Adding upstream version 1.34.4.

Signed-off-by: Daniel Baumann <daniel@debian.org>

docs/AGGREGATORS.md

@@ -0,0 +1,150 @@
+# Aggregator Plugins
+
+This section is for developers who want to create a new aggregator plugin.
+
+## Aggregator Plugin Guidelines
+
+* A aggregator must conform to the [telegraf.Aggregator][] interface.
+* Aggregators should call `aggregators.Add` in their `init` function to
+  register themselves.  See below for a quick example.
+* To be available within Telegraf itself, plugins must register themselves
+  using a file in `github.com/influxdata/telegraf/plugins/aggregators/all`
+  named according to the plugin name. Make sure you also add build-tags to
+  conditionally build the plugin.
+* Each plugin requires a file called `sample.conf` containing the sample
+  configuration for the plugin in TOML format. Please consult the
+  [Sample Config][] page for the latest style guidelines.
+* Each plugin `README.md` file should include the `sample.conf` file in a
+  section describing the configuration by specifying a `toml` section in the
+  form `toml @sample.conf`. The specified file(s) are then injected
+  automatically into the Readme.
+* The Aggregator plugin will need to keep caches of metrics that have passed
+  through it. This should be done using the builtin `HashID()` function of
+  each metric.
+* When the `Reset()` function is called, all caches should be cleared.
+* Follow the recommended [Code Style][].
+
+[telegraf.Aggregator]: https://godoc.org/github.com/influxdata/telegraf#Aggregator
+[Sample Config]: /docs/developers/SAMPLE_CONFIG.md
+[Code Style]: /docs/developers/CODE_STYLE.md
+
+### Aggregator Plugin Example
+
+### Registration
+
+Registration of the plugin on `plugins/aggregators/all/min.go`:
+
+```go
+//go:build !custom || aggregators || aggregators.min
+
+package all
+
+import _ "github.com/influxdata/telegraf/plugins/aggregators/min" // register plugin
+```
+
+The _build-tags_ in the first line allow to selectively include/exclude your
+plugin when customizing Telegraf.
+
+### Plugin
+
+Content of your plugin file e.g. `min.go`
+
+```go
+//go:generate ../../../tools/readme_config_includer/generator
+package min
+
+// min.go
+
+import (
+    _ "embed"
+
+    "github.com/influxdata/telegraf"
+    "github.com/influxdata/telegraf/plugins/aggregators"
+)
+
+//go:embed sample.conf
+var sampleConfig string
+
+type Min struct {
+    // caches for metric fields, names, and tags
+    fieldCache map[uint64]map[string]float64
+    nameCache  map[uint64]string
+    tagCache   map[uint64]map[string]string
+}
+
+func NewMin() telegraf.Aggregator {
+    m := &Min{}
+    m.Reset()
+    return m
+}
+
+func (*Min) SampleConfig() string {
+    return sampleConfig
+}
+
+func (m *Min) Init() error {
+    return nil
+}
+
+func (m *Min) Add(in telegraf.Metric) {
+    id := in.HashID()
+    if _, ok := m.nameCache[id]; !ok {
+        // hit an uncached metric, create caches for first time:
+        m.nameCache[id] = in.Name()
+        m.tagCache[id] = in.Tags()
+        m.fieldCache[id] = make(map[string]float64)
+        for k, v := range in.Fields() {
+            if fv, ok := convert(v); ok {
+                m.fieldCache[id][k] = fv
+            }
+        }
+    } else {
+        for k, v := range in.Fields() {
+            if fv, ok := convert(v); ok {
+                if _, ok := m.fieldCache[id][k]; !ok {
+                    // hit an uncached field of a cached metric
+                    m.fieldCache[id][k] = fv
+                    continue
+                }
+                if fv < m.fieldCache[id][k] {
+                    // set new minimum
+                    m.fieldCache[id][k] = fv
+                }
+            }
+        }
+    }
+}
+
+func (m *Min) Push(acc telegraf.Accumulator) {
+    for id, _ := range m.nameCache {
+        fields := map[string]interface{}{}
+        for k, v := range m.fieldCache[id] {
+            fields[k+"_min"] = v
+        }
+        acc.AddFields(m.nameCache[id], fields, m.tagCache[id])
+    }
+}
+
+func (m *Min) Reset() {
+    m.fieldCache = make(map[uint64]map[string]float64)
+    m.nameCache = make(map[uint64]string)
+    m.tagCache = make(map[uint64]map[string]string)
+}
+
+func convert(in interface{}) (float64, bool) {
+    switch v := in.(type) {
+    case float64:
+        return v, true
+    case int64:
+        return float64(v), true
+    default:
+        return 0, false
+    }
+}
+
+func init() {
+    aggregators.Add("min", func() telegraf.Aggregator {
+        return NewMin()
+    })
+}
+```