How to disable JSON format and send only the log message to Sumologic with Fluentbit? - amazon-web-services

Question

We are using Fluentbit as as Sidecar container in our ECS fargate Cluster which is running a dotnet application, initially we faced the issue of fluentbit sending the logs in multiline and we solved it using Fluentbit Multilne feature. Now the logs are being sent to Sumologic in Multiple however it is being sent as Json format whereas we just want fluentbit send only the raw log
Logs are currently
{
date:1675120653.269619,
container_id:"xvgbertytyuuyuyu",
container_name:"XXXXXXXXXX",
source:"stdout",
log:"2023-01-30 23:17:33.269Z DEBUG [.NET ThreadPool Worker] Connection.ManagedDbConnection - ComponentInstanceEntityAsync - Executing stored proc: dbo.prcGetComponentInstance"
}
We want only the line
2023-01-30 23:17:33.269Z DEBUG [.NET ThreadPool Worker] Connection.ManagedDbConnection - ComponentInstanceEntityAsync - Executing stored proc: dbo.prcGetComponentInstance

Answer 1

You need to modify Fluent Bit configuration to have the following filters and output configuration:
fluent.conf:
## prepare headers for Sumo Logic
[FILTER]
Name record_modifier
Match *
Record headers.content-type text/plain
## Set headers as headers attribute
[FILTER]
Name nest
Match *
Operation nest
Wildcard headers.*
Nest_under headers
Remove_prefix headers.
[OUTPUT]
Name http
...
# use log key as body
body_key $log
# use headers key as headers
headers_key $headers
That way, you are going to craft HTTP request manually. This is going to send request per log, which is not necessary a good idea. In order to mitigate that you can add the following parser and use it (flush_timeout may need an adjustment):
parsers.conf
# merge everything as one big log
[MULTILINE_PARSER]
name multiline-all
type regex
flush_timeout 500
#
# Regex rules for multiline parsing
# ---------------------------------
#
# configuration hints:
#
# - first state always has the name: start_state
# - every field in the rule must be inside double quotes
#
# rules | state name | regex pattern | next state
# ------|---------------|--------------------------------------------
rule "start_state" ".*" "cont"
rule "cont" ".*" "cont"
fluent.conf:
[INPUT]
name tail
...
multiline.parser multiline-all