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

1 files changed, 156 insertions, 0 deletions

diff --git a/libnetdata/config/appconfig.h b/libnetdata/config/appconfig.h
new file mode 100644
index 0000000000..bd37171e6c
--- /dev/null
+++ b/libnetdata/config/appconfig.h
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+/*
+ * This section manages ini config files, like netdata.conf and stream.conf
+ *
+ * It is organized like this:
+ *
+ * struct config (i.e. netdata.conf or stream.conf)
+ *   .sections    = a linked list of struct section
+ *   .mutex       = a mutex to protect the above linked list due to multi-threading
+ *   .index       = an AVL tree of struct section
+ *
+ * struct section (i.e. [global] or [health] of netdata.conf)
+ *   .value       = a linked list of struct config_option
+ *   .mutex       = a mutex to protect the above linked list due to multi-threading
+ *   .value_index = an AVL tree of struct config_option
+ *
+ * struct config_option (ie. a name-value pair for each ini file option)
+ *
+ * The following operations on name-value options are supported:
+ *    SET           to set the value of an option
+ *    SET DEFAULT   to set the value and the default value of an option
+ *    GET           to get the value of an option
+ *    EXISTS        to check if an option exists
+ *    MOVE          to move an option from a section to another section, and/or rename it
+ *
+ *    GET and SET operations are provided for the following data types:
+ *                  STRING
+ *                  NUMBER (long long)
+ *                  FLOAT (long double)
+ *                  BOOLEAN (false, true)
+ *                  BOOLEAN ONDEMAND (false, true, auto)
+ *
+ *   GET and SET operations create struct config_option, if it is not already present.
+ *   This allows netdata to run even without netdata.conf and stream.conf. The internal
+ *   defaults are used to create the structure that should exist in the ini file and the config
+ *   file can be downloaded from the server.
+ *
+ *   Also 2 operations are supported for the whole config file:
+ *
+ *     LOAD         To load the ini file from disk
+ *     GENERATE     To generate the ini file (this is used to download the ini file from the server)
+ *
+ * For each option (name-value pair), the system maintains 4 flags:
+ *   LOADED   to indicate that the value has been loaded from the file
+ *   USED     to indicate that netdata used the value
+ *   CHANGED  to indicate that the value has been changed from the loaded value or the internal default value
+ *   CHECKED  is used internally for optimization (to avoid an strcmp() every time GET is called).
+ *
+ * TODO:
+ * 1. The linked lists and the mutexes can be removed and the AVL trees can become DICTIONARY.
+ *    This part of the code was written before we add traversal to AVL.
+ *
+ * 2. High level data types could be supported, to simplify the rest of the code:
+ *       MULTIPLE CHOICE  to let the user select one of the supported keywords
+ *                        this would allow users see in comments the available options
+ *
+ *       SIMPLE PATTERN   to let the user define netdata SIMPLE PATTERNS
+ *
+ * 3. Sorting of options should be supported.
+ *    Today, when the ini file is downloaded from the server, the options are shown in the order
+ *    they appear in the linked list (the order they were added, listing changed options first).
+ *    If we remove the linked list, the order they appear in the AVL tree will be used (which is
+ *    random due to simple_hash()).
+ *    Ideally, we support sorting of options when generating the ini file.
+ *
+ * 4. There is no free() operation. So, memory is freed on netdata exit.
+ *
+ * 5. Avoid memory fragmentation
+ *    Since entries are created from multiple threads and a lot of allocations are required
+ *    for each config_option, fragmentation can be a problem for IoT.
+ *
+ * 6. Although this way of managing options is quite flexible and dynamic, it wastes memory
+ *    for the names of the options. Since most of the option names are static, we could provide
+ *    a method to allocate only the dynamic option names.
+ */
+
+#ifndef NETDATA_CONFIG_H
+#define NETDATA_CONFIG_H 1
+
+#include "../libnetdata.h"
+
+#define CONFIG_FILENAME "netdata.conf"
+
+#define CONFIG_SECTION_GLOBAL   "global"
+#define CONFIG_SECTION_WEB      "web"
+#define CONFIG_SECTION_STATSD   "statsd"
+#define CONFIG_SECTION_PLUGINS  "plugins"
+#define CONFIG_SECTION_REGISTRY "registry"
+#define CONFIG_SECTION_HEALTH   "health"
+#define CONFIG_SECTION_BACKEND  "backend"
+#define CONFIG_SECTION_STREAM   "stream"
+
+// these are used to limit the configuration names and values lengths
+// they are not enforced by config.c functions (they will strdup() all strings, no matter of their length)
+#define CONFIG_MAX_NAME 1024
+#define CONFIG_MAX_VALUE 2048
+
+struct config {
+    struct section *sections;
+    netdata_mutex_t mutex;
+    avl_tree_lock index;
+};
+
+extern struct config
+        netdata_config,
+        stream_config;
+
+#define CONFIG_BOOLEAN_NO   0
+#define CONFIG_BOOLEAN_YES  1
+
+#ifndef CONFIG_BOOLEAN_AUTO
+#define CONFIG_BOOLEAN_AUTO 2
+#endif
+
+extern int appconfig_load(struct config *root, char *filename, int overwrite_used);
+
+extern char *appconfig_get(struct config *root, const char *section, const char *name, const char *default_value);
+extern long long appconfig_get_number(struct config *root, const char *section, const char *name, long long value);
+extern LONG_DOUBLE appconfig_get_float(struct config *root, const char *section, const char *name, LONG_DOUBLE value);
+extern int appconfig_get_boolean(struct config *root, const char *section, const char *name, int value);
+extern int appconfig_get_boolean_ondemand(struct config *root, const char *section, const char *name, int value);
+
+extern const char *appconfig_set(struct config *root, const char *section, const char *name, const char *value);
+extern const char *appconfig_set_default(struct config *root, const char *section, const char *name, const char *value);
+extern long long appconfig_set_number(struct config *root, const char *section, const char *name, long long value);
+extern LONG_DOUBLE appconfig_set_float(struct config *root, const char *section, const char *name, LONG_DOUBLE value);
+extern int appconfig_set_boolean(struct config *root, const char *section, const char *name, int value);
+
+extern int appconfig_exists(struct config *root, const char *section, const char *name);
+extern int appconfig_move(struct config *root, const char *section_old, const char *name_old, const char *section_new, const char *name_new);
+
+extern void appconfig_generate(struct config *root, BUFFER *wb, int only_changed);
+
+// ----------------------------------------------------------------------------
+// shortcuts for the default netdata configuration
+
+#define config_load(filename, overwrite_used) appconfig_load(&netdata_config, filename, overwrite_used)
+#define config_get(section, name, default_value) appconfig_get(&netdata_config, section, name, default_value)
+#define config_get_number(section, name, value) appconfig_get_number(&netdata_config, section, name, value)
+#define config_get_float(section, name, value) appconfig_get_float(&netdata_config, section, name, value)
+#define config_get_boolean(section, name, value) appconfig_get_boolean(&netdata_config, section, name, value)
+#define config_get_boolean_ondemand(section, name, value) appconfig_get_boolean_ondemand(&netdata_config, section, name, value)
+
+#define config_set(section, name, default_value) appconfig_set(&netdata_config, section, name, default_value)
+#define config_set_default(section, name, value) appconfig_set_default(&netdata_config, section, name, value)
+#define config_set_number(section, name, value) appconfig_set_number(&netdata_config, section, name, value)
+#define config_set_float(section, name, value) appconfig_set_float(&netdata_config, section, name, value)
+#define config_set_boolean(section, name, value) appconfig_set_boolean(&netdata_config, section, name, value)
+
+#define config_exists(section, name) appconfig_exists(&netdata_config, section, name)
+#define config_move(section_old, name_old, section_new, name_new) appconfig_move(&netdata_config, section_old, name_old, section_new, name_new)
+
+#define config_generate(buffer, only_changed) appconfig_generate(&netdata_config, buffer, only_changed)
+
+#endif /* NETDATA_CONFIG_H */