vrwatch

Log the loading and unloading of R packages

Introduction

vrwatch is a tool that logs the loadings and unloadings of R packages on a system. Its goal is to measure which packages are used, and how often.

Requirements

• A version of R. Any version later than or equal to 3.0.0 is sufficient.

• To log to the system log, a logger daemon, and the logger command line tool must be available. The vrwatch RPM package configures rsyslog (http://www.rsyslog.com/), but in general any system compatible with logger can be used. rsyslog is standard and installed by default on most Linux distributions, including Debian Linux, Ubuntu Linux, CentOS and RedHat Linux.

  The vrwatch RPM package sets up rsyslog to log vrwatch events to /var/log/vrwatch.log. If an alternative logging system is used then these events go to the regular generic system log file by default.

• The vrwatch R package needs to be loaded in every R session that is to be logged. The vrwatch RPM package sets up the system-wide R profile in $R_HOME/etc/Rprofile.site to load vrwatch at the beginning of every R session.

Installation

vrwatch is an R package, and you can install it as a regular R package. We suggest to install it via the supplied RPM package, whenever possible; to set up the rsyslog system logger, and the automatic loading of vrwatch into every R session via a system-wide R profile.

To build the RPM, run the following comamnds:

cd tools/rpmbuild
./local-build.sh

You can then install the RPM using the following command:

yum install RPMS/x86_64/vrwatch-1.0.1-2.x86_64.rpm

For platforms unsupported by the supplied RPM package, vrwatch can be installed as a regular R package. The filtering of the vrwatch events to a separate log file can be set up by the system administrator. vrwatch events are logged with the vrwatch tag, so the following rsyslog configuration file can be used:

:syslogtag, isequal, "VRWATCH:" /var/log/vrwatch.log
& ~

Save this to /etc/rsyslog/23-vrwatch.conf and restart the rsyslog daemon.

To check that vrwatch is installed and working properly, start R, and check that the vrwatch package is loaded:

loadedNamespaces()
#> [1] "graphics"  "utils"     "grDevices" "stats"
#> [5] "datasets"  "vrwatch"   "methods"   "base"

Then load an R package (e.g. splines, which is not loaded by default, but included on almost all R installations: library(splines)). Try unloading a package as well, e.g. unloadNamespace("splines"). Then verify that the package loadings are logged to the log file, which is /var/log/vrwatch.log, unless configured otherwise.

Log entries

vrwatch log entries look similar to the following example. Note that there might be some differences depending on the logging configuration of the system.

Nov  3 10:27:01 centos6 VRWATCH: 21735 LOAD   splines /usr/lib64/R/library/splines
Nov  3 10:27:04 centos6 VRWATCH: 21735 UNLOAD splines /usr/lib64/R/library/splines

• The first three columns are a timestamp, in the regular log format
• The fourth column is the hostname
• The fifth column is a log tag, which is always VRWATCH:
• The six column is the process id of the R process
• The seventh column is LOAD or UNLOAD, the type of the event
• The eighth column is the name of the R package that was loaded or unloaded
• The last column is the directory where the R package is installed on the system

Logging to a system log

vrwatch logs to the system log via the logger command line program by default. To avoid this, set the VRWATCH_NOSYSLOG environment variable to any non-empty value, before loading the vrwatch R package.

Logging to a file

In addition or instead the system log, vrwatch can log to an arbitrary log file. For this the VRWATCH_LOGFILE environment variable must be set to the name of the file to be logged to, before loading the vrwatch package.

Impact on the system

vrwatch traces (see [base::trace()]) the [base::loadNamespace()] and the [base::unloadNamespace()] base R functions, and inserts an extra function call into them, to do the logging.

The impact of vrwatch on the system should be very minimal:

• Loading and unloading package will be slightly slower when vrwatch is loaded. In our measurements the difference in running time was less than 0.01 seconds, so this is only an issue for code that repeatedly loads and unloads R packages many times, and this is very atypical.
• The vrwatch package must be loaded at all times to perform the logging, so code that queries and manipulates the set of loaded packages can be potentially impacted. Again, this is very atypical.

In case of unwanted system impact, unload the vrwatch package:

unloadNamespace("vrwatch")

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