How to log JSON from a GCE Container VM to Stackdriver?

Question

I'm currently using GCE Container VMs (not GKE) to run Docker Containers which write their JSON formated log to the Console. The Log Information is automatically collected and stored in Stackdriver.

Problem: Stackdriver displays the data-field of the jsonPayload as text - not as JSON. It looks like the quotes of the fields within the payload are escaped and therefore not recognized as JSON structure.

I used both, logback-classic (like explained here) and slf4j/log4j (using JSONPattern) to generate JSON output (which looks fine), but the output is not parsed correctly.

I assume that, I have to configure somewhere that the output is JSON structured, not plain text. So far I haven't found an option where to do this when using a Container VM.

Answer 1

What does your logger output into stdout?

You shouldn't create a jsonPayload field yourself in your log output. That field gets automatically created when your logs get parsed and meet certain criteria.

Basically, write your log message into a message field of your JSON output and any additional data as additional fields. Stackdriver strips all special fields from your JSON payload and if there is nothing left then your message will end up as textPayload otherwise you'll get a jsonPayload with your message and other fields.

Full documentation is here: https://cloud.google.com/logging/docs/structured-logging