SecureSessionPool

An R6 class for a pool of SecureSession objects that are started ahead of time.

The pool starts all its sessions when you create it, so $execute() can use an idle one straight away instead of waiting for R to start. Each session goes back to the pool when its run finishes, whether it succeeded or failed.

Value

An R6 object of class SecureSessionPool.

Threads and forks

SecureSessionPool isn't thread-safe. Handing out and taking back sessions uses no locks. If you use pools from several processes (for example with parallel::mclapply or future), create a pool in each process. Two processes sharing one pool can end up grabbing the same session.

Methods

Public methods

• SecureSessionPool$new()

• SecureSessionPool$execute()

• SecureSessionPool$size()

• SecureSessionPool$available()

• SecureSessionPool$status()

• SecureSessionPool$format()

• SecureSessionPool$print()

• SecureSessionPool$close()

---

Method new()

Start a new SecureSessionPool

Usage

SecureSessionPool$new(
  size = 4L,
  tools = list(),
  sandbox = TRUE,
  limits = NULL,
  verbose = FALSE,
  reset_between_uses = FALSE
)

Arguments

size

Integer, number of sessions to start (default 4, minimum 1).

tools

A list of securer_tool() objects passed to each session.

sandbox

Logical, whether to use the OS sandbox.

limits

Optional named list of resource limits.

verbose

Logical, whether to print what each session is doing.

reset_between_uses

Logical, whether to restart each session before it goes back to the pool (default FALSE). With TRUE, the pool calls session$restart() after every $execute(), so variables, loaded packages, and options from one run don't carry over to the next.

---

Method execute()

Run R code on an idle session from the pool

Usage

SecureSessionPool$execute(code, timeout = NULL, acquire_timeout = NULL)

Arguments

code

Character string of R code to execute.

timeout

Timeout in seconds, or NULL for no timeout.

acquire_timeout

Optional number of seconds to wait for a free session. If NULL (the default), the call fails straight away when every session is busy. Otherwise the pool keeps trying, every 0.1 seconds, until the time is up.

Returns

The value of the last expression in code.

---

Method size()

Number of sessions in the pool

Usage

SecureSessionPool$size()

Returns

Integer

---

Method available()

Number of idle sessions

Usage

SecureSessionPool$available()

Returns

Integer

---

Method status()

Count sessions by state

Usage

SecureSessionPool$status()

Returns

A named list with total, busy, idle, and dead counts. dead counts sessions whose process has stopped and that need a restart.

---

Method format()

Format the pool for printing

Usage

SecureSessionPool$format(...)

Arguments

...

Ignored.

Returns

A character string describing the pool.

---

Method print()

Print method

Usage

SecureSessionPool$print(...)

Arguments

...

Ignored.

Returns

Invisible self.

---

Method close()

Close every session in the pool

Usage

SecureSessionPool$close()

Returns

Invisible self

Examples

# \donttest{
pool <- SecureSessionPool$new(size = 2, sandbox = FALSE)
pool$execute("1 + 1")
#> [1] 2
pool$execute("2 + 2")
#> [1] 4
pool$close()
# }