Difference between revisions of "Job Module"
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|- | |- | ||
| '''Summary''' | | '''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 | + | |Returns information on all jobs that are currently registered, or on a job with the specified {{Code|$id}} (or an empty sequence if this job is not found). The list includes scheduled, queued, running jobs, and cached jobs. A string representation of the job, or its URI, will be returned as value. The returned elements have additional attributes: |
* <code>id</code>: job id | * <code>id</code>: job id | ||
* <code>type</code>: type of the job (command, query, REST, RESTXQ, etc.) | * <code>type</code>: type of the job (command, query, REST, RESTXQ, etc.) | ||
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|- | |- | ||
| '''Summary''' | | '''Summary''' | ||
− | |Waits for the completion of a job with the specified {{Code|$id}}. If the function is called with the id of a repeatedly executed job, it may never terminate. | + | |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''' | | '''Errors''' | ||
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* {{Code|start}}: a dayTimeDuration, time or dateTime can be specified to delay the execution of the query: | * {{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 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> (2am), <code>12:00: | + | ** 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. |
** 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. | ** 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|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. | ||
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<pre class="brush:xquery"> | <pre class="brush:xquery"> | ||
jobs:eval("prof:sleep(1500)", (), map { 'interval': 'PT1S', 'end': 'PT10S' }) | jobs:eval("prof:sleep(1500)", (), map { 'interval': 'PT1S', 'end': 'PT10S' }) | ||
+ | </pre> | ||
+ | * The following expression, if stored as a file, calls and evaluates itself every 5 seconds: | ||
+ | <pre class="brush:xquery"> | ||
+ | jobs:eval( | ||
+ | file:read-text(static-base-uri()), | ||
+ | map { }, | ||
+ | map { 'start': 'PT5S' } | ||
+ | ) | ||
+ | </pre> | ||
+ | |} | ||
+ | |||
+ | ==jobs:invoke== | ||
+ | |||
+ | {{Mark|Introduced with Version 9.0}} | ||
+ | |||
+ | {| width='100%' | ||
+ | |- | ||
+ | | width='120' | '''Signatures''' | ||
+ | |{{Func|jobs:invoke|$uri as xs:string|xs:string}}<br />{{Func|jobs:invoke|$uri as xs:string, $bindings as map(*)?|xs:string}}<br />{{Func|jobs:invoke|$uri as xs:string, $bindings as map(*)?, $options as map(xs:string, xs:string)|xs:string}}<br /> | ||
+ | |- | ||
+ | | '''Summary''' | ||
+ | |Schedules the evaluation of the XQuery expression located at {{Code|$uri}} and returns a query id. The semantics and remaining arguments are identical to [[#jobs:eval|jobs:eval]]. | ||
+ | |- | ||
+ | | '''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. | ||
+ | |- | ||
+ | | '''Examples''' | ||
+ | | | ||
+ | * Runs an XQuery expression that may perform some cleanups: | ||
+ | <pre class='brush:xquery'> | ||
+ | jobs:invoke("cleanup.xq", (), ()) | ||
</pre> | </pre> | ||
|} | |} | ||
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jobs:result($query) | jobs:result($query) | ||
) | ) | ||
− | |||
</pre> | </pre> | ||
+ | Please note that queries of this kind can cause deadlocks. For example, if both the original query and the query to be executed asynchronously perform updates on the same database, the second query would only be run after the first one has been executed, and the first query will wait forever. This is why you should avoid this pattern in practice and resort to [[XQuery Module#xquery:fork-join|xquery:fork-join]] if you want to do things in parallel. | ||
|} | |} | ||
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=Changelog= | =Changelog= | ||
+ | |||
+ | ;Version 9.0 | ||
+ | |||
+ | * Added: [[#jobs:invoke|jobs:invoke]] | ||
;Version 8.6 | ;Version 8.6 |
Revision as of 11:43, 6 October 2017
This XQuery Module provides functions for organizing scheduled, queued, running and cached jobs. Jobs can be commands, queries, client or HTTP requests.
Contents
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 registered. The list includes scheduled, queued, running jobs, and cached jobs. |
Examples |
|
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, or on a job with the specified $id (or an empty sequence if this job is not found). The list includes scheduled, queued, running jobs, and cached jobs. A string representation of the job, or its URI, will be returned as value. The returned elements have additional attributes:
|
Examples |
<job id="job1" type="XQuery" state="running" user="admin" duration="PT0.001S"> XQUERY jobs:list-details() </job> |
jobs:finished
Signatures | jobs:finished($id as xs:string) as xs:boolean
|
Summary | Indicates if the evaluation of an already running job with the specified $id has finished. As the ids of finished jobs will usually be discarded, unless caching is enabled, the function will also return true for unknown jobs.
|
jobs:stop
Signatures | jobs:stop($id as xs:string) as empty-sequence()
|
Summary | Triggeres the cancelation of a job with the specified $id , drops the cached result of a query, or cancels a scheduled job. Unknown ids are ignored. All jobs are gracefully stopped; it is up to the process to decide when it is safe to shut down.
|
jobs:wait
Signatures | jobs:wait($id as xs:string) as empty-sequence()
|
Summary | Waits for the completion of a job with the specified $id :
|
Errors | self : if the current job is addressed. |
Asynchronous Execution
Asynchronous query execution is recommendable if a client does not, or cannot, wait until a request is fully processed. This is e. g. the case with web browsers, which will usually cancel a request after a specific timeout. In such cases, you can use asynchronous execution to trigger another server-side process, which will start the time-consuming process, and fetch the result later on as soon as it is available.
jobs:eval
Template:Mark: id
option added.
Signatures | jobs:eval($query as xs:string) as xs:string jobs:eval($query as xs:string, $bindings as map(*)?) as xs:string jobs:eval($query as xs:string, $bindings as map(*)?, $options as map(xs:string, xs:string)) as xs:string |
Summary | Schedules the evaluation of the supplied $query and returns a query id. The query will be queued, and the result will optionally be cached. Queries can be updating. Variables and context items can be declared via $bindings (see xquery:eval for more details). The $options parameter contains scheduling options:
|
Errors | overflow : Query execution is rejected, because too many jobs are queued or being executed. CACHETIMEOUT can be decreased if the default setting is too restrictive.range : A specified time or duration is out of range.id : The specified id is invalid or has already been assigned.
|
Examples |
jobs:eval("1+3", (), map { 'cache': true() })
jobs:eval("import module namespace mail='mail'; mail:send('Happy birthday!')", (), map { 'start': '2018-09-01T06:00:00' })}}
declare %rest:POST("{$query}") %rest:path('/start-scheduling') function local:start($query) { jobs:eval($query, (), map { 'start': '02:00:00', 'interval': 'P1D' }) }; declare %rest:path('/stop-scheduling/{$id}') function local:stop($id) { jobs:stop($id) };
jobs:eval("prof:sleep(1500)", (), map { 'interval': 'PT1S', 'end': 'PT10S' })
jobs:eval( file:read-text(static-base-uri()), map { }, map { 'start': 'PT5S' } ) |
jobs:invoke
Signatures | jobs:invoke($uri as xs:string) as xs:string jobs:invoke($uri as xs:string, $bindings as map(*)?) as xs:string jobs:invoke($uri as xs:string, $bindings as map(*)?, $options as map(xs:string, xs:string)) as xs:string |
Summary | Schedules the evaluation of the XQuery expression located at $uri and returns a query id. The semantics and remaining arguments are identical to jobs:eval.
|
Errors | overflow : Query execution is rejected, because too many jobs are queued or being executed. CACHETIMEOUT can be decreased if the default setting is too restrictive.range : A specified time or duration is out of range.id : The specified id is invalid or has already been assigned.
|
Examples |
jobs:invoke("cleanup.xq", (), ()) |
jobs:result
Signatures | jobs:result($id as xs:string) as item()*
|
Summary | Returns the cached result of a job with the specified job $id :
|
Errors | running : the job is still running.unknown : the supplied id is unknown: The id is unknown, or the result has already been retrieved. |
Examples |
declare %rest:path('/result/{$id}') function local:result($id) { jobs:result($id) };
let $query := jobs:eval('(1 to 10000000)[. = 1]', map{}, map{ 'cache': true() }) return ( jobs:wait($query), jobs:result($query) ) Please note that queries of this kind can cause deadlocks. For example, if both the original query and the query to be executed asynchronously perform updates on the same database, the second query would only be run after the first one has been executed, and the first query will wait forever. This is why you should avoid this pattern in practice and resort to xquery:fork-join if you want to do things in parallel. |
Errors
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. |
range
|
A specified time or duration is out of range. |
id
|
The specified is invalid or has already been assigned. |
self
|
The current job cannot be addressed. |
Changelog
- Version 9.0
- Added: jobs:invoke
- Version 8.6
- Updated: jobs:eval:
id
option added.
The module was introduced with Version 8.5.