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dhis2-tools-ng

Tools for setting up dhis2 on lxd. A very short install guide.

Note that this guide is supplementary to the Implementation Guide. Here we use that guide as a configuration reference, and implement those configurations into a set of automated tools for installation and management. It is not the intention here to repeat all the detailed explanation that is provided there.

Note also that DHIS2 is quite a complex system requiring some experience of linux, web based systems, database management etc to manage sustainably and securely. There are a number of organisations who provide hosting services as a business. If you do not have the skills or the resources in-house, you might be better outsourcing to one of these.

This install guide describes a particular setup approach which is already used by a number of country systems in production. The main reason you might want to follow this approach would be if it is important for you to take advantage of (and contribute to) a community supported process.

Prerequisites you need before you start:

  1. Your fully qualified domain name (FQDN), like hmis.mygov.org. Note this is just the name, not a URL like https:\\hmis.mygov.org This setup is designed for production use so it is assumed it will be using SSL/TLS which further assumes that you have a FQDN which will properly resolve to the public IP that you are exposing service on. Do not proceed further until you have sorted this.

  2. Your timezone. In order to see the list of available timezones type timedatectl list-timezones. Make a note of your desired timezone. Most likely you will want to also set the timezone on your host machine. You can do this by typing timedatectl set-timezone Africa/Dar_es_Salaam.

  3. Make sure that your host OS is minimally and securely setup, with ufw firewall enabled (don't forget to allow your ssh port). NOTE that the installation described below will fail if you have not enabled ufw on the host. You can follow a useful guide to do the initial steps to secure your base system here.

The install:

The steps outined below will take a bare server which is accessible to the internet via a public IP, and configure all the infrastructure required to create and maintain DHIS2 instances.

  1. grab the install scripts from github: git clone https://github.com/bobjolliffe/dhis2-tools-ng.git

  2. cd dhis2-tools-ng/setup

  3. cp configs/containers.json.sample configs/containers.json

  4. edit the top 3 lines of configs/containers.json to reflect your fqdn, email and tz:

    { "fqdn":"li621-168.members.linode.com", "email": "bob@dhis2.org", "environment": { "TZ": "Africa/Dar_es_Salaam" }, ....

(Resist the temptation of changing other things below these 3 lines for now. Some of what appear as configurable defaults are still a bit hard-coded. Will improve that soon)

  1. Run sudo ./lxd_setup.sh (this could be a good time to make tea or coffee .. it will take some minutes)

  2. Install the service scripts by running sudo ./install_scripts.sh

At this point your proxy, database and monitor servers should be up and running. You should be able to see them when you type sudo lxc list:

+----------+---------+---------------------+------+------------+-----------+
|   NAME   |  STATE  |        IPV4         | IPV6 |    TYPE    | SNAPSHOTS |
+----------+---------+---------------------+------+------------+-----------+
| monitor  | RUNNING | 192.168.0.30 (eth0) |      | PERSISTENT | 0         |
+----------+---------+---------------------+------+------------+-----------+
| postgres | RUNNING | 192.168.0.20 (eth0) |      | PERSISTENT | 0         |
+----------+---------+---------------------+------+------------+-----------+
| proxy    | RUNNING | 192.168.0.2 (eth0)  |      | PERSISTENT | 0         |
+----------+---------+---------------------+------+------------+-----------+

You should now be able to access your system by going to http://<your_domain_name>. You shoud see the default apache2 landing page (more on how to change this below).

  1. Setting up SSL/TLS The reverse proxy has a configuration file which is setup to use SSL/TLS certificates from letsencrypt.org. Previously this was part of the automatic install, but we decided to make it a seperate step so that users can verify that their infrastructure is working properly before attempting to acquite the letsencrypt certificate. To install:

8.1 Double check with your browser that you can access the default apache2 landing page at http:///your fqdn>. Only if this is is successful proceed to ...

8.2 Run sudo ./ssl_setup.sh to run certbot to fetch and install your ssl certificate.

If you encountered errors during the install, the easiest way to restart is just to run ./delete_all.sh. This will wipe all your containers and you can try again.

Note the IP addresses of the containers. When we install DHIS2 instances, each instance will also run in its own container and will require its own IP address. By convention we suggest creating containers starting at 192.168.0.10 through to 192.168.0.19. If you need (and have resources) for more than 10, then you might start giving them different IPs.

You are now ready to start installing DHIS2 instances.

Installing DHIS2 instances

  1. To create an instance you need to specify the name of the instance, the IP and the name of the database container (this is necessary as you might have more than one database container). For example to create an instance called hmis:

sudo dhis2-create-instance hmis 192.168.0.10 postgres

To create another instance called staging:

sudo dhis2-create-instance staging 192.168.0.11 postgres

  1. Deploy a DHIS2 war file to your new instance:

dhis2-deploy-war -l https://releases.dhis2.org/2.33/2.33.2/dhis.war hmis

  1. Browse to your new instance at https://<your_hostname>/hmis

Working with instances

Now that you are up and running you can start doing some basic activities.

Stopping, starting and restarting

Because each DHIS2 instance is running tomcat9 in its own container, the simplest way to do these operations is to just act directly on the lxc container:

sudo lxc stop hmis
sudo lxc stop staging
sudo lxc start hmis
sudo lxc restart staging

Executing commands inside containers

Sometimes you might want to execute commands inside the container. So for example if you wanted to edit the server.xml inside the staging container you might do:

bob@localhost:$ sudo lxc exec staging bash
root@staging:~# vi /etc/tomcat9/server.xml
root@staging:~# exit

Executing bash like this lands you at an interactive prompt. This can be useful, but is not always what you want. For example you might want to execute a query directly on the database like:

sudo lxc exec postgres -- psql -c 'select name,id from dataelement limit 5' hmis 

Note the "--" is necessary. It tells lxc exec that everything following (including commandline switches like -c in this case) are to be interpreted as part of the remote command.

Post install tasks

Database

The system should now be working, but you will probably want to tune your database a little to get the best performance from your available resources. A good start would be to determine first what is the total amount of memory your machine has (see total memory after executing 'free -gh'). Let us proceed as though there is 32GB RAM in total.

Deciding how much RAM to deidicate to postgresql depends a little on how many DHIS2 instances you are likely to run, but assuming you will have a production instance and perhaps a small test instance, giving 16GB exclusively to postgresql is a reasonable start. You can enforce that limit so that the postgresql container only sees 16GB RAM by typing:

`sudo lxc config set postgresql limits.memory 16GB'

If you run free -gh inside the postgresql container you will see that it no longer can see the full amount of RAM, but has been confined to 16GB. (try sudo lxc exec postgres -- free -gh).

Then sudo lxc exec postgres bash to get to your postgres container.

The file where all your custom settings are made is called /etc/postgresql/10/main/conf.d/dhispg.conf. The default contents of this file is shown below:

# Postgresql settings for DHIS2

# Adjust depending on number of DHIS2 instances and their pool size
# By default each instance requires up to 80 connections
# This might be different if you have set pool in dhis.conf
max_connections = 200

# Tune these according to your environment
# About 25% available RAM for postgres
# shared_buffers = 3GB

# Multiply by max_connections to know potentially how much RAM is required
# work_mem=20MB

# As much as you can reasonably afford.  Helps with index generation
# during the analytics generation task
# maintenance_work_mem=512MB

# Approx 80% of (Available RAM - maintenance_work_mem - max_connections*work_mem)
# effective_cache_size=8GB

# This setting is suitable for good SSD disk.  For slower spinning disk consider
# changing to 4
random_page_cost = 1.1

checkpoint_completion_target = 0.8
synchronous_commit = off
log_min_duration_statement = 300s
max_locks_per_transaction = 1024

The 4 settings that you should uncomment and give values to are shared_buffers, work_mem, maintenance_work_mem and effective_cache_size. With 16GB of RAM, reasonable settings for these would be:

shared_buffers = 4GB
work_mem=20MB
maintenance_work_mem=1GB
effective_cache_size=11GB

Before applying these settings you should shutdown any running DHIS2 instances. So, for example, back on the host:

sudo lxc stop covid19
sudo lxc restart postgresql
sudo lxc start covid19

Postgresql is an extremely configurable database with hundreds of configuration parameters. This brief installation guide only touches on the most important tunables.

(TODO: install postgresql munin plugin)

DHIS2 instances

When you install a dhis2 instance (with dhis2-create-instance), a lxc container is created with a standard system installation of tomcat 9. Whereas this is sufficient to run a dhis2 application war file (see dhis2-deploy-war above), you will want to make some adjustments to the memory settings and perhaps other configuration tweaks.

File locations

The following are locations within the container that you will find common files for DHIS2 tweaking:

  1. /etc/default/tomcat9 - this is where environment variables such as JAVA_OPTs are kept
  2. /etc/tomcat9/server.xml - you shouldn't need to do anything in here. Unless you want to change the http pool size
  3. /opt/dhis2 - this is where your DHIS2_HOME is. Most important file in there is dhis.conf.

Something which is quite different with tomcat9 on ubuntu is that it no longer uses catalina.out as its console log. Instead it is logging these messages using the standard syslog mechanism. So you can find your tomcat messages in /var/log/syslog rather than catalina.out. The dhis2-specific logs can be found at /opt/dhis2/logs/.

Environment settings (/etc/default/tomcat9)

The main thing to set in here is the JAVA_OPTS. Following our example, we have 16GB of RAM left, so we might want to give 8GB to our covid19 instance:

JAVA_OPTS="-Djava.awt.headless=true -XX:+UseG1GC -Xmx8G -Xms8G -Djava.security.egd=file:/dev/./urandom"

Change the 8G to whatever suits your environment. For example a small test instance might run with only 2GB heap size. We will discuss later in monitoring and troubleshooting how you know whether the setting is suitable for the load you are catering for.

The bit at the end (-Djava.security.egd=file:/dev/./urandom) can be important when running tomcat in virtual machines where it depends on a virtual source of randomness.

DHIS2 (/opt/dhis2/dhis.conf)

The important parameters, for example to make the database connection work, will already have been set in here. The file contains a copy of all the possible configuration parameters (mostly commented out). Refer to the implementation guide for a detailed explanation of each.

Three parameters you might consider uncommenting/changing:

  1. connection.pool.max_size - the default value of this is 80 which should be adequate for most systems. For a small test system consider reducing this to, say 10. In very rare instances, usually when there is some other problem in your database, you might need to increase this. You need to ensure as you modify this that you stay within the limits of max_connections in postgresql configuration.
  2. analytics.cache.expiration - if you uncomment this and keep the default setting of 3600, it will cache the results of SQL analytics queries for an hour. These can sometimes be a big load on your database so it is highly advisable to enable this. On large aggregate systems it can have a dramatic effect.
  3. system.session.timeout - this determines how long you can leave the application without being obliged to log back in again. The default setting (1 hour) is probably too long for sensitive applications in clinical settings. Something like 10 or 15 minutes might be more reasonable.

Monitoring agent

It is important to setup a monitoring agent on your DHIS2 instance. If you have run the standard setup you will have installed a monitor called munin in a container called monitor.

To enable detailed monitoring of your DHIS2 tomcat application, you should run:

sudo dhis2-tomcat-munin <instance_name> proxy

to setup the agent. (change <instance_name) to your instance, eg. hmis, covid19 ...

Web proxy

By default you will have instaled an apache2 reverse proxy server with an SSL/TLS certificate from letsencrypt. You will be able to browse to your DHIS2 instances with https://<server_name>/<instance_name>. You will also be able to browse to the syste monitor at https://server_name>/munin. It should soon be also possible to use an nginx proxy, but the apache2 one is currently the best tested.

If you browse to home page at https//:<server_name> you will reach the apache2 default page. Typically you will want to do one of two things:

Create a custom landing page

Sometimes people want to have a custom landing page with some basic information and perhaps links to the DHIS2 applications. To do this you just need to replace the index.html file at /var/lib/ww/html/index.html inside the proxy container.

To push a replacement page you could execute the following command: sudo lxc file push myindex.html proxy/var/lib/www/html/index.html

Redirect to a DHIS2 application

The other approach is to redirect requests directly to a DHIS2 application.

To do this you need make a small change to the apache2 configuration. You can do like:

sudo lxc exec proxy -- vi /etc/apache2/sites-enabled/apache-dhis2.conf

If you scroll down to somewhere around line 80, you will see:

        #===========================================================
        # Rewrite requests for / to main dhis application
        #===========================================================

        # RewriteRule   ^/$  /dhis/  [R]

Uncomment the line with the RewriteRule and replace with the DHIS2 instance you want to have as the default. For example: RewriteRule ^/$ /hmis/ [R]

You need to reload the apache2 configuration (restart would also work, but not necessary). You could do like: sudo lxc exec proxy -- service apache2 reload

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