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package ai.platon.pulsar.skeleton.crawl.schedule
import ai.platon.pulsar.common.config.Parameterized
import ai.platon.pulsar.persist.WebPage
import java.time.Duration
import java.time.Instant
data class ModifyInfo(
/**
* The actual latest fetch time, WebPage.fetchTime will be updated by this value
* */
var fetchTime: Instant,
/**
* The previous actual latest fetch time
* */
var prevFetchTime: Instant,
var prevModifiedTime: Instant,
var modifiedTime: Instant,
var modified: Int,
)
/**
* This interface defines the contract for implementations that manipulate fetch
* times and re-fetch intervals.
*/
interface FetchSchedule : Parameterized {
companion object {
/**
* It is unknown whether page was changed since our last visit.
*/
const val STATUS_UNKNOWN = 0
/**
* Page is known to have been modified since our last visit.
*/
const val STATUS_MODIFIED = 1
/**
* Page is known to remain unmodified since our last visit.
*/
const val STATUS_NOTMODIFIED = 2
}
val maxFetchInterval: Duration
/**
* Initialize fetch schedule related data. Implementations should at least set
* the `fetchTime` and `fetchInterval`. The default
* implementation set the `fetchTime` to now, using the default
* `fetchInterval`.
*
* @param page
*/
fun initializeSchedule(page: WebPage)
/**
* Sets the `fetchInterval` and `fetchTime` on a
* successfully fetched page. Implementations may use supplied arguments to
* support different re-fetching schedules.
*
* @param page The Web page
* @param prevFetchTime The prev fetch time, (prev fetch time) = (the latest actual fetch time)
* @param modifiedTime The previous value of modifiedTime, or 0 if not available
* @param fetchTime The current fetch time, it's almost now, will be updated to the further
* @param modifiedTime The last time the content was modified. This information comes from
* the protocol implementations, or is set to < 0 if not available.
* Most FetchSchedule implementations should update the value in
* @param state if [STATUS_MODIFIED], then the content is considered to be
* "changed" before the `fetchTime`, if
* [STATUS_NOTMODIFIED] then the content is known to be
* unchanged. This information may be obtained by comparing page
* signatures before and after fetching. If this is set to
* [STATUS_UNKNOWN], then it is unknown whether the page was
* changed; implementations are free to follow a sensible default
* behavior.
*/
fun setFetchSchedule(page: WebPage, m: ModifyInfo)
/**
* This method specifies how to schedule refetching of pages marked as GONE.
* Default implementation increases fetchInterval by 50%, and if it exceeds
* the `maxInterval` it calls
* [.forceRefetch].
*
* @param page The page
*/
fun setPageGoneSchedule(
page: WebPage,
prevFetchTime: Instant, prevModifiedTime: Instant, fetchTime: Instant,
)
/**
* This method adjusts the fetch schedule if fetching needs to be re-tried due
* to transient errors. The default implementation sets the next fetch time 1
* day in the future and increases the retry counter.Set
*
* @param page The page
* @param newPrevFetchTime previous fetch time
* @param prevModifiedTime previous modified time
* @param fetchTime current fetch time
*/
fun setPageRetrySchedule(
page: WebPage,
prevFetchTime: Instant, prevModifiedTime: Instant, fetchTime: Instant,
)
/**
* Calculates last fetch time of the given CrawlDatum.
*
* @return the date as a long.
*/
fun estimatePrevFetchTime(page: WebPage): Instant
/**
* This method provides information whether the page is suitable for selection
* in the current fetchlist. NOTE: a true return value does not guarantee that
* the page will be fetched, it just allows it to be included in the further
* selection process based on scores. The default implementation checks
* `fetchTime`, if it is higher than the
*
* @param curTime it returns false, and true otherwise. It will also check that
* fetchTime is not too remote (more than `maxInterval),
* in which case it lowers the interval and returns true.
* @param page The Web page
* @param curTime reference time(usually set to the time when the fetch list generation process was started).
* @return true, if the page should be considered for inclusion in the current fetch list, otherwise false.
* */
fun shouldFetch(page: WebPage, now: Instant): Boolean
/**
* This method resets fetchTime, fetchInterval, modifiedTime and page
* text, so that it forces refetching.
*
* @param page The Web page
* @param asap if true, force refetch as soon as possible - this sets the
* fetchTime to now. If false, force refetch whenever the next fetch
* time is set.
*/
fun forceRefetch(page: WebPage, prevFetchTime: Instant, asap: Boolean)
}
