From 4ed4a2e28f83d4474a927d57ecccdf8ef3325505 Mon Sep 17 00:00:00 2001
From: zhanghjster <zhanghjster@gmail.com>
Date: Thu, 5 Nov 2020 14:42:09 +0800
Subject: [PATCH 1/2] add tail_proxy_url option to the query_frontend_config
 section of configuration doc

---
 docs/sources/configuration/_index.md | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/docs/sources/configuration/_index.md b/docs/sources/configuration/_index.md
index 2d297b626f2a..04b4d2f1e38f 100644
--- a/docs/sources/configuration/_index.md
+++ b/docs/sources/configuration/_index.md
@@ -296,6 +296,10 @@ The query_frontend_config configures the Loki query-frontend.
 # Set to < 0 to enable on all queries.
 # CLI flag: -frontend.log-queries-longer-than
 [log_queries_longer_than: <duration> | default = 0s]
+
+# URL of querier for tail proxy.
+# CLI flag: -frontend.tail-proxy-url
+[tail_proxy_url: <string> | default = ""]
 ```
 
 ## queryrange_config

From 064abc08b51aef6709164c0699ec34724d86db6f Mon Sep 17 00:00:00 2001
From: zhanghjster <zhanghjster@gmail.com>
Date: Thu, 5 Nov 2020 16:27:50 +0800
Subject: [PATCH 2/2] If queryFrontend run in tail proxy mode, append the Host
 of the tail_proxy_url to the request header, because in some scenario
 queryFrontend forward tail to the queriers deployed behind nginx and "Host"
 is required.

---
 pkg/loki/modules.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/pkg/loki/modules.go b/pkg/loki/modules.go
index 57640983211f..0de2559c146a 100644
--- a/pkg/loki/modules.go
+++ b/pkg/loki/modules.go
@@ -383,6 +383,13 @@ func (t *Loki) initQueryFrontend() (_ services.Service, err error) {
 			return nil, err
 		}
 		tp := httputil.NewSingleHostReverseProxy(tailURL)
+
+		director := tp.Director
+		tp.Director = func(req *http.Request) {
+			director(req)
+			req.Host = tailURL.Host
+		}
+
 		defaultHandler = httpMiddleware.Wrap(tp)
 	} else {
 		defaultHandler = frontendHandler