Application was developed using Golang , language that I have been using for about 2 year. I am using go mod for the dependencies.

I could write the same in Java, but the final "binary" would be heavier than GO and we would need a lot of dependencies.

This app is split in two parts:

Monitoring :

1. Will tail the log and accumulate in counters the number of occurrences per section.
2. Will run every 10 seconds a routine to read the counter and compare with the previous observed value to find the number of hits during the 2 scraping times.
3. Will run every 2 minutes a routine to read the counter to trigger an alert if the Hits/s AVG is higher then the one received in the app arg.

Dashboard :

Will present the dashboard with the relevant information, updating the screen every 1 second (even if the collection is done in 10s and the alert 120s)

Testing:

The monitoring packaged is covered >85% using unit tests.

Didn't have time to cover more lines or create the unit test for the dashboard.

I also created a basic ( and ugly ) bash to append the log file to simulate the application server logging.

This will trigger the alert in the first 2 minutes and then recover it.

Application design improvement:

I would write my own "tail" using the system calls.

I would also store the metrics in a time series database and display it correctly with a smart FE like Grafana.

Running it:

Build the docker image:

docker build -t topineeu/logmonitor-homework .

This will produce a final docker image (from scratch) with less than 5 MB that contains the linux compiled binary.

To run, we need to have the TTY and STDIN open for the UI and we need also to mount the log file

docker run -i -t -v /tmp/access.log:/tmp/access.log topineeu/logmonitor-homework

The "integration test script" needs to be executed in another terminal in parallel with the monitoring application:

./test.sh

As requested, Ive added two args for the log location and the alert threshold :

apimenteldasilvatopi$ docker run -i -t -v /tmp/access.log:/tmp/access.log topineeu/logmonitor-homework --help
Usage of /app:
  -avg-threshold float
    	Total traffic threshold for alerting (hits/s) (default 10)
  -log-filename string
    	w3c-formatted HTTP access log to be consumed actively (default "/tmp/access.log")
    	

Feel free to contact for any additional information.

Thanks, Anderson TOPINE