transactions.md

Transactions (MULTI/EXEC)

Start a transaction by calling .multi(), then chaining your commands. When you're done, call .exec() and you'll get an array back with your results:

const [setReply, getReply] = await client.multi()
  .set('key', 'value')
  .get('another-key')
  .exec();

exec<'typed'>()/execTyped()

A transaction invoked with .exec<'typed'>/execTyped() will return types appropriate to the commands in the transaction:

const multi = client.multi().ping();
await multi.exec(); // Array<ReplyUnion>
await multi.exec<'typed'>(); // [string]
await multi.execTyped(); // [string]

⚠️ this only works when all the commands are invoked in a single "call chain"

WATCH

You can also watch keys by calling .watch(). Your transaction will abort if any of the watched keys change or if the client reconnected between the watch and exec calls.

The WATCH state is stored on the connection (by the server). In case you need to run multiple WATCH & MULTI in parallel you'll need to use a pool.

execAsPipeline

execAsPipeline will execute the commands without "wrapping" it with MULTI & EXEC (and lose the transactional semantics).

await client.multi()
  .get('a')
  .get('b')
  .execAsPipeline();

the diffrence between the above pipeline and Promise.all:

await Promise.all([
  client.get('a'),
  client.get('b')
]);

is that if the socket disconnects during the pipeline, any unwritten commands will be discarded. i.e. if the socket disconnects after GET a is written to the socket, but before GET b is:

• using Promise.all - the client will try to execute GET b when the socket reconnects
• using execAsPipeline - GET b promise will be rejected as well