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How to get this working?

Compile

First of all, you need to clone the repository with the server sources and build it using stack. Usually it is enough to just run stack build, all the libraries will be compiled automatically. Eventually building can crash because of some external libraries that are not installed on your machine. If you are using Linux, you can just install them yourself. For example, if you are using Ubuntu and the pq library is missing, just install libpq-dev package using # apt install libpq-dev. Generally, for most cases if (libname) is missing, the package lib(libname)-dev is what you need.

Create database

After the application is compiled, it still can't work as it needs also a database. Here PostgreSQL database is used, so you need to install it on you machine. First of all, you need to create database. The instruction here supposes that database works on the same machine with web-server; if it is not true, a little changes should be made: see postgreSQL documentaion. We will refer to the database name as databaseName. Also you will need the user for the application to work with the database. We will refer to it as to databaseOwner. So, next commands are to be run using postgreSQL superuser:

    CREATE DATABASE databaseName;
    CREATE USER databaseOwner PASSWORD <ownerPassword>;
    ALTER DATABASE databaseName OWNER TO databaseOwner;

The application gets all the data from the configuration file, so you need to put it there. See configuration file format below. In this section we will use file config.dhall.

After users are created, you need to create the entire database. It is rather easy since the web-server supports migrations and has a separate command-line argument to apply all the migrations to the given database. To run migrations, use stack exec weather-exe -- ./config.conf -m.

In the end, you should let PostgreSQL know, who can connect to the database and what authentication method should be used. If the database is on the same machine with the server, the next line is to be added to pg_hba.conf:

local databaseName databaseOwner password

Configuration file

The example of the configuration file is inside the src directory.

{ dhallDatabaseName = "weather_db"
, dhallDatabaseUser = "weather_owner"
, dhallDatabasePassword = "0000"

, dhallFillerCities =
    [ 499717 -- rzhev 
    , 543899 -- kostomuksha
    , 4171563 -- stPetersburg
    , 499622 -- moskvorechie-saburovo 
    ]

, dhallFillerSleepTimeSeconds = 600

, dhallServerTimeEpsSeconds = 1000
, dhallServerLatEps = 0.2
, dhallServerLonEps = 0.1
, dhallServerPort = 8081
}

Note that since Dhall is used for the configuration, you should use ./src/config.dhall, not src/config.dhall when starting the server.

Command line options

The first command-line option is always path to the configuration file. The second one is for the name of an environmental variable which contains OpenWeather API key. The order of subsequent options can be arbitrary.

  • -m is used to perform the migrations;
  • --test-config is used to test server configuration. Data from config file will be get and then process will terminate with success exitcode;
  • -l is used to define logging settings. Currently logger can only log messages with given priority or higher. For example, to log Warning, Error and Fatal messages use; -l Warning. The default is -l Debug, which logs all messages;
  • --logpathfillers <path> is used to define the path to the log file of fillers;
  • --logpathserver <path> is used to define the path to the log file of server.

API

The server supports one method, /weather. You can define the location by its id (see OpenWeather API website), city name or geographic coordinates (latitude and longitude). The time is defined as number of seconds since Epoch (UTC +0). Parameters:

  • dt (Integer, optional) - time since Epoch, seconds, UTC +0;
  • city_id (Integer) - city OpenWeather identifier;
  • city_name (Integer) - city name;
  • lat (Double) - location latitude;
  • lon (Double) - location longitude.

If incorrect combination of parameters is used, usage will be returned inside message field.

The returned record has following fields:

  • ok (Bool) - indicates if no error occured;
  • cod (Integer) - shows the response code;
  • message (String) - describes the result, either error or not;
  • data - the same record that OpenWeather API returns, if no error occured.