rembKnown limitations
Overview of the known limitations
Redis Open Source
Redis Software
Redis Cloud
Redis Open Source
Redis Enterprise for Kubernetes
clients
Limited write options
JavaScript remote functions are limited to read operations only. Any attempt to perform a write operation of the following functions on a shard different than the one executing the function will result in an error.
async_client.runOnShardsruns the remote function on all the shardsasync_client.runOnKeyruns the remote function on the shard responsible for a given key
In addition, keyspace modification performed by JavaScript functions that are registered using any of the methods available should perform write operations locally:
- If the function is registered with
registerFunctionorregisterAsyncFunction, it can insert, modify or delete keys that are in the same shard where the function is executed. - If the function is registered with
registerKeySpaceTriggerorregisterStreamTrigger, keyspace modification must be local to the shard that originated the events.
It is also recommended to co-locate the keys to be modified in the same hash slot as the key or Stream that originated the event. As an example, if the user profile stored in the Hash myserv:user:1234 is subject to changes and we'd like to count them in an external counter, we would name the counter using hash tags: {myserv:user:1234}:cnt.
Exclusive access to the keyspace
By design, asynchronous functions guarantee exclusive single-threaded access to the keyspace, the distinctive feature of Redis. In asynchronous programming with JavaScript functions, access to the keyspace in read or write mode must be blocking, while if not accessing the keyspace, the execution may be non-blocking. This implementation maintains the same level of data consistency as Redis standard commands or Lua scripts and functions but takes advantage of asynchronous execution, a feature of the JavaScript engine.
JavaScript variables
Not all the JavaScript global variables are made available by the JavaScript engine loaded by Redis (e.g. console, document). The redis global variable can be used to manage functions registration, logging etc.
Sandboxed
This feature is sandboxed, meaning, from within a function, it’s not possible to make calls to external services, including other Redis databases, or APIs.