recodex-wiki/Installation.md

# Installation

Installation of whole ReCodEx solution is a very complex process. It is
recommended to have good unix skills with basic knowledge of project
architecture.

There are a lot of different GNU/Linux distributions with different package
management, naming convention and version release policies. So it is impossible
to cover all of the possible variants. We picked one distribution, which is
fully supported by automatic installation script, but there are also steps for
manual installation of all components which should work on most of the Linux
distributions.

The distribution of our choice is CentOS, currently in version 7. It is a well
known server distribution, derived from enterprise distrubution from Red Hat, so
it is very stable and widely used system with long term support. There are
[EPEL](https://fedoraproject.org/wiki/EPEL) additional repositories from Fedora
project, which adds newer versions of some packages into CentOS, which allows us
to use current environment. Also, _rpm_ packages are much easier to build than
_deb_ packages (for example from Python sources).

The big rival of CentOS in server distributions field is Debian. We are running
one instance of ReCodEx on Debian too. You need to use _testing_ repositories to
use some decent package versions. It is easy to mess your system easily, so
create file `/etc/apt/apt.conf` with content of `APT::Default-Release
"stable";`. After you add testing repos to `/etc/apt/sources.list`, you can
install packages from there like `$ sudo apt-get -t testing install gcc`.

Some components are also capable of running in Windows environment. However
setting up Windows OS is a little bit of pain and it is not supposed to run
ReCodEx in this way. Only worker component may be needed to run on Windows, so
we are providing clickable installer including dependencies. Just for info, all
components should be able to run on Windows, only broker was not tested and may
require small tweaks to work properly.

## Ansible installer

For automatic installation is used a set of Ansible scripts. Ansible is one of
the best known and used tools for automatic server management. It is required
only to have SSH access to the server and ansible installed on the client
machine. For further reading is supposed basic Ansible knowledge. For more info
check their [documentation](http://docs.ansible.com/ansible/intro.html).

All Ansible scripts are located in _utils_ repository, _installation_
[directory](https://github.com/ReCodEx/utils/tree/master/installation). Ansible
files are pretty self-describing, they can be also use as template for
installation to different systems. Before installation itself it is required to
edit two files -- set addresses of hosts and values of some variables.

### Hosts configuration

First, it is needed to set IP addresses of your computers. Common practise is to
have multiple files with definitions, one for development, another for
production for example. Example configuration is in _development_ file. Each
component of ReCodEx project can be installed on different server. Hosts can be
specified as hostnames or IP addresses, optionally with port of SSH after colon.

Shorten example of hosts config:

```
[workers]
127.0.0.1:22

[broker]
127.0.0.1:22

[all:children]
workers
broker
```

### Variables

Configurable variables are saved in _group_vars/all.yml_ file. Syntax is basic
key-value pair per line, separated by colon. Values with brief description:

- _source_dir_ -- Directory, where to store all sources from GitHub. Defaults
  `/opt/recodex`.
- _mysql_root_password_ -- Password of root user of MySQL database. Will be set
  after installation and saved to `/root/.my.cnf` file.
- _mysql_recodex_username_ -- MySQL username for ReCodEx API access.
- _mysql_recodex_password_ -- Password for the user above.
- _admin_email_ -- Email of administrator. Used when configuring Apache
  webserver.
- _recodex_hostname_ -- Hostname where the API and web app will be accessible.
  For example "recodex.projekty.ms.mff.cuni.cz".
- _webapp_node_addr_ -- IP address of NodeJS server running web app. Defaults to
  "127.0.0.1" and should not be changed.
- _webapp_node_port_ -- Port to above.
- _webapp_public_addr_ -- Public address, where web server for web app will
  listen. Defaults to "*".
- _webapp_public_port_ -- Port to above.
- _webapp_firewall_ -- Open port for web app in firewall, values "yes" or "no".
- _webapi_public_endpoint_ -- Public URL when the API will be running, for
  example "https://recodex.projekty.ms.mff.cuni.cz:4000/v1".
- _webapi_public_addr_ -- Public address, where web server for API will listen.
  Defaults to "*".
- _webapi_public_port_ -- Port to above.
- _webapi_firewall_ -- Open port for API in firewall, values "yes" or "no".
- _database_firewall_ -- Open port for database in firewall, values "yes" or
  "no".
- _broker_to_webapi_addr_ -- Address, where API can reach broker. Private one is
  recommended.
- _broker_to_webapi_port_ -- Port to above.
- _broker_firewall_api_ -- Open above port in firewall, "yes" or "no".
- _broker_to_workers_addr_ -- Address, where workers can reach broker. Private
  one is recommended.
- _broker_to_workers_port_ -- Port to above.
- _broker_firewall_workers_ -- Open above port in firewall, "yes" or "no".
- _broker_notifier_address_ -- URL (on API), where broker will send
  notifications, for example
  "https://recodex.projekty.ms.mff.cuni.cz/v1/broker-reports".
- _broker_notifier_port_ -- Port to above, should be the same as for API itself
  (_webapi_public_port_)
- _broker_notifier_username_ -- Username for HTTP Authentication for reports
- _broker_notifier_password_ -- Password for HTTP Authentication for reporst
- _monitor_websocket_addr_ -- Address, where websocket connection from monitor
  will be available
- _monitor_websocket_port_ -- Port to above.
- _monitor_firewall_websocket_ -- Open above port in firewall, "yes" or "no".
- _monitor_zeromq_addr_ -- Address, where monitor will be available on ZeroMQ
  socket for broker to receive reports.
- _monitor_zeromq_port_ -- Port to above.
- _monitor_firewall_zeromq_ -- Open above port in firewall, "yes" or "no".
- _fileserver_addr_ -- Address, where fileserver will serve files.
- _fileserver_port_ -- Port to above.
- _fileserver_firewall_ -- Open above port in firewall, "yes" or "no".
- _fileserver_username_ -- Username for HTTP Authentication for access the
  fileserver.
- _fileserver_password_ -- Password for HTTP Authentication for access the
  fileserver.
- _worker_cache_dir_ -- File cache storage for workers. Defaults to
  "/tmp/recodex/cache".
- _worker_cache_age_ -- How long hold fetched files in worker cache, in seconds.
- _isolate_version_ -- Git tag of Isolate version worker depends on.

### Installation itself

With your computers installed with CentOS and configuration modified it is time
to run the installation. 

```
$ ansible-playbook -i development recodex.yml
```

This command installs all components of ReCodEx onto machines listed in
_development_ file. It is possible to install only specified parts of project,
just use component's YAML file instead of _recodex.yml_.

Ansible expects to have password-less access to the remote machines. If you have
not such setup, use options `--ask-pass` and `--ask-become-pass`.


## Manual installation

### Worker

#### Dependencies

Worker specific requirements are written in this section. It covers only basic
requirements, additional runtimes or tools may be needed depending on type of
use. The package names are for CentOS if not specified otherwise. 

- ZeroMQ in version at least 4.0, packages `zeromq` and `zeromq-devel`
  (`libzmq3-dev` on Debian)
- YAML-CPP library, `yaml-cpp` and `yaml-cpp-devel` (`libyaml-cpp0.5v5` and
  `libyaml-cpp-dev` on Debian)
- libcurl library `libcurl-devel` (`libcurl4-gnutls-dev` on Debian)
- libarchive library as optional dependency. Installing will speed up build
  process, otherwise libarchive is built from source during installation.
  Package name is `libarchive` and `libarchive-devel` (`libarchive-dev` on
  Debian)

**Isolate** (only for Linux installations)

First, we need to compile sandbox Isolate from source and install it. Current
worker is tested against version 1.3, so this version needs to be checked out.
Assume that we keep source code in `/opt/src` dir. For building man page you
need to have package `asciidoc` installed.

```
$ cd /opt/src
$ git clone https://github.com/ioi/isolate.git
$ cd isolate
$ git checkout v1.3
$ make
# make install && make install-doc
```

For proper work Isolate depends on several advanced features of the Linux
kernel. Make sure that your kernel is compiled with `CONFIG_PID_NS`,
`CONFIG_IPC_NS`, `CONFIG_NET_NS`, `CONFIG_CPUSETS`, `CONFIG_CGROUP_CPUACCT`,
`CONFIG_MEMCG`. If your machine has swap enabled, also check
`CONFIG_MEMCG_SWAP`. With which flags was your kernel compiled with can be found
in `/boot` directory, file `config-` and version of your kernel. Red Hat based
distributions should have these enabled by default, for Debian you you may want
to add the parameters `cgroup_enable=memory swapaccount=1` to the kernel
command-line, which can be set by adding value `GRUB_CMDLINE_LINUX_DEFAULT` to
`/etc/default/grub` file.

For better reproducibility of results, some kernel parameters can be tweaked:

- Disable address space randomization. Create file
  `/etc/sysctl.d/10-recodex.conf` with content `kernel.randomize_va_space=0`.
  Changes will take effect after restart or run `sysctl
  kernel.randomize_va_space=0` command.
- Disable dynamic CPU frequency scaling. This requires setting the cpufreq
  scaling governor to _performance_.

#### Clone worker source code repository

```
$ git clone https://github.com/ReCodEx/worker.git
$ git submodule update --init
```

#### Install worker on Linux

It is supposed that your current working directory is that one with clonned
worker source codes.

- Prepare environment running `mkdir build && cd build`
- Build sources by `cmake ..` following by `make`
- Build binary package by `make package` (may require root permissions).  Note
  that `rpm` and `deb` packages are build in the same time. You may need to have
  `rpmbuild` command (usually as `rpmbuild` or `rpm` package) or edit
  CPACK_GENERATOR variable in _CMakeLists.txt_ file in root of source code tree.
- Install generated package through your package manager (`yum`, `dnf`, `dpkg`).

The worker installation process is composed of following steps:

- create config file `/etc/recodex/worker/config-1.yml`
- create systemd unit file `/etc/systemd/system/recodex-worker@.service`
- put main binary to `/usr/bin/recodex-worker`
- put judges binaries to `/usr/bin/` directory
- create system user and group `recodex` with `/sbin/nologin` shell (if not
  already existing)
- create log directory `/var/log/recodex`
- set ownership of config (`/etc/recodex`) and log (`/var/log/recodex`)
  directories to `recodex` user and group

_Note:_ If you do not want to generate binary packages, you can just install the
project with `make install` (as root). But installation through your
distribution's package manager is preferred way to keep your system clean and
manageable in long term horizon.

#### Install worker on Windows

There are basically two main dependencies needed, **Windows 7** or higher and
**Visual Studio 2015+**. Provided simple installation batch script should do all
the work on Windows machine. Officially only VS2015 and 32-bit compilation is
supported, because of hardcoded compile options in installation script. If
different VS or different platform is needed, the script should be changed to
appropriate values.

Mentioned script is placed in *install* directory alongside supportive scripts
for UNIX systems and is named *win-build.cmd*. Provided script will do almost
all the work connected with building and dependency resolving (using
**NuGet** package manager and `msbuild` building system). Script should be
run under 32-bit version of _Developer Command Prompt for VS2015_ and from
*install* directory.

Building and installing of worker is then quite simple, script has command line
parameters which can be used to specify what will be done:

- *-build* -- It is the default options if none specified. Builds worker and its
  tests, all is saved in *build* folder and subfolders.
- *-clean* -- Cleanup of downloaded NuGet packages and built
  application/libraries.
- *-test* -- Build worker and run tests on compiled test cases.
- *-package* -- Generation of clickable installation using cpack and
  [NSIS](http://nsis.sourceforge.net/) (has to be installed on machine to get
  this to work).

```
install> win-build.cmd  # same as: win-build.cmd -build
install> win-build.cmd -clean
install> win-build.cmd -test
install> win-build.cmd -package
```

All build binaries and cmake temporary files can be found in *build* folder,
classically there will be subfolder *Release* which will contain compiled
application with all needed dlls. Once if clickable installation binary is
created, it can be found in *build* folder under name 
*recodex-worker-VERSION-win32.exe*. Sample screenshot can be found on following
picture.

![NSIS Installation](https://github.com/ReCodEx/wiki/blob/master/images/nsis_installation.png)

#### Usage

A systemd unit file is distributed with the worker to simplify its launch. It 
integrates worker nicely into your Linux system and allows you to run it 
automatically on system startup. It is possible to have more than one worker on 
every server, so the provided unit file is templated. Each instance of the 
worker unit has a unique string identifier, which is used for managing that 
instance through systemd. By default, only one worker instance is ready to use 
after installation and its ID is "1".

- Starting worker with id "1" can be done this way:
```
# systemctl start recodex-worker@1.service
```
Check with
```
# systemctl status recodex-worker@1.service
```
if the worker is running. You should see "active (running)" message.

- Worker can be stopped or restarted accordigly using `systemctl stop` and
  `systemctl restart` commands.
- If you want to run worker after system startup, run:
```
# systemctl enable recodex-worker@1.service
```
For further information about using systemd please refer to systemd
documentation.

##### Adding new worker

To add a new worker you need to do a few steps:

- Make up an unique string ID.
- Copy default configuration file `/etc/recodex/worker/config-1.yml` to the same
  directory and name it `config-<your_unique_ID>.yml`
- Edit that config file to fit your needs. Note that you must at least change
  _worker-id_ and _logger file_ values to be unique.
- Run new instance using
```
# systemctl start recodex-worker@<your_unique_ID>.service
```

### Broker

#### Dependencies

Broker has similar basic dependencies as worker, for recapitulation:

- ZeroMQ in version at least 4.0, packages `zeromq` and `zeromq-devel`
  (`libzmq3-dev` on Debian)
- YAML-CPP library, `yaml-cpp` and `yaml-cpp-devel` (`libyaml-cpp0.5v5` and
  `libyaml-cpp-dev` on Debian)
- libcurl library `libcurl-devel` (`libcurl4-gnutls-dev` on Debian)

#### Clone broker source code repository

```
$ git clone https://github.com/ReCodEx/broker.git
$ git submodule update --init
```

#### Installation itself

Installation of broker program does following step to your computer:

- create config file `/etc/recodex/broker/config.yml`
- create _systemd_ unit file `/etc/systemd/system/recodex-broker.service`
- put main binary to `/usr/bin/recodex-broker`
- create system user and group `recodex` with nologin shell (if not existing)
- create log directory `/var/log/recodex`
- set ownership of config (`/etc/recodex`) and log (`/var/log/recodex`)
  directories to `recodex` user and group

It is supposed that your current working directory is that one with clonned
worker source codes.

- Prepare environment running `mkdir build && cd build`
- Build sources by `cmake ..` following by `make`
- Build binary package by `make package` (may require root permissions).  Note
  that `rpm` and `deb` packages are build in the same time. You may need to have
  `rpmbuild` command (usually as `rpmbuild` or `rpm` package) or edit
  CPACK_GENERATOR variable _CMakeLists.txt_ file in root of source code tree.
- Install generated package through your package manager (`yum`, `dnf`, `dpkg`).

_Note:_ If you do not want to generate binary packages, you can just install the
project with `make install` (as root). But installation through your
distribution's package manager is preferred way to keep your system clean and
manageable in long term horizon.

#### Usage

Running broker is very similar to the worker setup. There is also provided
systemd unit file for convenient usage. There is only one broker per whole
ReCodEx solution, so there is no need for systemd templates.

- Running broker can be done by following command:
```
# systemctl start recodex-broker.service
```
Check with
```
# systemctl status recodex-broker.service
```
if the broker is running. You should see "active (running)" message.

- Broker can be stopped or restarted accordigly using `systemctl stop` and
  `systemctl restart` commands.
- If you want to run broker after system startup, run:
```
# systemctl enable recodex-broker.service
```

For further information about using systemd please refer to systemd
documentation.

### Fileserver

To install and use the fileserver, it is necessary to have Python3 with `pip`
package manager installed. It is needed to install the dependencies. From
clonned repository run the following command:

```
$ pip install -r requirements.txt
```

That is it. Fileserver does not need any special installation. It is possible to
build and install _rpm_ package or install it without packaging the same way as
monitor, but it is only optional. The installation would provide you with script
`recodex-fileserver` in you `PATH`. No systemd unit files are provided, because
of the configuration and usage of fileserver component is much different to our
other Python parts.

#### Usage

There are several ways of running the ReCodEx fileserver. We will cover three 
typical use cases.

##### Running in development mode

For simple development usage, it is possible to run the fileserver in the
command line. Allowed options are described below.

```
usage: fileserver.py [--directory WORKING_DIRECTORY]
                     {runserver,shell} ...
```

- **runserver** argument starts the Flask development server (i.e. `app.run()`).
  As additional argument can be given a port number.
- **shell** argument instructs Flask to run a Python shell inside application
  context.

Simple development server on port 9999 can be run as

```
$ python3 fileserver.py runserver 9999
```

When run like this command, the fileserver creates a temporary directory where
it stores all the files and which is deleted when it exits.

##### Running as WSGI script in a web server

If you need features such as HTTP authentication (recommended) or efficient
serving of static files, it is recommended to run the app in a full-fledged web
server (such as Apache or Nginx) using WSGI. Apache configuration can be
generated by `mkconfig.py` script from the repository.

```
usage: mkconfig.py apache [-h] [--port PORT] --working-directory
                          WORKING_DIRECTORY [--htpasswd HTPASSWD]
                          [--user USER]
```

- **port** -- port where the fileserver should listen
- **working_directory** -- directory where the files should be stored
- **htpasswd** -- path to user file for HTTP Basic Authentication
- **user** -- user under which the server should be run

##### Running using uWSGI

Another option is to run fileserver as a standalone app via uWSGI service. Setup
is also quite simple, configuration file can be also generated by `mkconfig.py`
script.

1. (Optional) Create a user for running the fileserver
2. Make sure that your user can access your clone of the repository
3. Run `mkconfig.py` script.
	```
	usage: mkconfig.py uwsgi [-h] [--user USER] [--port PORT]
	                         [--socket SOCKET]
                             --working-directory WORKING_DIRECTORY
	```

	- **user** -- user under which the server should be run
	- **port** -- port where the fileserver should listen
	- **socket** -- path to UNIX socket where the fileserver should listen
	- **working_directory** -- directory where the files should be stored
	
4. Save the configuration file generated by the script and run it with uWSGI, 
   either directly or using systemd. This depends heavily on your distribution.
5. To integrate this with another web server, see the [uWSGI 
   documentation](http://uwsgi-docs.readthedocs.io/en/latest/WebServers.html)

Note that the ways distributions package uWSGI can vary wildly. In Debian 8 it
is necessary to convert the configuration file to XML and make sure that the
python3 plugin is loaded instead of python. This plugin also uses Python 3.4,
even though the rest of the system uses Python 3.5 - make sure to install
dependencies for the correct version. 

### Monitor

For monitor functionality there are some required packages. All of them are
listed in _requirements.txt_ file in the repository and can be installed by
`pip` package manager as

```
$ pip install -r requirements.txt
```

**Description of dependencies:**

- zmq -- binding to ZeroMQ framework
- websockets -- framework for communication over WebSockets
- asyncio -- library for fast asynchronous operations
- pyyaml -- parsing YAML configuration files
- argparse -- parsing command line arguments

Installation will provide you following files:

- `/usr/bin/recodex-monitor` -- simple startup script located in PATH
- `/etc/recodex/monitor/config.yml` -- configuration file
- `/etc/systemd/system/recodex-monitor.service` -- systemd startup script
- code files will be installed in location depending on your system settings,
  mostly into `/usr/lib/python3.5/site-packages/monitor/` or similar

Systemd script runs monitor binary as specific _recodex_ user, so in `postinst`
script user and group of this name are created. Also, ownership of configuration
file will be granted to that user.

- RPM distributions can make and install binary package. This can be done like
  this:
	- run command
	```
	$ python3 setup.py bdist_rpm --post-install ./install/postints
	```
	to generate binary `.rpm` package or download precompiled one from releases
	tab of monitor GitHub repository (it is architecture independent package)
	- install package using
	```
	# yum install ./dist/recodex-monitor-<version>-1.noarch.rpm
	```
- Other Linux distributions can install cleaner straight
	```
	$ python3 setup.py install --install-scripts /usr/bin
	# ./install/postinst
	```
	
#### Usage

Preferred way to start monitor as a service is via systemd as the other parts of
ReCodEx solution.

- Running monitor is fairly simple:
```
# systemctl start recodex-monitor.service
```
- Current state can be obtained by
```
# systemctl status recodex-monitor.service
```
You should see green **Active (running)**.
- Setting up monitor to be started on system startup:
```
# systemctl enable recodex-monitor.service
```

Alternatively monitor can be started directly from command line with specifying
path to configuration file. Note that this command will not start monitor as a
daemon.

```
$ recodex-monitor -c /etc/recodex/monitor/config.yml
```


### Cleaner

To install and use the cleaner, it is necessary to have Python3 with package
manager `pip` installed.

- Dependencies of cleaner has to be installed:
```
$ pip install -r requirements.txt
```
- RPM distributions can make and install binary package. This can be done like
  this:
```
$ python setup.py bdist_rpm --post-install ./cleaner/install/postinst
```
- Installing generated package using YUM:
```
# yum install ./dist/recodex-cleaner-<version>-1.noarch.rpm
```
- Other Linux distributions can install cleaner straight
```
$ python setup.py install --install-scripts /usr/bin
# ./cleaner/install/postinst
```
- For Windows installation do following:
	- start `cmd` with administrator permissions
	- run installation with
	```
	> python setup.py install --install-scripts \
	  "C:\Program Files\ReCodEx\cleaner"
	```
	where path specified with `--install-scripts` can be changed
	- copy configuration file alongside with installed executable using
	```
	> copy install\config.yml \
	  "C:\Program Files\ReCodEx\cleaner\config.yml"
	```

#### Usage

As stated before cleaner should be cronned, on linux systems this can be done by
built in `cron` service or if there is `systemd` present cleaner itself provides
`*.timer` file which can be used for cronning from `systemd`. On Windows systems
internal scheduler should be used.

- Running cleaner from command line is fairly simple:
```
$ recodex-cleaner -c /etc/recodex/cleaner
```
- Enable cleaner service using systemd:
```
$ systemctl start recodex-cleaner.timer
```
- Add cleaner to linux cron service using following configuration line: 
```
0 0 * * * /usr/bin/recodex-cleaner -c /etc/recodex/cleaner/config.yml
```
- Add cleaner to Windows cheduler service with following command:
```
> schtasks /create /sc daily /tn "ReCodEx Cleaner" /tr \
  "\"C:\Program Files\ReCodEx\cleaner\recodex-cleaner.exe\" \
  -c \"C:\Program Files\ReCodEx\cleaner\config.yml\""
```

### REST API

The web API requires a PHP runtime version at least 7. Which one depends on
actual configuration, there is a choice between _mod_php_ inside Apache,
_php-fpm_ with Apache or Nginx proxy or running it as standalone uWSGI script.
It is common that there are some PHP extensions, that have to be installed on
the system. Namely ZeroMQ binding (`php-zmq` package or similar), MySQL module
(`php-mysqlnd` package) and ldap extension module for CAS authentication
(`php-ldap` package). Make sure that the extensions are loaded in your `php.ini`
file (`/etc/php.ini` or files in `/etc/php.d/`).

The API depends on some other projects and libraries. For managing them
[Composer](https://getcomposer.org/) is used. It can be installed from system
repositories or downloaded from the website, where detailed instructions are as
well. Composer reads `composer.json` file in the project root and installs
dependencies to the `vendor/` subdirectory. To do that, run:

```
$ composer install
```

#### Database preparation

When the API is installed and configured (_doctrine_ section is sufficient here)
the database schema can be generated. There is a prepared command to do that
from command line:

```
$ php www/index.php orm:schema-tool:update --force
```

With API comes some initial values, for example default user roles with proper
permissions. To fill your database with these values there is another command
line command:

```
$ php www/index.php db:fill
```

Check the outputs of both commands for errors. If there are any, try to clean
temporary API cache in `temp/cache/` directory and repeat the action.

#### Webserver configuration

The simplest way to get started is to start the built-in PHP server in the root
directory of your project:

```
$ php -S localhost:4000 -t www
```

Then visit `http://localhost:4000` in your browser to see the welcome page of
API project.

For Apache or Nginx, setup a virtual host to point to the `www/` directory of
the project and you should be ready to go. It is **critical** that whole `app/`,
`log/` and `temp/` directories are not accessible directly via a web browser
(see [security warning](https://nette.org/security-warning)). Also it is
**highly recommended** to set up a HTTPS certificate for public access to the
API.

#### Troubleshooting

In case of any issues first remove the Nette cache directory `temp/cache/` and
try again. This solves most of the errors. If it does not help, examine API logs
from `log/` directory of the API source or logs of your webserver.

### Web application

Web application requires [NodeJS](https://nodejs.org/en/) server as its runtime
environment. This runtime is needed for executing JavaScript code on server and
sending the pre-render parts of pages to clients, so the final rendering in
browsers is a lot quicker and the page is accessible to search engines for
indexing.

But some functionality is better in other full fledged web servers like *Apache*
or *Nginx*, so the common practice is to use a tandem of both. *NodeJS* takes
care of basic functionality of the app while the other server (Apache) is set as
reverse proxy and providing additional functionality like SSL encryption, load
balancing or caching of static files. The recommended setup contains both NodeJS
and one of Apache and Nginx web servers for the reasons discussed above. 

Stable versions of 4th and 6th series of NodeJS server are sufficient, using at
least 6th series is highly recommended. Please check the most recent version of
the packages in your distribution's repositories, there are often outdated ones.
However, there are some third party repositories for all main Linux
distributions.

The app depends on several libraries and components, all of them are listed in
`package.json` file in source repository. For managing dependencies is used node
package manager (`npm`), which can come with NodeJS installation otherwise can
be installed separately. To fetch and install all dependencies run:

```
$ npm install
```

For easy production usage there is an additional package for managing NodeJS
processes, `pm2`. This tool can run your application as a daemon, monitor
occupied resources, gather logs and provide simple console interface for
managing app's state. To install it globally into your system run:

```
# npm install pm2 -g
```

#### Usage

The application can be run in two modes, development and production. Development
mode uses only client rendering and tracks code changes with rebuilds of the
application in real time. In production mode the compilation (transpile to _ES5_
standard using *Babel* and bundle into single file using *webpack*) has to be
done separately prior to running. The scripts for compilation are provided as
additional `npm` commands.

- Development mode can be use for local testing of the app. This mode uses
  webpack dev server, so all code runs on a client, there is no server side
  rendering available. Starting is simple command, default address is
  http://localhost:8080.
```
$ npm run dev
```
- Production mode is mostly used on the servers. It provides all features such
  as server side rendering. This can be run via:
```
$ npm run build
$ npm start
```

Both modes can be configured to use different ports or set base address of used
API server. This can be configured in `.env` file in root of the repository.
There is `.env-sample` file which can be just copied and altered.

The production mode can be run also as a demon controled by `pm2` tool. First
the web application has to be built and then the server javascript file can run
as a daemon.

```
$ npm run build
$ pm2 start bin/server.js
```

The `pm2` tool has several options, most notably _status_, _stop_, _restart_ and
_logs_. Further description is available on project
[website](http://pm2.keymetrics.io).


## Security

One of the most important aspects of ReCodEx instance is security. It is crucial
to keep gathered data safe and not to allow unauthorized users modify restricted
pieces of information. Here is a small list of recommendations to keep running
ReCodEx instance safe.

- Secure MySQL installation. The installation script does not do any security
  actions, so please run at least `mysql_secure_installation` script on database
  computer.
- Get HTTPS certificate and set it in Apache for web application and API.
  Monitor should be proxied through the web server too with valid certificate.
  You can get free DV certificate from [Let's
  Encrypt](https://letsencrypt.org/). Do not forget to set up automatic
  renewing!
- Hide broker, workers and fileserver behind firewall, private subnet or IPsec
  tunnel. They are not required to be reached from public internet, so it is
  better keep them isolated.
- Keep your server updated and well configured. For automatic installation of
  security updates on CentOS system refer to `yum-cron` package. Configure SSH
  and Apache to use only strong ciphers, some recommendations can be found
  [here](https://bettercrypto.org/static/applied-crypto-hardening.pdf).
- Do not put actually used credentials on web, for example do not commit your
  passwords (in Ansible variables file) on GitHub.
- Regularly check logs for anomalies.


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