# Latency configuration

These Liberator configuration items allow Liberator to add timestamps to objects for the purpose of latency measurement.

Because Liberator is a [Datasource application](../datasource/index.md), you can also set the [DataSource latency chain configuration items](../datasource/datasource-latency-chains-configuration.md).

## timestamp-field

`timestamp-field` specifies the name of a timestamp field that Liberator should add to an update message, if a field of the same name is not included in the update. This timestamp field is only added to update messages; it is not included each time the object is requested from Liberator’s cache.

This timestamping facility is independent of [latency chain timestamps](../datasource/datasource-latency-chains-configuration.md), and it isn’t controlled by the value of the [latency-chain-enable](../datasource/datasource-latency-chains-configuration.md#latency-chain-enable) configuration item.. It is useful for timestamping the time of exit from Liberator of updates that do not already contain a latency-chain timestamp field (usually added in the originating integration adapter).

Liberator automatically adds latency-chain timestamps to update messages that contain a latency-chain timestamp field, so to avoid `timestamp-field` adding a duplicate timestamp, we recommend setting `timestamp-field` to the name of the field used to record latency-chain timestamps. On updates that already contain this field, the `timestamp-field` option does nothing.

This configuration item is overridden by the [timestamp-field](liberator-object-configuration-part-1.md#timestamp-field) option of [add-object](liberator-object-configuration-part-1.md#add-object) for that particular object only.

By default, the value of `timestamp-field` is null (unset), and Liberator only writes timestamps to objects that have been defined by [add-object](liberator-object-configuration-part-1.md#add-object) and have the [timestamp-field](liberator-object-configuration-part-1.md#timestamp-field) _option_ specified.

**Timestamp format and precision**

| Liberator version | Format | Example |
| --- | --- | --- |
| < 7.1.0 | Milliseconds since 1 Jan 1970 | `1509967184123` |
| 7.1.0 | Microseconds since 1 Jan 1970 | `1509967184123456` |
| > 7.1.0 | Seconds since 1 Jan 1970, with a nanosecond fractional component | `1509967184.123456789` |

**Syntax:** `timestamp-field <field-name>`

**Type:** string

**Default value:** `null`

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**See also:**

* Reference: [Latency chains configuration](../datasource/datasource-latency-chains-configuration.md) in DataSource applications
* How can I... [Record latency in record updates](../datasource/datasource-record-latency-in-record-updates.md)
* How can I... [Monitor latency statistics using the CMC](../cmc/cmc-monitor-latency-using-the-cmc.md)