IRequestLoader
Hierarchy
- IRequestLoader
Implemented by
Index
Methods
[asyncIterator]
Can be used to iterate over the loader instance in a
for await .. ofloop. Provides an alternative for the repeated use offetchNextRequest.Returns AsyncGenerator<CrawleeRequest<Dictionary>, any, any>
checkReadiness
Reports whether the loader has a request to hand over, is waiting on one, or is done — see RequestSourceStatus.
A consumer's task loop is gated on this, so implementations MUST answer
readybefore evaluating anything else.finishedmay arrive late behind distributed storage, but it is never wrong.Returns Promise<RequestSourceStatus>
fetchNextRequest
Gets the next Request to process, or
nullif there are no more pending requests.The returned request is marked as in progress and remains so until it is passed to IRequestLoader.markRequestAsHandled. The caller is responsible for eventually marking every fetched request as handled; otherwise the loader never considers itself finished and the request may be re-served after a restart. See the request lifecycle contract on IRequestLoader.
Returns Promise<null | CrawleeRequest<T>>
getHandledCount
Returns the number of requests in the loader that have been handled.
Returns Promise<number>
getPendingCount
Returns an approximation of the number of pending requests in the loader.
Returns Promise<number>
getTotalCount
Returns an approximation of the total number of requests in the loader (i.e. pending + handled).
Returns Promise<number>
markRequestAsHandled
Marks a request previously returned by IRequestLoader.fetchNextRequest as handled, removing it from the set of in-progress requests.
Call this once you are done with the request — whether processing succeeded or was abandoned after exhausting retries. Because a loader cannot take a request back, marking it handled is the only way to signal completion; failing to do so prevents IRequestLoader.checkReadiness from ever reporting
finishedand skews the handled and pending counts. See the request lifecycle contract on IRequestLoader.Parameters
request: CrawleeRequest<Dictionary>
Returns Promise<null | void | RequestQueueOperationInfo>
optionalpersistState
Persists the current state of the loader into the default KeyValueStore.
Not all loaders support persistence; implementations that do not should leave this
undefined.Returns Promise<void>
optionaltoTandem
Combines the loader with a request manager to support adding and reclaiming requests.
Parameters
optionalrequestManager: IRequestManager
Request manager to combine the loader with. If not provided, the default RequestQueue is used.
Returns Promise<IRequestManager>
An abstract interface defining a read-only stream of requests to crawl.
Request loaders are used to manage and provide access to a storage of crawling requests.
Key responsibilities:
Request lifecycle contract
Every request returned by IRequestLoader.fetchNextRequest is considered in progress until it is passed to IRequestLoader.markRequestAsHandled. Once you fetch a request, you are obligated to eventually mark it as handled — there is no way to hand a request back to a loader (only an IRequestManager can reclaim requests for a retry). "Handled" therefore means "finished with this request", whether processing succeeded or was abandoned after exhausting retries.
Honoring this contract matters for three reasons:
finishedonce nothing is in progress. Leaving a request unmarked keeps the crawler running indefinitely.Concrete implementations such as RequestList or SitemapRequestLoader build on this interface. The IRequestManager interface extends it with the capability to enqueue and reclaim requests.