The recommended logging format according to [Splunk best practice](https://dev.splunk.com/enterprise/docs/developapps/addsupport/logging/loggingbestpractices/#Use-developer-friendly-formats) looks like this:
- This also means the log file is not a valid JSON file.
- Each event is separated by newline.
The format can be achieved by exporting live event in JSON and append to a log file. However, I encountered a situation where the log file can only be generated by batch. Exporting the equivalent of the previous "example.log" in JSON without string manipulation looks like this:
I will detail the required configurations in this post, so that Splunk is able to parse it correctly even though "example.json" is not a valid JSON file.
[**monitor**](https://docs.splunk.com/Documentation/Splunk/latest/Admin/Inputsconf#MONITOR:) directive is made up of two parts: `monitor://` and the path, e.g. `/var/log/app_a`. Unlike most Splunk configs, this directive does't require the backslash (used in Windows path) to be escaped, e.g. `monitor://C:\foo\bar`.
A path can be a file or a folder. When (\*) wildcard matching is used to match multiple folders, another wildcard needs to be specified again to match files in those matched folders. The wildcard works for a single path segment only. For example, to match all the following files, use `monitor:///var/log/app_*/*`. Splunk also supports "..." for recursive matching.
```
/var/log/
├── app_a
│ ├── 1.log
│ ├── 2.log
│ └── 3.log
├── app_b
│ ├── 1.log
│ ├── 2.log
│ └── 3.log
└── app_c
├── 1.log
├── 2.log
└── 3.log
```
Specify an appropriate value in **sourcetype** config, the value will be the value of `sourcetype` field in the ingested events under the "monitor" directive. Take note of the value you have configured, it will be used in the rest of configurations.
The directive name should be the **sourcetype** value specified in the [inputs.conf](#App-specific-inputs-conf). The following configs apply to the universal forwarder is because [`INDEXED_EXTRACTIONS`](https://docs.splunk.com/Documentation/Splunk/latest/Data/Extractfieldsfromfileswithstructureddata#Field_extraction_settings_for_forwarded_structured_data_must_be_configured_on_the_forwarder) is used.
- LINE_BREAKER: Search for string that matches the regex and replace only the capturing group with newline (\n). This is to separate each event into separate line.
-`}(,){\"datetime\"` searches for `},{"datetime"` and replaces "," with "\n".
- SHOULD_LINEMERGE: only used for event that spans multiple lines. In this case, it's the reverse, the log file has all events in one line.
- TIMESTAMP_FIELDS: Refers to `datetime` key in the `example.json`.
- MAX_DAYS_AGO (optional): Specify the value if there are events older than 2,000 days.
- TIME_FORMAT: Optional if Unix time is used, but recommended to specify whenever possible. When Unix time is used, it is not necessary to specify `%s%3N` when there is [subsecond](https://docs.splunk.com/Documentation/Splunk/latest/SearchReference/Commontimeformatvariables).
If there is a deployment server, then the config file should be in path A, in which the server will automatically deploy it to path B in the UF. If the UF is not centrally managed, it should head straight to path B.
Since index-time field extraction is already enabled using `INDEXED_EXTRACTIONS`, search-time field extraction is no longer necessary. If `KV_MODE` and `AUTO_KV_JSON` are not disabled, there will be duplicate fields in the search result.
In Splunk Enterprise, the above file can be saved in a custom app, e.g. "$SPLUNK_HOME/etc/app/custom-app/default/props.conf"
For Splunk Cloud deployment, the above configuration can be added through a custom app or Splunk Web: **Settings > [Source types](https://docs.splunk.com/Documentation/SplunkCloud/latest/Data/Managesourcetypes)**.
It is important to note `SEDCMD` [runs](https://www.aplura.com/assets/pdf/props_conf_order.pdf) [after](https://wiki.splunk.com/Community:HowIndexingWorks) `INDEXED_EXTRACTIONS`. I noticed [this behaviour](https://community.splunk.com/t5/Getting-Data-In/SEDCMD-not-actually-replacing-data-during-indexing/m-p/387812/highlight/true#M69511) when I tried to ingest API response of [LibreNMS](https://gitlab.com/curben/splunk-scripts/-/tree/main/TA-librenms-data-poller?ref_type=heads).
In this scenario, I only wanted to ingest "devices" array where each item is an event. The previous approach not only did not split the array, but "status" and "count" fields still existed in each event despite the use of SEDCMD to remove them.
The solution is not to use INDEXED_EXTRACTIONS (index-time field extraction), but use KV_MODE (search-time field extraction) instead. INDEXED_EXTRACTIONS is not enabled so that SEDCMD works more reliably. If it's enabled, the JSON parser can unpredictably split part of the prefix (in this case `{"status": "ok", "devices": [`) or suffix into separate events and SEDCMD does not work across events. SEDCMD does work with INDEXED_EXTRACTIONS, but you have to make sure the replacement is within an event
