Wait for and return any notifications that return within timeout
Once you subscribe to notifications with LISTEN, use this to wait for responses on each channel.
postgresWaitForNotify(conn, timeout = 1)
conn |
a PqConnection object, produced by
|
timeout |
How long to wait, in seconds. Default 1 |
If a notification was available, a list of:
Name of channel
PID of notifying server process
Content of notification
If no notifications are available, return NULL
# For running the examples on systems without PostgreSQL connection:
if (postgresHasDefault()) {
library(DBI)
library(callr)
# listen for messages on the grapevine
db_listen <- dbConnect(RPostgres::Postgres())
dbExecute(db_listen, "LISTEN grapevine")
# Start another process, which sends a message after a delay
rp <- r_bg(function () {
library(DBI)
Sys.sleep(0.3)
db_notify <- dbConnect(RPostgres::Postgres())
dbExecute(db_notify, "NOTIFY grapevine, 'psst'")
dbDisconnect(db_notify)
})
# Sleep until we get the message
n <- NULL
while (is.null(n)) {
n <- RPostgres::postgresWaitForNotify(db_listen, 60)
}
stopifnot(n$payload == 'psst')
# Tidy up
rp$wait()
dbDisconnect(db_listen)
}Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.