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# See https://www.tidyverse.org/blog/2019/09/callr-task-q/
# for a detailed explanation on how the task queue works.
#
# Changes in this version, compared to the blog post:
# * We use data frames instead of tibbles. This requires some caution
# and the df_add_row() function below.
# * We do not collect the results in a result column, because we
# just return them immediately, as we get them.
# * We do not need a pop() method, because poll() will just return
# every message.
PROCESS_DONE <- 200L
PROCESS_STARTED <- 201L
PROCESS_MSG <- 301L
PROCESS_EXITED <- 500L
PROCESS_CRASHED <- 501L
PROCESS_CLOSED <- 502L
PROCESS_FAILURES <- c(PROCESS_EXITED, PROCESS_CRASHED, PROCESS_CLOSED)
task_q <- R6::R6Class(
"task_q",
public = list(
initialize = function(concurrency = 4L, ...) {
private$start_workers(concurrency, ...)
invisible(self)
},
list_tasks = function() private$tasks,
get_num_waiting = function()
sum(!private$tasks$idle & private$tasks$state == "waiting"),
get_num_running = function()
sum(!private$tasks$idle & private$tasks$state == "running"),
get_num_done = function() sum(private$tasks$state == "done"),
is_idle = function() sum(!private$tasks$idle) == 0,
push = function(fun, args = list(), id = NULL) {
if (is.null(id)) id <- private$get_next_id()
if (id %in% private$tasks$id) stop("Duplicate task id")
before <- which(private$tasks$idle)[1]
private$tasks <- df_add_row(private$tasks, .before = before,
id = id, idle = FALSE, state = "waiting", fun = I(list(fun)),
args = I(list(args)), worker = I(list(NULL))
)
private$schedule()
invisible(id)
},
poll = function(timeout = 0) {
limit <- Sys.time() + timeout
as_ms <- function(x)
if (x==Inf) -1 else as.integer(as.double(x, "secs") * 1000)
repeat{
topoll <- which(private$tasks$state == "running")
conns <- lapply(
private$tasks$worker[topoll],
function(x) x$get_poll_connection())
pr <- processx::poll(conns, as_ms(timeout))
ready <- topoll[pr == "ready"]
results <- lapply(ready, function(i) {
msg <- private$tasks$worker[[i]]$read()
## TODO: why can this be NULL?
if (is.null(msg) || msg$code == PROCESS_MSG) {
private$tasks$state[[i]] <- "running"
} else if (msg$code == PROCESS_STARTED) {
private$tasks$state[[i]] <- "ready"
msg <- NULL
} else if (msg$code == PROCESS_DONE) {
private$tasks$state[[i]] <- "ready"
} else if (msg$code %in% PROCESS_FAILURES) {
private$handle_error(msg, i)
} else {
file <- private$tasks$args[[i]][[1]]
errmsg <- paste0(
"unknown message from testthat subprocess: ", msg$code, ", ",
"in file `", file, "`"
)
abort(
errmsg,
test_file = file,
class = c("testthat_process_error", "testthat_error")
)
}
msg
})
results <- results[! vapply(results, is.null, logical(1))]
private$schedule()
if (is.finite(timeout)) timeout <- limit - Sys.time()
if (length(results) || timeout < 0) break;
}
results
}
),
private = list(
tasks = NULL,
next_id = 1L,
get_next_id = function() {
id <- private$next_id
private$next_id <- id + 1L
paste0(".", id)
},
start_workers = function(concurrency, ...) {
nl <- I(replicate(concurrency, NULL))
private$tasks <- data.frame(
stringsAsFactors = FALSE,
id = paste0(".idle-", seq_len(concurrency)),
idle = TRUE,
state = "running",
fun = nl,
args = nl,
worker = nl)
rsopts <- callr::r_session_options(...)
for (i in seq_len(concurrency)) {
rs <- callr::r_session$new(rsopts, wait = FALSE)
private$tasks$worker[[i]] <- rs
}
},
schedule = function() {
ready <- which(private$tasks$state == "ready")
if (!length(ready)) return()
rss <- private$tasks$worker[ready]
private$tasks$worker[ready] <- replicate(length(ready), NULL)
private$tasks$state[ready] <-
ifelse(private$tasks$idle[ready], "waiting", "done")
done <- which(private$tasks$state == "done")
if (any(done)) private$tasks <- private$tasks[-done, ]
waiting <- which(private$tasks$state == "waiting")[1:length(ready)]
private$tasks$worker[waiting] <- rss
private$tasks$state[waiting] <-
ifelse(private$tasks$idle[waiting], "ready", "running")
lapply(waiting, function(i) {
if (! private$tasks$idle[i]) {
private$tasks$worker[[i]]$call(private$tasks$fun[[i]],
private$tasks$args[[i]])
}
})
},
handle_error = function(msg, task_no) {
inform("\n") # get out of the progress bar, if any
fun <- private$tasks$fun[[task_no]]
file <- private$tasks$args[[task_no]][[1]]
if (is.null(fun)) {
msg$error$stdout <- msg$stdout
msg$error$stderr <- msg$stderr
abort(
paste0(
"testthat subprocess failed to start, stderr:\n",
msg$error$stderr
),
test_file = NULL,
parent = msg$error,
class = c("testthat_process_error", "testthat_error")
)
} else {
abort(
paste0("testthat subprocess exited in file `", file, "`"),
test_file = file,
parent = msg$error,
class = c("testthat_process_error", "testthat_error")
)
}
}
)
)
df_add_row <- function(df, ..., .before = NULL) {
before <- .before %||% (nrow(df) + 1L)
row <- data.frame(stringsAsFactors = FALSE, ...)
if (before > nrow(df)) {
rbind(df, row)
} else if (before <= 1L) {
rbind(row, df)
} else {
rbind(df[1:(before-1), ], row, df[before:nrow(df), ])
}
}
silence_r_cmd_check <- function() callr::r_session
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