Reclaim reader slots from processes that died

A process holding a read transaction occupies a slot in the environment's reader table. If it exits without ending the transaction — killed, crashed, or SIGKILLed — the slot stays occupied. Enough of those and new readers fail with MDBX_READERS_FULL even though nothing is actually reading.

Usage

mdbx_env_reader_check(env)

Arguments

env

An mdbx_env object, from mdbx_env_open().

Value

The number of stale slots that were released, invisibly. Zero when every occupied slot belongs to a live process.

Details

This asks 'libmdbx' to check every occupied slot and release the ones whose owning process is gone. It is safe to call at any time and costs nothing when there is nothing to reclaim, so it is a reasonable thing to run when opening a long-lived environment that other processes also use.

Raising mdbx_env_open()'s max_readers makes the table bigger; this makes room in the table you have. See mdbx-concurrency.

See also

mdbx_env_info(), which reports numreaders and maxreaders.

Examples

path <- tempfile(fileext = ".mdbx")
env <- mdbx_env_open(path)

# Nothing has died, so nothing is reclaimed.
mdbx_env_reader_check(env)

mdbx_env_close(env)
unlink(c(path, paste0(path, "-lck")))