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package main
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import (
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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"net/http"
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"sync"
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)
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type ClusterManager struct {
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sync.Mutex
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Zone string
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metricMapCounters map[string]string
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metricMapGauges map[string]string
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}
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// Simulate prepare the data
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func (c *ClusterManager) ReallyExpensiveAssessmentOfTheSystemState() (
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metrics map[string]float64,
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) {
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metrics = map[string]float64{
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"oom_crashes_total": 42.00,
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"ram_usage": 6.023e23,
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}
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return
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}
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// 通过NewClusterManager方法创建结构体及对应的指标信息，代码如下所示。
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// NewClusterManager creates the two Descs OOMCountDesc and RAMUsageDesc. Note
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// that the zone is set as a ConstLabel. (It's different in each instance of the
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// ClusterManager, but constant over the lifetime of an instance.) Then there is
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// a variable label "host", since we want to partition the collected metrics by
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// host. Since all Descs created in this way are consistent across instances,
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// with a guaranteed distinction by the "zone" label, we can register different
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// ClusterManager instances with the same registry.
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func NewClusterManager(zone string) *ClusterManager {
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return &ClusterManager{
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Zone: zone,
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metricMapGauges: map[string]string{
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"ram_usage": "ram_usage_bytes",
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},
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metricMapCounters: map[string]string{
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"oom_crashes": "oom_crashes_total",
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},
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}
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}
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//首先，采集器必须实现prometheus.Collector接口，也必须实现Describe和Collect方法。实现接口的代码如下所示。
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// Describe simply sends the two Descs in the struct to the channel.
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// Prometheus的注册器调用Collect来抓取参数
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// 将收集的数据传递到Channel中并返回
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// 收集的指标信息来自Describe，可以并发地执行抓取工作，但是必须要保证线程的安全
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func (c *ClusterManager) Describe(ch chan<- *prometheus.Desc) {
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// prometheus.NewDesc(prometheus.BuildFQName(namespace, "", metricName), docString, labels, nil)
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for _, v := range c.metricMapGauges {
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ch <- prometheus.NewDesc(prometheus.BuildFQName(c.Zone, "", v), v, nil, nil)
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}
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for _, v := range c.metricMapCounters {
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ch <- prometheus.NewDesc(prometheus.BuildFQName(c.Zone, "", v), v, nil, nil)
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}
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}
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// Collect方法是核心，它会抓取你需要的所有数据，根据需求对其进行分析，然后将指标发送回客户端库。
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// 用于传递所有可能指标的定义描述符
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// 可以在程序运行期间添加新的描述，收集新的指标信息
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// 重复的描述符将被忽略。两个不同的Collector不要设置相同的描述符
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func (c *ClusterManager) Collect(ch chan<- prometheus.Metric) {
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c.Lock()
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defer c.Unlock()
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m := c.ReallyExpensiveAssessmentOfTheSystemState()
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for k, v := range m {
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t := prometheus.GaugeValue
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if c.metricMapCounters[k] != "" {
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t = prometheus.CounterValue
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}
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c.registerConstMetric(ch, k, v, t)
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}
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}
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// 用于传递所有可能指标的定义描述符给指标
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func (c *ClusterManager) registerConstMetric(ch chan<- prometheus.Metric, metric string, val float64, valType prometheus.ValueType, labelValues ...string) {
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descr := prometheus.NewDesc(prometheus.BuildFQName(c.Zone, "", metric), metric, nil, nil)
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if m, err := prometheus.NewConstMetric(descr, valType, val, labelValues...); err == nil {
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ch <- m
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}
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}
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func main() {
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workerCA := NewClusterManager("xiaodian")
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reg := prometheus.NewPedanticRegistry()
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reg.MustRegister(workerCA)
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//当promhttp.Handler()被执行时，所有metric被序列化输出。题外话，其实输出的格式既可以是plain text，也可以是protocol Buffers。
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http.Handle("/metrics", promhttp.HandlerFor(reg, promhttp.HandlerOpts{}))
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http.ListenAndServe(":9100", nil)
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}
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