Ingester Custom Time Formats#

Many ingesters can support the inclusion of custom time formats that can extend the capability of the Gravwell timegrinder time resolution system. The timegrinder has a wide array of timestamp formats that it can automatically identify and resolve. However, in the real world with real developers there is no telling what time format a system may decide to use. That is why we enable users to specify custom time formats for inclusion in the timegrinder system.

Custom time formats are a fallback when the usual timestamp extraction fails; refer to the main ingesters page for more general information on timestamp extraction.

Supported Ingesters#

Not all ingesters support custom time formats. One-off or standalone ingesters such as singlefile are applications meant to be invoked by hand and do not have a configuration file. Dedicated ingesters like netflow don’t need to resolve timestamps, so there is no need for custom formats.

The following ingesters support the inclusion of custom time formats:

Defining a Custom Format#

A custom format requires three items to function:

  • Name

  • Regular Expression

  • Format

The given name for a custom time format must be unique across other custom time formats and the included timegrinder formats. For a complete up-to-date listing of included time formats and their names, check out our timegrinder documentation.

Custom time formats are declared in the configuration files for supported ingesters by specifying a named TimeFormat INI block. Here is an example format named “foo” which handles timestamps that are delimited using underscores:

[TimeFormat "foo"]

This format would properly handle the timestamps in the following logs:

2021_02_05_09_00_00 and my id is 1
2021_02_05_09_00_00 and my id is 2
2021_02_05_09_00_00 and my id is 3
2021_02_05_09_00_00 and my id is 4
2021_02_05_09_00_00 and my id is 5
2021_02_05_09_00_00 and my id is 6

Here is another format that handles logs with only a timestamp:

[TimeFormat "foo2"]

This format would handle the following logs, appropriately applying the current date to each extracted timestamp:

09^00^00 and my id is 1
09^00^00 and my id is 2
09^00^00 and my id is 3
09^00^00 and my id is 4
09^00^00 and my id is 5
09^00^00 and my id is 6


The custom timestamp format names can be used in Timestamp-Format-Override values. For example we can force the timestamp format to our custom format using Timestamp-Format-Override="foo".


Sometimes, incoming data contains multiple timestamps or timestamp-like fields in the same format. For instance, consider the following log entry:

{ "message": "task completed", "start_time": "2023_11_28_09_00_00", "end_time": "2023_11_28_09_32_01" }

There are two fields (start_time and end_time) in the data, both using the same time format. If we want to be sure to extract the end_time field, we can add a pre-extractor to our TimeFormat definition with the Extraction-Regex option:

[TimeFormat "foo"]

A pre-extractor is a regular expression which will match the desired timestamp and which contains a single named capture group (in this example, the group is named ts). The pre-extractor is evaluated first, then the contents of the named capture group will be evaluated against the Format and Regex arguments as normal.

In our example, Extraction-Regex looks for the string "end_time":, followed by a space, followed by a quoted string; the capture group is the contents of the quoted string. This means that the time parser will be operating on just the substring 2023_11_28_09_32_01 instead of the entire entry.


Exactly one named capture group in the Extraction-Regex must be defined. If no named capture groups are contained in the regex the configuration will be rejected.

Pre-extractions With Named Time Formats#

Incoming data may also contain timestamps in formats that have already been defined in [timegrinder]( but that cannot be reliably extracted without first performing a pre-extraction. This is often the case with embedded unix, unixmilli, and unixnano timestamps. The Pre-extraction Extraction-Regex can be combined with a named format so that timestamp formats that are already defined in Timegrinder. For example, consider the following entry:

[task completed] tss:1701200161 tse:1701200161.1234 value:1700000000

There are two Unix timestamps in the JSON data and one other value that would probably match a Unix timestamp. We can use a Pre-Extraction to grab a specific field and then pass it to the already defined UnixMilli timestamp processor. An example definition which extracts the timestamp from the tse field and treats it as a UnixSeconds timestamp would look like this:

[TimeFormat "tseextractor"]


Notice that a Regex is not defined because we are using an already-defined timestamp extraction format.

Time Formats#

The Format component uses the Go standard time format specification. Long story short, you must describe the date Mon Jan 2 15:04:05 MST 2006 using whatever format you choose.

Time formats can omit the date component. When the custom format system identifies that a custom time format does not include a date component, it will automatically update the extracted timestamp’s date to today.

Time Zones#

All custom time formats will attempt to operate in UTC unless otherwise indicated using the Format directive. This means that if you have a time format without a date component you must pay special attention to the timezone. If an application emits a timestamp of 12:00:00 in MST and there is no timezone component or timezone overrides, timegrinder will interpret the timestamp as UTC and the extracted date will be 7 hours in the past.

If your timestamp does contain a timezone you must include that in your Format directive so that the timegrinder system knows to interpret the timestamp in the correct time zone. For example here is the previously described “foo” custom format but with a timezone component:

[TimeFormat "foo"]

This example will properly handle timestamps in their respective time zones and apply the correct timestamp on extraction.


Here is an example File Follower configuration which adds two custom time formats:

Ingest-Secret = IngestSecrets
Connection-Timeout = 0
Pipe-Backend-Target=/opt/gravwell/comms/pipe #a named pipe connection, this should be used when ingester is on the same machine as a backend
Log-Level=INFO #options are OFF INFO WARN ERROR
Max-Files-Watched=64 # Maximum number of files to watch before rotating out old ones, this can be bumped but will need sysctl flags adjusted

#basic default logger, all entries will go to the default tag
#no Tag-Name means use the default tag
[Follower "auth"]
	File-Filter="*.log" #we are looking for all authorization log files
	Assume-Local-Timezone=true #Default for assume localtime is false

[TimeFormat "foo"]

[TimeFormat "foo2"]

The file follower will handle timestamps that are specified as 2021_02_14_12_33_52 and 15!05!22 properly due to the additional custom time formats.