Failed to allocate bytes in slab allocator for memtx_tuple Tarantool

This means that memtx engine runs out of memory. Memory available for data and indexes stored in memtx is limited by memtx_memory option of box.cfg, which is default to 256Mb. It's possible to increase this limit in runtime:

-- add 512Mb
box.cfg({memtx_memory = box.cfg.memtx_memory + 512 * 2^20})

Here is documentation section about function for monitoring memory usage:

https://www.tarantool.io/en/doc/latest/reference/reference_lua/box_slab/#lua-function.box.slab.info