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RESP3 Support - Some commands responses in RESP3 aren't stable yet and therefore return an "untyped" ReplyUnion. Sentinel TypeMapping Correctly types Multi commands Note: some API changes to be further documented in v4-to-v5.md
75 lines
2.9 KiB
Markdown
75 lines
2.9 KiB
Markdown
# `RedisClientPool`
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Sometimes you want to run your commands on an exclusive connection. There are a few reasons to do this:
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- You want to run a blocking command that will take over the connection, such as `BLPOP` or `BLMOVE`.
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- You're using [transactions](https://redis.io/docs/interact/transactions/) and need to `WATCH` a key or keys for changes.
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- Some more...
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For those use cases you'll need to create a connection pool.
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## Creating a pool
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You can create a pool using the `createClientPool` function:
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```javascript
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import { createClientPool } from 'redis';
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const pool = await createClientPool()
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.on('error', err => console.error('Redis Client Pool Error', err));
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```
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the function accepts two arguments, the client configuration (see [here](./client-configuration.md) for more details), and the pool configuration:
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| Property | Default | Description |
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|----------------|---------|--------------------------------------------------------------------------------------------------------------------------------|
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| minimum | 1 | The minimum clients the pool should hold to. The pool won't close clients if the pool size is less than the minimum. |
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| maximum | 100 | The maximum clients the pool will have at once. The pool won't create any more resources and queue requests in memory. |
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| acquireTimeout | 3000 | The maximum time (in ms) a task can wait in the queue. The pool will reject the task with `TimeoutError` in case of a timeout. |
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| cleanupDelay | 3000 | The time to wait before cleaning up unused clients. |
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You can also create a pool from a client (reusing it's configuration):
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```javascript
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const pool = await client.createPool()
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.on('error', err => console.error('Redis Client Pool Error', err));
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```
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## The Simple Scenario
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All the client APIs are exposed on the pool instance directly, and will execute the commands using one of the available clients.
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```javascript
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await pool.sendCommand(['PING']); // 'PONG'
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await client.ping(); // 'PONG'
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await client.withTypeMapping({
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[RESP_TYPES.SIMPLE_STRING]: Buffer
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}).ping(); // Buffer
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```
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## Transactions
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Things get a little more complex with transactions. Here we are `.watch()`ing some keys. If the keys change during the transaction, a `WatchError` is thrown when `.exec()` is called:
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```javascript
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try {
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await pool.execute(async client => {
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await client.watch('key');
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const multi = client.multi()
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.ping()
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.get('key');
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if (Math.random() > 0.5) {
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await client.watch('another-key');
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multi.set('another-key', await client.get('another-key') / 2);
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}
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return multi.exec();
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});
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} catch (err) {
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if (err instanceof WatchError) {
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// the transaction aborted
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}
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}
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```
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