# `redis.open { PARAMS }`

Opens a connection to a [Redis](https://redis.io/) data store and returns a connection handle.

```lua
local redis = require 'redis'

-- Open a connection and increment a counter, returning its new value
local conn = redis.open { node = 'redis://127.0.0.1/' }
print(conn:query('incr', 'test-count'))
```

*PARAMS* is a lua table with the following keys:

* `node` - the redis URL string identifying the server.  Can be a table listing
  multiple servers if you have a redis cluster deployed.

* `pool_size` - optional integer. Specifies the maximum number of spare
  connections to be maintained by the connection pool.  The default is 10.

* `read_from_replicas` - optional boolean. If true, when connecting to a redis
  cluster, reads are issued to replicas while writes are issued to the primary
  data stores.

* `username` - optional string. convenience for working with the cluster, so
  that you only need to specify the username once. This is not used for connecting
  to a single node.

* `password` - optional string. convenience for working with the cluster, so
  that you only need to specify the password once. This is not used for connecting
  to a single node.

The returned connection handle has a single `"query"` method:

## `conn:query(CMD, [ARGS])`

Issue a redis command and return the result.

See [Redis Commands](https://redis.io/commands/) for a list of commands.

The redis [INCRBY](https://redis.io/commands/incrby/) command increments a key by a value; it has the syntax:

```
INCRBY key increment
```

To use *INCRBY* to increment `my-key` by `2`:

```
conn:query("INCRBY", "my-key", 2)
```