The Nest Filter plugin allows you to operate on or with nested data. Its modes of operation are

  • nest - Take a set of records and place them in a map

  • lift - Take a map by key and lift its records up

Example usage (nest)

As an example using JSON notation, to nest keys matching the Wildcard value Key* under a new key NestKey the transformation becomes,

Example (input)

{
"Key1" : "Value1",
"Key2" : "Value2",
"OtherKey" : "Value3"
}

Example (output)

{
"OtherKey" : "Value3"
"NestKey" : {
"Key1" : "Value1",
"Key2" : "Value2",
}
}

Example usage (lift)

As an example using JSON notation, to lift keys nested under the Nested_under value NestKey* the transformation becomes,

Example (input)

{
"OtherKey" : "Value3"
"NestKey" : {
"Key1" : "Value1",
"Key2" : "Value2",
}
}

Example (output)

{
"Key1" : "Value1",
"Key2" : "Value2",
"OtherKey" : "Value3"
}

Configuration Parameters

The plugin supports the following configuration parameters:

Key

Value Format

Operation

Description

Operation

ENUM [nest or lift]

Select the operation nest or lift

Wildcard

FIELD WILDCARD

nest

Nest records which field matches the wildcard

Nest_under

FIELD STRING

nest

Nest records matching the Wildcard under this key

Nested_under

FIELD STRING

lift

Lift records nested under the Nested_under key

Add_prefix

FIELD STRING

ANY

Prefix affected keys with this string

Remove_prefix

FIELD STRING

ANY

Remove prefix from affected keys if it matches this string

Getting Started

In order to start filtering records, you can run the filter from the command line or through the configuration file. The following invokes the Memory Usage Input Plugin, which outputs the following (example),

[0] memory: [1488543156, {"Mem.total"=>1016044, "Mem.used"=>841388, "Mem.free"=>174656, "Swap.total"=>2064380, "Swap.used"=>139888, "Swap.free"=>1924492}]

Example #1 - nest

Command Line

Note: Using the command line mode requires quotes parse the wildcard properly. The use of a configuration file is recommended.

The following command will load the mem plugin. Then the nest filter will match the wildcard rule to the keys and nest the keys matching Mem.* under the new key NEST.

$ bin/fluent-bit -i mem -p 'tag=mem.local' -F nest -p 'Operation=nest' -p 'Wildcard=Mem.*' -p 'Nest_under=Memstats' -p 'Remove_prefix=Mem.' -m '*' -o stdout

Configuration File

[INPUT]
Name mem
Tag mem.local
[OUTPUT]
Name stdout
Match *
[FILTER]
Name nest
Match *
Operation nest
Wildcard Mem.*
Nest_under Memstats
Remove_prefix Mem.

Result

The output of both the command line and configuration invocations should be identical and result in the following output.

[2018/04/06 01:35:13] [ info] [engine] started
[0] mem.local: [1522978514.007359767, {"Swap.total"=>1046524, "Swap.used"=>0, "Swap.free"=>1046524, "Memstats"=>{"total"=>4050908, "used"=>714984, "free"=>3335924}}]

Example #1 - nest and lift undo

This example nests all Mem.* and Swap,* items under the Stats key and then reverses these actions with a lift operation. The output appears unchanged.

Configuration File

[INPUT]
Name mem
Tag mem.local
[OUTPUT]
Name stdout
Match *
[FILTER]
Name nest
Match *
Operation nest
Wildcard Mem.*
Wildcard Swap.*
Nest_under Stats
Add_prefix NESTED
[FILTER]
Name nest
Match *
Operation lift
Nested_under Stats
Remove_prefix NESTED

Result

[2018/06/21 17:42:37] [ info] [engine] started (pid=17285)
[0] mem.local: [1529566958.000940636, {"Mem.total"=>8053656, "Mem.used"=>6940380, "Mem.free"=>1113276, "Swap.total"=>16532988, "Swap.used"=>1286772, "Swap.free"=>15246216}]

Example #2 - nest 3 levels deep

This example takes the keys starting with Mem.* and nests them under LAYER1, which itself is then nested under LAYER2, which is nested under LAYER3.

Configuration File

[INPUT]
Name mem
Tag mem.local
[OUTPUT]
Name stdout
Match *
[FILTER]
Name nest
Match *
Operation nest
Wildcard Mem.*
Nest_under LAYER1
[FILTER]
Name nest
Match *
Operation nest
Wildcard LAYER1*
Nest_under LAYER2
[FILTER]
Name nest
Match *
Operation nest
Wildcard LAYER2*
Nest_under LAYER3

Result

[0] mem.local: [1524795923.009867831, {"Swap.total"=>1046524, "Swap.used"=>0, "Swap.free"=>1046524, "LAYER3"=>{"LAYER2"=>{"LAYER1"=>{"Mem.total"=>4050908, "Mem.used"=>1112036, "Mem.free"=>2938872}}}}]
{
"Swap.total"=>1046524,
"Swap.used"=>0,
"Swap.free"=>1046524,
"LAYER3"=>{
"LAYER2"=>{
"LAYER1"=>{
"Mem.total"=>4050908,
"Mem.used"=>1112036,
"Mem.free"=>2938872
}
}
}
}

Example #3 - multiple nest and lift filters with prefix

This example starts with the 3-level deep nesting of Example 2 and applies the lift filter three times to reverse the operations. The end result is that all records are at the top level, without nesting, again. One prefix is added for each level that is lifted.

Configuration file

[INPUT]
Name mem
Tag mem.local
[OUTPUT]
Name stdout
Match *
[FILTER]
Name nest
Match *
Operation nest
Wildcard Mem.*
Nest_under LAYER1
[FILTER]
Name nest
Match *
Operation nest
Wildcard LAYER1*
Nest_under LAYER2
[FILTER]
Name nest
Match *
Operation nest
Wildcard LAYER2*
Nest_under LAYER3
[FILTER]
Name nest
Match *
Operation lift
Nested_under LAYER3
Add_prefix Lifted3_
[FILTER]
Name nest
Match *
Operation lift
Nested_under Lifted3_LAYER2
Add_prefix Lifted3_Lifted2_
[FILTER]
Name nest
Match *
Operation lift
Nested_under Lifted3_Lifted2_LAYER1
Add_prefix Lifted3_Lifted2_Lifted1_

Result

[0] mem.local: [1524862951.013414798, {"Swap.total"=>1046524, "Swap.used"=>0, "Swap.free"=>1046524, "Lifted3_Lifted2_Lifted1_Mem.total"=>4050908, "Lifted3_Lifted2_Lifted1_Mem.used"=>1253912, "Lifted3_Lifted2_Lifted1_Mem.free"=>2796996}]
{
"Swap.total"=>1046524,
"Swap.used"=>0,
"Swap.free"=>1046524,
"Lifted3_Lifted2_Lifted1_Mem.total"=>4050908,
"Lifted3_Lifted2_Lifted1_Mem.used"=>1253912,
"Lifted3_Lifted2_Lifted1_Mem.free"=>2796996
}