Re­cent­ly I wrote an app called Grafi­to to view sys­temd/jour­nald logs (those are the logs in most Lin­ux sys­tem­s) and be able to fil­ter them, see de­tails of a spe­cif­ic en­try, etc.

One prob­lem with this kind of tool is that I can't just open it to the world be­cause then ev­ery­one would be able to see the logs in a re­al ma­chine. While that is usu­al­ly not a prob­lem be­cause the in­for­ma­tion is not ter­ri­bly use­ful (sure, you will know what's run­ning, big whoop­s), it may dis­play a dan­ger­ous piece of da­ta which I may not want to ex­pose.

So, the right way to do this is to cre­ate a de­mo site. It could be show­ing the re­al da­ta from a throw­away sys­tem (like a vir­tu­al ma­chine) or like I did show fake da­ta.

To show fake da­ta you can use a fak­er. Fak­ers are fun! I am us­ing askn/­fak­er which is a Crys­tal one. Fak­ers let you ask for, you guessed it... fake da­ta.

For ex­am­ple, you can ask for an ad­dress or a cred­it card num­ber and it would give you some­thing ran­dom that match­es the ob­vi­ous pat­terns of what you ask.

One I love is to ask for say_something_smart which gives you smart things!

Faker::Hacker.say_something_smart #=> 
"Try to compress the SQL interface, maybe it will program the 
back-end hard drive!"

So, I wrote a function that works like journalctl but is totally fake. The source code is just a quick hack.

Then, I used a con­di­tion­al com­pile flag to route the in­fo re­quests in­to that fake func­tion:

{% if flag?(:fake_journal) %}
  require "./fake_journal_data" # For fake data generation
{% end %}

{% if flag?(:fake_journal) %}
    Log.info { "Journalctl.known_service_units: Using FAKE service units." }
    fake_units = FakeJournalData::SAMPLE_UNIT_NAMES.compact.uniq.sort
    Log.debug { "Returning #{fake_units.size} fake service units." }
    return fake_units
{% else %}
    # Return actual good stuff
{% end %}

And that's it! If I compile with -Dfake_journal it builds a binary that is using only fake data. Then I had it run in my home server and voilá: a demo!

See it in ac­tion! grafi­to-de­mo.ralsi­na.me

Tl; DR: If you go to http­s://github.­com/ralsi­na/­grafi­to you can get a sin­gle bi­na­ry which will give you a web fron­tend for your logs, which looks like this:

Slight­ly longer ver­sion:

• It sup­ports fil­ter­ing with dif­fer­ent cri­te­ria
• It us­es very, very few re­sources
• It takes no or very lit­tle con­fig­u­ra­tion

En­joy!

PS: This project is an im­ple­men­ta­tion of this post