Basic Searching Concepts
Simple searches look like the following examples. Note that there are literals with and without quoting and that there are field selections with an "=":
Exception # just the word
One Two Three # those three words in any order
"One Two Three" # the exact phrase
# Filter all lines where field "status" has value 500 from access.log
# Give me all fatal errors from syslog of the blog host
host="myblog" source="/var/log/syslog" Fatal
Two important filters are "rex" and "regex".
"rex" is for extraction a pattern and storing it as a new field. This is why you need to specifiy a named extraction group in Perl like manner "(?...)" for example
source="some.log" Fatal | rex "(?i) msg=(?P[^,]+)"
When running above query check the list of "interesting fields" it now should have an entry "FIELDNAME" listing you the top 10 fatal messages from "some.log"
What is the difference to "regex" now? Well "regex" is like grep. Actually you can rephrase
source="some.log" | regex _raw=".*Fatal.*"
and get the same result. The syntax of "regex" is simply "=". Using it makes sense once you want to filter for a specific field.
Sum up a field and do some arithmetics:
... | stats sum(<field>) as result | eval result=(result/1000)
Determine the size of log events by checking len() of _raw. The p10() and p90() functions are returning the 10 and 90 percentiles:
| eval raw_len=len(_raw) | stats avg(raw_len), p10(raw_len), p90(raw_len) by sourcetype
Simple Useful Examples
Splunk usually auto-detects access.log fields so you can do queries like:
source="/var/log/nginx/access.log" HTTP 500
source="/var/log/nginx/access.log" HTTP (200 or 30*)
source="/var/log/nginx/access.log" status=404 | sort - uri
source="/var/log/nginx/access.log" | head 1000 | top 50 clientip
source="/var/log/nginx/access.log" | head 1000 | top 50 referer
source="/var/log/nginx/access.log" | head 1000 | top 50 uri
source="/var/log/nginx/access.log" | head 1000 | top 50 method
By appending "sendemail" to any query you get the result by mail!
... | sendemail to="firstname.lastname@example.org"
Create a timechart from a single field that should be summed up
... | table _time, <field> | timechart span=1d sum(<field>)
... | table _time, <field>, name | timechart span=1d sum(<field>) by name
List All Indices
| eventcount summarize=false index=* | dedup index | fields index
| eventcount summarize=false report_size=true index=* | eval size_MB = round(size_bytes/1024/1024,2)
| REST /services/data/indexes | table title
| REST /services/data/indexes | table title splunk_server currentDBSizeMB frozenTimePeriodInSecs maxTime minTime totalEventCount
on the command line you can call
$SPLUNK_HOME/bin/splunk list index
To query write amount of per index the metrics.log can be used:
index=_internal source=*metrics.log group=per_index_thruput series=* | eval MB = round(kb/1024,2) | timechart sum(MB) as MB by series