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diff --git a/collectors/charts.d.plugin/README.md b/collectors/charts.d.plugin/README.md new file mode 100644 index 0000000..3d318f2 --- /dev/null +++ b/collectors/charts.d.plugin/README.md @@ -0,0 +1,195 @@ +# 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/`. + + +[]() |