From 1136e2cfeed5cc06a0811d39c2560c06f9dd74a2 Mon Sep 17 00:00:00 2001
From: Matthew Holt <mholt@users.noreply.github.com>
Date: Sat, 4 May 2019 10:49:50 -0600
Subject: Add reverse proxy

---
 modules/caddyhttp/reverseproxy/healthchecker.go | 64 +++++++++++++++++++++++++
 1 file changed, 64 insertions(+)
 create mode 100755 modules/caddyhttp/reverseproxy/healthchecker.go

(limited to 'modules/caddyhttp/reverseproxy/healthchecker.go')

diff --git a/modules/caddyhttp/reverseproxy/healthchecker.go b/modules/caddyhttp/reverseproxy/healthchecker.go
new file mode 100755
index 0000000..add3aa0
--- /dev/null
+++ b/modules/caddyhttp/reverseproxy/healthchecker.go
@@ -0,0 +1,64 @@
+package reverseproxy
+
+import (
+	"net/http"
+	"time"
+)
+
+// Upstream represents the interface that must be satisfied to use the healthchecker.
+type Upstream interface {
+	SetHealthiness(bool)
+}
+
+// HealthChecker represents a worker that periodically evaluates if proxy upstream host is healthy.
+type HealthChecker struct {
+	upstream   Upstream
+	Ticker     *time.Ticker
+	HTTPClient *http.Client
+}
+
+// ScheduleChecks periodically runs health checks against an upstream host.
+func (h *HealthChecker) ScheduleChecks(url string) {
+	// check if a host is healthy on start vs waiting for timer
+	h.upstream.SetHealthiness(h.IsHealthy(url))
+
+	for {
+		select {
+		case <-h.Ticker.C:
+			h.upstream.SetHealthiness(h.IsHealthy(url))
+		}
+	}
+}
+
+// Stop stops the healthchecker from makeing further requests.
+func (h *HealthChecker) Stop() {
+	h.Ticker.Stop()
+}
+
+// IsHealthy attempts to check if a upstream host is healthy.
+func (h *HealthChecker) IsHealthy(url string) bool {
+	req, err := http.NewRequest(http.MethodGet, url, nil)
+	if err != nil {
+		return false
+	}
+
+	resp, err := h.HTTPClient.Do(req)
+	if err != nil {
+		return false
+	}
+
+	if resp.StatusCode < 200 || resp.StatusCode >= 400 {
+		return false
+	}
+
+	return true
+}
+
+// NewHealthCheckWorker returns a new instance of a HealthChecker.
+func NewHealthCheckWorker(u Upstream, interval time.Duration, client *http.Client) *HealthChecker {
+	return &HealthChecker{
+		upstream:   u,
+		Ticker:     time.NewTicker(interval),
+		HTTPClient: client,
+	}
+}
-- 
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