feat: agent health monitor

internal/watcher/health/monitor/agent_proxied.go

@@ -0,0 +1,75 @@
+package monitor
+
+import (
+	"encoding/json"
+	"errors"
+	"net/http"
+	"net/url"
+
+	agentPkg "github.com/yusing/go-proxy/agent/pkg/agent"
+	"github.com/yusing/go-proxy/internal/net/types"
+	"github.com/yusing/go-proxy/internal/watcher/health"
+)
+
+type (
+	AgentProxiedMonitor struct {
+		agent       *agentPkg.AgentConfig
+		endpointURL string
+		*monitor
+	}
+	AgentCheckHealthTarget struct {
+		Scheme string
+		Host   string
+		Path   string
+	}
+)
+
+func AgentTargetFromURL(url *types.URL) *AgentCheckHealthTarget {
+	return &AgentCheckHealthTarget{
+		Scheme: url.Scheme,
+		Host:   url.Host,
+		Path:   url.Path,
+	}
+}
+
+func (target *AgentCheckHealthTarget) buildQuery() string {
+	query := make(url.Values, 3)
+	query.Set("scheme", target.Scheme)
+	query.Set("host", target.Host)
+	query.Set("path", target.Path)
+	return query.Encode()
+}
+
+func (target *AgentCheckHealthTarget) displayURL() *types.URL {
+	return types.NewURL(&url.URL{
+		Scheme: target.Scheme,
+		Host:   target.Host,
+		Path:   target.Path,
+	})
+}
+
+func NewAgentProxiedMonitor(agent *agentPkg.AgentConfig, config *health.HealthCheckConfig, target *AgentCheckHealthTarget) *AgentProxiedMonitor {
+	mon := &AgentProxiedMonitor{
+		agent:       agent,
+		endpointURL: agentPkg.EndpointHealth + "?" + target.buildQuery(),
+	}
+	mon.monitor = newMonitor(target.displayURL(), config, mon.CheckHealth)
+	return mon
+}
+
+func (mon *AgentProxiedMonitor) CheckHealth() (result *health.HealthCheckResult, err error) {
+	result = new(health.HealthCheckResult)
+	ctx, cancel := mon.ContextWithTimeout("timeout querying agent")
+	defer cancel()
+	data, status, err := mon.agent.Fetch(ctx, mon.endpointURL)
+	if err != nil {
+		return result, err
+	}
+	switch status {
+	case http.StatusOK:
+		err = json.Unmarshal(data, result)
+	default:
+		err = errors.New(string(data))
+	}
+	return
+}