Sending InfluxDB Line Protocol to QuestDB

At QuestDB we’ve had a UDP version of the InfluxDB Line Protocol (ILP) reader in QuestDB for quite some time, but we’ve had customers ask for a TCP version of it, so we delivered!

Using it, and configuring it, are relatively simple so don’t expect this to be a long post but I’ll walk you through the basics of how to set it up and use it.

For an added bonus I’ll show you how to migrate from using InfluxDB to using QuestDB with a less than a line of configuration.

Configuring TCP InfluxDB Line Protocol Listener

Here’s the best part, at least for a basic implementation that you don’t need to performance tune at all: It’s already set up.

That’s right, as soon as you start QuestDB both the UDP and TCP ILP listeners start automatically on port 9009. Yes, TCP and UDP both use the same port. No, that’s not a problem since one is UDP and one is TCP.

There are a bunch of configuration options you can tune in your conf/server.conf file if you’re interested. I won’t go through them here, but you can read all about them in our docs. I hope they are relatively self-explanatory.

InfluxDB Line Protocol (ILP) Refresher

If you have used ILP before, this should all be review. If you’re new to ILP, this will tell you how you should write your data to QuestDB.

Basic Structure

TOML

1

table_name,tagset valueset timestamp

Pretty basic. So let’s dive into what each element actually is, and how to structure a line of ILP for writing.

The first element is the table_name portion, which tells the ILP writer which database table to write values into.

Next comes the set of tags you want to use. These are standard key=value pairs, and you can add as many of them as you want or need. Just separate them with commas.

There should only ever be 2 spaces in your line protocol. No more. The first space separates your tags from the values you want to associate with those tagss. The second space separates the values from the timestamp for those tags and values.

The values are also key=value pairs, and again you can send as many as you want in a line.

Finally comes your timestamp value, typically in µSeconds.

Example ILP

Let’s use an example of writing some environmental data to QuestDB. I have a sensor that reads temperature, atmospheric pressure, humidity, and the altitude.

ReadingValueTemperature23.180000Humidity51.982422Pressure1002.112061Altitude93.146370

And I want to use the following tags:

Tag NameTag Valuedev_idTHP002dev_locApexdev_nameBME280

And my table_name is iot

Now I have all the basic elements I need to construct my ILP, which will look like this:

iot,dev_id=THP002,dev_loc=Apex,dev_name=BME280 temp_c=23.18,altitude=93.10,humidity=52.16,pressure=1002.12

And yes, I rounded those values. But you’ll notice that I did not add a timestamp value. In this case, it’s because I am sending the values from a small, embedded sensor device that really doesn’t have a great sense of time. By sending the ILP without a timestamp I’m telling the database itself to add one for me, using the arrival time as the timestamp.

Database Structure

One of the cool features of using the ILP reader (well, QuestDB in general really) is the ability to do ‘Schema on Write’.

What that means is that if an ILP message arrives, QuestDB will automatically create tables and columns to fit the incoming ILP. So if you need to add a tag later, you can add it to the new device’s tagset and start writing. The new tag will get added to the schema.

If you leave a tag value off, and it exists in the database, it will get filled with a null value.

When I start writing the above ILP to QuestDB, I’ll get a table that looks like this:

dev_iddev_nametemp_chumiditytimestampdev_localtitudepressureTHP002BME28026.5251.942020-07-21T14:54:59.156202ZApex76.271004.12THP002BME28026.5451.852020-07-21T14:54:59.157358ZApex75.971004.16THP002BME28026.5651.832020-07-21T14:54:59.157389ZApex75.841004.17THP002BME28026.5851.792020-07-21T14:54:59.287416ZApex75.931004.16

This is what that table looks like in the QuestDB Web Console:

#tutorial #devops #iot #influxdb #observability

Sending InfluxDB Line Protocol to QuestDB