Charles Givre created DRILL-7751:
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Summary: Add Storage Plugin for Splunk
Key: DRILL-7751
URL: https://issues.apache.org/jira/browse/DRILL-7751
Project: Apache Drill
Issue Type: Improvement
Components: Storage - Other
Affects Versions: 1.17.0
Reporter: Charles Givre
Assignee: Charles Givre
Fix For: 1.18.0
# Drill Connector for Splunk
This plugin enables Drill to query Splunk.
## Configuration
To connect Drill to Splunk, create a new storage plugin with the following
configuration:
To successfully connect, Splunk uses port `8089` for interfaces. This port
must be open for Drill to query Splunk.
```json
{
"type":"splunk",
"username": "admin",
"password": "changeme",
"hostname": "localhost",
"port": 8089,
"earliestTime": "-14d",
"latestTime": "now",
"enabled": false
}
```
## Understanding Splunk's Data Model
Splunk's primary use case is analyzing event logs with a timestamp. As such,
data is indexed by the timestamp, with the most recent data being indexed
first. By default, Splunk
will sort the data in reverse chronological order. Large Splunk installations
will put older data into buckets of hot, warm and cold storage with the "cold"
storage on the
slowest and cheapest disks.
With this understood, it is **very** important to put time boundaries on your
Splunk queries. The Drill plugin allows you to set default values in the
configuration such that every
query you run will be bounded by these boundaries. Alternatively, you can set
the time boundaries at query time. In either case, you will achieve the best
performance when
you are asking Splunk for the smallest amount of data possible.
## Understanding Drill's Data Model with Splunk
Drill treats Splunk indexes as tables. Splunk's access model does not restrict
to the catalog, but does restrict access to the actual data. It is therefore
possible that you can
see the names of indexes to which you do not have access. You can view the
list of available indexes with a `SHOW TABLES IN splunk` query.
```
apache drill> SHOW TABLES IN splunk;
+--------------+----------------+
| TABLE_SCHEMA | TABLE_NAME |
+--------------+----------------+
| splunk | summary |
| splunk | splunklogger |
| splunk | _thefishbucket |
| splunk | _audit |
| splunk | _internal |
| splunk | _introspection |
| splunk | main |
| splunk | history |
| splunk | _telemetry |
+--------------+----------------+
9 rows selected (0.304 seconds)
```
To query Splunk from Drill, use the following format:
```sql
SELECT <fields>
FROM splunk.<index>
```
## Bounding Your Queries
When you learn to query Splunk via their interface, the first thing you learn
is to bound your queries so that they are looking at the shortest time span
possible. When using
Drill to query Splunk, it is advisable to do the same thing, and Drill
offers two ways to accomplish this: via the configuration and at query time.
### Bounding your Queries at Query Time
The easiest way to bound your query is to do so at querytime via special
filters in the `WHERE` clause. There are two special fields, `earliestTime` and
`latestTime` which can
be set to bound the query. If they are not set, the query will be bounded to
the defaults set in the configuration.
You can use any of the time formats specified in the Splunk documentation
here:
https://docs.splunk.com/Documentation/Splunk/8.0.3/SearchReference/SearchTimeModifiers
So if you wanted to see your data for the last 15 minutes, you could execute
the following query:
```sql
SELECT <fields>
FROM splunk.<index>
WHERE earliestTime='-15m' AND latestTime='now'
```
The variables set in a query override the defaults from the configuration.
## Data Types
Splunk does not have sophisticated data types and unfortunately does not
provide metadata from its query results. With the exception of the fields
below, Drill will interpret
all fields as `VARCHAR` and hence you will have to convert them to the
appropriate data type at query time.
#### Timestamp Fields
* `_indextime`
* `_time`
#### Numeric Fields
* `date_hour`
* `date_mday`
* `date_minute`
* `date_second`
* `date_year`
* `linecount`
### Nested Data
Splunk has two different types of nested data which roughly map to Drill's
`LIST` and `MAP` data types. Unfortunately, there is no easy way to identify
whether a field is a
nested field at querytime as Splunk does not provide any metadata and
therefore all fields are treated as `VARCHAR`.
However, Drill does have built in functions to easily convert Splunk
multifields into Drill `LIST` and `MAP` data types. For a LIST, simply use the
`SPLIT(<field>, ' ')` function to split the field into a `LIST`.
`MAP` data types are rendered as JSON in Splunk. Fortunately JSON can easily
be parsed into a Drill Map by using the `convert_fromJSON()` function. The
query below
demonstrates how to convert a JSON column into a Drill `MAP`.
```sql
SELECT convert_fromJSON(_raw)
FROM splunk.spl
WHERE spl = '| makeresults
| eval _raw="{\"pc\":{\"label\":\"PC\",\"count\":24,\"peak24\":12},\"ps3\":
{\"label\":\"PS3\",\"count\":51,\"peak24\":10},\"xbox\":
{\"label\":\"XBOX360\",\"count\":40,\"peak24\":11},\"xone\":
{\"label\":\"XBOXONE\",\"count\":105,\"peak24\":99},\"ps4\":
{\"label\":\"PS4\",\"count\":200,\"peak24\":80}}"'
```
### Selecting Fields
When you execute a query in Drill for Splunk, the fields you select are pushed
down to Splunk. Therefore, it will always be more efficient to explicitly
specify fields to push
down to Splunk rather than using `SELECT *` queries.
### Special Fields
There are several fields which can be included in a Drill query
* `spl`: If you just want to send an SPL query to Splunk, this will do that.
* `earliestTime`: Overrides the `earliestTime` setting in the configuration.
* `latestTime`: Overrides the `latestTime` setting in the configuration.
### Sorting Results
Due to the nature of Splunk indexes, data will always be returned in reverse
chronological order. Thus, sorting is not necessary if that is the desired
order.
## Sending Arbitrary SPL to Splunk
There is a special table called `spl` which you can use to send arbitrary
queries to Splunk. If you use this table, you must include a query in the `spl`
filter as shown below:
```sql
SELECT *
FROM splunk.spl
WHERE spl='<your SPL query'
```
# Testing the Plugin
This plugin includes a series of unit tests in the `src/test/` directory,
however you will need an active Splunk installation to run them. Since Splunk
is not an open source
project, nor is available as a Docker container, simply follow the
instructions below to test Splunk with Drill.
### Step 1: Get Splunk
From Splunk's website, simply download and install the free version here:
https://www.splunk.com/en_us/download/splunk-enterprise.html
Once you've downloaded Splunk, start it up, and make sure everything is
working properly.
### Step 2: Add Data
Next, go here:
https://docs.splunk.com/Documentation/Splunk/7.0.3/SearchTutorial/Systemrequirements
and download the dummy datasets that Splunk provides. Once you've downloaded
this data, have Splunk index this data and you're ready to go from the Splunk
end.
## Known Limitations
* At present, Drill will not interpret Splunk multifields as anything other
than a String. If there is interest, this feature can be implemented.
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