Should I Use golang/glog?

Background and Problem Definition

I am currently working on an open source cli tool, namely mccurdyc/neighbor , that concurrently clones and executes an arbitrary binary on the repositories returned from a GitHub search query. This tool aims to assist both developers in academia when collecting projects for analyses and those in industry for automating redundant tasks e.g., adding a CODEOWNERS or LICENSE file to all of an organization’s repositories.

Why is logging important for neighbor?

neighbor executes an arbitrary binary, specified by the user e.g., ls -al. Therefore, neighbor cannot be prescriptive in it’s output format e.g., a CSV file with the “results”. But instead, the output is specified by the executed binary. The logs are the focal point for a user interacting with neighbor. neighbor also aims to not be restrictive e.g., only writing to a file, but rather flexible, in regards to the output format. If a user wants to write to a file, they can still do so by redirecting output streams — both stdout and stderr — to files, even separate files with the Unix redirection operator >. This is why the logging library that is used by neighbor is important.

Example:

neighbor --query="org:neighbor-projects NOT minikube" \
         --external_command="ls -al" \
         > out.log 2>error.log

Originally, neighbor used sirupsen/logrus , which would allow a user to specify log severity levels — debug, info, warning, error, etc. — through an environment variable, LOG_LEVEL. logrus also provides the ability for structured logging, which actually wasn’t necessary for this tool. Similar to many logging libraries, logrus provides too many unnecessary features for neighbor. logrus is a great logging library and I actually default to using it when building servers in Go.

One reason that I wanted to move away from logrus was because I didn’t want a user to have to be concerned about which logs were debug and which were info or error, but instead only specify whether they wanted more or less verbosity. Admittedly, neighbor could output all of its logs as debug-level (or error-level where necessary), while the binary’s logs are info-level and maybe this is something that I later decide to revert back to, but I’m also interested in gaining experience with other logging libraries. I think that this concern can be combatted by providing an explicit definition of the N verbosity levels, similar to what kubectl has done (shown below).

Finding neighbor’s future logging library

Having used kubectl, I wanted to have similar verbosity-level logging interface i.e., -v=N, available via cli flags rather than an environment variable. Admittedly, I could have exposed and parsed my own -v flag and set the logrus log level based on that.

After checking out log libraries, I actually expected to find that kubectl was using golang/glog , but instead when I searched the Kubernetes repository on GitHub for “golang/glog” there were only two pages of results, none of which were what I was looking for. I continued my search for the library used and that is when I came across a discussion in Issue#61006 where it was stated that the main Kubernetes repository was using k8s.io/klog , a drop-in replacement for golang/glog that could safely co-exist and addressed major issues faced in the Kubernetes project. The primary issue with golang/glog was that it is no longer under active development and the Kubernetes project wanted to have more control over the log library and that is when they decided to fork the golang/glog project. A few other generally applicable issues to those using golang/glog outside of Kubernetes are as follows:

  1. Initializing “hidden” global flags in init()
  2. If golang/glog fails to write, it calls os.Exit

The first point is a major issue if you are creating a library that will be used by others because now, you have “infected” all consumers and transitive consumers of your library with these flags and the consumer project will have to call flag.Parse() in init() to register the flags. The second point, if glog fails to write, os.Exit is called. Again, this is actually acceptable behavior for neighbor because logs are the primary interface for the user and the binary run.

Prior to my investigation, I did recall seeing a few tweets from Peter Bourgon, where glog was strongly advised against being used.

After seeing people pointing out the challenges of using glog, I expected to run into a few myself. A couple of resources that I came across once I had decided to use glog were this blog post and this GitHub gist. Both of these resources display the usage in code with only a single, main package, but did effectively display the use of flag.Parse() before logging.

Right now, I am happy with results and there is a limited set of users. If neighbor gains traction and users would like a different interface to the logs, this will be something that I will consider. At the end of the day, neighbor is a small project and swapping the logging library used is relatively easy. If nothing else, it will be a learning experience with a new (for me) logging library.

I’m curious to hear your thoughts, here is a Twitter thread where I’ve started the discussion.