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, 229 insertions, 0 deletions

diff --git a/libnetdata/threads/Makefile.am b/libnetdata/threads/Makefile.am
new file mode 100644
index 0000000000..1cb69ed99a
--- /dev/null
+++ b/libnetdata/threads/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/threads/README.md b/libnetdata/threads/README.md
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/libnetdata/threads/README.md
diff --git a/libnetdata/threads/threads.c b/libnetdata/threads/threads.c
new file mode 100644
index 0000000000..133d9a5471
--- /dev/null
+++ b/libnetdata/threads/threads.c
@@ -0,0 +1,183 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include "../libnetdata.h"
+
+static size_t default_stacksize = 0, wanted_stacksize = 0;
+static pthread_attr_t *attr = NULL;
+
+// ----------------------------------------------------------------------------
+// per thread data
+
+typedef struct {
+    void *arg;
+    pthread_t *thread;
+    const char *tag;
+    void *(*start_routine) (void *);
+    NETDATA_THREAD_OPTIONS options;
+} NETDATA_THREAD;
+
+static __thread NETDATA_THREAD *netdata_thread = NULL;
+
+const char *netdata_thread_tag(void) {
+    return ((netdata_thread && netdata_thread->tag && *netdata_thread->tag)?netdata_thread->tag:"MAIN");
+}
+
+// ----------------------------------------------------------------------------
+// compatibility library functions
+
+pid_t gettid(void) {
+#ifdef __FreeBSD__
+
+    return (pid_t)pthread_getthreadid_np();
+
+#elif defined(__APPLE__)
+
+    #if (defined __MAC_OS_X_VERSION_MIN_REQUIRED && __MAC_OS_X_VERSION_MIN_REQUIRED >= 1060)
+        uint64_t curthreadid;
+        pthread_threadid_np(NULL, &curthreadid);
+        return (pid_t)curthreadid;
+    #else /* __MAC_OS_X_VERSION_MIN_REQUIRED */
+        return (pid_t)pthread_self;
+    #endif /* __MAC_OS_X_VERSION_MIN_REQUIRED */
+
+#else /* __APPLE__*/
+
+    return (pid_t)syscall(SYS_gettid);
+
+#endif /* __FreeBSD__, __APPLE__*/
+}
+
+// ----------------------------------------------------------------------------
+// early initialization
+
+size_t netdata_threads_init(void) {
+    int i;
+
+    // --------------------------------------------------------------------
+    // get the required stack size of the threads of netdata
+
+    attr = callocz(1, sizeof(pthread_attr_t));
+    i = pthread_attr_init(attr);
+    if(i != 0)
+        fatal("pthread_attr_init() failed with code %d.", i);
+
+    i = pthread_attr_getstacksize(attr, &default_stacksize);
+    if(i != 0)
+        fatal("pthread_attr_getstacksize() failed with code %d.", i);
+    else
+        debug(D_OPTIONS, "initial pthread stack size is %zu bytes", default_stacksize);
+
+    return default_stacksize;
+}
+
+// ----------------------------------------------------------------------------
+// late initialization
+
+void netdata_threads_init_after_fork(size_t stacksize) {
+    wanted_stacksize = stacksize;
+    int i;
+
+    // ------------------------------------------------------------------------
+    // set default pthread stack size
+
+    if(attr && default_stacksize < wanted_stacksize && wanted_stacksize > 0) {
+        i = pthread_attr_setstacksize(attr, wanted_stacksize);
+        if(i != 0)
+            fatal("pthread_attr_setstacksize() to %zu bytes, failed with code %d.", wanted_stacksize, i);
+        else
+            debug(D_SYSTEM, "Successfully set pthread stacksize to %zu bytes", wanted_stacksize);
+    }
+}
+
+
+// ----------------------------------------------------------------------------
+// netdata_thread_create
+
+static void thread_cleanup(void *ptr) {
+    if(netdata_thread != ptr) {
+        NETDATA_THREAD *info = (NETDATA_THREAD *)ptr;
+        error("THREADS: internal error - thread local variable does not match the one passed to this function. Expected thread '%s', passed thread '%s'", netdata_thread->tag, info->tag);
+    }
+
+    if(!(netdata_thread->options & NETDATA_THREAD_OPTION_DONT_LOG_CLEANUP))
+        info("thread with task id %d finished", gettid());
+
+    freez((void *)netdata_thread->tag);
+    netdata_thread->tag = NULL;
+
+    freez(netdata_thread);
+    netdata_thread = NULL;
+}
+
+static void *thread_start(void *ptr) {
+    netdata_thread = (NETDATA_THREAD *)ptr;
+
+    if(!(netdata_thread->options & NETDATA_THREAD_OPTION_DONT_LOG_STARTUP))
+        info("thread created with task id %d", gettid());
+
+    if(pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL) != 0)
+        error("cannot set pthread cancel type to DEFERRED.");
+
+    if(pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL) != 0)
+        error("cannot set pthread cancel state to ENABLE.");
+
+    void *ret = NULL;
+    pthread_cleanup_push(thread_cleanup, ptr);
+            ret = netdata_thread->start_routine(netdata_thread->arg);
+    pthread_cleanup_pop(1);
+
+    return ret;
+}
+
+int netdata_thread_create(netdata_thread_t *thread, const char *tag, NETDATA_THREAD_OPTIONS options, void *(*start_routine) (void *), void *arg) {
+    NETDATA_THREAD *info = mallocz(sizeof(NETDATA_THREAD));
+    info->arg = arg;
+    info->thread = thread;
+    info->tag = strdupz(tag);
+    info->start_routine = start_routine;
+    info->options = options;
+
+    int ret = pthread_create(thread, attr, thread_start, info);
+    if(ret != 0)
+        error("failed to create new thread for %s. pthread_create() failed with code %d", tag, ret);
+
+    else {
+        if (!(options & NETDATA_THREAD_OPTION_JOINABLE)) {
+            int ret2 = pthread_detach(*thread);
+            if (ret2 != 0)
+                error("cannot request detach of newly created %s thread. pthread_detach() failed with code %d", tag, ret2);
+        }
+    }
+
+    return ret;
+}
+
+// ----------------------------------------------------------------------------
+// netdata_thread_cancel
+
+int netdata_thread_cancel(netdata_thread_t thread) {
+    int ret = pthread_cancel(thread);
+    if(ret != 0)
+        error("cannot cancel thread. pthread_cancel() failed with code %d.", ret);
+
+    return ret;
+}
+
+// ----------------------------------------------------------------------------
+// netdata_thread_join
+
+int netdata_thread_join(netdata_thread_t thread, void **retval) {
+    int ret = pthread_join(thread, retval);
+    if(ret != 0)
+        error("cannot join thread. pthread_join() failed with code %d.", ret);
+
+    return ret;
+}
+
+int netdata_thread_detach(pthread_t thread) {
+    int ret = pthread_detach(thread);
+    if(ret != 0)
+        error("cannot detach thread. pthread_detach() failed with code %d.", ret);
+
+    return ret;
+}
diff --git a/libnetdata/threads/threads.h b/libnetdata/threads/threads.h
new file mode 100644
index 0000000000..eec6ad0e31
--- /dev/null
+++ b/libnetdata/threads/threads.h
@@ -0,0 +1,37 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef NETDATA_THREADS_H
+#define NETDATA_THREADS_H 1
+
+#include "../libnetdata.h"
+
+extern pid_t gettid(void);
+
+typedef enum {
+    NETDATA_THREAD_OPTION_DEFAULT          = 0 << 0,
+    NETDATA_THREAD_OPTION_JOINABLE         = 1 << 0,
+    NETDATA_THREAD_OPTION_DONT_LOG_STARTUP = 1 << 1,
+    NETDATA_THREAD_OPTION_DONT_LOG_CLEANUP = 1 << 2,
+    NETDATA_THREAD_OPTION_DONT_LOG         = NETDATA_THREAD_OPTION_DONT_LOG_STARTUP|NETDATA_THREAD_OPTION_DONT_LOG_CLEANUP,
+} NETDATA_THREAD_OPTIONS;
+
+#define netdata_thread_cleanup_push(func, arg) pthread_cleanup_push(func, arg)
+#define netdata_thread_cleanup_pop(execute) pthread_cleanup_pop(execute)
+
+typedef pthread_t netdata_thread_t;
+
+#define NETDATA_THREAD_TAG_MAX 100
+extern const char *netdata_thread_tag(void);
+
+extern size_t netdata_threads_init(void);
+extern void netdata_threads_init_after_fork(size_t stacksize);
+
+extern int netdata_thread_create(netdata_thread_t *thread, const char *tag, NETDATA_THREAD_OPTIONS options, void *(*start_routine) (void *), void *arg);
+extern int netdata_thread_cancel(netdata_thread_t thread);
+extern int netdata_thread_join(netdata_thread_t thread, void **retval);
+extern int netdata_thread_detach(pthread_t thread);
+
+#define netdata_thread_self pthread_self
+#define netdata_thread_testcancel pthread_testcancel
+
+#endif //NETDATA_THREADS_H