TICK

Returns a monotonically increasing 64-bit integer.

Syntax

TICK <FRESH | CACHED>

Parameters

Parameter	Description
FRESH	Fetches the latest value from the cluster. One round trip per call.
CACHED	Serves the value from a node-local cache that may be up to one second behind. No cluster round trip.

The mode parameter is mandatory and case-insensitive.

Return Value

Integer: the current value.

Guarantees

• The value never decreases. FRESH values are monotonic across the whole cluster. CACHED values are monotonic per node: a client that switches nodes within one second may observe a smaller value.
• The same value can be returned more than once, even with FRESH. TICK is not a unique identifier generator.
• The value does not advance at a fixed rate. Consecutive calls can return the same value; the only ordering guarantee is that it never goes backwards.

Choosing a mode

FRESH gives the strongest guarantee at the cost of one cluster round trip per call. Use it when a decision depends on the latest value, such as fencing checks or watermarks that must not lag.

CACHED targets high-volume, low-precision use. It serves callers that need a monotonic number frequently and can tolerate up to one second of slack, without putting load on the cluster. Typical examples are coarse-grained ordering markers, periodic checkpoints, and staleness checks.

Behavior

The value is a FoundationDB read version. The read version reflects the latest committed state of the database and advances only when new commits arrive. FoundationDB advances it at a rate of roughly one million per second of wall-clock time. On an idle cluster nothing commits, so the read version stands still and consecutive calls return the same value, even with FRESH. The next commit moves it forward by the amount of time that has passed, which is why the value appears to jump.

With CACHED, all connections to a node share a single cache. If the cached value is younger than one second, it is returned without contacting the cluster. Otherwise, the latest value is fetched and the cache is refreshed. Cache refreshes are monotonic: a refresh never replaces a cached value with a smaller one.

This command does not require an active transaction.

Errors

Error Code	Description
ERR	illegal argument for TICK: '<value>': The mode is not recognized.

Examples

Get the latest value:

> TICK FRESH
(integer) 1377052400154

Consecutive calls can return the same value, even with FRESH:

> TICK FRESH
(integer) 1377275302623

> TICK FRESH
(integer) 1377275302623

> TICK FRESH
(integer) 1377275302623

Cached calls within one second return the same value without a cluster round trip:

> TICK CACHED
(integer) 1377275302623

> TICK CACHED
(integer) 1377275302623

Attempt with an invalid mode:

> TICK FOO
(error) ERR illegal argument for TICK: 'FOO'