New upstream version 1.11.0+dfsgupstream/1.11.0+dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+# Data Collection Plugins
+
+netdata supports **internal** and **external** data collection plugins:
+
+- **internal** plugins are written in `C` and run as threads inside the netdata daemon.
+
+- **external** plugins may be written in any computer language and are spawn as independent long-running processes by the netdata daemon.
+   They communicate with the netdata daemon via `pipes` (`stdout` communication).
+
+To minimize the number of processes spawn for data collection, netdata also supports **plugin orchestrators**.
+
+- **plugin orchestrators** are external plugins that do not collect any data by themeselves.
+   Instead they support data collection **modules** written in the language of the orchestrator.
+   Usually the orchestrator provides a higher level abstraction, making it ideal for writing new
+   data collection modules with the minimum of code.
+   
+   Currently netdata provides plugin orchestrators
+   BASH v4+ [charts.d.plugin](charts.d.plugin),
+   node.js [node.d.plugin](node.d.plugin) and
+   python v2+ (including v3) [python.d.plugin](python.d.plugin).
+
+## Netdata Plugins
+
+plugin|lang|O/S|runs as|modular|description
+:---:|:---:|:---:|:---:|:---:|:---
+[apps.plugin](apps.plugin/)|`C`|linux, freebsd|external|-|monitors the whole process tree on Linux and FreeBSD and breaks down system resource usage by **process**, **user** and **user group**.
+[cgroups.plugin](cgroups.plugin/)|`C`|linux|internal|-|collects resource usage of **Containers**, libvirt **VMs** and **systemd services**, on Linux systems
+[charts.d.plugin](charts.d.plugin/)|`BASH` v4+|any|external|yes|a **plugin orchestrator** for data collection modules written in `BASH` v4+.
+[checks.plugin](checks.plugin/)|`C`|any|internal|-|a debugging plugin (by default it is disabled)
+[diskspace.plugin](diskspace.plugin/)|`C`|linux|internal|-|collects disk space usage metrics on Linux mount points
+[fping.plugin](fping.plugin/)|`C`|any|external|-|measures network latency, jitter and packet loss between the monitored node and any number of remote network end points.
+[freebsd.plugin](freebsd.plugin/)|`C`|freebsd|internal|yes|collects resource usage and performance data on FreeBSD systems
+[freeipmi.plugin](freeipmi.plugin/)|`C`|linux, freebsd|external|-|collects metrics from enterprise hardware sensors, on Linux and FreeBSD servers.
+[idlejitter.plugin](idlejitter.plugin/)|`C`|any|internal|-|measures CPU latency and jitter on all operating systems
+[macos.plugin](macos.plugin/)|`C`|macos|internal|yes|collects resource usage and performance data on MacOS systems
+[nfacct.plugin](nfacct.plugin/)|`C`|linux|internal|-|collects netfilter firewall, connection tracker and accounting metrics using `libmnl` and `libnetfilter_acct`
+[node.d.plugin](node.d.plugin/)|`node.js`|any|external|yes|a **plugin orchestrator** for data collection modules written in `node.js`.
+[plugins.d](plugins.d/)|`C`|any|internal|-|implements the **external plugins** API and serves external plugins
+[proc.plugin](proc.plugin/)|`C`|linux|internal|yes|collects resource usage and performance data on Linux systems
+[python.d.plugin](python.d.plugin/)|`python` v2+|any|external|yes|a **plugin orchestrator** for data collection modules written in `python` v2 or v3 (both are supported).
+[statsd.plugin](statsd.plugin/)|`C`|any|internal|-|implements a high performance **statsd** server for netdata
+[tc.plugin](tc.plugin/)|`C`|linux|internal|-|collects traffic QoS metrics (`tc`) of Linux network interfaces
+
+## Enabling and Disabling plugins
+
+Each plugin can be enabled or disabled via `netdata.conf`, section `[plugins]`.
+
+At this section there a list of all the plugins with a boolean setting to enable them or disable them. 
+
+The exception is `statsd.plugin` that has its own `[statsd]` section.
+
+Once a plugin is enabled, consult the page of each plugin for additional configuration options.
+
+All **external plugins** are managed by [plugins.d](plugins.d/), which provides additional management options.
+
+### Internal Plugins
+
+Each of the internal plugins runs as a thread inside the netdata daemon.
+Once this thread has started, the plugin may spawn additional threads according to its design.
+
+#### Internal Plugins API
+
+The internal data collection API consists of the following calls:
+
+```c
+collect_data() {
+    // collect data here (one iteration)
+    
+    collected_number collected_value = collect_a_value();
+    
+    // give the metrics to netdata
+    
+    static RRDSET *st = NULL; // the chart
+    static RRDDIM *rd = NULL; // a dimension attached to this chart
+    
+    if(unlikely(!st)) {
+        // we haven't created this chart before
+        // create it now
+        st = rrdset_create_localhost(
+                "type"
+                , "id"
+                , "name"
+                , "family"
+                , "context"
+                , "Chart Title"
+                , "units"
+                , "plugin-name"
+                , "module-name"
+                , priority
+                , update_every
+                , chart_type
+        );
+
+        // attach a metric to it
+        rd = rrddim_add(st, "id", "name", multiplier, divider, algorithm);
+    }
+    else {
+        // this chart is already created
+        // let netdata know we start a new iteration on it
+        rrdset_next(st);
+    }
+    
+    // give the collected value(s) to the chart
+    rrddim_set_by_pointer(st, rd, collected_value);
+    
+    // signal netdata we are done with this iteration
+    rrdset_done(st);
+}
+```
+
+Of course netdata has a lot of libraries to help you also in collecting the metrics.
+The best way to find your way through this, is to examine what other similar plugins do.
+
+
+### External Plugins
+
+**External plugins** use the API and are managed by [plugins.d](plugins.d/).
+