Module Tezos_dal_node_lib.Process_worker

A unix worker process, that includes a tiny ipc protocol using unix pipes. A message in this protocol involves sending the size, followed by the payload.

Error in inter process communication (IPC) between the main and forked process.

pid pw returns the pid of the process worker pw

output_channel pw accesses the output channel of the process_worker pw

input_channel pw accesses the input channel of the process_worker pw

read_message inchan reads the message msg from the Lwt_io.input_channel inchan. The promise is fulfilled when the entire message, as sent by the write_message is received. It returns `End_of_file if the channel was closed, or Error if an unexpected error is raised.

write_message outchan msg writes the message msg to the Lwt_io.output_channel The size of the message msg is implicitly sent, ensuring the whole message to be sent. The promise is fulfilled and returns `Write_ok is the whole message was correctly written on the output channel, or `End_of_file if the channel was closed. Returns Error for unexpected errors

run f arg will run the function f : input_channel output_channel arg, in an forked process. This run function forks, open some pipes ends between the parent and the child. The f function is expected to read and write on the provided unix pipes. The returned value is a process manager containing the other pipe ends, on which read_message and write_message can be used. As of now, only one reader and one writer are supported. There is not yet a locking mechanism and lwt channels are publicly accessible. On parent termination, a sigterm signal is sent to the child process, triggering a Lwt.cancel of the f function.