Tag: macOS

Monitoring Tomcat

Tools for Testing No Comments

Recently, I faced an issue with an application which is deployed in a Tomcat web container: In one of the environments it started to consume a lot of CPU cycles and memory.

My first attempt to investigate, is to run things locally and have a look at the Activity Monitor that comes with macOS. Often enough it’s enough to notice which app uses a lot of memory or CPU cycles.

This time though, I wanted some deeper insight and I already knew what I was looking for. Some searching in the net brought up Glowroot.

Even though I’m not experienced in using Tomcat, it was pleasantly easy and quick to get going:

  • Download a zip file and unpack it.
  • Copy the folder to a place where it’s convenient. I copied it into an existing folder I’m using to keep configuration info for Tomcat anyway.
  • Set up a way for Tomcat to find and use the Glowroot jar file.
  • Start Tomcat
  • Open a Browser at http://localhost:4000

The details for these steps are nicely explained on the GitHub Wiki of this project.

An example graph is this, taken from the projects demo site at https://demo.glowroot.org/

The my project this (so far) only confirmed that memory consumption can increase a lot when the system gets some traffic. Using well over 10GB of memory within a few minutes is a lot, especially when that memory isn’t released any time soon.

Are you using a tool that was particularly easy to use and provided what you were looking for? Which one?

Moving Left and Right in zsh (in macOS)

shell Uncategorized No Comments

I use the command line a lot on my Macs, in particular, I use iTerm2.

When moving left and right in a command the shortcuts I knew about so far were:

Key (combination)Moves Cursor…
Right Arrow ‘→’One character right
Left Arrow ‘←’One character left
CTRL + aBeginning of the line
CTRL+ eEnd of the line

After adding the following lines to ~/.zshrc, I now can also move left and right per word using ALT-← and ALT-→ respectively: 

bindkey "[D" backward-word # ALT-left-arrow  ⌥ + ←
bindkey "[C" forward-word  # ALT-right-arrow ⌥ + →

Especially when moving around in long command lines, this is really convenient & saves a lot of time.

Do you have keyboard shortcuts that you use regularly on the command line (or elsewhere)? I’d love to hear about them!

Seeing And Saying On The Command Line

Note To Self Tools for Testing No Comments

Occasionally I like command line tools to also say the output, in addition to ‘printing’ it (to STDOUT).

A current context is starting a server locally with updated information. The start up takes time, so I tend to not wait at the command line for it to fully boot.

I wanted a noticeable signal when the thing is up – and also a confirmation that the version of the information source *is* actually updated. The commands tee and (the macOS) say do this for me:

tee >(say&)

tee copies the output of its input to STDOUT (usually the terminal) and the given file. The construction >(other command&) causes tee to send the input not to a file but to othercommand and the & causes that command to return immediately (instead of returning only after the command to finish).

Overall, I do something like this. The system returns a lengthy JSON string, so I use jq to get to the version information I’m looking for:

curl -s -u <username:thepassword> “<url_to_locally_running_service>” | jq “<path_to_version_info_in_json>” | tee >(say&)

The GitHub page explains that

jq is a lightweight and flexible command-line JSON processor.

https://stedolan.github.io/jq/

It’s well worth trying, if you’re dealing with JSON input on the command line.

A Quick Way To Sort Text on macOS

Note To Self 2 Comments

One way to quickly sort text on macOS that I’m currently using is this:

I copy the text (Mark text & CMD-C) and them do this in iTerm:

pbpaste | sort | pbcopy

And that’s it, already. The text is sorted and copied back to the clip board.

Update: this small change fits my actual needs even better: Sort the input case-insensitive:

pbpaste | sort -f | pbcopy

And as an Alfred App user I can even do this (and don’t have to open a terminal):

After Updating to macOS 11.0 Big Sur

Testing Tools for Testing Uncategorized No Comments

The Context

In my current project, we’re using Apache Tomat and Eclipse as the IDE. The Java Platform is Amazon Corretto 11. I’m using macOS and the working setup before upgrading was this:

  • Tomcat is installed using Homebrew:
    brew install tomcat
  • Java was installed by downloading the package (see link above) and running the installer.
  • I have set
    export JAVA_HOME=/Library/…/amazon-corretto-11.jdk/Contents/Home
    in .zprofile so the right Java version is used.
  • I’d start Tomcat from the command line and our tests from inside Eclipse.

This worked nicely.

After The Upgrade

The upgrade went smoothly for most of the software I am using: Other IDEs, installations of Ruby, Elixir, databases, REST clients, git, etc. all continued to work nicely.

The tests however failed in an interesting way: While basic REST calls worked (e.g. a GET request to retrieve version info), the tests that were using the actual functionality were receiving a plain “Internal Server Error” from Tomcat and the application logs showed some getContext method that ended up receiving null instead of the expected object.

Running the same tests on the same machine using the way the tests are started in CI still worked well. The difference between running from within the IDE & the command line: The command line starts Tomcat and runs the tests against that (and then stops Tomcat), while the IDE uses the already running Tomcat. — Aha!

The Solution

Tomcat logs several environment variables it’s using when it starts, among them JRE_HOME.

And this environment variable pointed to another Java environment, that came from a different source, had a different Java version, and furthermore was (obviously) incompatible with the Java environment set up in JAVA_HOME.

Pointing JRE_HOME to the same Java environment solved the problem and tests are running just fine again. Phew!

The documentation has a section about this (docs can be so useful!):

(3.2) Set JRE_HOME or JAVA_HOME (required)

These variables are used to specify location of a Java Runtime
Environment or of a Java Development Kit that is used to start Tomcat.

The JRE_HOME variable is used to specify location of a JRE. The JAVA_HOME
variable is used to specify location of a JDK.

Using JAVA_HOME provides access to certain additional startup options that
are not allowed when JRE_HOME is used.

If both JRE_HOME and JAVA_HOME are specified, JRE_HOME is used.

The recommended place to specify these variables is a “setenv” script. See
below.

…/tomcat/9.0.39/libexec/webapps/docs/RUNNING.txt in my Tomcat installation

Furthermore, there are comments explaining what to expect with respect to JAVA_HOME & JRE_HOME in catalina.sh:

# JRE_HOME Must point at your Java Runtime installation.
# Defaults to JAVA_HOME if empty. If JRE_HOME and JAVA_HOME
# are both set, JRE_HOME is used.

…/9.0.39/libexec/bin/catalina.sh. lns 61 ff

It’s still not entirely clear what caused this behaviour.
If you have an idea or ran into a similar problem, I’d definitely like to known about it.

© 2012-2023 Stephan Kämper — Mastodon

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