Job Module
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This XQuery Module provides functions for registering new query jobs and orchestrating existing jobs. Jobs can be queries, commands, operations performed by a database client, and HTTP requests.
Conventions[edit]
All functions in this module are assigned to the http://basex.org/modules/job namespace, which is statically bound to the job prefix. Errors will be bound to the same prefix.
Services[edit]
A job can be registered as service by supplying the service option to job:eval:
(: register job as service; will be run every day at 1 am :)
job:eval('db:drop("tmp")', (), map { 'id':'cleanup', 'start':'01:00:00', 'interval':'P1D', 'service': true() }),
(: list registered services :)
job:services(),
(: result: <job base-uri="..." id="cleanup" interval="P1D" start="01:00:00">db:drop("tmp")</job> :)
(: unregister job :)
job:remove('cleanup', map { 'service': true() })
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- If a job service is outdated (e.g. because a supplied end time has been exceeded), it will be removed from the jobs file at startup time.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
jobs.xmlfile in the database directory. It can also be edited manually.
Executing Jobs[edit]
There are cases in which a client does not, or cannot, wait until a request is fully processed. The client may be a browser, which sends an HTTP request to the server to start another time-consuming query job. The functions in this section allow you to register new query jobs and access existing ones. Jobs can be executed immediately (i.e., as soon as a free slot 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.
job:eval[edit]
| Signature | job:eval(
$query as xs:anyAtomicType,
$bindings as map(*)? := map { },
$options as map(*)? := map { }
) as xs:string
|
| Summary | Schedules the evaluation a new query job for the supplied $query (of type xs:string, or of type xs:anyURI if points to a resource), and returns a job ID. The job will be queued until a free slot is available, and the query result can be cached. Queries can be updating, and variables and the context value can be declared via $bindings (see xquery:eval for more details). The following $options can be supplied:
|
| Errors | overflow: Query execution is rejected because too many jobs are queued or being executed. CACHETIMEOUT can be decreased if the default setting is too restrictive.range: A specified time or duration is out of range.id: The specified ID is invalid or has already been assigned.options: The specified options are conflicting.
|
| Examples |
job:eval("1+3", (), map { 'cache': true() })
job:eval("import module namespace mail='mail'; mail:send('Happy birthday!')",
(), map { 'start': '2018-09-01T06:00:00' })}}
declare %rest:POST("{$query}") %rest:path('/start-scheduling') function local:start($query) {
job:eval($query, (), map { 'start': '02:00:00', 'interval': 'P1D' })
};
declare %rest:path('/stop-scheduling/{$id}') function local:stop($id) {
job:remove($id)
};
job:eval("prof:sleep(1500)", (), map { 'interval': 'PT1S', 'end': 'PT10S' })
job:eval(xs:anyURI('cleanup.xq'))
job:eval(
static-base-uri(),
map { },
map { 'start': 'PT5S' }
)
|
job:result[edit]
| Signature | job:result(
$id as xs:string,
$options as map(*)? := map { }
) as item()*
|
| Summary | Returns the cached result of a job with the specified job $id:
The following
|
| Examples |
declare %rest:path('/result/{$id}') function local:result($id) {
job:result($id)
};
let $query := job:eval('(1 to 10000000)[. = 1]', map { }, map { 'cache': true() })
return (
job:wait($query),
job:result($query)
)
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 |
job:remove[edit]
| Signature | job:remove(
$id as xs:string,
$options as map(*)? := map { }
) as empty-sequence()
|
| Summary | Triggers the cancelation of a job with the specified $id, cancels a scheduled job or removes a cached result. 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 $options can be supplied:
|
| Examples |
|
job:wait[edit]
| Signature | job: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. |
Listing Jobs[edit]
job:current[edit]
| Signature | job:current() as xs:string |
| Summary | Returns the ID of the current job. |
job:list[edit]
| Signature | job: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 | job:list() returns the same job ID as job:current if no other job is registered.
|
job:list-details[edit]
| Signature | job: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 a value. The returned elements have additional attributes:
|
| Examples | job: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 job:list-details()
</job>
|
job:bindings[edit]
| Signature | job:bindings( $id as xs:string ) as map(*) |
| Summary | Returns the variable bindings of an existing job with the specified $id. If no variables have been bound to this job, an empty map is returned.
|
job:finished[edit]
| Signature | job: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.
|
job:services[edit]
| Signature | job:services() as element(job)* |
| Summary | Returns a list of all jobs that have been persistently registered as Services. |
| Errors | services: Registered services cannot be parsed. |
Errors[edit]
| 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. |
service
|
Registered services cannot be parsed, added or removed. |
Changelog[edit]
- Version 10.0
- Updated: Renamed from Jobs Module to Job Module. The namespace URI has been updated as well.
- Updated:
job:removerenamed fromjobs:stop. - Updated:
job:result: options argument added. - Added:
job:bindings
- Version 9.7
- Updated:
job:result: return empty sequence if no result is cached.
- Version 9.5
- Updated:
job:eval: integers added as valid start and end times.
- Version 9.4
- Updated:
job:eval: option added for writing log entries. - Updated:
job:list-details: interval added.
- Version 9.2
- Deleted: job:invoke (merged with
job:eval)
- Version 9.1
- Updated:
job:list-details: registration time added.
- Version 9.0
- Added:
job:invoke, Services
- Version 8.6
- Updated:
job:eval:idoption added.
The module was introduced with Version 8.5.
