The Climate Explorer application backend utilizes Apollo GraphQL to provide access to data and services required by the frontend application.
The API is based on Apollo GraphQL and makes the following queries and mutations available to the frontend application.
| Type | Name | Description |
|---|---|---|
| Query | user(email) | Retrieves a specific user given an email address |
| Mutation | login(email) | Retrieves a login token for the user with the specified email address |
To start the application in development mode simply run npm run startfrom
the command line. The application will automatically open a new tab in your
browser with the url localhost:4000.
To start the application in production mode run npm run serve
from the command line. In production mode the app will automatically create a
new browser tab with the url localhost:5000. The main difference between
production and development modes is a Service Worker runs in productin mode to
support offline execution.
The production version of the app on GitHub Pages is built by running npm run publish.
Climate Explorer uses MongoDB as an intermediate staging area for the ingestion
and cleansing of data prior to adding it to the Postgres database. Due to this
dependency this application requires a running instance of a MongoDB database.
For example, on MacOS MongoDB is started by opening a new terminal window and
entering the command mongodb --replSet rs0.
Since the ETL process relies on MongoDB transactions the instance that supports our test environment is a single-node replica set.
The steps required to install MongoDB are be found here.
PostgreSQL is used as the operational database for climate data and is populated from the staging database. At this time the PostgreSQL instance is started from the pgAdmin tool.
The steps required to install PostgreSQL are found here.
Environment variables that control the operation of the app are defined in the
.env file in the application root. These variables and their usage are shown
in the following table. It's important to keep in mind that when these settings
in the .env file are changed npm run build must be run before they will
take effect.
Environment variables maintained in the .env file are made available to the
application code via process.env.<variable-name>. For example, the
homepage for the NOAA site is accessed in the code by referencing
process.env.NOAA_HOMEPAGE.
Remember that even though this keeps secure tokens like client id's and secrets out of application code it does not make them secure.
| Environment Variable | Description | Example Setting |
|---|---|---|
| MONGODB_URL | MongoDB instance | MONGODB_URL="mongodb://localhost:27017/etl" |
| MONGODB_CE_DBNAME | Climate Explorer database name | MONGODB_CE_DBNAME="etl" |
| PG_CONNECTION_USER | Postgres User id | PG_CONNECTION_USER="xxxxxxxx" |
| PG_CONNECTION_PASSWORD | Postgres Password | PG_CONNECTION_PASSWORD="xxxxxxxx" |
| PG_CONNECTION_HOSTADDR | Postgres instance host address | PG_CONNECTION_HOSTADDR="127.0.0.1" |
| PG_CONNECTION_PORT | Postgres instance port number | PG_CONNECTION_PORT="5432" |
| PG_CONNECTION_DBNAME | Postgres database name | PG_CONNECTION_DBNAME="climateexplorer" |
| PG_CONNECTION_SCHEMA | Postgres schema name | PG_CONNECTION_SCHEMA="ce" |
This app has the following dependencies
| Module/Library | Environment | Description | Related Files |
|---|---|---|---|
| apollo | Developmenbt | Apollo CLI | N/a |
| apollo-datasource | Runtime | - | N/a |
| apollo-link | Runtime | GraphQL Transport Layer | N/a |
| apollo-link-http | Runtime | GraphQL HTTP Transport | N/a |
| apollo-server | Runtime | GraphQL Server | N/a |
| babel-plugin-transform-object-rest-spread | Development | Babel plugin | .babelrc |
| babel-preset-env | Development | Babel ES6 presets | .babelrc |
| dotenv | Runtime | Environment variables | .env |
| graphql | Runtime | GraphQL Reference implementation | N/a |
| isemail | Runtime | Email address validator | N/a |
| mongodb | Runtime | MongoDB Driver | N/a |
| nodemon | Development | NodeJS Monitor | package.json scripts |
| pg | Runtime | PostgreSQL Driver | N/a |
The MongoDB and Postgres databases files required by Climate Explorer are
stored in a file system outside the project directory. In the case of MongoDB
the database files are maintained in /data/db, and the PostgreSQL files are
in /data/pg.
The architecture of the server is shown in the following diagram.
