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Hosting multiple Heroku apps on a single domain
In this guest engineering post from Plane's CEO Matt Pelc, he discusses how a single application on Heroku can have any number of domains assigned to it, but you can only add a domain to one app.
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Read Story →A single application on Heroku can have any number of domains assigned to it, but you can only add a domain to one app. This means that by default you can’t serve
example.com from the example-1 while example.com/blog is served from example-2.We ran into this problem with plane.com recently where we have a constellation of apps (pilot-co, pilot-blog, pilot-stories, etc.) which we wanted to host under a single domain.We found a way to do that by putting a custom HAProxy instance, also hosted on Heroku, in front of all other Heroku apps we use.1. Set up
Let’s say you have two apps on Heroku already:example-comrunninghttps://example.comexample-blogrunninghttps://blog.example.com
1$ mkdir load-balancer2$ cd load-balancer3$ git init .Then create an app on Heroku:1$ heroku apps:create example-lb2Creating example-lb... done, stack is cedar-143http://example-lb.herokuapp.com/ | https://git.heroku.com/example-lb.git4Git remote heroku added2. Installing Docker
You will deploy it to Heroku using Docker. We found it to be easier to manage than creating a custom buildpack.Luckily, installing Docker on your machine is easy. Get Docker Toolbox and follow its setup instructions.To verify that you have a working Docker installation, open your terminal and run:1docker ps2CONTAINER ID IMAGE COMMAND ...3$ docker-compose --version4docker-compose version: 1.4.0To deploy a Docker container to Heroku you will need heroku-docker:1$ heroku plugins:install heroku-dockerHeroku requires an app.json and Procfile manifests to be able to run your app.1{2 "name": "Pilot Load Balancer",3 "description": "A load balancer for pilot.co",4}Your Procfile should look something like this:1web: sbin/haproxy -f haproxy.cfgThen initialise Docker assets for the app:1$ heroku docker:init2Wrote Dockerfile3Wrote docker-compose.yml3. Configuring HAProxy
YourDockerfile is where we add instructions for Heroku on how to compile HAProxy:1FROM heroku/cedar:142RUN mkdir -p /app/user3WORKDIR /app/user4# Install HAProxy5RUN apt-get update && apt-get install -y libssl1.0.0 libpcre3 --no-install-recommends && rm -rf /var/lib/apt/lists/*6ENV HAPROXY_MAJOR 1.57ENV HAPROXY_VERSION 1.5.148ENV HAPROXY_MD5 ad9d7262b96ba85a0f8c6acc6cb9edde9# see http://sources.debian.net/src/haproxy/1.5.8-1/debian/rules/ for some helpful navigation of the possible "make" arguments10RUN buildDeps='curl gcc libc6-dev libpcre3-dev libssl-dev make' \11 && set -x \12 && apt-get update && apt-get install -y $buildDeps --no-install-recommends && rm -rf /var/lib/apt/lists/* \13 && curl -SL "http://www.haproxy.org/download/${HAPROXY_MAJOR}/src/haproxy-${HAPROXY_VERSION}.tar.gz" -o haproxy.tar.gz \14 && echo "${HAPROXY_MD5} haproxy.tar.gz" | md5sum -c \15 && mkdir -p /app/user/src/haproxy \16 && tar -xzf haproxy.tar.gz -C /app/user/src/haproxy --strip-components=1 \17 && rm haproxy.tar.gz \18 && make -C /app/user/src/haproxy \19 TARGET=linux2628 \20 USE_PCRE=1 PCREDIR= \21 USE_OPENSSL=1 \22 USE_ZLIB=1 \23 PREFIX=/app/user \24 all \25 install-bin \26 && rm -rf /app/user/src/haproxy \27 && apt-get purge -y --auto-remove $buildDeps28COPY haproxy.cfg /app/user/haproxy.cfgOne last thing we need to do is configure HAProxy to route requests from our main app (called frontend) to all other apps (called backends).HAProxy’s configuration manual is relatively easy to understand, and after some fine-tuning you should end up with something like this:1global2 maxconn 2563defaults4 mode http5 timeout connect 5000ms6 timeout client 50000ms7 timeout server 50000ms8frontend http9 bind 0.0.0.0:$PORT10 option forwardfor11 # Force SSL12 redirect scheme https code 301 if ! { hdr(x-forwarded-proto) https }13 # Redirect all requests to /blog* to the example-blog app.14 use_backend example-blog if { path_beg /blog }15 # And all other requests to example-com.16 default_backend pilot-com17backend pilot-com18 http-request set-header X-Forwarded-Host example.com19 http-request set-header X-Forwarded-Port %[dst_port]20 reqirep ^Host: Host:\ example-com.herokuapp.com 21 server example-com example-com.herokuapp.com:443 ssl verify none22backend example-blog23 http-request set-header X-Forwarded-Host example.com24 http-request set-header X-Forwarded-Port %[dst_port]25 reqirep ^Host: Host:\ example-blog.herokuapp.com26 server example-blog example-blog.herokuapp.com:443 ssl verify noneYou can verify your setup locally by starting Docker:1$ docker-compose up weband opening the browser:1$ open "http://$(docker-machine ip default):8080"4. Deploying your load balancer to Heroku
If you’re satisfied with the outcome, it’s time to deploy it to Heroku:1heroku docker:release2heroku openAfter you verified that your new setup works on https://example-lb.herokuapp.com, you can remove the example.com domain from example-com and attach it to example-lb.5. After you’re done
- Requests to
https://example.comwill go throughexample-lband be served fromexample-com. - Requests to
https://example.com/blogwill also go throughexample-lbbut be served fromexample-bloginstead. - All this will be completely hidden from your users. At no point they should see
example-blog.herokuapp.comor any domain other thanexample.com.
example-lb. Traffic between Heroku apps will be encrypted using their *.herokuapp.com certificate.Additional resources
Build and Deploy with Docker on HerokuHAProxy Configuration ManualRelated articles
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