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Phil (aka MP3Monster)'s Blog

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Category Archives: logsimulator

OCI Notifications through the LogSimulator

04 Friday Nov 2022

Posted by mp3monster in development, General, logsimulator, Oracle, Technology

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Tags

events, loggenerator, logsimulator, Notifications, OCI, open-source, Oracle, tool

We’ve been busy putting together a number of Oracle Architecture Center assets over the last week. This has included building LogSimulator extensions that can either be run in a very simple manner using just a single file, but limited in the payloads that can be sent to OCI (if you take the appropriate custom file from the LogSimulator you do need to make one minor tweak. But the code has also been added to the Oracle GitHub repository here in a manner that doesn’t require the full tool. There of course a price to pay for the simplified implementation. This comes in the form of the notifications being sent and received being hardwired into the code rather than driven through the insulator’s configuration options.

The decoupling has been done by implementing the interface for the custom methods in a class without the implements declaration, and then we extend the base class and apply the implements declaration at that level.

While notifications could take log events, it is more suited to JSON payloads. But as the simulator can tailor the content being sent using some formatting, it does not care if the provided events to send are pre-formatted as JSON objects making it an easy tool to test the configuration of OCI Notifications.

Unit testing as well

In addition to the new channel, as previously mentioned we have been making some code improvements. To support that we have started to add unit tests, and double checking code will compile under Java. To keep the dependencies down we’re making use of Java assert statements rather than a pretty JUnit. But the implementation ideas are very similar. As the tests use Java asserts the use of asserts does need to be enabled in the command line; for example:

Groovy test.groovy -enableasserts

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LogSimulator New Feature – Custom Targets with OCI Logging example

14 Friday Oct 2022

Posted by mp3monster in Cloud, development, General, logsimulator, Oracle, Technology

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Tags

book, loggenerator, logging, logsimulator, OCI, Prometheus

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.

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Handling multi-line log entries with Fluentd

19 Tuesday Apr 2022

Posted by mp3monster in Books, Fluentd, General, logsimulator, manning, Technology

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book, Fluentd, multiline, parser, regex

One aspect of logging I didn’t directly address with my Fluentd book was consuming multiline logs, such as those you’ll often see when a stack trace is included in the log output. Implementing the feature with Fluentd isn’t hugely complex as it leverages the use of regular expressions (addressed in the book in more depth) to recognize the 1st line in a multiline log entry and for subsequent lines.

I didn’t address it for a couple of reasons:

  • Using parsers is fairly inefficient, particularly when you’re using a parser to just decide how to then transform a line (this is why I’m not a huge fan of some of the 12 Factor App‘s recommendations when it comes to logging).
  • Incorporating into your Fluentd parser configurations for specific app log setups is arguably increasing the level of coupling.
  • Many logging frameworks can talk directly to Fluentd as we saw in the book. This is can be more efficient, which means that the log event is more likely to be passed over in a structured format (therefore less work to do).
  • Alternatively, frameworks like Log4J2 have the means to strip line feeds, etc at source – https://logging.apache.org/log4j/2.x/manual/layouts.html (see replace)

But let’s also be realistic, many applications will be configured to simply log to a file and aren’t likely to be changed. At which point we do need to process such situations, so is it done? The process remains largely the same as the tail plugin we illustrated. Except we introduce a different parser called multiline. The documentation provided by Fluentd includes several examples of multiline configurations that will work for default log formats (such as Log4J and Rails). If we took our most basic source setup:

<source>
  @type tail
  path ./Chapter3/basic-file.*
  read_lines_limit 5
  tag simpleFile
  <parse>
    @type none
  </parse>
</source>

Then assuming our log Simulator played back multiline logs (the provided configuration doesn’t do that) extended to consume standard Log4J2 logs we would have a configuration as follows:

<source>
  @type tail
  path ./Chapter3/basic-file.*
  read_lines_limit 5
  tag simpleFile
  <parse>
     @type multiline
     format_firstline /\d{4}-\d{1,2}-\d{1,2}/
     format1 /^(?<time>\d{4}-\d{1,2}-\d{1,2} \d{1,2}:\d{1,2}:\d{1,2}) \[(?<thread>.*)\] (?<level>[^\s]+)(?<message>.*)/
  </parse>
</source>

As you can see we’ve set the parser type to multiline. Then there are two regular expressions, format_firstline is used to help recognize the start of a log event. Every line of the log is tested with this expression as we now assume unless this produces a valid result that the line will be part of a multiline event. If you look at the expression you’ll realize it is looking for a DateTime stamp in the form YYYY-MM-DD. This does mean if you generate a log that starts with the date even if it is part of a multiline output then you’ll trip up the parser. You could extend the expression – but the longer it is the slower the processing.

Following format_firstline we have in our example format1 which describes how to process the first line. This can be extended to define how to handle subsequent lines but this could be multiple format definitions. They do need to be presented in numerical order eg. format1, format2, format, and so on.

LogSimulator – Playing back multi-line logs

The Log simulator uses a very similar mechanism to Fluentd to understand how to playback multiple line logs. When it is reading the log lines in for replay it uses a regular expression to recognize the start of a new log entry (FIRSTOFMULTILINEREGEX) defined in the properties file. The simulator will concatenate lines together until it either hits the end of the file or has a new line that complies with the REGEX. It stores the line with an encoded /n (newline character). It will then print the log using the format specified and will allow the /n to create a newline (or not) based on another config parameter (ALLOWNL).

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LogSimulator new features

03 Friday Sep 2021

Posted by mp3monster in development, Fluentd, General, logsimulator, Technology

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Tags

Log, logging, tool, utility

The log simulator we’ve built and written about in the past has had a release made that lines up with the Logging In Action book (v0.1). I am now continuing to add improvements on the main line. Not best Git branching practice, but as I’m working on this solo it doesn’t represent a problem.

If you expect multi line events all you need to do, is add to the properties file a name value pair, with the name FIRSTOFMULTILINEREGEX and the value is a Java/Groovy regular expression which can be used to determine if a line in a log entry is the 1st line in a new log. Then all subsequent log lines are appended to the previous line until a line identifies as a new log entry. The log entry will be written with newline characters in the same place as the read.

In addition to this if the synthetic log events need to be set to be new line then using the ALLOWNL property to be set to true will result in any new line escape sequences (\n) to be made into proper new lines in the output.

The details are all included in the documentation in GitHub.

Continue reading →

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