Redis client won't set values upon message received - redis

Question

The initial set of the values happens on the server (\complex\server\index.js):
app.post('/values', async (req, res) => {
const index = req.body.index;
if (parseInt(index) > 40) {
return res.status(422).send('Index too high');
}
redisClient.hset('values', index, 'Nothing yet!');
redisPublisher.publish('insert', index);
pgClient.query('INSERT INTO values(number) VALUES($1)', [index]);
res.send({ working: true });
});
On value submit in component (\complex\client\src\Fib.js):
handleSubmit = async (event) => {
event.preventDefault();
await axios.post('/api/values', {
index: this.state.index
});
this.setState({ index: '' });
};
the worker sets the value for the Redis client:
sub.on('message', (channel, message) => {
redisClient.hset('values', message, fib(parseInt(message)));
});
sub.subscribe('insert');
However when list all the values inside the Fib.js component for each submitted index the component receives 'Nothing yet!'.
Why would it not receive the calculated values?
The complete repo is on https://github.com/ElAnonimo/docker-complex

Answer 1

redisClient.hset('values', index, 'Nothing yet!'); is asynchronous -- it needs to connect to Redis, send a message, wait for a response, etc.
So what probably happens is a race-condition, redisPublisher.publish('insert', index); runs before hset is completes.
I haven't gone over the code, so you'd also want to make sure to avoid a similiar race-condition with subscribe() being called after publish().
Try this:
app.post('/values', async (req, res) => {
const index = req.body.index;
if (parseInt(index) > 40) {
return res.status(422).send('Index too high');
}
redisClient.hset('values', index, 'Nothing yet!', () => redisPublisher.publish('insert', index));
pgClient.query('INSERT INTO values(number) VALUES($1)', [index]);
res.send({ working: true });
});

Answer 2

The problem is with your docker-compose.yml file.
You have to specify the environment variables for the worker container and specify the redis host and port (just like how you specified for the server container):
worker:
environment:
- REDIS_HOST=redis
- REDIS_PORT=6379