App Developer Hosting

Hosting the CHT when developing apps

Getting started

Be sure to meet the CHT hosting requirements first. As well, if any other medic-os instances using the main docker-compose.yml file are running locally, stop them otherwise port, storage volume and container name conflicts may occur.

After meeting these requirements, download the developer YAML file in the directory you want to store them:

curl -o docker-compose-developer-3.x-only.yml https://raw.githubusercontent.com/medic/cht-core/master/scripts/docker-helper/docker-compose-developer-3.x-only.yml

To start the first developer CHT instance, run docker-compose and specify the file that was just download:

docker-compose -f docker-compose-developer-3.x-only.yml up

This may take some minutes to fully start depending on the speed of the Internet connection and speed of the bare-metal host. This is because docker needs to download all the storage layers for all the containers and the CHT needs to run the first run set up. After downloads and setup has completed, the CHT should be accessible on https://localhost.

When connecting to a new dev CHT instance for the first time, an error will be shown, “Your connection is not private” (see screenshot). To get past this, click “Advanced” and then click “Proceed to localhost”.

Running the Nth CHT instance

After running the first instance of the CHT, it’s easy to run as many more as are needed. This is achieved by specifying different:

  • port for HTTP redirects (CHT_HTTP)
  • port for HTTPS traffic (CHT_HTTPS)
  • project to for the docker compose call (-p PROJECT)

Assuming you want to start a new project called the_second and start the instance on HTTP port 8081 and HTTPS port 8443, this would be the command:

CHT_HTTP=8081 CHT_HTTPS=8443 docker-compose -p the_second -f docker-compose-developer-3.x-only.yml up

The second instance is now accessible at https://localhost:8443.

The .env file

Often times it’s convenient to use revision control, like GitHub, to store and publish changes in a CHT app. A nice compliment to this is to store the specifics on how to run the docker-compose command for each app. By using a shared docker-compose configuration for all developers on the same app, it avoids any port collisions and enables all developers to have a unified configuration.

Using the above the_second sample project, we can create another directory to host this project’s configuration:

mkdir ../the_second

Create a file ../the_second/.env-docker-compose with this contents:

COMPOSE_PROJECT_NAME=the_second
CHT_HTTP=8081
CHT_HTTPS=8443

Now it’s easy to boot this environment by specifying which .env file to use:

docker-compose --env-file ../the_second/.env-docker-compose -f docker-compose-developer-3.x-only.yml up

Switching & concurrent projects

The easiest way to switch between projects is to stop the first set of containers and start the second set. Cancel the first project running in the foreground with ctrl + c. Then start the second project using either the .env file or use the explicit command with ports and project name as shown above.

To run projects concurrently, instead of cancelling the first one, open a second terminal and start the second project.

To read more about how docker-compose works, be sure to read the helpful docker-compose commands page.

CHT Docker Helper

The cht-docker-compose.sh scripts builds on the docker-compose-developer-3.x-only.yml and .env files used above by helping start CHT instances with a simple text based GUI:

The cht-docker-compose.sh script showing the URL and version of the CHT instance as well as number of containers launched, global container count, medic images downloaded count and OS load average. Finally a “Successfully started my_first_project” message is shown and denotes the login is “medic” and the password is “password”.

Prerequisites

OS

This script has been heavily tested on Ubuntu and should work very well there. It has been lightly tested on WSL2 on Windows 10 and macOS (x86, not Apple silicon like M1 etc.) - both should likely work as well.

Software

The script will check and require these commands. All but docker and docker-compose should be installed by default on Ubuntu:

  • awk
  • curl
  • cut
  • dirname
  • docker (At least version 20.x)
  • docker-compose (At least version 1.27)
  • file
  • grep
  • head
  • nc
  • tail
  • tr
  • wc

Optionally you can install jq so that the script can parse JSON and tell you which version of the CHT is running.

Docker compose file and helper scripts

An up-to-date clone of cht-core has everything you need including:

  • docker-compose-developer-3.x-only.yml
  • cht-docker-compose.sh
  • docker-status.sh

Using

Syntax

The helper script is run by calling ./cht-docker-compose.sh. It accepts one required and one optional arguments:

  • -e | --env-file - path to the environment file. Required
  • -d | --docker_action - docker action to run: up, down or destory. Optional, defaults to up

Nomenclature

Docker containers, networks and volumes are always named after the project you’re using. So if your project is called my_first_project, you will see:

  • Two containers: my_first_project_medic-os_1 and my_first_project_haproxy_1
  • One storage volume: my_first_project_medic-data
  • One network: my_first_project_medic-net

First Run

These steps assume:

  • the first project is my_first_project
  • one .env_docker environment file per project
  • my_first_project and cht-core directories are next to each other in the same parent directory
  • you have Internet connectivity (See booting with no connectivity)

Follow these steps to create your first developer instance. You can create as many as you’d like:

  1. create ./my_first_project/.env_docker with the contents:
    COMPOSE_PROJECT_NAME=my_first_project
    CHT_HTTP=8080
    CHT_HTTPS=8443   
    
  2. Change into the docker-help directory: cd ./cht-core/scripts/docker-helper/
  3. Run the helper script and specify your .env_docker file:
    ./cht-docker-compose.sh -e ../../../my_first_project/.env_docker
    
  4. Your CHT instance will be started when you see the text:
    Successfully started project my_first_project
    

Second Run

When you’re done with an instance, be sure to shut it down:

./cht-docker-compose.sh -e ../../../my_first_project/.env_docker -d down

All information will be saved, and it should be quick to start for the Nth time.

To start an existing instance again, just run the command from the “First Run” section:

./cht-docker-compose.sh -e ../../../my_first_project/.env_docker 

This command is safe to run as many times as you’d like if you forget the state of your project’s Docker containers.

Last Run

When you’re done with a project and want to completely destroy it, run destroy:

./cht-docker-compose.sh -e ../../../my_first_project/.env_docker -d destroy

NOTE - Be sure you want to run destroy. The script will not prompt “are you sure?” and it will just delete all your project’s data.

Troubleshooting

The main issue you’re likely to run into is that the CHT doesn’t correctly start up, the very reason this script was created. If the script either hangs on one step, or fails to start and quits after 5 tries, try these steps:

  1. Ensure your Internet is working.
  2. Destroy everything by using the -d destroy option. While this will delete any data, if you can’t start the CHT instance, you won’t be loosing any data you care about ;). This will delete the containers and volumes. Then run -d up and try again.
  3. Quit apps that may be causing a high load on your computer. Possibly consider rebooting and running nothing else. In one instance this helped!

If you still get stuck review the items below as possible issues you may find workarounds to. If none of these work, see the debug file which is always output in the same directory as your env_file. File a ticket in this repository and attach this log file. To read more about the contents of the cht-docker-compose.log see the CHT Docker Compose Log section.

Running without the ip utility

If you’re on macOS, or other OS without the ip utility, your IP address will always show as 127.0.0.1. You can not connect to this IP from a mobile client on your LAN because it always references the host it’s on, not a foreign host.

To work around this, you can find out your IP on your LAN and just replace the 127-0-0-1 part of the https://127-0-0-1.my.local-ip.co:8443 URL to be your IP address. So if your local IP was 192.168.0.22 your URL would be https://192-168-0-22.my.local-ip.co:8443.

Booting with no connectivity

This script can work without connectivity after the initial boot. However, it needs connectivity to do DNS lookups for the *.my.local-ip.co URLs. To work around this, when you have no connectivity, add an entry in your /etc/hosts for the URL showing up in the script. For example, if you’re seeing https://127-0-0-1.my.local-ip.co:8443 as your IP, add this line to the top of your /etc/hosts file.

127.0.0.1   127-0-0-1.my.local-ip.co

NOTE - You need connectivity on the initial boot of the VM to connect to staging.dev.medicmobile.org to download the base version of the CHT. As well, certificates for *.my.local-ip.co are downloaded. Subsequent boots do not require connectivity as long as you do not run destroy.

Port conflicts

If you have two .env_docker files that have the same ports or re-use the same project name, bad things will happen. Don’t do this.

Medic recommends setting up unique project names and unique ports for each project. Commit these .env_docker files to your app config’s revision control so all app developers use the same .env_docker files.

Slow downloads and wait periods

During testing on an Internet connection with high latency (>1000ms) and packet loss, this script had trouble booting the CHT instance because it was taking too long to download the assets from staging.dev.medicmobile.org. Each version is about 38 MB.

To account for this, the wait time is multiplied times the boot iteration for each time it reboots. It starts at 100 seconds and then 200, 300, 400 up to the fifth time it will wait 500 seconds.

Too many containers

If you’re on a resource constrained computer, like a very old or very slow laptop, be sure to watch the total number of containers you’re running. More than one or two projects (2 or 4 containers) and you may notice a slow-down. You can use the ./docker-status.sh script if you forgot which projects you have running:

The docker-status.sh script showing 4 sections. The top section lists the running CHT containers, their IP, their mapped ports and the state (running time). The second section found on the left is a list of docker networks. The third section is on the top right and lists downloaded docker images. The furth section on the bottom right, shows docker volumes

A word of caution though - for now this script doesn’t scale well if you have 10s of containers and volumes. Content can scroll off the screen and seem confusing!

Output on macOS is too narrow

There’s a known bug with the bash library we’re using that causes it to always render at 80 characters wide. The fix is to use brew to run a more recent version of ncurses.

“Device ’’ does not exist’” and “curl: (6) Could not resolve host” errors

If you see either of these errors, you’re very likely off-line such that you effectively cannot reach the Internet. The script will not work as is. See the “Booting with no connectivity” section above for work-arounds.

Resetting everything

If you REALLY get stuck and want to destroy ALL docker containers/volumes/networks, even those not started by this script, run this (but be extra sure that’s what you want to do):

docker stop $(docker ps -q)&&docker system prune&&docker volume prune

cht-docker-compose.log

This log will be output every time you call the script. It will be created and appended to in the directory where you specified your environment file (-e PATH/TO/env_file).

There are three types of lines in this file. The first line will always be the Start line: item="start". Then there will be a Status line: item="status". Finally, there will be two lines, one for each docker container: item="docker_logs".

Shared head

All lines start with a date, PID and count:

Name in logNoteExample
(none - first item)value from date command with DAY DATE MONTH YEAR TIME AM/PMFri 15 Oct 2021 02:19:30 PM
pidprocess ID of the shell script. Will always be an integer398399
counthow many times the shell script has looped internally2

item = start

When you first call the script, a line is output with generic information about the project. This is only shown once per call:

Name in logNoteExample(s)
itemwhich log item this isstart
URLthe full URL of the instance, with porthttps://192-168-68-17.my.local-ip.co:443
IPthe IP address of the instance192.168.68.17
port_httpsport used for https443 or 8443
port_httpport used for http80 or 8080
project_nameThe user specified project name. This will be used in docker container and volume nameshelper_test
total_containersTotal docker containers running on the host. Useful for catching high load scenarios. Healthy is under 10.2

item = status

For each internal loop of the script, each one taking 1-5 seconds, a status line is output:

Name in logNoteExample(s)
itemwhich log item this isstatus
CHT_countnumber of CHT contianers running for this project. Healthy is 22
port_statStatus of the https port. Healhty is openopen or closed
http_codeIf the https port is open by the web server, what HTTP response code is returned for a GET. Healthy is 200. If you see 000, see workarounds.200 or 404
ssl_verifyIf the https port is open by the web server, is the valid local-ip.co certificate installed. Healthy is yesyes or no
reboot_countHow many times docker restart has been called. Max is 53
docker_callThe docker action call to the scriptup
last_msgLast message the user was shownRunning "down" then "up"
load_nowLoad average for the past minute. Healthy can vary, but should be < 102.66
*_haproxy_1Name of container based on project_name. Showing the “has booted” status, healthy is truefalse
*_medic-os_1Name of container based on project_name. Showing the “has booted” status, healthy is truefalse

item = docker_logs

Name in logNoteExample(s)
itemwhich log item this isdocker_logs
containerContainer name based on project_namehelper_test_medic-os_1
processesNumber of process running in the container. Medic OS should have 60-90, Nginx 4-1064
last_logResult from calling docker logs on the container. Will never have " in them and date may differ from start of line date[2021/10/15 19:53:39] Info: Horticulturalist has already bootstrapped

Sample

Fri 15 Oct 2021 02:30:26 PM PDT pid="410066" count="1" item="start" URL="https://192-168-68-17.my.local-ip.co:443" IP="192.168.68.17" port_https="443" port_http="80" project_name="helper_test" total_containers="2"
Fri 15 Oct 2021 02:30:26 PM PDT pid="410066" count="1" item="docker_logs" container="helper_test_medic-os_1" processes="64" last_log="[2021/10/15 19:53:39] Info: Horticulturalist has already bootstrapped"
Fri 15 Oct 2021 02:30:26 PM PDT pid="410066" count="1" item="docker_logs" container="helper_test_haproxy_1" processes="4" last_log="Oct 15 21:30:20 576ca039cd88 haproxy[25]: 172.20.0.3,200,GET,/medic/_design/medic,-,medic,'-',21703,5,21402,'curl/7.68.0'"
Fri 15 Oct 2021 02:30:26 PM PDT pid="410066" count="1" item="status" CHT_count="2" port_stat="open" http_code="200" ssl_verify="yes" reboot_count="0" docker_call="up" last_msg="Initializing" load_now="2.66" helper_test_haproxy_1="true" helper_test_medic-os_1="true" 
Fri 15 Oct 2021 02:30:28 PM PDT pid="410066" count="2" item="docker_logs" container="helper_test_medic-os_1" processes="67" last_log="[2021/10/15 19:53:39] Info: Horticulturalist has already bootstrapped"
Fri 15 Oct 2021 02:30:28 PM PDT pid="410066" count="2" item="docker_logs" container="helper_test_haproxy_1" processes="4" last_log="Oct 15 21:30:27 576ca039cd88 haproxy[25]: 172.20.0.3,200,GET,/medic/_design/medic,-,medic,'-',21703,5,21402,'curl/7.68.0'"
Fri 15 Oct 2021 02:30:28 PM PDT pid="410066" count="2" item="status" CHT_count="2" port_stat="open" http_code="200" ssl_verify="yes" reboot_count="0" docker_call="up" last_msg=" :) " load_now="2.69" helper_test_haproxy_1="true" helper_test_medic-os_1="true"

The CHT stores its cookies based on the domain. This means if you’re running two concurrent instances on https://192-168-68-40.my.local-ip.co:8443 and https://192-168-68-40.my.local-ip.co:8440 (note different ports), the CHT would write the cookie under the same 192-168-68-40.my.local-ip.co domain. When logging out of one instance, you would get logged out of both and other consistencies.

To avoid this collision of cookies, you can use different IP addresses to access the instances. This works because of two reasons:

  1. the TLS certificate being used is valid for any subdomain of *.my.local-ip.co. Further, the URL always resolves to the IP passed in the * section, so you can use any IP
  2. the IPs that are available to reference your localhost are actually a /8 netmask, meaning there are 16 million addresses to choose from!

Using the above two reasons, these URLs could work to avoid the cookie collision:

  • https://127-0-0-1.my.local-ip.co:8443
  • https://127-0-0-2.my.local-ip.co:8440

This would result in the domains being 127.0.0.1 and 127.0.0.2 from the CHT’s perspective. When using a mobile device for testing, you’re limited to use the LAN ip output in the helper and can not use the 127.x.x.x IPs.