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app.ts
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app.ts
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import express from 'express';
import {WebSocketServer} from 'ws';
import {Extra, useServer} from 'graphql-ws/lib/use/ws';
import {buildSchema, parse, validate} from 'graphql';
import MaterializeClient from './MaterializeClient';
import EventEmitter from 'events';
import {Pool} from 'pg';
import {Context, SubscribeMessage} from 'graphql-ws';
/**
* Materialize Client
*/
const mzHost = process.env.MZ_HOST || 'materialized';
const mzPort = Number(process.env.MZ_PORT) || 6875;
const mzUser = process.env.MZ_USER || 'materialize';
const mzPassword = process.env.MZ_PASSWORD || 'materialize';
const mzDatabase = process.env.MZ_DATABASE || 'materialize';
const materializeClient = new MaterializeClient({
host: mzHost,
port: mzPort,
user: mzUser,
password: mzPassword,
database: mzDatabase,
ssl: true,
query_timeout: 5000,
});
/**
* Postgres Client
*/
const pgPass = process.env.POSTGRES_PASSWORD || 'pg_password';
const postgresPool = new Pool({
// host: "localhost",
host: 'postgres',
port: 5432,
user: 'postgres',
password: pgPass,
database: 'postgres',
});
/**
* Build GraphQL Schema
*/
const schema = buildSchema(`
type Antenna {
antenna_id: String
geojson: String
performance: Float
diff: Int
timestamp: Float
}
type Query {
getAntennas: [Antenna]
}
type Mutation {
crashAntenna(antenna_id: String!): Antenna
}
type Subscription {
antennasUpdates: [Antenna]
}
`);
/**
* Map to follow connections and subscribes
*/
const connectionEventEmitter = new EventEmitter();
/**
* Build a custom Postgres insert with a low performance value to crash antenna
* @param antennaId Antenna Identifier
* @returns
*/
function buildQuery(antennaId: number) {
return `
INSERT INTO antennas_performance (antenna_id, clients_connected, performance, updated_at) VALUES (
${antennaId},
${Math.ceil(Math.random() * 100)},
-100,
now()
);
`;
}
/**
* Queries
*/
const getAntennas = async () => {
try {
const {rows} = await materializeClient.query('SELECT * FROM antennas;');
/**
* Stringify GEOJson
*/
const mappedRows = rows.map((x) => ({
...x,
geojson: JSON.stringify(x.geojson),
}));
return mappedRows;
} catch (err) {
console.log('Error running query.');
console.error(err);
}
return 'Hello!';
};
/**
* Mutations
*/
const crashAntenna = async (context) => {
const {antenna_id: antennaId} = context;
postgresPool.connect(async (err, client, done) => {
if (err) {
console.error(err);
return;
}
try {
/**
* Smash the performance
*/
const query = buildQuery(antennaId);
await client.query(query);
} catch (clientErr) {
console.error(clientErr);
} finally {
done();
}
});
return {
antenna_id: antennaId,
};
};
/**
* Subscriptions
*/
async function* antennasUpdates(_, ctxVars) {
const [subscriptionId] = ctxVars;
try {
/**
* Yield helpers
*/
let results = [];
let resolve: (value: unknown) => void;
let promise = new Promise((r) => (resolve = r));
let done = false;
/**
* Listen subscribe events
*/
const eventEmmiter = new EventEmitter();
eventEmmiter.on('data', (data) => {
const mappedData: Array<any> = data.map((x) => ({
...x,
geojson: JSON.stringify(x.geojson),
diff: x.mz_diff,
timestamp: x.mz_timestamp,
}));
results = mappedData;
resolve(mappedData);
promise = new Promise((r) => (resolve = r));
});
materializeClient
.subscribe('SUBSCRIBE (SELECT * FROM last_half_minute_performance_per_antenna)', eventEmmiter)
.catch((subscribeErr) => {
console.error('Error running SUBSCRIBE.');
console.error(subscribeErr);
})
.finally(() => {
console.log('Finished SUBSCRIBE.');
done = true;
resolve([]);
});
connectionEventEmitter.on('disconnect', (unsubscriptionId) => {
if (subscriptionId === unsubscriptionId) {
eventEmmiter.emit('disconnect');
done = true;
}
});
/**
* Yield results
*/
while (!done) {
await promise;
yield {antennasUpdates: results};
results = [];
}
console.log('Outside done.');
} catch (error) {
console.error('Error running antennas updates subscription.');
console.error(error);
}
}
/**
* The roots provide resolvers for each GraphQL operation
*/
const roots = {
query: {
getAntennas,
},
mutation: {
crashAntenna,
},
subscription: {
antennasUpdates,
},
};
/**
* Connection handlers
*/
const onClose = () => {
console.log('onClose ids');
};
const onConnect = () => {
console.log('onConnect.');
};
const onDisconnect = (ctx) => {
const ids = Object.keys(ctx.subscriptions);
ids.forEach((id) => connectionEventEmitter.emit('disconnect', id));
};
const onError = (ctx, msg, errors) => {
console.error('onError: ', ctx, msg, errors);
};
const onSubscribe: (
ctx: Context<Extra & Partial<Record<PropertyKey, never>>>,
message: SubscribeMessage
) => any = (ctx, msg) => {
const ids = Object.keys(ctx.subscriptions);
console.log('OnSubscribe ids: ', ids);
const args = {
schema,
operationName: msg.payload.operationName,
document: parse(msg.payload.query),
variableValues: msg.payload.variables,
};
// dont forget to validate when returning custom execution args!
const errors = validate(args.schema, args.document);
if (errors.length > 0) {
return errors; // return `GraphQLError[]` to send `ErrorMessage` and stop subscription
}
return {...args, contextValue: ids};
};
/**
* Setup server
*/
const app = express();
const server = app.listen(4000, () => {
const wsServer = new WebSocketServer({
server,
path: '/graphql',
});
wsServer.on('error', (serverError) => {
console.error('Server error: ', serverError);
});
wsServer.on('connection', (ws) => {
ws.on('error', (socketError) => {
console.error('Socket error: ', socketError);
});
});
useServer({schema, roots, onClose, onDisconnect, onError, onSubscribe, onConnect}, wsServer);
console.log(
"🚀 GraphQL web socket server listening on port 4000. \n\nUse 'ws://localhost:4000/graphql' to connect."
);
});