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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.
{{Mark|Updated with Version 8.6}}: <code>id</code> option added.
Please remember that this query will cause a deadlock if the asynchronously executed query will be queued. In practice. In practice, you should avoid this pattern and resort to [[XQuery Module#xquery:fork-join|xquery:fork-join]] if you want to do things in parallel.
→jobs:eval
All functions in this module are assigned to the <code><nowiki>http://basex.org/modules/jobs</nowiki></code> namespace, which is statically bound to the {{Code|jobs}} prefix. Errors will be bound to the same prefix.
=Services= A job can be registered as ''service'' by supplying the {{Code|service}} option to {{Function|Jobs|jobs:eval}}: <pre class="brush: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() })</pre> '''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services will be scheduled for evaluation when the BaseX server or BaseX HTTP server is started.* If a job service is outdated (e.g. because a supplied end time has been exceeded), it will be removed from the jobs file at startup time.* Job services can be updated: If a new job is registered, and if there is already a job with the same id, the old entry will be replaced.* The job definitions are stored in a {{Code|jobs.xml}} file in the database directory. It can also be edited manually. =Basic Functions=
==jobs:current==
|-
| '''Summary'''
|Returns the ids of all jobs that are currently registered. The list includes scheduled, queued, running jobs, stopped, and finished jobs with cached jobsresults.
|-
| '''Examples'''
|* <code>jobs:list()</code> returns the same job id as [[#jobs:current{{Function|Jobs|jobs:current]] }} if no other job is registered.* <code>jobs:list()[. != jobs:current()] ! jobs:stop(.)</code> stops and invalidates all asynchronous queries and results except for the current one.
|}
|-
| '''Summary'''
|Returns information on all jobs that are currently registered, or on a job with the specified {{Code|$id}} (or an empty sequence if this job is not found). The list includes scheduled, queued, running jobs, and cached jobs. A string representation of the job , or its URI, will be returned in the text nodeas value. The returned elements have additional attributes:
* <code>id</code>: job id
* <code>type</code>: type of the job (command, query, REST, RESTXQ, etc.)
* <code>state</code>: current state of the job (: <code>scheduled</code>, <code>queued</code>, <code>running</code>, or <code>cached)</code>* <code>user</code>: the user who started the job* <code>duration</code>: evaluation time (for included if a job is running and or if the result was cached jobs)* <code>start</code>: dateTime string with next start of job (for jobs that included if a job will be executed repeatedly)* <code>time</code>: time when job was registered
|-
| '''Examples'''
|* <code>jobs:list-details()</code> returns information on the currently running job and possibly others:
<pre class="brush:xml">
<job id="job1" type="XQuery" state="running" user="admin" duration="PT0.001S">
|}
==jobs:stop== {| width='100%'|-| width='120' | '''Signatures'''|{{Func|jobs:stop|$id as xs:string|empty-sequence()}}|-| '''Summary'''|Triggeres the cancelation of a job with the specified {{Code|$id}}, drops the cached result of a query, or cancels a scheduled job. Unknown ids are ignored. All jobs are gracefully stopped; it is up to the process to decide when it is safe to shut down.|} ==jobs:waitservices==
{| width='100%'
|-
| width='120' | '''Signatures'''
|{{Func|jobs:waitservices|$id as xs:string|empty-sequenceelement(job)*}}
|-
| '''Summary'''
|Waits for the completion Returns a list of a job with the specified {{Codeall jobs that have been persistently registered as [[#Services|$id}}. If the function is called with the id of a repeatedly executed job, it may never terminateServices]].
|-
| '''Errors'''
|{{Error|selfservices|#Errors}} if the current job is addressedRegistered services cannot be parsed.<br/>
|}
=Asynchronous Execution=
==jobs:eval==
{| width='100%'
|-
| width='120' | '''Signatures'''
|{{Func|jobs:eval|$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(*)?, $options as map(xs:string, xs:string*)?|xs:string}}<br />
|-
| '''Summary'''
|Schedules the evaluation of the supplied {{Code|$query}} and returns a query id. The query will be queued, and the result will optionally be cached. Queries can be updating. 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 scheduling optionscan be supplied:
* {{Code|cache}}: indicates if the query result will be cached or ignored (default: <code>false</code>):
** The result will be cached in main-memory until it is fetched via [[#jobs:result|jobs:result]], or until {{Option|CACHETIMEOUT}} is exceeded.
* {{Code|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: <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 time is specified, the query will be executed at this time of the day. Examples for valid times are: <code>02:00:00</code> (2amlocal time), <code>12:00:0000Z</code> (noon, UTC). If the time lies in the past, the query will be executed the next day.
** If a dateTime is specified, the query will 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.
* {{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, it will be skipped.
* {{Code|base-uri}}: 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, such as with {{Code|fn:doc}}.
* {{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.
|-
| '''Errors'''
|{{Error|overflow|#Errors}} Query execution is rejected, because too many jobs are queued or being executed. {{Option|CACHETIMEOUT}} can be decreased if the default 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.
|-
| '''Examples'''
<pre class="brush:xquery">
jobs:eval("prof:sleep(1500)", (), map { 'interval': 'PT1S', 'end': 'PT10S' })
</pre>
* The query in the specified file will be evaluated once:
<pre class='brush:xquery'>
jobs:eval(xs:anyURI('cleanup.xq'))
</pre>
* The following expression, if stored in a file, will be evaluated every 5 seconds:
<pre class="brush:xquery">
jobs:eval(
static-base-uri(),
map { },
map { 'start': 'PT5S' }
)
</pre>
|}
};
</pre>
* The following query demonstrates how the results of an asynchronously executed query can be returned within the same query(see below why you should avoid this pattern in practice):
<pre class='brush:xquery'>
let $query := jobs:eval('(1 to 10000000)[. = 1]', map{}, map{ 'cache': true() })
return (
jobs:wait($query),
jobs:result($query)
)
</pre>
Queries of this kind can cause deadlocks! If the original query and the new query perform updates on the same database, the second query will only be run after the first one has been executed, and the first query will wait for the second query forever. You should resort to [[XQuery Module#xquery:fork-join|xquery:fork-join]] if you want to have full control on parallel query execution.
|}
==jobs:stop==
{| width='100%'
|-
| width='120' | '''Signatures'''
|{{Func|jobs:stop|$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/>
|}
|Description
|-
|{{Code|unknownoptions}}| The supplied query id is unknown or not available anymorespecified options are conflicting.
|-
|{{Code|runningid}}| A query The specified id is still runninginvalid or has already been assigned.
|-
|{{Code|overflow}}
| A specified time or duration is out of range.
|-
|{{Code|idrunning}}| The specified A query is invalid or has already been assignedstill running.
|-
|{{Code|self}}
| The current job cannot be addressed.
|-
|{{Code|service}}
| Registered services cannot be parsed, added or removed.
|-
|{{Code|unknown}}
| The supplied query id is unknown or not available anymore.
|}
=Changelog=
;Version 9.2
* Deleted: jobs:invoke (merged with [[#jobs:eval|jobs:eval]])
;Version 9.1
* Updated: {{Function|Jobs|jobs:list-details}}: registration time added.
;Version 9.0
* Added: {{Function|Jobs|jobs:invoke}}, [[#Services|Services]]
;Version 8.6
