plugin_name: python.d.plugin
modules:
  - meta:
      plugin_name: python.d.plugin
      module_name: go_expvar
      monitored_instance:
        name: Go applications (EXPVAR)
        link: "https://pkg.go.dev/expvar"
        categories:
          - data-collection.apm
        icon_filename: "go.png"
      related_resources:
        integrations:
          list: []
      info_provided_to_referring_integrations:
        description: ""
      keywords:
        - go
        - expvar
        - application
      most_popular: false
    overview:
      data_collection:
        metrics_description: "This collector monitors Go applications that expose their metrics with the use of the `expvar` package from the Go standard library. It produces charts for Go runtime memory statistics and optionally any number of custom charts."
        method_description: "It connects via http to gather the metrics exposed via the `expvar` package."
      supported_platforms:
        include: []
        exclude: []
      multi_instance: true
      additional_permissions:
        description: ""
      default_behavior:
        auto_detection:
          description: ""
        limits:
          description: ""
        performance_impact:
          description: ""
    setup:
      prerequisites:
        list:
          - title: "Enable the go_expvar collector"
            description: |
              The `go_expvar` collector is disabled by default. To enable it, use `edit-config` from the Netdata [config directory](https://github.com/netdata/netdata/blob/master/docs/configure/nodes.md), which is typically at `/etc/netdata`, to edit the `python.d.conf` file.

              ```bash
              cd /etc/netdata   # Replace this path with your Netdata config directory, if different
              sudo ./edit-config python.d.conf
              ```

              Change the value of the `go_expvar` setting to `yes`. Save the file and restart the Netdata Agent with `sudo systemctl restart netdata`, or the [appropriate method](https://github.com/netdata/netdata/blob/master/docs/configure/start-stop-restart.md) for your system.
          - title: "Sample `expvar` usage in a Go application"
            description: |
              The `expvar` package exposes metrics over HTTP and is very easy to use.
              Consider this minimal sample below:
              
              ```go
              package main
              
              import (
                      _ "expvar"
                      "net/http"
              )
              
              func main() {
                      http.ListenAndServe("127.0.0.1:8080", nil)
              }
              ```
              
              When imported this way, the `expvar` package registers a HTTP handler at `/debug/vars` that
              exposes Go runtime's memory statistics in JSON format. You can inspect the output by opening
              the URL in your browser (or by using `wget` or `curl`).
              
              Sample output:
              
              ```json
              {
              "cmdline": ["./expvar-demo-binary"],
              "memstats": {"Alloc":630856,"TotalAlloc":630856,"Sys":3346432,"Lookups":27, <omitted for brevity>}
              }
              ```
              
              You can of course expose and monitor your own variables as well.
              Here is a sample Go application that exposes a few custom variables:
              
              ```go
              package main
              
              import (
                  "expvar"
                  "net/http"
                  "runtime"
                  "time"
              )
              
              func main() {
              
                  tick := time.NewTicker(1 * time.Second)
                  num_go := expvar.NewInt("runtime.goroutines")
                  counters := expvar.NewMap("counters")
                  counters.Set("cnt1", new(expvar.Int))
                  counters.Set("cnt2", new(expvar.Float))
              
                  go http.ListenAndServe(":8080", nil)
              
                  for {
                      select {
                      case <- tick.C:
                          num_go.Set(int64(runtime.NumGoroutine()))
                          counters.Add("cnt1", 1)
                          counters.AddFloat("cnt2", 1.452)
                      }
                  }
              }
              ```
              
              Apart from the runtime memory stats, this application publishes two counters and the
              number of currently running Goroutines and updates these stats every second.
      configuration:
        file:
          name: python.d/go_expvar.conf
        options:
          description: |
            There are 2 sections:
            
            * Global variables
            * One or more JOBS that can define multiple different instances to monitor.
            
            The following options can be defined globally: priority, penalty, autodetection_retry, update_every, but can also be defined per JOB to override the global values.
            
            Additionally, the following collapsed table contains all the options that can be configured inside a JOB definition.
            
            Every configuration JOB starts with a `job_name` value which will appear in the dashboard, unless a `name` parameter is specified. Each JOB can be used to monitor a different Go application.
          folding:
            title: "Config options"
            enabled: true
          list:
            - name: update_every
              description: Sets the default data collection frequency.
              default_value: 5
              required: false
            - name: priority
              description: Controls the order of charts at the netdata dashboard.
              default_value: 60000
              required: false
            - name: autodetection_retry
              description: Sets the job re-check interval in seconds.
              default_value: 0
              required: false
            - name: penalty
              description: Indicates whether to apply penalty to update_every in case of failures.
              default_value: yes
              required: false
            - name: name
              description: Job name. This value will overwrite the `job_name` value. JOBS with the same name are mutually exclusive. Only one of them will be allowed running at any time. This allows autodetection to try several alternatives and pick the one that works.
              default_value: ""
              required: false
            - name: url
              description: the URL and port of the expvar endpoint. Please include the whole path of the endpoint, as the expvar handler can be installed in a non-standard location.
              default_value: ""
              required: true
            - name: user
              description: If the URL is password protected, this is the username to use.
              default_value: ""
              required: false
            - name: pass
              description: If the URL is password protected, this is the password to use.
              default_value: ""
              required: false
            - name: collect_memstats
              description: Enables charts for Go runtime's memory statistics.
              default_value: ""
              required: false
            - name: extra_charts
              description: Defines extra data/charts to monitor, please see the example below.
              default_value: ""
              required: false
        examples:
          folding:
            enabled: false
            title: "Config"
          list:
            - name: Monitor a Go app1 application
              description: |
                The example below sets a configuration for a Go application, called `app1`. Besides the `memstats`, the application also exposes two counters and the number of currently running Goroutines and updates these stats every second.
                
                The `go_expvar` collector can monitor these as well with the use of the `extra_charts` configuration variable.
                
                The `extra_charts` variable is a YaML list of Netdata chart definitions.
                Each chart definition has the following keys:
                
                ```
                id:         Netdata chart ID
                options:    a key-value mapping of chart options
                lines:      a list of line definitions
                ```
                
                **Note: please do not use dots in the chart or line ID field.
                See [this issue](https://github.com/netdata/netdata/pull/1902#issuecomment-284494195) for explanation.**
                
                Please see these two links to the official Netdata documentation for more information about the values:
                
                -   [External plugins - charts](https://github.com/netdata/netdata/blob/master/collectors/plugins.d/README.md#chart)
                -   [Chart variables](https://github.com/netdata/netdata/blob/master/collectors/python.d.plugin/README.md#global-variables-order-and-chart)
                
                **Line definitions**
                
                Each chart can define multiple lines (dimensions).
                A line definition is a key-value mapping of line options.
                Each line can have the following options:
                
                ```
                # mandatory
                expvar_key: the name of the expvar as present in the JSON output of /debug/vars endpoint
                expvar_type: value type; supported are "float" or "int"
                id: the id of this line/dimension in Netdata
                
                # optional - Netdata defaults are used if these options are not defined
                name: ''
                algorithm: absolute
                multiplier: 1
                divisor: 100 if expvar_type == float, 1 if expvar_type == int
                hidden: False
                ```
                
                Please see the following link for more information about the options and their default values:
                [External plugins - dimensions](https://github.com/netdata/netdata/blob/master/collectors/plugins.d/README.md#dimension)
                
                Apart from top-level expvars, this plugin can also parse expvars stored in a multi-level map;
                All dicts in the resulting JSON document are then flattened to one level.
                Expvar names are joined together with '.' when flattening.
                
                Example:
                
                ```
                {
                    "counters": {"cnt1": 1042, "cnt2": 1512.9839999999983},
                    "runtime.goroutines": 5
                }
                ```
                
                In the above case, the exported variables will be available under `runtime.goroutines`,
                `counters.cnt1` and `counters.cnt2` expvar_keys. If the flattening results in a key collision,
                the first defined key wins and all subsequent keys with the same name are ignored.
              config: |
                app1:
                 name : 'app1'
                 url  : 'http://127.0.0.1:8080/debug/vars'
                 collect_memstats: true
                 extra_charts:
                   - id: "runtime_goroutines"
                     options:
                       name: num_goroutines
                       title: "runtime: number of goroutines"
                       units: goroutines
                       family: runtime
                       context: expvar.runtime.goroutines
                       chart_type: line
                     lines:
                       - {expvar_key: 'runtime.goroutines', expvar_type: int, id: runtime_goroutines}
                   - id: "foo_counters"
                     options:
                       name: counters
                       title: "some random counters"
                       units: awesomeness
                       family: counters
                       context: expvar.foo.counters
                       chart_type: line
                     lines:
                       - {expvar_key: 'counters.cnt1', expvar_type: int, id: counters_cnt1}
                       - {expvar_key: 'counters.cnt2', expvar_type: float, id: counters_cnt2}
    troubleshooting:
      problems:
        list: []
    alerts: []
    metrics:
      folding:
        title: Metrics
        enabled: false
      description: ""
      availability: []
      scopes:
        - name: global
          description: "These metrics refer to the entire monitored application."
          labels: []
          metrics:
            - name: expvar.memstats.heap
              description: "memory: size of heap memory structures"
              unit: "KiB"
              chart_type: line
              dimensions:
                - name: alloc
                - name: inuse
            - name: expvar.memstats.stack
              description: "memory: size of stack memory structures"
              unit: "KiB"
              chart_type: line
              dimensions:
                - name: inuse
            - name: expvar.memstats.mspan
              description: "memory: size of mspan memory structures"
              unit: "KiB"
              chart_type: line
              dimensions:
                - name: inuse
            - name: expvar.memstats.mcache
              description: "memory: size of mcache memory structures"
              unit: "KiB"
              chart_type: line
              dimensions:
                - name: inuse
            - name: expvar.memstats.live_objects
              description: "memory: number of live objects"
              unit: "objects"
              chart_type: line
              dimensions:
                - name: live
            - name: expvar.memstats.sys
              description: "memory: size of reserved virtual address space"
              unit: "KiB"
              chart_type: line
              dimensions:
                - name: sys
            - name: expvar.memstats.gc_pauses
              description: "memory: average duration of GC pauses"
              unit: "ns"
              chart_type: line
              dimensions:
                - name: avg