weave-scope/render/detailed/links.go

package detailed

import (
	"bytes"
	"net/url"
	"strings"
	"text/template"

	"github.com/weaveworks/scope/probe/docker"
	"github.com/weaveworks/scope/report"

	"github.com/ugorji/go/codec"
)

// MetricLink describes a URL referencing a metric.
type MetricLink struct {
	// References the metric id
	ID       string `json:"id"`
	Label    string `json:"label"`
	URL      string `json:"url"`
	Priority int    `json:"priority"`
}

// Variable name for the query within the metrics graph url
const urlQueryVarName = ":query"

var (
	// Available metric links
	linkTemplates = []MetricLink{
		{ID: docker.CPUTotalUsage, Label: "CPU", Priority: 1},
		{ID: docker.MemoryUsage, Label: "Memory", Priority: 2},
	}

	// Prometheus queries for topologies
	topologyQueries = map[string]map[string]*template.Template{
		report.Pod: {
			// `container_memory_usage_bytes` is provided by cAdvisor in Kubelets.
			docker.MemoryUsage: parsedTemplate(`sum(container_memory_usage_bytes{pod_name="{{.Label}}"})`),
			// `container_cpu_usage_seconds_total` is provided by cAdvisor in Kubelets.
			docker.CPUTotalUsage: parsedTemplate(`sum(rate(container_cpu_usage_seconds_total{pod_name="{{.Label}}"}[1m]))`),
		},
		report.Deployment: {
			// `container_memory_usage_bytes` is provided by cAdvisor in Kubelets.
			// Pod names are automatically generated by k8s using the deployment name:
			// https://kubernetes.io/docs/concepts/workloads/controllers/deployment/#pod-template-hash-label
			docker.MemoryUsage: parsedTemplate(`sum(container_memory_usage_bytes{pod_name=~"^{{.Label}}-[^-]+-[^-]+$"})`),
			// `container_cpu_usage_seconds_total` is provided by cAdvisor in Kubelets.
			docker.CPUTotalUsage: parsedTemplate(`sum(rate(container_cpu_usage_seconds_total{pod_name=~"^{{.Label}}-[^-]+-[^-]+$"}[1m]))`),
		},
		report.DaemonSet: {
			// `container_memory_usage_bytes` is provided by cAdvisor in Kubelets.
			// Pod names are automatically generated by k8s using the DaemonSet name.
			docker.MemoryUsage: parsedTemplate(`sum(container_memory_usage_bytes{pod_name=~"^{{.Label}}-[^-]+$"})`),
			// `container_cpu_usage_seconds_total` is provided by cAdvisor in Kubelets.
			docker.CPUTotalUsage: parsedTemplate(`sum(rate(container_cpu_usage_seconds_total{pod_name=~"^{{.Label}}-[^-]+$"}[1m]))`),
		},
		report.Service: {
			// These recording rules must be defined in the prometheus config.
			// NB: Pods need to be labeled and selected by their respective Service name, meaning:
			// - The Service's `spec.selector` needs to select on `name`
			// - The Service's `metadata.name` needs to be the same value as `spec.selector.name`
			docker.MemoryUsage: parsedTemplate(`namespace_label_name:container_memory_usage_bytes:sum{label_name="{{.Label}}"}`),
			docker.CPUTotalUsage: parsedTemplate(`namespace_label_name:container_cpu_usage_seconds_total:sum_rate{label_name="{{.Label}}}`),
		},
	}
)

// NodeMetricLinks returns the links of a node. The links are collected
// by a predefined set but filtered depending on whether a query
// is configured or not for the particular topology.
func NodeMetricLinks(_ report.Report, n report.Node) []MetricLink {
	queries := topologyQueries[n.Topology]
	if len(queries) == 0 {
		return nil
	}

	links := []MetricLink{}
	for _, link := range linkTemplates {
		if _, ok := queries[link.ID]; ok {
			links = append(links, link)
		}
	}

	return links
}

// RenderMetricLinks executes the templated links by supplying the node summary as data.
// `metricsGraphURL` supports placeholders such as `:orgID` and `:query`. If the `:query`
// part is missing, a JSON version will be appended, see `queryParamsAsJSON()` for more info.
// It returns the modified summary.
func RenderMetricLinks(summary NodeSummary, n report.Node, metricsGraphURL string) NodeSummary {
	queries := topologyQueries[n.Topology]
	if len(queries) == 0 || len(summary.MetricLinks) == 0 {
		return summary
	}

	links := []MetricLink{}
	var bs bytes.Buffer
	for _, link := range summary.MetricLinks {
		tpl := queries[link.ID]
		if tpl == nil {
			continue
		}

		bs.Reset()
		if err := tpl.Execute(&bs, summary); err != nil {
			continue
		}

		link.URL = buildURL(bs.String(), metricsGraphURL)
		links = append(links, link)
	}
	summary.MetricLinks = links

	return summary
}

// buildURL puts together the URL by looking at the configured
// `metricsGraphURL`.
func buildURL(query, metricsGraphURL string) string {
	if strings.Contains(metricsGraphURL, urlQueryVarName) {
		return strings.Replace(metricsGraphURL, urlQueryVarName, url.PathEscape(query), -1)
	}

	params, err := queryParamsAsJSON(query)
	if err != nil {
		return ""
	}

	if metricsGraphURL[len(metricsGraphURL)-1] != '/' {
		metricsGraphURL += "/"
	}

	return metricsGraphURL + url.PathEscape(params)
}

// queryParamsAsJSON packs the query into a JSON of the
// format `{"cells":[{"queries":[$query]}]}`.
func queryParamsAsJSON(query string) (string, error) {
	type cell struct {
		Queries []string `json:"queries"`
	}
	type queryParams struct {
		Cells []cell `json:"cells"`
	}
	params := &queryParams{[]cell{{[]string{query}}}}

	buf := &bytes.Buffer{}
	encoder := codec.NewEncoder(buf, &codec.JsonHandle{})
	if err := encoder.Encode(params); err != nil {
		return "", err
	}

	return buf.String(), nil
}

// parsedTemplate initializes unnamed text templates.
func parsedTemplate(query string) *template.Template {
	tpl, err := template.New("").Parse(query)
	if err != nil {
		panic(err)
	}

	return tpl
}