While
Repeat a body subgraph until a condition holds or the iteration cap is reached, carrying state in shift registers.
Repeats its body until until comes out true, carrying values from one iteration into the next.
The other frame module, and the only looping one that can feed itself. Each shift register in shiftRegisters mints an sr_<id> port pair on the node: the in-port seeds it from outside, the out-port carries its value when the loop ends. Inside the body the frame is addressed by the While's own id, so an edge out of the frame reads a register and an edge into it writes what the next iteration will see; a register the body never writes carries unchanged.
until is evaluated after each pass and the loop breaks the moment it holds. maxIterations breaks it regardless, and checkpointEvery decides how often the loop's state is persisted, so a worker that dies mid-loop resumes rather than restarts. Durable only.
At a glance
Module type
While
Category
Intelligence
Default tier
durable
Runs on
durable
Starts a flow
no
Holds a body
yes
Keeps state between runs
no
Available in
every application type
Parameters
shiftRegisters
object[] · required · defaults to []
The values carried from one iteration to the next. Each has an id, the port kind it carries, and a starting value — either initialValue or initialFromPortId, never both — and each mints an sr_<id> port pair.
until
string · required · defaults to ""
Evaluated after each iteration; the loop breaks the moment it comes out true.
maxIterations
number · required · defaults to 12
The hard bound, whatever until says.
checkpointEvery
number · required · defaults to 4
How many iterations between persisted checkpoints, so a dead worker resumes rather than restarts.
body
FrameBody · required · defaults to {"modules":[],"edges":[]}
The flow run each iteration: its own modules and edges.
Inputs
on
event
no
Implicit on every module that does not itself start a flow: wire an event here to make this module the start of what that event runs.
Outputs
iterationLog
dataframe
dataframe, signal
One row per iteration: when it ran, what until evaluated to, and how it ended.
Ports it grows
Minted as the module is configured, so a freshly dropped one does not have them yet.
sr_<registerId>
in
A register's initial value; optional, because it may come from initialValue instead.
sr_<registerId>
out
A shift register's value after the final iteration; one port per register.
Last updated