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

4 files changed, 298 insertions, 0 deletions

diff --git a/libnetdata/clocks/Makefile.am b/libnetdata/clocks/Makefile.am
new file mode 100644
index 0000000000..1cb69ed99a
--- /dev/null
+++ b/libnetdata/clocks/Makefile.am
@@ -0,0 +1,9 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+AUTOMAKE_OPTIONS = subdir-objects
+MAINTAINERCLEANFILES = $(srcdir)/Makefile.in
+
+
+dist_noinst_DATA = \
+	README.md \
+	$(NULL)
diff --git a/libnetdata/clocks/README.md b/libnetdata/clocks/README.md
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/libnetdata/clocks/README.md
diff --git a/libnetdata/clocks/clocks.c b/libnetdata/clocks/clocks.c
new file mode 100644
index 0000000000..e644aeeb09
--- /dev/null
+++ b/libnetdata/clocks/clocks.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "../libnetdata.h"
+
+#ifndef HAVE_CLOCK_GETTIME
+inline int clock_gettime(clockid_t clk_id, struct timespec *ts) {
+    struct timeval tv;
+    if(unlikely(gettimeofday(&tv, NULL) == -1)) {
+        error("gettimeofday() failed.");
+        return -1;
+    }
+    ts->tv_sec = tv.tv_sec;
+    ts->tv_nsec = (tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC;
+    return 0;
+}
+#endif
+
+static inline time_t now_sec(clockid_t clk_id) {
+    struct timespec ts;
+    if(unlikely(clock_gettime(clk_id, &ts) == -1)) {
+        error("clock_gettime(%d, &timespec) failed.", clk_id);
+        return 0;
+    }
+    return ts.tv_sec;
+}
+
+static inline usec_t now_usec(clockid_t clk_id) {
+    struct timespec ts;
+    if(unlikely(clock_gettime(clk_id, &ts) == -1)) {
+        error("clock_gettime(%d, &timespec) failed.", clk_id);
+        return 0;
+    }
+    return (usec_t)ts.tv_sec * USEC_PER_SEC + (ts.tv_nsec % NSEC_PER_SEC) / NSEC_PER_USEC;
+}
+
+static inline int now_timeval(clockid_t clk_id, struct timeval *tv) {
+    struct timespec ts;
+
+    if(unlikely(clock_gettime(clk_id, &ts) == -1)) {
+        error("clock_gettime(%d, &timespec) failed.", clk_id);
+        tv->tv_sec = 0;
+        tv->tv_usec = 0;
+        return -1;
+    }
+
+    tv->tv_sec = ts.tv_sec;
+    tv->tv_usec = (suseconds_t)((ts.tv_nsec % NSEC_PER_SEC) / NSEC_PER_USEC);
+    return 0;
+}
+
+inline time_t now_realtime_sec(void) {
+    return now_sec(CLOCK_REALTIME);
+}
+
+inline usec_t now_realtime_usec(void) {
+    return now_usec(CLOCK_REALTIME);
+}
+
+inline int now_realtime_timeval(struct timeval *tv) {
+    return now_timeval(CLOCK_REALTIME, tv);
+}
+
+inline time_t now_monotonic_sec(void) {
+    return now_sec(CLOCK_MONOTONIC);
+}
+
+inline usec_t now_monotonic_usec(void) {
+    return now_usec(CLOCK_MONOTONIC);
+}
+
+inline int now_monotonic_timeval(struct timeval *tv) {
+    return now_timeval(CLOCK_MONOTONIC, tv);
+}
+
+inline time_t now_boottime_sec(void) {
+    return now_sec(CLOCK_BOOTTIME);
+}
+
+inline usec_t now_boottime_usec(void) {
+    return now_usec(CLOCK_BOOTTIME);
+}
+
+inline int now_boottime_timeval(struct timeval *tv) {
+    return now_timeval(CLOCK_BOOTTIME, tv);
+}
+
+inline usec_t timeval_usec(struct timeval *tv) {
+    return (usec_t)tv->tv_sec * USEC_PER_SEC + (tv->tv_usec % USEC_PER_SEC);
+}
+
+inline msec_t timeval_msec(struct timeval *tv) {
+    return (msec_t)tv->tv_sec * MSEC_PER_SEC + ((tv->tv_usec % USEC_PER_SEC) / MSEC_PER_SEC);
+}
+
+inline susec_t dt_usec_signed(struct timeval *now, struct timeval *old) {
+    usec_t ts1 = timeval_usec(now);
+    usec_t ts2 = timeval_usec(old);
+
+    if(likely(ts1 >= ts2)) return (susec_t)(ts1 - ts2);
+    return -((susec_t)(ts2 - ts1));
+}
+
+inline usec_t dt_usec(struct timeval *now, struct timeval *old) {
+    usec_t ts1 = timeval_usec(now);
+    usec_t ts2 = timeval_usec(old);
+    return (ts1 > ts2) ? (ts1 - ts2) : (ts2 - ts1);
+}
+
+inline void heartbeat_init(heartbeat_t *hb)
+{
+    hb->monotonic = hb->realtime = 0ULL;
+}
+
+// waits for the next heartbeat
+// it waits using the monotonic clock
+// it returns the dt using the realtime clock
+
+usec_t heartbeat_next(heartbeat_t *hb, usec_t tick) {
+    heartbeat_t now;
+    now.monotonic = now_monotonic_usec();
+    now.realtime  = now_realtime_usec();
+
+    usec_t next_monotonic = now.monotonic - (now.monotonic % tick) + tick;
+
+    while(now.monotonic < next_monotonic) {
+        sleep_usec(next_monotonic - now.monotonic);
+        now.monotonic = now_monotonic_usec();
+        now.realtime  = now_realtime_usec();
+    }
+
+    if(likely(hb->realtime != 0ULL)) {
+        usec_t dt_monotonic = now.monotonic - hb->monotonic;
+        usec_t dt_realtime  = now.realtime - hb->realtime;
+
+        hb->monotonic = now.monotonic;
+        hb->realtime  = now.realtime;
+
+        if(unlikely(dt_monotonic >= tick + tick / 2)) {
+            errno = 0;
+            error("heartbeat missed %llu monotonic microseconds", dt_monotonic - tick);
+        }
+
+        return dt_realtime;
+    }
+    else {
+        hb->monotonic = now.monotonic;
+        hb->realtime  = now.realtime;
+        return 0ULL;
+    }
+}
+
+// returned the elapsed time, since the last heartbeat
+// using the monotonic clock
+
+inline usec_t heartbeat_monotonic_dt_to_now_usec(heartbeat_t *hb) {
+    if(!hb || !hb->monotonic) return 0ULL;
+    return now_monotonic_usec() - hb->monotonic;
+}
diff --git a/libnetdata/clocks/clocks.h b/libnetdata/clocks/clocks.h
new file mode 100644
index 0000000000..c66dda4369
--- /dev/null
+++ b/libnetdata/clocks/clocks.h
@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef NETDATA_CLOCKS_H
+#define NETDATA_CLOCKS_H 1
+
+#include "../libnetdata.h"
+
+#ifndef HAVE_STRUCT_TIMESPEC
+struct timespec {
+    time_t tv_sec;  /* seconds */
+    long   tv_nsec; /* nanoseconds */
+};
+#endif
+
+#ifndef HAVE_CLOCKID_T
+typedef int clockid_t;
+#endif
+
+typedef unsigned long long nsec_t;
+typedef unsigned long long msec_t;
+typedef unsigned long long usec_t;
+typedef long long susec_t;
+
+typedef struct heartbeat {
+    usec_t monotonic;
+    usec_t realtime;
+} heartbeat_t;
+
+/* Linux value is as good as any other */
+#ifndef CLOCK_REALTIME
+#define CLOCK_REALTIME  0
+#endif
+
+#ifndef CLOCK_MONOTONIC
+/* fallback to CLOCK_REALTIME if not available */
+#define CLOCK_MONOTONIC CLOCK_REALTIME
+#endif
+
+#ifndef CLOCK_BOOTTIME
+
+#ifdef CLOCK_UPTIME
+/* CLOCK_BOOTTIME falls back to CLOCK_UPTIME on FreeBSD */
+#define CLOCK_BOOTTIME CLOCK_UPTIME
+#else // CLOCK_UPTIME
+/* CLOCK_BOOTTIME falls back to CLOCK_MONOTONIC */
+#define CLOCK_BOOTTIME  CLOCK_MONOTONIC
+#endif // CLOCK_UPTIME
+
+#else // CLOCK_BOOTTIME
+
+#ifdef HAVE_CLOCK_GETTIME
+#define CLOCK_BOOTTIME_IS_AVAILABLE 1 // required for /proc/uptime
+#endif // HAVE_CLOCK_GETTIME
+
+#endif // CLOCK_BOOTTIME
+
+#define NSEC_PER_MSEC   1000000ULL
+
+#define NSEC_PER_SEC    1000000000ULL
+#define NSEC_PER_USEC   1000ULL
+
+#define USEC_PER_SEC    1000000ULL
+#define MSEC_PER_SEC    1000ULL
+
+#define USEC_PER_MS     1000ULL
+
+#ifndef HAVE_CLOCK_GETTIME
+/* Fallback function for POSIX.1-2001 clock_gettime() function.
+ *
+ * We use a realtime clock from gettimeofday(), this will
+ * make systems without clock_gettime() support sensitive
+ * to time jumps or hibernation/suspend side effects.
+ */
+extern int clock_gettime(clockid_t clk_id, struct timespec *ts);
+#endif
+
+/*
+ * Three clocks are available (cf. man 3 clock_gettime):
+ *
+ * REALTIME clock (i.e. wall-clock):
+ *  This clock is affected by discontinuous jumps in the system time
+ *  (e.g., if the system administrator manually changes the clock), and by the incremental adjustments performed by adjtime(3) and NTP.
+ *
+ * MONOTONIC clock
+ *  Clock that cannot be set and represents monotonic time since some unspecified starting point.
+ *  This clock is not affected by discontinuous jumps in the system time
+ *  (e.g., if the system administrator manually changes the clock), but is affected by the incremental adjustments performed by adjtime(3) and NTP.
+ *  If not available on the system, this clock falls back to REALTIME clock.
+ *
+ * BOOTTIME clock
+ *  Identical to  CLOCK_MONOTONIC, except it also includes any time that the system is suspended.
+ *  This allows applications to get a suspend-aware monotonic clock without having to deal with the complications of CLOCK_REALTIME,
+ *  which may have discontinuities if the time is changed using settimeofday(2).
+ *  If not available on the system, this clock falls back to MONOTONIC clock.
+ *
+ * All now_*_timeval() functions fill the `struct timeval` with the time from the appropriate clock.
+ * Those functions return 0 on success, -1 else with errno set appropriately.
+ *
+ * All now_*_sec() functions return the time in seconds from the approriate clock, or 0 on error.
+ * All now_*_usec() functions return the time in microseconds from the approriate clock, or 0 on error.
+ */
+extern int now_realtime_timeval(struct timeval *tv);
+extern time_t now_realtime_sec(void);
+extern usec_t now_realtime_usec(void);
+
+extern int now_monotonic_timeval(struct timeval *tv);
+extern time_t now_monotonic_sec(void);
+extern usec_t now_monotonic_usec(void);
+
+extern int now_boottime_timeval(struct timeval *tv);
+extern time_t now_boottime_sec(void);
+extern usec_t now_boottime_usec(void);
+
+
+extern usec_t timeval_usec(struct timeval *tv);
+extern msec_t timeval_msec(struct timeval *tv);
+
+extern usec_t dt_usec(struct timeval *now, struct timeval *old);
+extern susec_t dt_usec_signed(struct timeval *now, struct timeval *old);
+
+extern void heartbeat_init(heartbeat_t *hb);
+
+/* Sleeps until next multiple of tick using monotonic clock.
+ * Returns elapsed time in microseconds since previous heartbeat
+ */
+extern usec_t heartbeat_next(heartbeat_t *hb, usec_t tick);
+
+/* Returns elapsed time in microseconds since last heartbeat */
+extern usec_t heartbeat_monotonic_dt_to_now_usec(heartbeat_t *hb);
+
+#endif /* NETDATA_CLOCKS_H */