Job Module
This XQuery Module provides functions for organizing scheduled, queued, running and cached jobs. Jobs can be commands, queries, client or HTTP 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 registered. The list includes scheduled, queued, running, stopped, and finished jobs with cached results. |
Examples | jobs:list() returns the same job id as jobs:current if no other job is registered.
|
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 $id (or an empty sequence if this job is not found). The list includes scheduled, queued, running jobs, and cached jobs. A string representation of the job, or its URI, will be returned as value. The returned elements have additional attributes:
|
Examples | jobs:list-details() returns information on the currently running job and possibly others:
<job id="job1" type="XQuery" state="running" user="admin" duration="PT0.001S"> XQUERY jobs:list-details() </job> |
jobs:finished
Signatures | jobs:finished($id as xs:string) as xs:boolean
|
Summary | Indicates if the evaluation of 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 | Triggers the cancelation of a job with the specified $id , drops the cached result of a query, or cancels a scheduled job. Unknown ids are ignored. All jobs are gracefully stopped; it is up to the process to decide when it is safe to shut down.
|
Examples | jobs:list()[. != jobs:current()] ! jobs:stop(.) stops and discards all jobs except for the current one.
|
jobs:wait
Signatures | jobs:wait($id as xs:string) as empty-sequence()
|
Summary | Waits for the completion of a job with the specified $id :
|
Errors | self : The current job is addressed. |
Asynchronous Execution
Asynchronous query execution is recommendable if a client does not, or cannot, wait until a request is fully processed. This is e. g. the case with web browsers, which will usually cancel a request after a specific timeout. In such cases, you can use asynchronous execution to trigger another server-side process, which will start the time-consuming process, and fetch the result later on as soon as it is available.
jobs:eval
Signatures | jobs:eval($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(*)?) 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 $options parameter contains scheduling options:
|
Errors | overflow : Query execution is rejected, because too many jobs are queued or being executed. CACHETIMEOUT can be decreased if the default setting is too restrictive.range : A specified time or duration is out of range.id : The specified id is invalid or has already been assigned.options : The specified options are conflicting.
|
Examples |
jobs:eval("1+3", (), map { 'cache': true() })
jobs:eval("import module namespace mail='mail'; mail:send('Happy birthday!')", (), map { 'start': '2018-09-01T06:00:00' })}}
declare %rest:POST("{$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(*)?) as xs:string |
Summary | Schedules the evaluation of the XQuery expression located at $uri and returns a query id. The semantics and remaining arguments are identical to jobs:eval.
|
Errors | overflow : Query execution is rejected, because too many jobs are queued or being executed. CACHETIMEOUT can be decreased if the default setting is too restrictive.range : A specified time or duration is out of range.id : The specified id is invalid or has already been assigned.options : The specified options are conflicting.
|
Examples | Run XQuery expression that may perform some cleanups:
jobs:invoke("cleanup.xq", (), ()) |
jobs:result
Signatures | jobs:result($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 |
---|---|
options
|
The specified options are conflicting. |
id
|
The specified id is invalid or has already been assigned. |
overflow
|
Too many queries or query results are queued. |
range
|
A specified time or duration is out of range. |
running
|
A query is still running. |
self
|
The current job cannot be addressed. |
unknown
|
The supplied query id is unknown or not available anymore. |
Changelog
- Version 9.0
- Added: jobs:invoke
- Version 8.6
- Updated: jobs:eval:
id
option added.
The module was introduced with Version 8.5.