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, 64 insertions, 0 deletions

diff --git a/database/rrdvar.h b/database/rrdvar.h
new file mode 100644
index 0000000000..48c27cf7e6
--- /dev/null
+++ b/database/rrdvar.h
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#ifndef NETDATA_RRDVAR_H
+#define NETDATA_RRDVAR_H 1
+
+#include "rrd.h"
+
+extern int rrdvar_compare(void *a, void *b);
+
+typedef enum rrdvar_type {
+    RRDVAR_TYPE_CALCULATED              = 1,
+    RRDVAR_TYPE_TIME_T                  = 2,
+    RRDVAR_TYPE_COLLECTED               = 3,
+    RRDVAR_TYPE_TOTAL                   = 4,
+    RRDVAR_TYPE_INT                     = 5
+} RRDVAR_TYPE;
+
+typedef enum rrdvar_options {
+    RRDVAR_OPTION_DEFAULT                    = 0,
+    RRDVAR_OPTION_ALLOCATED                  = (1 << 0), // the value ptr is allocated (not a reference)
+    RRDVAR_OPTION_CUSTOM_HOST_VAR            = (1 << 1), // this is a custom host variable, not associated with a dimension
+    RRDVAR_OPTION_CUSTOM_CHART_VAR           = (1 << 2), // this is a custom chart variable, not associated with a dimension
+    RRDVAR_OPTION_RRDCALC_LOCAL_VAR          = (1 << 3), // this is a an alarm variable, attached to a chart
+    RRDVAR_OPTION_RRDCALC_FAMILY_VAR         = (1 << 4), // this is a an alarm variable, attached to a family
+    RRDVAR_OPTION_RRDCALC_HOST_CHARTID_VAR   = (1 << 5), // this is a an alarm variable, attached to the host, using the chart id
+    RRDVAR_OPTION_RRDCALC_HOST_CHARTNAME_VAR = (1 << 6), // this is a an alarm variable, attached to the host, using the chart name
+} RRDVAR_OPTIONS;
+
+// the variables as stored in the variables indexes
+// there are 3 indexes:
+// 1. at each chart   (RRDSET.rrdvar_root_index)
+// 2. at each context (RRDFAMILY.rrdvar_root_index)
+// 3. at each host    (RRDHOST.rrdvar_root_index)
+struct rrdvar {
+    avl avl;
+
+    char *name;
+    uint32_t hash;
+
+    RRDVAR_TYPE type;
+    RRDVAR_OPTIONS options;
+
+    void *value;
+
+    time_t last_updated;
+};
+
+extern RRDVAR *rrdvar_custom_host_variable_create(RRDHOST *host, const char *name);
+extern void rrdvar_custom_host_variable_set(RRDHOST *host, RRDVAR *rv, calculated_number value);
+extern int foreach_host_variable_callback(RRDHOST *host, int (*callback)(RRDVAR *rv, void *data), void *data);
+extern void rrdvar_free_remaining_variables(RRDHOST *host, avl_tree_lock *tree_lock);
+
+extern int  rrdvar_callback_for_all_host_variables(RRDHOST *host, int (*callback)(void *rrdvar, void *data), void *data);
+
+extern calculated_number rrdvar2number(RRDVAR *rv);
+
+#define RRDVAR_MAX_LENGTH 1024
+
+extern int rrdvar_fix_name(char *variable);
+
+extern RRDVAR *rrdvar_create_and_index(const char *scope, avl_tree_lock *tree, const char *name, RRDVAR_TYPE type, RRDVAR_OPTIONS options, void *value);
+extern void rrdvar_free(RRDHOST *host, avl_tree_lock *tree, RRDVAR *rv);
+
+#endif //NETDATA_RRDVAR_H