From 3fa3c73d0e8ae57ee462b46f28dd91743c4971c7 Mon Sep 17 00:00:00 2001
From: Mike Lang <mikelang3000@gmail.com>
Date: Sun, 23 Jun 2019 19:35:50 -0700
Subject: [PATCH] Fix nginx when some services are disabled

nginx tries to resolve everything at startup, which doesn't work
if some of the services aren't present.

we instead generate the config file from a passed in env var, so that only
enabled services are present.
---
 docker-compose.jsonnet | 16 ++++++++++++++++
 nginx/Dockerfile       |  3 ++-
 nginx/generate-config  | 35 +++++++++++++++++++++++++++++++++++
 nginx/nginx.conf       | 37 -------------------------------------
 4 files changed, 53 insertions(+), 38 deletions(-)
 create mode 100755 nginx/generate-config
 delete mode 100644 nginx/nginx.conf

diff --git a/docker-compose.jsonnet b/docker-compose.jsonnet
index eea2b09..444ed04 100644
--- a/docker-compose.jsonnet
+++ b/docker-compose.jsonnet
@@ -208,9 +208,25 @@
     },
 
     [if $.enabled.nginx then "nginx"]: {
+      # mapping of services to internal ports for nginx to forward
+      local forward_ports = {
+        restreamer: 8000,
+        downloader: 8001,
+        backfiller: 8002,
+        cutter: 8003,
+        thrimshim: 8004,
+        sheetsync: 8005,
+      },
       image: "quay.io/ekimekim/wubloader-nginx:%s" % $.image_tag,
       restart: "on-failure",
       [if "nginx" in $.ports then "ports"]: ["%s:80" % $.ports.nginx],
+      environment: {
+        SERVICES: std.join("\n", [
+          "%s %s" % [service, forward_ports[service]]
+          for service in std.objectFields(forward_ports)
+          if service in $.enabled && $.enabled[service]
+        ]),
+      },
     },
 
     [if $.enabled.postgres then "postgres"]: {
diff --git a/nginx/Dockerfile b/nginx/Dockerfile
index 6a6a9ff..7a12782 100644
--- a/nginx/Dockerfile
+++ b/nginx/Dockerfile
@@ -1,3 +1,4 @@
 # nginx container contains config that exposes all the various services metrics
 FROM nginx:latest
-ADD nginx/nginx.conf /etc/nginx/nginx.conf
+ADD nginx/generate-config /
+ENTRYPOINT ["/bin/sh", "-c", "/generate-config && nginx -g \"daemon off;\""]
diff --git a/nginx/generate-config b/nginx/generate-config
new file mode 100755
index 0000000..b837428
--- /dev/null
+++ b/nginx/generate-config
@@ -0,0 +1,35 @@
+#!/bin/bash
+
+# This script expects a mapping of services and ports in the SERVICES env var,
+# with one line per service containing "NAME PORT".
+
+generate_location() {
+	# generate_location PATH URL
+	echo -e "\t\tlocation $1 { proxy_pass $2; }"
+}
+
+LOCATIONS=$(
+	echo "$SERVICES" | while read name port; do
+		# restreamer is the catch-all
+		[ "$name" == "restreamer" ] && generate_location / "http://restreamer:$port"
+		# thrimshim takes any calls to thrimshim/
+		[ "$name" == "thrimshim" ] && generate_location /thrimshim "http://thrimshim:$port"
+		# all services have metrics under /metrics/SERVICE
+		generate_location "/metrics/$name" "http://$name:$port/metrics"
+	done
+)
+
+cat > /etc/nginx/nginx.conf <<EOF
+worker_processes 1;
+
+events {
+	worker_connections 1024;
+}
+
+http {
+	server {
+		listen 80;
+$LOCATIONS
+	}
+}
+EOF
diff --git a/nginx/nginx.conf b/nginx/nginx.conf
deleted file mode 100644
index c442cd1..0000000
--- a/nginx/nginx.conf
+++ /dev/null
@@ -1,37 +0,0 @@
-
-worker_processes 1;
-
-events {
-	worker_connections 1024;
-}
-
-http {
-	server {
-		listen 80;
-		location / {
-			proxy_pass http://restreamer:8000;
-		}
-		location /thrimshim {
-			proxy_pass http://thrimshim:8004;
-		}
-		# Restreamer metrics would be available regardless, this is just for consistency
-		location /metrics/restreamer {
-			proxy_pass http://restreamer:8000/metrics;
-		}
-		location /metrics/downloader {
-			proxy_pass http://downloader:8001/metrics;
-		}
-		location /metrics/backfiller {
-			proxy_pass http://backfiller:8002/metrics;
-		}
-		location /metrics/cutter {
-			proxy_pass http://cutter:8003/metrics;
-		}
-		location /metrics/thrimshim {
-			proxy_pass http://thrimshim:8004/metrics;
-		}
-		location /metrics/sheetsync {
-			proxy_pass http://sheetsync:8005/metrics;
-		}
-	}
-}