Middleware or request lifecycle hook to run after procedure?

Mminty

11/16/2023

Hi, I am using trpc context to create a database client for an incoming request. My understanding is this runs for every request, which is what I want. I want to be able to systematically close the databaase client at the end of any TRPC request. Is there any way of doing this? Perhaps with a middleware or request lifecycle hook? I couldn't find any documentation on it. This is the structure I want:

1. Request start
2. Context is created --> DB open
3. Procedure runs
4. DB is closed

1. Request start
2. Context is created --> DB open
3. Procedure runs
4. DB is closed

Thank you!

Solution:

is this sort of what you mean? ``` const withDb = middleware((opts) => { const db = getServerlessDBInstance();...

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Nnlucas

11/16/2023

Yep just await next() into a variable, do your work, and then return the variable But generally with DBs you want to have a persistent pool, opening and closing connections is expensive, so maintaining a pool instance means there are always some open connections available

Mminty

11/16/2023

I am using Neon (neon.tech) as my DB provider and they explicitly say to close it at the end of every request:

The Pool and Client objects must be connected, used, and closed within a single request handler. Don't create the objects outside a request handler; don't create them in one handler and try to reuse them in another; and to avoid exhausting available connections, don't forget to close them.

The Pool and Client objects must be connected, used, and closed within a single request handler. Don't create the objects outside a request handler; don't create them in one handler and try to reuse them in another; and to avoid exhausting available connections, don't forget to close them.

from here: https://neon.tech/docs/serverless/serverless-driver Can you explain what you mean why the awaiting the next() variable? I would like the procedure to have access to the ctx.db, but not have to remember to close it Oh I think I see what you mean. Like the middleware would be:

openDB()

const result = await next()

closeDB()

return result

openDB()

const result = await next()

closeDB()

return result

is that what you mean?

Nnlucas

11/16/2023

Fair enough then! Obviously their advice takes precedence 🙂 Yep! Middlewares are flexible 🙂

Mminty

11/16/2023

got it, thank you! I will try that out

Nnlucas

11/16/2023

You can add the DB in to the ctx by passing it to next() as well

Mminty

11/16/2023

ahh perfect ok

Nnlucas

11/16/2023

it will be merged, no pain needed from you

Solution

Mminty

11/16/2023

is this sort of what you mean?

const withDb = middleware((opts) => {
  const db = getServerlessDBInstance();

  const result = opts.next({ ctx: { db } });

  return result;
});

const withDb = middleware((opts) => {
  const db = getServerlessDBInstance();

  const result = opts.next({ ctx: { db } });

  return result;
});

Mminty

11/16/2023

(obviously I will add the db.end() as well)

Nnlucas

11/16/2023