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This [[Module Library|XQuery Module]] provides functions for organizing scheduled, queued, running and cached jobs. Jobs can be commands and , queries (…more to come), client or HTTP requests.

=Services= A job can be registered as ''service'' by supplying the {{Code|service}} option to {{Function|Jobs|jobs:eval}}: <syntaxhighlight lang="xquery">(: register job as service; will be run every day at 1 am :)jobs:eval('db:drop("tmp")', (), map { 'id':'cleanup', 'start':'01:00:00', 'interval':'P1D', 'service': true() }), (: list registered services :)jobs:services(),(: result: <job base-uri="..." id="cleanup" interval="P1D" start="01:00:00">db:drop("tmp")</job> :) (: unregister job :)jobs:stop('cleanup', map { 'service': true() })</syntaxhighlight> '''Some more notes:''' * All job services will be scheduled for evaluation when the BaseX server or BaseX HTTP server is started.* If a job service is outdated (e.g. because a supplied end time has been exceeded), it will be removed from the jobs file at startup time.* The job definitions are stored in a {{Code|jobs.xml}} file in the database directory. It can also be edited manually. =Basic Functions=

|Returns the id of the current query job.

|Returns the ids of all jobs that are either being executed asynchronouslycurrently registered. The list includes scheduled, queued, running, or that are still registered because their stopped, and finished jobs with cached results have been cached.

|* <code>jobs:list()</code> returns the same job id as [[#jobs:current{{Function|Jobs|jobs:current]] }} if no other job is runningregistered.|} ==jobs:list-details== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|jobs:list-details||element(job)* }}<codebr/>{{Func|jobs:list-details|$id as xs:string|element(job) ! *}}|-| '''Summary'''|Returns information on all jobsthat are currently registered, or on a job with the specified {{Code|$id}} (or an empty sequence if this job is not found). The list includes scheduled, queued, running jobs, and cached jobs. A string representation of the job, or its URI, will be returned as value. The returned elements have additional attributes:* <code>id</code>:stopjob id* <code>type</code>: type of the job (command, query, REST, RESTXQ, etc.)* <code>state</code>: current state of the job: <code>scheduled</code>, <code>queued</code>, <code>running</code>, <code>cached</code>* <code>user</code>: user who started the job* <code>duration</code>: evaluation time (included if a job is running or if the result was cached)* <code>start</code> stops : next start of job (included if a job will be executed repeatedly)* <code>time</code>: time when job was registered|-| '''Examples'''| <code>jobs:list-details()</code> returns information on the currently running job and invalidates all asynchronous queries and resultspossibly others:<syntaxhighlight lang="xml"><job id="job1" type="XQuery" state="running" user="admin" duration="PT0.001S"> XQUERY jobs:list-details()</job></syntaxhighlight>

|Indicates if the evaluation of a an already running job with the specified query {{Code|$id}} has finished. If As the ids of finished jobs will usually be discarded, unless caching is enabled, the function will also return <code>true</code> for unknown jobs.* <code>false</code> indicates that the job id is scheduled, queued, or currently running.* <code>true</code> will be returned, if the job has either finished, or if the query id is unknown(because the ids of all finished jobs will not be cached).

==jobs:stopservices==

|{{Func|jobs:stopservices|$id as xs:string|empty-sequenceelement(job)*}}

|Cancels the execution Returns a list of a job with the specified all jobs that have been persistently registered as [[#Services|Services]].|-| '''Errors'''|{{CodeError|$idservices|#Errors}}, or drops the cached result of a query. Unknown query ids are ignoredRegistered services cannot be parsed.<br/>

=Asynchronous Execution=

Asynchronous query execution is recommendable if There are cases in which a client does not, or cannot, wait until a request is fully processed. This is e. g. the case with web browsersThe client may be a browser, which will usually cancel a sends an HTTP request after a specific timeout. In such cases, you can use asynchronous execution to trigger another the server-side process, which will in order to start the another time-consuming processquery job. The functions in this section allow you to register a new query job from a running query. Jobs can be executed immediately (i.e., and fetch the result later on as soon as the [[Transaction Management#Concurrency Control|Concurrency Control]] allows it is available) or scheduled for repeated execution. Each registered job gets a job id, and the id can be used to retrieve a query result, stop a job, or wait for its termination.

|{{Func|jobs:eval|$query as xs:stringanyAtomicItem|xs:string}}<br />{{Func|jobs:eval|$query as xs:stringanyAtomicItem, $bindings as map(*)?|xs:string}}<br />{{Func|jobs:eval|$query as xs:stringanyAtomicItem, $bindings as map(*)?, $options as map(xs:string, xs:string*)?|xs:string}}<br />

|Prepares Schedules the evaluation of the supplied {{Code|$query}} string for asynchronous execution and returns a query id. The query will be queued as described in the article on [[Transaction Management]], and the result will optionally be cached in main-memory until it is fetched via [[#jobs:result|jobs:result]], or until {{Option|ASYNCTIMEOUT}} is exceeded. Queries may can be updating.<br/>Variables The query can be a URI or a string, and variables and context items can be declared via {{Code|$bindings}} (see [[XQuery Module#xquery:eval|xquery:eval]] for more details). The following {{Code|$options}} parameter contains evaluation optionscan be supplied:* {{Code|cache}}: indicates if the query result will be cached or ignored (default: <code>truefalse</code>):** The result will be cached in main-memory until it is fetched via [[#jobs:result|jobs:result]], or until {{Option|CACHETIMEOUT}} is exceeded. ** If the query result raises an error, it will not be cachedand returned instead.* {{Code|start}}: a dayTimeDuration, time, dateTime or integer can be specified to delay the execution of the query:** If a dayTimeDuration is specified, the query id will immediately be discarded queued after the specified duration has passed. Examples for valid values are: <code>P1D</code> (1 day), <code>PT5M</code> (5 minutes), <code>PT0.1S</code> (100 ms). An error will be raised if a negative value is specified.** If a dateTime is specified, the query executionwill be executed at this date. Examples for valid values are: <code>2018-12-31T23:59:59</code> (New Year's Eve 2018, close to midnight). An error will be raised if the specified time lies in the past.** If a time is specified, the query will be executed at this time of the day. Examples for valid times are: <code>02:00:00</code> (2am local time), <code>12:00:00Z</code> (noon, UTC). If the time lies in the past, the query will be executed the next day.** An integer will be interpreted as minutes. If the specified number exceeds the minutes of the current hour, the query will be executed one hour later.* {{Code|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 (<code>PT1S</code>). If the next scheduled call is due, and if a query with the same id is still running, tooit will be skipped.* {{Code|end}}: scheduling can be stopped after a given time or duration. The string format is the same as for {{Code|start}}. An error is raised if the resulting end time is smaller than the start time.* {{Code|base-uri}}: set sets the [https://www.w3.org/TR/xquery-31/#dt-static-base-uri base-uri property] for the query. This URI will be used when resolving relative URIs by functions , such as with {{Code|fn:doc}} (default.* {{Code|id}}: sets a custom job id. The id must not start with the standard <code>job</code> prefix, and it can only be assigned if no job with the same name exists.* {{Code|service}}: additionally registers the job as [[#Services|service]]. Registered services must have no variable bindings.* {{Code|log}}: ''empty writes the specified string'')to the [[Logging|database logs]]. Two log entries are stored, one at the beginning and another one after the execution of the job.

|{{Error|overflow|#Errors}} Too Query execution is rejected, because too many queries or query results jobs are queuedor being executed. To fix this, {{Option|CACHETIMEOUT}} can be decreased if the query results should be retrieveddefault setting is too restrictive.<br/>{{Error|range|#Errors}} A specified time or duration is out of range.<br/>{{Error|id|#Errors}} The specified id is invalid or has already been assigned.<br/>{{Error|options|#Errors}} The specified options are conflicting.

* {{CodeCache query result. The returned id can be used to pick up the result with [[#jobs:result|jobs:result]]:<syntaxhighlight lang="xquery">jobs:eval("1+3", ()}} returns a query id, e.g. map {{Code|Query-abc'cache': true() }}. The result can )</syntaxhighlight>* A happy birthday mail will be retrieved via a second query in sent at the same BaseX contextgiven date: {{Code|<syntaxhighlight lang="xquery">jobs:resulteval("import module namespace mail='mail'; mail:send('Happy birthday!')"Query, (), map { 'start': '2018-abc"09-01T06:00:00' })}}<br /syntaxhighlight>* The following [[RESTXQ]] function functions can be called to execute a query at 2 am every day. An id will return be returned by the id of the query threadfirst function, which evaluates can be used to stop the query that has been specified in scheduler via the body of a POST requestsecond function:<pre classsyntaxhighlight lang='brush:"xquery'">declare %rest:POST("{$query}") %rest:path('/evalstart-scheduling') function local:evalstart($query) { jobs:eval($query, (), map { 'start': '02:00:00', 'interval': 'P1D' })};declare %rest:path('/stop-scheduling/{$id}') function local:stop($id) { jobs:stop($id)

</presyntaxhighlight>* Query execution is scheduled for every second, and for 10 seconds in total. As the query itself will take 1.5 seconds, it will only be executed every second time:<syntaxhighlight lang="xquery">jobs:eval("prof:sleep(1500)", (), map { 'interval': 'PT1S', 'end': 'PT10S' })</syntaxhighlight>* The query in the specified file will be evaluated once:<syntaxhighlight lang="xquery">jobs:eval(xs:anyURI('cleanup.xq'))</syntaxhighlight>* The following expression, if stored in a file, will be evaluated every 5 seconds:<syntaxhighlight lang="xquery">jobs:eval( static-base-uri(), map { }, map { 'start': 'PT5S' })</syntaxhighlight>

|Returns the cached result of a query job with the specified job {{Code|$id}}:

* If the query original job has raised an error, the cached error will be raised instead.

|{{Error|running|#Errors}} the query job is still running.<br/>{{Error|unknown|#Errors}} the supplied query id is unknown: The query id is unknown, or the result may has already have been retrieved, or query execution may have been stopped.<br/>

* The following [[RESTXQ]] function will either return the result of a previously started query job or raise an error:<pre classsyntaxhighlight lang='brush:"xquery'">

</presyntaxhighlight>* The following query demonstrates how the results of an asynchronously executed query can be returned in a single within the same query. Please remember that (see below why you should avoid this is not the common way how these functions are used pattern in practice):<pre classsyntaxhighlight lang='brush:"xquery'">let $query := jobs:eval('(1 to 10000000)[. = 1]', map { }, map { 'cache': true() })

hof:until( function($result) { jobs:finishedwait($query) }, function($curr) { prof:sleep(10) }, () ),

</presyntaxhighlight>Queries of this kind can cause deadlocks! If the original query and the new query perform updates on the same database, the second query will only be run after the first one has been executed, and the first query will wait for the second query forever. You should resort to [[XQuery Module#xquery:fork-join|xquery:fork-join]] if you want to have full control on parallel query execution.|} ==jobs:stop== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|jobs:stop|$id as xs:string|empty-sequence()}}|-| '''Summary'''|Triggers the cancelation of a job with the specified {{Code|$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. The following {{Code|$options}} can be supplied:* {{Code|service}}: additionally removes the job from the [[#Services|job services]] list.|-| '''Examples'''| <code>jobs:list()[. != jobs:current()] ! jobs:stop(.)</code> stops and discards all jobs except for the current one.|} ==jobs:wait== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|jobs:wait|$id as xs:string|empty-sequence()}}|-| '''Summary'''|Waits for the completion of a job with the specified {{Code|$id}}:* The function will terminate immediately if the job id is unknown. This is the case if a future job has not been queued yet, or if the id has already been discarded after job evaluation.* If the function is called with the id of a queued job, or repeatedly executed job, it may stall and never terminate.|-| '''Errors'''|{{Error|self|#Errors}} The current job is addressed.<br/>

|{{Code|unknownoptions}}| The supplied query specified options are conflicting.|-|{{Code|id}}| The specified id is unknown invalid or has already been assigned.|-|{{Code|overflow}}| Too many queries or not available anymorequery results are queued.|-|{{Code|range}}| A specified time or duration is out of range.

|{{Code|overflowself}}| Too many queries The current job cannot be addressed.|-|{{Code|service}}| Registered services cannot be parsed, added or removed.|-|{{Code|unknown}}| The supplied query results are queuedid is unknown or not available anymore.