Improve the impact of health code on netdata scalability (#8407)

* Add support for spawning processes without pipes.

* Port health_alarm_execute() from mypopen() to netdata_spawn()

* Make alarm notifications asynchronous within a single health thread iteration

* Initial version of spawn server.

* preliminary integration of spawn client with health

2 files changed, 11 insertions, 0 deletions

diff --git a/daemon/common.h b/daemon/common.h
index f86e61543f..742ca4a766 100644
--- a/daemon/common.h
+++ b/daemon/common.h
@@ -68,6 +68,9 @@
 // netdata agent cloud link
 #include "aclk/agent_cloud_link.h"
 
+// netdata agent spawn server
+#include "spawn/spawn.h"
+
 // the netdata deamon
 #include "daemon.h"
 #include "main.h"
diff --git a/daemon/main.c b/daemon/main.c
index 098ddbac5b..d921f83a86 100644
--- a/daemon/main.c
+++ b/daemon/main.c
@@ -906,6 +906,11 @@ int main(int argc, char **argv) {
             else i++;
         }
     }
+    if (argc > 1 && strcmp(argv[1], SPAWN_SERVER_COMMAND_LINE_ARGUMENT) == 0) {
+        // don't run netdata, this is the spawn server
+        spawn_server();
+        exit(0);
+    }
 
     // parse options
     {
@@ -1377,6 +1382,9 @@ int main(int argc, char **argv) {
 
     netdata_threads_init_after_fork((size_t)config_get_number(CONFIG_SECTION_GLOBAL, "pthread stack size", (long)default_stacksize));
 
+    // fork the spawn server
+    spawn_init();
+
     // ------------------------------------------------------------------------
     // initialize rrd, registry, health, rrdpush, etc.