| Title: | 'Rcpp' Bindings for 'Redis' using the 'hiredis' Library |
|---|---|
| Description: | Connection to the 'Redis' key/value store using the C-language client library 'hiredis' (included as a fallback) with 'MsgPack' encoding provided via 'RcppMsgPack' headers. It now also includes the pub/sub functions from the 'rredis' package. |
| Authors: | Dirk Eddelbuettel and Bryan W. Lewis |
| Maintainer: | Dirk Eddelbuettel <[email protected]> |
| License: | GPL (>= 2) |
| Version: | 0.2.4 |
| Built: | 2024-11-25 06:48:45 UTC |
| Source: | CRAN |
The Redis module is created using Rcpp modules and wraps a
minimal class Redis around an Redis connection context object
which permits bi-directional communication with a Redis in-memory database.
New instances can be created using either a default constructor (using localhost and the default port) and either host and port, or just the host.
Currently, the module has just one worker command which sends a string to the Redis instance and returns a string.
The helper functions serializeToChar() and
unserializeFromChar convert R objects to/from a character
representation (and internalize the conversion from raw
to char representation at the compiled level).
The helper functions serializeToRaw() and
unserializeFromRaw convert R objects to/from raw vectors.
Please consult the Redis documentation for details on the available commands. See the Rcpp-modules vignette for details on Rcpp modules.
Dirk Eddelbuettel [email protected]
Listen for messages on subscribed Redis message channels.
redisMonitorChannels(context, type=c("rdata", "raw", "string"))redisMonitorChannels(context, type=c("rdata", "raw", "string"))
context |
A valid Redis context (see example). |
type |
The expected message value type. |
(From the Redis.io documentation): implement the Publish/Subscribe messaging paradigm where (citing Wikipedia) senders (publishers) are not programmed to send their messages to specific receivers (subscribers). Rather, published messages are characterized into channels, without knowledge of what (if any) subscribers there may be. Subscribers express interest in one or more channels, and only receive messages that are of interest, without knowledge of what (if any) publishers there are.
The redisMonitorChannels function may be called repeatedly in an
event loop to service messages on all subscribed channels. When a message
is received, the redisMonitorChannels function will attempt to
evaluate a callback function with same name as the channel, with the message
as its single argument. If no such function can be found, the message is
returned. See the help page for redisGetResponse for a description
of the message format.
WARNING: The redisMonitorChannels function blocks indefinitely until a
message is received.
Use the lower-level listen context method to simply poll channels
for messages without evaluating function callbacks.
The result of an evaluated function callback message, or if no matching callback exists, the message.
B. W. Lewis
http://redis.io/commands
## Not run: x <- new(Redis) y <- new(Redis) # Define a callback function to process messages from channel 1: channel1 <- function(x) { cat("Message received from channel 1: ",x,"\n") } # Define a callback function to process messages from channel 2: channel2 <- function(x) { cat("Message received from channel 2: ",x,"\n") } # Subscribe to the channels... x$subscribe(c("channel1", "channel2")) y$publish("channel2", pi) redisMonitorChannels(x) # Unsubscribe x$unsubscribe(c("channel1", "channel2")) ## End(Not run)## Not run: x <- new(Redis) y <- new(Redis) # Define a callback function to process messages from channel 1: channel1 <- function(x) { cat("Message received from channel 1: ",x,"\n") } # Define a callback function to process messages from channel 2: channel2 <- function(x) { cat("Message received from channel 2: ",x,"\n") } # Subscribe to the channels... x$subscribe(c("channel1", "channel2")) y$publish("channel2", pi) redisMonitorChannels(x) # Unsubscribe x$unsubscribe(c("channel1", "channel2")) ## End(Not run)