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

66 files changed, 5817 insertions, 0 deletions

diff --git a/collectors/charts.d.plugin/Makefile.am b/collectors/charts.d.plugin/Makefile.am
new file mode 100644
index 0000000000..1d580c947d
--- /dev/null
+++ b/collectors/charts.d.plugin/Makefile.am
@@ -0,0 +1,94 @@
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+MAINTAINERCLEANFILES = $(srcdir)/Makefile.in
+
+CLEANFILES = \
+	charts.d.plugin \
+	$(NULL)
+
+include $(top_srcdir)/build/subst.inc
+SUFFIXES = .in
+
+dist_libconfig_DATA = \
+    charts.d.conf \
+    $(NULL)
+
+dist_plugins_SCRIPTS = \
+	charts.d.dryrun-helper.sh \
+	charts.d.plugin \
+	loopsleepms.sh.inc \
+	$(NULL)
+
+dist_noinst_DATA = \
+	charts.d.plugin.in \
+	ap/README.md \
+    apache/README.md \
+    apcupsd/README.md \
+    cpu_apps/README.md \
+    cpufreq/README.md \
+    example/README.md \
+    exim/README.md \
+    hddtemp/README.md \
+    libreswan/README.md \
+    load_average/README.md \
+    mem_apps/README.md \
+    mysql/README.md \
+    nginx/README.md \
+    nut/README.md \
+    opensips/README.md \
+    phpfpm/README.md \
+    postfix/README.md \
+    sensors/README.md \
+    squid/README.md \
+    tomcat/README.md \
+	$(NULL)
+
+dist_charts_SCRIPTS = \
+	$(NULL)
+
+dist_charts_DATA = \
+	ap/ap.chart.sh \
+	apcupsd/apcupsd.chart.sh \
+	apache/apache.chart.sh \
+	cpu_apps/cpu_apps.chart.sh \
+	cpufreq/cpufreq.chart.sh \
+	example/example.chart.sh \
+	exim/exim.chart.sh \
+	hddtemp/hddtemp.chart.sh \
+	libreswan/libreswan.chart.sh \
+	load_average/load_average.chart.sh \
+	mem_apps/mem_apps.chart.sh \
+	mysql/mysql.chart.sh \
+	nginx/nginx.chart.sh \
+	nut/nut.chart.sh \
+	opensips/opensips.chart.sh \
+	phpfpm/phpfpm.chart.sh \
+	postfix/postfix.chart.sh \
+	sensors/sensors.chart.sh \
+	squid/squid.chart.sh \
+	tomcat/tomcat.chart.sh \
+	$(NULL)
+
+chartsconfigdir=$(libconfigdir)/charts.d
+dist_chartsconfig_DATA = \
+    ap/ap.conf \
+    apache/apache.conf \
+    apcupsd/apcupsd.conf \
+    cpu_apps/cpu_apps.conf \
+    cpufreq/cpufreq.conf \
+    example/example.conf \
+    exim/exim.conf \
+    hddtemp/hddtemp.conf \
+    libreswan/libreswan.conf \
+    load_average/load_average.conf \
+    mem_apps/mem_apps.conf \
+    mysql/mysql.conf \
+    nginx/nginx.conf \
+    nut/nut.conf \
+    opensips/opensips.conf \
+    phpfpm/phpfpm.conf \
+    postfix/postfix.conf \
+    sensors/sensors.conf \
+    squid/squid.conf \
+    tomcat/tomcat.conf \
+    $(NULL)
diff --git a/collectors/charts.d.plugin/README.md b/collectors/charts.d.plugin/README.md
new file mode 100644
index 0000000000..b224bffe3a
--- /dev/null
+++ b/collectors/charts.d.plugin/README.md
@@ -0,0 +1,193 @@
+# charts.d.plugin
+
+`charts.d.plugin` is a netdata external plugin. It is an **orchestrator** for data collection modules written in `BASH` v4+.
+
+1. It runs as an independent process `ps fax` shows it
+2. It is started and stopped automatically by netdata
+3. It communicates with netdata via a unidirectional pipe (sending data to the netdata daemon)
+4. Supports any number of data collection **modules**
+
+`charts.d.plugin` has been designed so that the actual script that will do data collection will be permanently in
+memory, collecting data with as little overheads as possible
+(i.e. initialize once, repeatedly collect values with minimal overhead).
+
+`charts.d.plugin` looks for scripts in `/usr/lib/netdata/charts.d`.
+The scripts should have the filename suffix: `.chart.sh`.
+
+## Configuration
+
+`charts.d.plugin` itself can be configured using the configuration file `/etc/netdata/charts.d.conf`
+(to edit it on your system run `/etc/netdata/edit-config charts.d.conf`). This file is also a BASH script.
+
+In this file, you can place statements like this:
+
+```
+enable_all_charts="yes"
+X="yes"
+Y="no"
+```
+
+where `X` and `Y` are the names of individual charts.d collector scripts.
+When set to `yes`, charts.d will evaluate the collector script (see below).
+When set to `no`, charts.d will ignore the collector script.
+
+The variable `enable_all_charts` sets the default enable/disable state for all charts.
+
+## A charts.d module
+
+A `charts.d.plugin` module is a BASH script defining a few functions.
+
+For a module called `X`, the following criteria must be met:
+
+1. The module script must be called `X.chart.sh` and placed in `/usr/libexec/netdata/charts.d`.
+
+2. If the module needs a configuration, it should be called `X.conf` and placed in `/etc/netdata/charts.d`.
+   The configuration file `X.conf` is also a BASH script itself.
+   To edit the default files supplied by netdata run `/etc/netdata/edit-config charts.d/X.conf`,
+   where `X` is the name of the module.
+
+3. All functions and global variables defined in the script and its configuration, must begin with `X_`.
+
+4. The following functions must be defined:
+
+   - `X_check()` - returns 0 or 1 depending on whether the module is able to run or not
+      (following the standard Linux command line return codes: 0 = OK, the collector can operate and 1 = FAILED,
+      the collector cannot be used).
+
+   - `X_create()` - creates the netdata charts, following the standard netdata plugin guides as described in
+      **[External Plugins](../plugins.d/)** (commands `CHART` and `DIMENSION`).
+      The return value does matter: 0 = OK, 1 = FAILED.
+
+   - `X_update()` - collects the values for the defined charts, following the standard netdata plugin guides
+      as described in **[External Plugins](../plugins.d/)** (commands `BEGIN`, `SET`, `END`).
+      The return value also matters: 0 = OK, 1 = FAILED.
+
+5. The following global variables are available to be set:
+   - `X_update_every` - is the data collection frequency for the module script, in seconds.
+
+The module script may use more functions or variables. But all of them must begin with `X_`.
+
+The standard netdata plugin variables are also available (check **[External Plugins](../plugins.d/)**). 
+
+### X_check()
+
+The purpose of the BASH function `X_check()` is to check if the module can collect data (or check its config).
+
+For example, if the module is about monitoring a local mysql database, the `X_check()` function may attempt to
+connect to a local mysql database to find out if it can read the values it needs.
+
+`X_check()` is run only once for the lifetime of the module.
+
+### X_create()
+
+The purpose of the BASH function `X_create()` is to create the charts and dimensions using the standard netdata
+plugin guides (**[External Plugins](../plugins.d/)**).
+
+`X_create()` will be called just once and only after `X_check()` was successful.
+You can however call it yourself when there is need for it (for example to add a new dimension to an existing chart).
+
+A non-zero return value will disable the collector.
+
+### X_update()
+
+`X_update()` will be called repeatedly every `X_update_every` seconds, to collect new values and send them to netdata,
+following the netdata plugin guides (**[External Plugins](../plugins.d/)**).
+
+The function will be called with one parameter: microseconds since the last time it was run. This value should be
+appended to the `BEGIN` statement of every chart updated by the collector script.
+
+A non-zero return value will disable the collector.
+
+### Useful functions charts.d provides
+
+Module scripts can use the following charts.d functions:
+
+#### require_cmd command
+
+`require_cmd()` will check if a command is available in the running system.
+
+For example, your `X_check()` function may use it like this:
+
+```sh
+mysql_check() {
+    require_cmd mysql || return 1
+    return 0
+}
+```
+
+Using the above, if the command `mysql` is not available in the system, the `mysql` module will be disabled.
+
+#### fixid "string"
+
+`fixid()` will get a string and return a properly formatted id for a chart or dimension.
+
+This is an expensive function that should not be used in `X_update()`.
+You can keep the generated id in a BASH associative array to have the values availables in `X_update()`, like this:
+
+```sh
+declare -A X_ids=()
+X_create() {
+   local name="a very bad name for id"
+
+   X_ids[$name]="$(fixid "$name")"
+}
+
+X_update() {
+   local microseconds="$1"
+
+   ...
+   local name="a very bad name for id"
+   ...
+
+   echo "BEGIN ${X_ids[$name]} $microseconds"
+   ...
+}
+```
+
+### Debugging your collectors
+
+You can run `charts.d.plugin` by hand with something like this:
+
+```sh
+# become user netdata
+sudo su -s /bin/sh netdata
+
+# run the plugin in debug mode
+/usr/libexec/netdata/plugins.d/charts.d.plugin debug 1 X Y Z
+```
+
+Charts.d will run in `debug` mode, with an update frequency of `1`, evaluating only the collector scripts
+`X`, `Y` and `Z`. You can define zero or more module scripts. If none is defined, charts.d will evaluate all
+module scripts available.
+
+Keep in mind that if your configs are not in `/etc/netdata`, you should do the following before running
+`charts.d.plugin`:
+
+```sh
+export NETDATA_USER_CONFIG_DIR="/path/to/etc/netdata"
+```
+
+Also, remember that netdata runs `chart.d.plugin` as user `netdata` (or any other user netdata is configured to run as).
+
+
+## Running multiple instances of charts.d.plugin
+
+`charts.d.plugin` will call the `X_update()` function one after another. This means that a delay in collector `X`
+will also delay the collection of `Y` and `Z`.
+
+You can have multiple `charts.d.plugin` running to overcome this problem.
+
+This is what you need to do:
+
+1. Decide a new name for the new charts.d instance: example `charts2.d`.
+
+2. Create/edit the files `/etc/netdata/charts.d.conf` and `/etc/netdata/charts2.d.conf` and enable / disable the
+   module you want each to run. Remember to set `enable_all_charts="no"` to both of them, and enable the individual
+   modules for each.
+   
+3. link `/usr/libexec/netdata/plugins.d/charts.d.plugin` to `/usr/libexec/netdata/plugins.d/charts2.d.plugin`.
+   Netdata will spawn a new charts.d process.
+
+Execute the above in this order, since netdata will (by default) attempt to start new plugins soon after they are
+created in `/usr/libexec/netdata/plugins.d/`.
+
diff --git a/collectors/charts.d.plugin/ap/README.md b/collectors/charts.d.plugin/ap/README.md
new file mode 100644
index 0000000000..1b82f49bac
--- /dev/null
+++ b/collectors/charts.d.plugin/ap/README.md
@@ -0,0 +1,86 @@
+# Access Point Plugin (ap)
+
+The `ap` collector visualizes data related to access points.
+
+The source code is [here](https://github.com/netdata/netdata/blob/master/charts.d/ap.chart.sh).
+
+## Example netdata charts
+
+![image](https://cloud.githubusercontent.com/assets/2662304/12377654/9f566e88-bd2d-11e5-855a-e0ba96b8fd98.png)
+
+## How it works
+
+It does the following:
+
+1. Runs `iw dev` searching for interfaces that have `type AP`.
+
+   From the same output it collects the SSIDs each AP supports by looking for lines `ssid NAME`.
+
+   Example:
+```sh
+# iw dev
+phy#0
+        Interface wlan0
+                ifindex 3
+                wdev 0x1
+                addr 7c:dd:90:77:34:2a
+                ssid TSAOUSIS
+                type AP
+                channel 7 (2442 MHz), width: 20 MHz, center1: 2442 MHz
+```
+
+
+2. For each interface found, it runs `iw INTERFACE station dump`.
+
+   From the output is collects:
+
+   - rx/tx bytes
+   - rx/tx packets
+   - tx retries
+   - tx failed
+   - signal strength
+   - rx/tx bitrate
+   - expected throughput
+
+   Example:
+
+```sh
+# iw wlan0 station dump
+Station 40:b8:37:5a:ed:5e (on wlan0)
+        inactive time:  910 ms
+        rx bytes:       15588897
+        rx packets:     127772
+        tx bytes:       52257763
+        tx packets:     95802
+        tx retries:     2162
+        tx failed:      28
+        signal:         -43 dBm
+        signal avg:     -43 dBm
+        tx bitrate:     65.0 MBit/s MCS 7
+        rx bitrate:     1.0 MBit/s
+        expected throughput:    32.125Mbps
+        authorized:     yes
+        authenticated:  yes
+        preamble:       long
+        WMM/WME:        yes
+        MFP:            no
+        TDLS peer:      no
+```
+
+3. For each interface found, it creates 6 charts:
+
+   - Number of Connected clients
+   - Bandwidth for all clients
+   - Packets for all clients
+   - Transmit Issues for all clients
+   - Average Signal among all clients
+   - Average Bitrate (including average expected throughput) among all clients
+
+## Configuration
+
+You can only set `ap_update_every=NUMBER` to `/etc/netdata/charts.d/ap.conf`, to give the data collection frequency.
+To edit this file on your system run `/etc/netdata/edit-config charts.d/ap.conf`.
+
+## Auto-detection
+
+The plugin is able to auto-detect if you are running access points on your linux box.
diff --git a/collectors/charts.d.plugin/ap/ap.chart.sh b/collectors/charts.d.plugin/ap/ap.chart.sh
new file mode 100644
index 0000000000..ccc36120cd
--- /dev/null
+++ b/collectors/charts.d.plugin/ap/ap.chart.sh
@@ -0,0 +1,182 @@
+# shellcheck shell=bash
+# no need for shebang - this file is loaded from charts.d.plugin
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+# netdata
+# real-time performance and health monitoring, done right!
+# (C) 2016 Costa Tsaousis <costa@tsaousis.gr>
+#
+
+# _update_every is a special variable - it holds the number of seconds
+# between the calls of the _update() function
+ap_update_every=
+ap_priority=6900
+
+declare -A ap_devs=()
+
+# _check is called once, to find out if this chart should be enabled or not
+ap_check() {
+	require_cmd iw || return 1
+	local ev
+	ev=$(run iw dev | awk '
+		BEGIN {
+			i = "";
+			ssid = "";
+			ap = 0;
+		}
+		/^[ \t]+Interface / {
+			if( ap == 1 ) {
+				print "ap_devs[" i "]=\"" ssid "\""
+			}
+
+			i = $2;
+			ssid = "";
+			ap = 0;
+		}
+		/^[ \t]+ssid / { ssid = $2; }
+		/^[ \t]+type AP$/ { ap = 1; }
+		END {
+			if( ap == 1 ) {
+				print "ap_devs[" i "]=\"" ssid "\""
+			}
+		}
+	')
+	eval "${ev}"
+
+	# this should return:
+	#  - 0 to enable the chart
+	#  - 1 to disable the chart
+
+	[ ${#ap_devs[@]} -gt 0 ] && return 0
+	error "no devices found in AP mode, with 'iw dev'"
+	return 1
+}
+
+# _create is called once, to create the charts
+ap_create() {
+	local ssid dev
+
+	for dev in "${!ap_devs[@]}"
+	do
+		ssid="${ap_devs[${dev}]}"
+
+		# create the chart with 3 dimensions