Job Module

This XQuery Module provides functions for organizing queued and running jobs (commands, queries, REST, RESTXQ and WebDAV requests).

Conventions

All functions in this module are assigned to the http://basex.org/modules/jobs namespace, which is statically bound to the jobs prefix. Errors will be bound to the same prefix.

Functions

jobs:current

Signatures	jobs:current() as xs:string
Summary	Returns the id of the current job.

jobs:list

Signatures	jobs:list() as xs:string*
Summary	Returns the ids of all jobs that are currently queued or executed.
Examples	jobs:list() returns the same job id as jobs:current if no other job is running. jobs:list()[. != jobs:current()] ! jobs:stop(.) stops and invalidates all asynchronous queries and results except for the current one.

jobs:list-details

Signatures	jobs:list-details() as element(job)* jobs:list-details($id as xs:string) as element(job)*
Summary	Returns information on all jobs that are currently registered. The list includes scheduled, queued, running jobs, and cached jobs. A string representation of the job will be returned in the text node. The returned elements have additional attributes: id: job id type: type of the job (command, query, REST, RESTXQ, etc.) state: current state of the job (scheduled, queued, running, finished, cached) user: the user who started the job duration: evaluation time (for running and cached jobs) start: dateTime string with next start (for jobs that will be executed repeatedly)
Examples	jobs:list-details() returns information on the currently running job and possibly others: <job id="job1" type="XQuery" state="running" user="admin" duration="PT0.001S"> XQUERY jobs:list-details() </job>

jobs:finished

Signatures	jobs:finished($id as xs:string) as xs:boolean
Summary	Indicates if the evaluation of a job with the specified $id has finished: true indicates that the job has either finished, or that the id is unknown. false indicates that the job id is still queued or currently running.

jobs:stop

Signatures	jobs:stop($id as xs:string) as empty-sequence()
Summary	Cancels the execution of a job with the specified $id, drops the cached result of a query, or cancels a scheduled job. Unknown ids are ignored. All jobs are gracefully stopped; it is up to the process to decide when it is safe to shut down.

Asynchronous Execution

Asynchronous query execution is recommendable if a client does not, or cannot, wait until a request is fully processed. This is e. g. the case with web browsers, which will usually cancel a request after a specific timeout. In such cases, you can use asynchronous execution to trigger another server-side process, which will start the time-consuming process, and fetch the result later on as soon as it is available.

jobs:schedule

Signatures	jobs:schedule($query as xs:string) as xs:string jobs:schedule($query as xs:string, $bindings as map(*)?) as xs:string jobs:schedule($query as xs:string, $bindings as map(*)?, $options as map(xs:string, xs:string)) as xs:string
Summary	Schedules the execution of the supplied $query and returns a query id. The query will be queued, and the result will optionally be cached. Queries may be updating. Variables and context items can be declared via $bindings (see xquery:eval for more details). The $options parameter contains scheduling options: cache: indicates if the query result will be cached or ignored (default: false): The result will be cached in main-memory until it is fetched via jobs:result, or until CACHETIMEOUT is exceeded. If the query raises an error, it will be cached and returned instead. start: a dayTimeDuration, time or dateTime can be specified to delay the execution of the query: If a dayTimeDuration is specified, the query will be queued after the specified duration has passed. Examples for valid values are: P1D (1 day), PT5M (5 minutes), PT0.1S (100 ms). An error will be raised if a negative value is specified. If a time is specified, the query will be executed at this time of the day. Examples for valid times are: 02:00:00 (2am), 12:00:00 (noon). If the time lies in the past, the query will be executed next day. If a dateTime is specified, the query will be executed at this date. Examples for valid values are: 2018-12-31T23:59:59 (New Year's Eve 2018, close to midnight). An error will be raised if the specified time lies in the past. interval: a dayTimeDuration string can be specified to execute the query periodically. An error is raised if the specified interval is less than one second (PT1S). If the next scheduled call is due, and if a query with the same id is still running, it will be skipped. base-uri: set the base-uri property for the query. This URI will be used when resolving relative URIs, such as with fn:doc.
Errors	overflow: Query execution is rejected, because too many jobs are queued or being executed. CACHETIMEOUT can be decreased if the default setting is too restrictive. range: A specified time or duration is out of range.
Examples	Cache query result. The returned id can be used to pick up the result with jobs:result: jobs:schedule("1+3", (), map { 'cache': true() }) A happy birthday mail will be sent at the given date: jobs:schedule("import module namespace mail='mail'; mail:send('Happy birthday!')", (), map { 'start': '2018-09-01T06:00:00' })}} The following RESTXQ functions can be called to execute a query at 2 am every day. An id will be returned by the first function, which can be used to stop the scheduler via the second function: declare %rest:POST("{$query}") %rest:path('/start-scheduling') function local:start($query) { jobs:schedule($query, (), map { 'start': '02:00:00', 'interval': 'P1D' }) }; declare %rest:path('/stop-scheduling/{$id}') function local:stop($id) { jobs:stop($id) }; Query execution is scheduled for every second. As the query itself will take 1.5 seconds, it will only be executed every second time: jobs:schedule("prof:sleep(1500)", (), map { 'interval': 'PT1S' })

jobs:result

Signatures	jobs:result($id as xs:string) as item()*
Summary	Returns the cached result of a query with the specified job $id: Results can only be retrieved once. After retrieval, the cached result will be dropped. If the original query has raised an error, the cached error will be raised instead.
Errors	running: the job is still running. unknown: the supplied id is unknown: The id is unknown, or the result has already been retrieved.
Examples	The following RESTXQ function will either return the result of a previously started query or an error: declare %rest:path('/result/{$id}') function local:result($id) { jobs:result($id) }; The following query demonstrates how the results of an asynchronously executed query can be returned within the same query. Please remember that this is not the common way how these functions will be used in practice: let $query := jobs:schedule('(1 to 10000000)[. = 1]', map{}, map{ 'cache': true() }) return ( hof:until( function($f) { jobs:finished($query) }, function($f) { prof:sleep(10) }, () ), jobs:result($query) )

Errors

range

Code	Description
unknown	The supplied query id is unknown or not available anymore.
running	A query is still running.
overflow	Too many queries or query results are queued.
A specified time or duration is out of range.

Changelog

The module was introduced with Version 8.5.