The goal of interprocess
is to synchronize concurrent R processes.
Allows R to access low-level operating system mechanisms for performing atomic operations on shared data structures. Mutexes provide shared and exclusive locks. Semaphores act as counters. Message queues move text strings from one process to another. All these interprocess communication (IPC) tools can optionally block with or without a timeout.
Works cross-platform, including Windows, MacOS, and Linux, and can be used to synchronize a mixture of R sessions and other types of processes if needed.
Implemented using the Boost C++ library.
Installation
# Install the latest stable version from CRAN:
install.packages("interprocess")
# Or the development version from GitHub:
install.packages("pak")
pak::pak("cmmr/interprocess")
Usage
Mutexes, semaphores, and message queues are managed by the operating system. Any process that knows the resource’s name can access it. Therefore, sharing the resource name (a short text string) amongst cooperating processes enables communication and synchronization.
These names can be any alphanumeric string that starts with a letter and is no longer than 250 characters. The mutex()
, semaphore()
, and queue()
functions will default to generating a unique identifier, or you can provide a custom or pre-existing one with the name
parameter. If the resource is associated with a specific file or directory, the file
parameter can be used to derive a name from normalizing and hashing that path.
Setting cleanup = TRUE
will automatically remove the resource when the R session exits. Otherwise, the resource will persist until $remove()
is called or the operating system is restarted.
Semaphores
The semaphore’s value can be incremented with $post()
and decremented with $wait()
. The initial value can also be set in the constructor.
sem <- interprocess::semaphore('mySemaphore', value = 1)
sem$name
#> [1] "mySemaphore"
sem$post()
sem$wait(timeout_ms = 0)
#> [1] TRUE
sem$wait(timeout_ms = 0)
#> [1] TRUE
sem$wait(timeout_ms = 0)
#> [1] FALSE
sem$remove()
Message Queues
The constructor’s max_count
and max_nchar
parameters determine how much memory is allocated for the queue.
mq <- interprocess::queue(max_count = 2, max_nchar = 5)
mq$name
#> [1] "akRKb4iymMcAFV"
mq$send('Hello')
mq$send('Hi', priority = 1)
mq$receive(timeout_ms = 0)
#> [1] "Hi"
mq$receive(timeout_ms = 0)
#> [1] "Hello"
mq$receive(timeout_ms = 0)
#> [1] NULL
mq$remove()