Job Module

This XQuery Module provides functions for organizing running commands and queries (…more to come).

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 queued or executed. The input comprises the job id, the type (XQuery, a command, REST, RESTXQ), the time a job is already being evaluated, the state (queued, running, stopped, timeout, memory) and the user who started the job.
Examples	jobs:list-details() returns information on the currently running job and possibly others: <job id="job1" type="XQuery" duration="PT0S" state="running" user="admin"> 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, or drops the cached result of a query. 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	Prepares the supplied $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 be cached in main-memory until it is fetched via jobs:result, or until CACHETIMEOUT is exceeded. Queries may be updating. Variables and context items can be declared via $bindings (see xquery:eval for more details). The $options parameter contains evaluation options: cache: indicates if the query result will be cached or ignored (default: true). If the query result will not be cached, the query id will immediately be discarded after query execution, too. base-uri: set base-uri property for the query. This URI will be used when resolving relative URIs by functions such as fn:doc (default: empty string).
Errors	overflow: Too many queries or query results are queued. CACHETIMEOUT can be decreased if the default setting is too restrictive.
Examples	jobs:schedule("1+3", map{}, map{ 'cache': true() }) returns a query id, e.g. Job-123. The result can be retrieved via a second query in the same BaseX context: jobs:result("Job-123") The following RESTXQ function will return the id of the query thread, which evaluates the query that has been specified in the body of a POST request: declare %rest:POST("{$query}") %rest:path('/eval') function local:schedule($query) { jobs:schedule($query) };

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 $query := jobs:schedule('(1 to 10000000)[. = 1]', map{}, map{ 'cache': true() }) return ( hof:until( function($result) { jobs:finished($query) }, function($curr) { prof:sleep(10) }, () ), jobs:result($query) )

jobs:results

Signatures	jobs:results() as xs:string*
Summary	Returns the ids of all jobs for which results are cached.

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.

Changelog

The module was introduced with Version 8.5.