Tag Archives: logsimulator

LogSimulator New Feature – Custom Targets with OCI Logging example

14 Friday Oct 2022

Posted by in Cloud, development, General, logsimulator, Oracle, Technology

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Those who have been using my Logging in Action book will know that to help test the configuration of monitoring tools including Fluentd we have built a LogGenerator that can very easily play and replay logging events into a variety of destinations and formats. all written in Groovy to make the utility easy to run as a script and extend without needing to set up a proper Java development environment.

With the number of different destinations built into the script and the logic to load the source log events and format them the utility is getting rather large for a single file. Rather than letting it continue to grow as we add more destinations to pump log events too, I’ve extended the implementation so you can point to a Groovy file that implements the logic to send the log events. It only requires three simple methods to be implemented.

To demonstrate the feature we have created a custom extension and fully documented it. The extension allows you to send log events to the OCI Logging service. This includes an optional crude aggregation mechanism as sending individual log events is a little inefficient over REST. By doing this we can send synthetic or playback logs as if we’re an application in real-life to ensure that any alerting or routing for the logging works properly before we get anywhere production and do not need to run the application and induce error events.

Beyond this, we’re also thinking about creating a plugin to fire log events at Prometheus so we can send events using the Prometheus pushgateway. As a result, we can tune Prometheus’ configuration.

More improvements – refactoring the existing code

We will refactor the existing code to use the same approach which should make the code more maintainable, but the changes won’t stop the utility from working as it always has (so we won’t break out the existing output channels from the core).

We have also started to improve the code commenting – so hopefully it will make the code a bit more navigable.

Running Groovy scripts as JARs

03 Monday Aug 2020

Posted by in General

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For those who regularly follow my blog, I like Groovy as a way of scripting given its portability, proximity to Java, its use of the JVM means its really easy to work with. With the extra language features it makes it easy to work with without needing to setup Maven builds to manage dependencies for something simple. As a result, the utils I’ve produced to support Oracle API Platform CS (here) for example are written with Groovy.

However, not everyone is such a fan, or sees Groovy as niche and, to be honest in the last few years Python has made huge in roads in the scripting space. So I can appreciate the preference for Python to be used. This was really brought home to me by a peer review comments for my latest book project. This got me to thinking what options do I have to remove Groovy from the equation, without resulting in needing to mess with maven POM files. The options as I saw it are:

  • Replace any use of Groovy extensions with Java libraries
  • Switch to using Java 11 and the shebang feature (more in a minute)
  • Compile code with Groovyc and package the jars manually including dependencies.

From Java 11, the ability for a single Java file to be executed without compiling etc was introduced – known as shebang (more here). The issue here is a lot of applications have been certified against Java 8, and in an Enterprise environment this is important. Which means either installing Java 11 locally without changing environment variables, or you need to add code to switch Java versions as necessary. The upside being that you can run your code as a script, and then if necessary build it into a jar to distribute. Aside from the need to switch between JDK versions, Java’s language gets ever richer, but Groovy has a nice set of extensions that make JSON object navigation really nice, and these aren’t necessarily in core Java.

Groovy provides a tool to compile Groovy to bytecode for the JVM (i.e. create class files). From which we can create a JAR file with using the javac command. But this doesn’t bundle the Groovy dependencies necessary to run the jar, as a result Groovy still needs to be installed. You could do this through the use of a maven, Gradle or other build tools. But we’re back to creating a POM file or equivalent., and to be honest creating a POM file from scratch is slow going unless everything lines up neatly with file structures, which it won’t because when you produce a script you’re not expecting to need to worry about packages and associated folder structures.

In looking to see if someone had simplified the process I came across this excellent tool scriptjar (more here). Script jar takes the location of the class files, creates a jar file and loads it with the Groovy jar dependencies, and assembles the manifest file etc. Net result, a jar file created in 2 lines that has no Groovy deployment dependencies to use, and will work with older Java versions such as Java 8.

I started out referring to the API tools, but the same mechanism can be applied to the LogSimulator tool I’ve created that allows you to generate or replay existing logs in real-time or faster than real-time, making it easy to test log monitoring setups from a monitored source all the way through (today it only handles log file replaying or the use of the Java native logging).