Lock

Lets only one record at a time pass through to the components behind it. Use it when concurrent requests (for example several HTTP calls, Fork tasks or a parallel For each) must not run a section of the flow at the same time, such as updating a shared file or a counter.

Pins

Pin	Kind	Types	Description
Input	input	any	Records entering the locked section.
Output	output	same as input	The unchanged record; the components connected here run under the lock.

Configuration

None besides the common settings.

Behaviour

• Each record waits until no other record is inside the locked section, then it is sent to Output. The lock is held until the downstream processing of that record returns; then the next waiting record enters.
• The lock belongs to this component instance in this flow: two Lock components do not block each other, and other flows (or other instances of the flow) are not affected.
• Records are not dropped; they wait without a timeout.

Notes

• Only synchronous downstream work is protected. Anything handed to a background task inside the section (for example a Fork) leaves the lock immediately.
• Keep the locked section short: every waiting record blocks a thread. A slow or hanging component behind the lock stalls all callers.
• Do not route a record back into the same Lock from inside the locked section (the same thread re-enters, so it is not blocked, but the section is then not exclusive).

Example

Http listener → Lock → File writer (append) → Http response