heartbeat: Create a heartbeat instance
In richfitz/RedisHeartbeat: Heartbeat Support using 'Redis'

Description Usage Arguments Details Examples

View source: R/heartbeat.R

Create a heartbeat instance. This can be used by running obj$start() which will reset the TTL (Time To Live) on key every period seconds (don't set this too high). If the R process dies, then the key will expire after 3 * period seconds (or set expire) and another application can tell that this R instance has died.

heartbeat(
  key,
  period,
  expire = 3 * period,
  value = expire,
  config = NULL,
  start = TRUE,
  timeout = 10
)

`key`	Key to use
`period`	Timeout period (in seconds)
`expire`	Key expiry time (in seconds)
`value`	Value to store in the key. By default it stores the expiry time, so the time since last heartbeat can be computed.
`config`	Configuration parameters passed through to `redux::redis_config`. Provide as either a named list or a `redis_config` object. This allows host, port, password, db, etc all to be set. Socket connections (i.e., using `path` to access Redis over a socket) are not currently supported.
`start`	Should the heartbeat be started immediately?
`timeout`	Time, in seconds, to wait for the heartbeat to appear. It should generally appear very quickly (within a second unless your connection is very slow) so this can be generally left alone.

The heartbeat object has three methods:

is_running() which returns TRUE or FALSE if the heartbeat is/is not running.
start() which starts a heartbeat
stop() which requests a stop for the heartbeat

Heavily inspired by the doRedis package.

if (redux::redis_available()) {
  rand_str <- function() {
    paste(sample(letters, 20, TRUE), collapse = "")
  }
  key <- sprintf("heartbeatr:test:%s", rand_str())
  h <- heartbeatr::heartbeat(key, 1, expire = 2)
  con <- redux::hiredis()

  # The heartbeat key exists
  con$EXISTS(key)

  # And has an expiry of less than 2000ms
  con$PTTL(key)

  # We can manually stop the heartbeat, and 2s later the key will
  # stop existing
  h$stop()

  # Sys.sleep(2)
  # con$EXISTS(key) # 0
}