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Is the Julia session still usable?

Source: R/julia_alive.R
julia_alive.Rd

julia_ready() records that setup has run and returns immediately when called again. That leaves a session stuck once its Julia process goes away, whether it was stopped, interrupted or died: the packages are no longer loaded, while the flag still says they are.

Usage

julia_alive(state_env, probe = NULL)

Arguments

state_env

The environment given to julia_ready().

probe

Julia code returning a Bool, evaluated to decide whether the session still holds what the caller needs. The default checks that this is the server state_env was set up in. A caller can ask for something more specific, e.g. "isdefined(Main, :MyBridge)".

Value

TRUE when the session is usable, otherwise FALSE.

Details

This checks the running session and clears the flag when the check fails. The next julia_ready() call then sets Julia up again. The environment itself is kept, because callers may use its identity.

The check itself may start Julia, because JuliaConnectoR starts a new server whenever its connection has gone. The default probe is FALSE in such a server: only the server julia_ready() ran in holds the token it recorded.

Examples

if (FALSE) { # \dontrun{
if (!julia_alive(.my_pkg_env, "isdefined(Main, :MyBridge)")) {
  setup_my_pkg()
}
} # }