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

1 files changed, 8 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 56f3a2416e..866e602b27 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -641,6 +641,13 @@ set(ACLK_PLUGIN_FILES
         aclk/mqtt.h
         )
 
+set(SPAWN_PLUGIN_FILES
+        spawn/spawn.c
+        spawn/spawn_server.c
+        spawn/spawn_client.c
+        spawn/spawn.h
+        )
+
 set(ACLK_STATIC_LIBS
         ${CMAKE_SOURCE_DIR}/externaldeps/mosquitto/libmosquitto.a
         ${CMAKE_SOURCE_DIR}/externaldeps/libwebsockets/libwebsockets.a
@@ -741,6 +748,7 @@ set(NETDATA_FILES
         ${STREAMING_PLUGIN_FILES}
         ${WEB_PLUGIN_FILES}
         ${CLAIM_PLUGIN_FILES}
+        ${SPAWN_PLUGIN_FILES}
 )
 
 set(NETDATACLI_FILES