modularized all source code (#4391)

* modularized all external plugins

* added README.md in plugins

* fixed title

* fixed typo

* relative link to external plugins

* external plugins configuration README

* added plugins link

* remove plugins link

* plugin names are links

* added links to external plugins

* removed unecessary spacing

* list to table

* added language

* fixed typo

* list to table on internal plugins

* added more documentation to internal plugins

* moved python, node, and bash code and configs into the external plugins

* added statsd README

* fix bug with corrupting config.h every 2nd compilation

* moved all config files together with their code

* more documentation

* diskspace info

* fixed broken links in apps.plugin

* added backends docs

* updated plugins readme

* move nc-backend.sh to backends

* created daemon directory

* moved all code outside src/

* fixed readme identation

* renamed plugins.d.plugin to plugins.d

* updated readme

* removed linux- from linux plugins

* updated readme

* updated readme

* updated readme

* updated readme

* updated readme

* updated readme

* fixed README.md links

* fixed netdata tree links

* updated codacy, codeclimate and lgtm excluded paths

* update CMakeLists.txt

* updated automake options at top directory

* libnetdata slit into directories

* updated READMEs

* updated READMEs

* updated ARL docs

* updated ARL docs

* moved /plugins to /collectors

* moved all external plugins outside plugins.d

* updated codacy, codeclimate, lgtm

* updated README

* updated url

* updated readme

* updated readme

* updated readme

* updated readme

* moved api and web into webserver

* web/api web/gui web/server

* modularized webserver

* removed web/gui/version.txt

3 files changed, 162 insertions, 0 deletions

diff --git a/collectors/checks.plugin/Makefile.am b/collectors/checks.plugin/Makefile.am
new file mode 100644
index 0000000000..babdcf0df3
--- /dev/null
+++ b/collectors/checks.plugin/Makefile.am
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+AUTOMAKE_OPTIONS = subdir-objects
+MAINTAINERCLEANFILES = $(srcdir)/Makefile.in
diff --git a/collectors/checks.plugin/plugin_checks.c b/collectors/checks.plugin/plugin_checks.c
new file mode 100644
index 0000000000..f8a2008a8f
--- /dev/null
+++ b/collectors/checks.plugin/plugin_checks.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "plugin_checks.h"
+
+#ifdef NETDATA_INTERNAL_CHECKS
+
+static void checks_main_cleanup(void *ptr) {
+    struct netdata_static_thread *static_thread = (struct netdata_static_thread *)ptr;
+    static_thread->enabled = NETDATA_MAIN_THREAD_EXITING;
+
+    info("cleaning up...");
+
+    static_thread->enabled = NETDATA_MAIN_THREAD_EXITED;
+}
+
+void *checks_main(void *ptr) {
+    netdata_thread_cleanup_push(checks_main_cleanup, ptr);
+
+    usec_t usec = 0, susec = localhost->rrd_update_every * USEC_PER_SEC, loop_usec = 0, total_susec = 0;
+    struct timeval now, last, loop;
+
+    RRDSET *check1, *check2, *check3, *apps_cpu = NULL;
+
+    check1 = rrdset_create_localhost(
+            "netdata"
+            , "check1"
+            , NULL
+            , "netdata"
+            , NULL
+            , "Caller gives microseconds"
+            , "a million !"
+            , "checks.plugin"
+            , ""
+            , NETDATA_CHART_PRIO_CHECKS
+            , localhost->rrd_update_every
+            , RRDSET_TYPE_LINE
+    );
+
+    rrddim_add(check1, "absolute", NULL, -1, 1, RRD_ALGORITHM_ABSOLUTE);
+    rrddim_add(check1, "incremental", NULL, 1, 1, RRD_ALGORITHM_INCREMENTAL);
+
+    check2 = rrdset_create_localhost(
+            "netdata"
+            , "check2"
+            , NULL
+            , "netdata"
+            , NULL
+            , "Netdata calcs microseconds"
+            , "a million !"
+            , "checks.plugin"
+            , ""
+            , NETDATA_CHART_PRIO_CHECKS
+            , localhost->rrd_update_every
+            , RRDSET_TYPE_LINE
+    );
+    rrddim_add(check2, "absolute", NULL, -1, 1, RRD_ALGORITHM_ABSOLUTE);
+    rrddim_add(check2, "incremental", NULL, 1, 1, RRD_ALGORITHM_INCREMENTAL);
+
+    check3 = rrdset_create_localhost(
+            "netdata"
+            , "checkdt"
+            , NULL
+            , "netdata"
+            , NULL
+            , "Clock difference"
+            , "microseconds diff"
+            , "checks.plugin"
+            , ""
+            , NETDATA_CHART_PRIO_CHECKS
+            , localhost->rrd_update_every
+            , RRDSET_TYPE_LINE
+    );
+    rrddim_add(check3, "caller", NULL, 1, 1, RRD_ALGORITHM_ABSOLUTE);
+    rrddim_add(check3, "netdata", NULL, 1, 1, RRD_ALGORITHM_ABSOLUTE);
+    rrddim_add(check3, "apps.plugin", NULL, 1, 1, RRD_ALGORITHM_ABSOLUTE);
+
+    now_realtime_timeval(&last);
+    while(!netdata_exit) {
+        usleep(susec);
+
+        // find the time to sleep in order to wait exactly update_every seconds
+        now_realtime_timeval(&now);
+        loop_usec = dt_usec(&now, &last);
+        usec = loop_usec - susec;
+        debug(D_PROCNETDEV_LOOP, "CHECK: last loop took %llu usec (worked for %llu, sleeped for %llu).", loop_usec, usec, susec);
+
+        if(usec < (localhost->rrd_update_every * USEC_PER_SEC / 2ULL)) susec = (localhost->rrd_update_every * USEC_PER_SEC) - usec;
+        else susec = localhost->rrd_update_every * USEC_PER_SEC / 2ULL;
+
+        // --------------------------------------------------------------------
+        // Calculate loop time
+
+        last.tv_sec = now.tv_sec;
+        last.tv_usec = now.tv_usec;
+        total_susec += loop_usec;
+
+        // --------------------------------------------------------------------
+        // check chart 1
+
+        if(check1->counter_done) rrdset_next_usec(check1, loop_usec);
+        rrddim_set(check1, "absolute", 1000000);
+        rrddim_set(check1, "incremental", total_susec);
+        rrdset_done(check1);
+
+        // --------------------------------------------------------------------
+        // check chart 2
+
+        if(check2->counter_done) rrdset_next(check2);
+        rrddim_set(check2, "absolute", 1000000);
+        rrddim_set(check2, "incremental", total_susec);
+        rrdset_done(check2);
+
+        // --------------------------------------------------------------------
+        // check chart 3
+
+        if(!apps_cpu) apps_cpu = rrdset_find_localhost("apps.cpu");
+        if(check3->counter_done) rrdset_next_usec(check3, loop_usec);
+        now_realtime_timeval(&loop);
+        rrddim_set(check3, "caller", (long long) dt_usec(&loop, &check1->last_collected_time));
+        rrddim_set(check3, "netdata", (long long) dt_usec(&loop, &check2->last_collected_time));
+        if(apps_cpu) rrddim_set(check3, "apps.plugin", (long long) dt_usec(&loop, &apps_cpu->last_collected_time));
+        rrdset_done(check3);
+    }
+
+    netdata_thread_cleanup_pop(1);
+    return NULL;
+}
+
+#endif // NETDATA_INTERNAL_CHECKS
diff --git a/collectors/checks.plugin/plugin_checks.h b/collectors/checks.plugin/plugin_checks.h
new file mode 100644
index 0000000000..93494765d7
--- /dev/null
+++ b/collectors/checks.plugin/plugin_checks.h
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef NETDATA_PLUGIN_CHECKS_H
+#define NETDATA_PLUGIN_CHECKS_H 1
+
+#include "../../daemon/common.h"
+
+#ifdef NETDATA_INTERNAL_CHECKS
+
+#define NETDATA_PLUGIN_HOOK_CHECKS \
+    { \
+        .name = "PLUGIN[check]", \
+        .config_section = CONFIG_SECTION_PLUGINS, \
+        .config_name = "checks", \
+        .enabled = 0, \
+        .thread = NULL, \
+        .init_routine = NULL, \
+        .start_routine = checks_main \
+    },
+
+extern void *checks_main(void *ptr);
+
+#else // !NETDATA_INTERNAL_CHECKS
+
+#define NETDATA_PLUGIN_HOOK_CHECKS
+
+#endif // NETDATA_INTERNAL_CHECKS
+
+#endif // NETDATA_PLUGIN_CHECKS_H