support */

lightningd/options.c

@@ -553,6 +553,9 @@ static void dev_register_opts(struct lightningd *ld)
 	opt_register_noarg("--dev-fail-process-onionpacket", opt_set_bool,
 			   &dev_fail_process_onionpacket,
 			   "Force all processing of onion packets to fail");
+	opt_register_noarg("--dev-no-version-checks", opt_set_bool,
+			   &ld->dev_no_version_checks,
+			   "Skip calling subdaemons with --version on startup");
 }
 #endif /* DEVELOPER */