Changes

This [[Module Library|XQuery Module]] provides functions for evaluating XQuery expressions in separate threadsregistering new query jobs and orchestrating existing jobs. Query execution Jobs can both be parallelized queries, commands, operations performed by a database client, and postponed to be executed asynchronouslyHTTP requests.

All functions in this module are assigned to the <code><nowiki>http://basex.org/modules/asyncjob</nowiki></code> namespace, which is statically bound to the {{Code|asyncjob}} prefix. Errors will be bound to the same prefix.

=Parallelized ExecutionServices=

A job can be registered as ''service'' by supplying the {{Code|service}} option to {{Function||job:eval}}: <pre lang='xquery'>(: 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=async"cleanup" interval="P1D" start="01:fork00:00">db:drop("tmp")</job> :) (: unregister job :)job:remove('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services will be scheduled for evaluation when the BaseX server or BaseX HTTP server is started.* If a job service is outdated (e.g. because a supplied end time has been exceeded), it will be removed from the jobs file at startup time.* The job definitions are stored in a {{Code|jobs.xml}} file in the database directory. It can also be edited manually. =Executing Jobs= 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-joinconsuming 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 [[Transaction Management#Concurrency Control|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==

|-valign="top"| width='120' | '''SignaturesSignature'''|{{Func|async<pre>job:fork-join|eval( $functions query as function(*)*|item()*}}<br/ >{{Func|asyncxs:fork-join|anyAtomicType, $functions bindings as functionmap(*)*? := map { }, $options as map(xs*)? :string, = map { }) as xs:string)|item()*}}<br/ pre>|-valign="top"|'''Summary'''|This function executes Schedules the evaluation a new query job for the supplied functions in parallel{{Code|$query}} (of type {{Code|xs:string}}, or of type {{Code|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 {{Code|$bindings}} (see {{Function|XQuery|xquery:eval}} for more details). The following {{Code|$options}} can be supplied:* {{Code|cache}}: indicates if the query result will be cached or ignored (default: {{Code|false}}):** The result will be cached in main-memory until it is fetched via {{Function||job:result}}, or until {{Option|CACHETIMEOUT}} is exceeded.** If the query raises an error, it will be cached and returned instead.* {{Code|start}}: a dayTimeDuration, time, dateTime or integer 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 of valid values are available:<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 dateTime is specified, the query will be executed at this date. Examples for valid values are: <code>threads2018-12-31T23:59:59</code>(New Year's Eve 2018, close to midnight). An error will be raised if the specified time lies in the past.** If a time is specified, the query will be executed at this time of the day. Examples of valid times are: <code>02: maximum number of parallel threads 00:00</code> (default2am local time), <code>12:00: available 00Z</code> (noon, UTC). If the time lies in the past, the query will be executed the next day.** An integer will be interpreted as minutes. If the specified number is greater than the elapsed minutes of coresthe current hour, the query will be executed one hour later.* {{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|end}}: scheduling can be stopped after a given time or duration. The string format is the same as for {{Code|start}}. An error is raised if the resulting end time is smaller than the start time.* {{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>thread-sizejob</code>prefix, and it can only be assigned if no job with the same name exists.* {{Code|service}}: number additionally registers the job as [[#Services|service]]. Registered services must have no variable bindings.* {{Code|log}}: writes the specified string to the [[Logging|database logs]]. Two log entries are stored, one at the beginning and another one after the execution of functions to the job.|- valign="top"| '''Errors'''|{{Error|overflow|#Errors}} Query execution is rejected because too many jobs are queued or being executed. {{Option|CACHETIMEOUT}} can be evaluated by each thread (decreased if the default: setting is too restrictive.<br/>{{Error|range|#Errors}} A specified time or duration is out of range.<codebr/>1{{Error|id|#Errors}} The specified ID is invalid or has already been assigned.<br/code>){{Error|options|#Errors}} The specified options are conflicting.|-valign="top"

* Cache query result. The returned ID can be used to pick up the result with {{Function||job:result}}:<pre lang='xquery'>job:eval("1+3", (), map { 'cache': true() })</pre>* A happy birthday mail will be sent at the given date:<pre lang='xquery'>job:eval("import module namespace mail='mail'; mail:send('Happy birthday!')", (), map { 'start': '2018-09-01T06:00:00' })}}</pre>* The following [[RESTXQ]] functions can be called to execute a query at 2 am every day. An ID will be returned by the first function sleeps in parallel; it will , which can be finished in 1 used to stop the scheduler via the second if your system has at least 2 coresfunction:<pre classlang='brush:xquery'>asyncdeclare %rest:POST("{$query}") %rest:forkpath('/start-joinscheduling') function local:start($query) { for job:eval($i in 1 to 2query, (), map { 'start': '02:00:00', 'interval': 'P1D' })}; return declare %rest:path('/stop-scheduling/{$id}') functionlocal:stop($id) { job:remove($id)};</pre>* Query execution is scheduled for every second, and for 10 seconds in total. As the query itself will take 1.5 seconds, it will only be executed every second time:<pre lang='xquery'>job:eval("prof:sleep(10001500)", (), map { 'interval': 'PT1S', 'end': 'PT10S' }) </pre>* The query in the specified file will be evaluated once:<pre lang='xquery'>job:eval(xs:anyURI('cleanup.xq'))</pre>* The following expression, if stored in a file, will be evaluated every 5 seconds:<pre lang='xquery'>job:eval( static-base-uri(), map { }, map { 'start': 'PT5S' }

|} ==job:result== {| width='100%'|- valign="top"| width='120' | '''Signature'''|<pre>job:result( $id as xs:string, $options as map(*)? := map { }) as item()*</pre>|- valign="top"| '''Summary'''|Returns the cached result of a job with the specified job {{Code|$id}}:* In If the following queryoriginal job has raised an error, up to two URLs the cached error will be raised instead.* The cached result or error will be requested in paralleldropped after it has been retrieved.* If the result has not been cached or if it has been dropped, an empty sequence is returned.The following {{Code|$options}} can be supplied:* {{Code|keep}}: Keep the cached result or error after retrieval. |- valign="top"| '''Examples'''|* The following [[RESTXQ]] function will either return the result of a previously started job or raise an error:<pre classlang='brush:xquery'>let declare %rest:path('/result/{$funcs id}') function local:=result($id) { for job:result($segment id)};</pre>* The following query demonstrates how the results of an executed query can be returned within the same query (see below why you should avoid this pattern in 1 to 4practice):<pre lang='xquery'> let $url query := 'httpjob://url.com/patheval(' || $segment return function(1 to 10000000) [. = 1]', map { }, map { http'cache':send-request(true(), $url}) }return async( job:fork-joinwait($funcsquery), map { 'threads' job: 2 }result($query))

|-|'''Errors'''|{{Error|unexpected|#Errors}} an unexpected error occurred while running a 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 or function in a separate threadforever.<br/>You should resort to {{ErrorFunction|XQuery|out-ofxquery:fork-range|#Errorsjoin}} a supplied option is out of rangeif you want to have full control on parallel query execution.<br/>

=Asynchronous Execution= ==asyncjob:evalremove==

|-valign="top"| width='120' | '''SignaturesSignature'''|{{Func|async:eval|$query as xs:string|xs:string}}<br /pre>{{Func|asyncjob:eval|remove( $query id as xs:string, $bindings options as map(*)|xs? :string= map { }}<br />{{Func|async:eval|$query as xs:string, $bindings as map(*), $options as mapempty-sequence(xs:string, xs:string)|xs:string}}<br /pre>|-valign="top"

|Prepares Triggers the supplied cancelation of a job with the specified {{Code|$queryid}} string for asynchronous execution and returns , cancels a query idscheduled job or removes a cached result. Unknown IDs are ignored. The query will be queued as described in All jobs are gracefully stopped; it is up to the article on [[Transaction Management]], and the result will be cached in main-memory until process to decide when it is fetched via [[#async:result|async:result]], or until {{Option|ASYNCTIMEOUT}} is exceeded.<br/>Variables and context items can be declared via {{Code|$bindings}} (see [[XQuery Module#xquery:eval|xquery:eval]] for more details)safe to shut down. The following {{Code|$options}} parameter contains evaluation optionscan be supplied:* {{Code|cacheservice}}: indicates if additionally removes the query result will be cached or ignored (default: <code>true</code>). If job from the query result will not be cached, the query id will immediately be discarded after query execution, too.* {{Code|base-uri}}: set [https://www.w3.org/TR/xquery-31/[#dt-static-base-uri base-uri propertyServices|job services]] for the query. This URI will be used when resolving relative URIs by functions such as {{Code|fn:doc}} (default: ''empty string'').|-| '''Errors'''|{{Error|updating|#Errors}} the query contains update operationslist.|-valign="top"

* {{Code|async<code>job:evallist("1+3")}} returns a query id, e[.g!= job:current()] ! job:remove(. {{Code|Query-abc}})</code> stops and discards all jobs except for the current one. The result can be retrieved via a second query in the same BaseX context* <code>job: {{Code|asyncremove(job:resultcurrent("Query-abc")}})<br /code>interrupts the current job.

==asyncjob:updatewait==

|-valign="top"| width='120' | '''SignaturesSignature'''|{{Func|async:update|$query as xs:string|xs:string}}<br /pre>{{Func|asyncjob:update|$query as xs:string, $bindings as mapwait(*)|xs:string}}<br />{{Func|async:update| $query id as xs:string, $bindings as map(*), $options as mapempty-sequence(xs:string, xs:string)|xs:string}}<br /pre>|-valign="top"

|Prepares Waits for the completion of a job with the supplied specified {{Code|$queryid}} string for asynchronous execution and returns a query id. :* The query function will be terminate immediately if the job ID is unknown. This is the case if a future job has not been queued as described in yet, or if the article on [[Transaction Management]]ID has already been discarded after job evaluation.<br/>See [[#async:eval|async:eval]] for information on * If the function is called with the <code>$bindings</code> ID of a queued job, or repeatedly executed job, it may stall and <code>$options</code> argumentsnever terminate.|-valign="top"

|{{Error|non-updatingself|#Errors}} The current job is addressed.<br/>|} =Listing Jobs= ==job:current== {| width='100%'|- valign="top"| width='120' | '''Signature'''|<pre>job:current() as xs:string</pre>|- valign="top"| '''Summary'''|Returns the query does not contain any update operationsID of the current job.|} ==job:list== {| width='100%'|- valign="top"| width='120' | '''Signature'''|<pre>job:list() as xs:string*<br/pre>|-valign="top"| '''Summary'''|Returns the IDs of all jobs that are currently registered. The list includes scheduled, queued, running, stopped, and finished jobs with cached results.|- valign="top"

|* <code>asyncjob:update("delete node db:open('db')//text()", map {}, map { 'cache': falselist() })</code> returns a query id. The text nodes of the database <code>db</code> will be deleted once the database same job ID as {{Function||job:current}} if no other job is available for write accessregistered.

==asyncjob:resultlist-details==

|-valign="top"| width='120' | '''SignaturesSignature'''|{{Func|async<pre>job:result|list-details( $id as xs:string|item := ()) as element(job)*}}</pre>|-valign="top"

|Returns the result of an asynchronously executed query information on all jobs that are currently registered, or on a job with the specified query {{Code|$id}}:* Results can only be retrieved once(or an empty sequence if this job is not found). After retrievalThe list includes scheduled, queued, running jobs, and cached jobs. A string representation of the cached result job, or its URI, will be discardedreturned as a value.The returned elements have additional attributes:* If <code>id</code>: job ID* <code>type</code>: type of the job (command, query raised an error, the error will be raised insteadREST, RESTXQ, etc.)|-* <code>state</code>: current state of the job: <code>scheduled</code>, <code>queued</code>, <code>running</code>, <code>cached</code>| '''Errors'''* <code>user</code>: user who started the job|{{Error|* <code>duration</code>: evaluation time (included if a job is-running|#Errors}} or if the query is still running.result was cached)* <code>start<br/code>{{Error|unknown|#Errors}} the supplied query id is unknown: The query result may already have been retrieved, or query execution may have been stopped.next start of job (included if a job will be executed repeatedly)* <code>time<br/code>: time when job was registered|-valign="top"

| The following query <code>job:list-details()</code> returns information on the results of an asynchronously executed query. It will succeed, because both the main currently running job and the asynchronous query do not include write operations on concurrently used databasespossibly others:<pre classlang='brush:xquery'"xml">let $query :<job id="job1" type="XQuery" state="running" user="admin" duration= async:eval('(1 to 10000000)["PT0. = 1]')return (001S"> hofXQUERY job:until( functionlist-details($result) { async:finished($query) }, function($curr) { prof:sleep(10) }, () ), async:result($query))</job>

==asyncjob:finishedbindings==

|-valign="top"| width='120' | '''SignaturesSignature'''|{{Func|async<pre>job:finished|bindings( $id as xs:string|xs:boolean}}) as map(*)</pre>|-valign="top"

|Indicates if Returns the evaluation variable bindings of a query an existing job with the specified query {{Code|$id}} has finished. If <code>false</code> is returned, the query is still running. An error will be raised if the query result was not cached or has already been retrieved.|-| '''Errors'''|{{Error|unknown|#Errors}} the supplied query id is unknown: The query result may already no variables have been retrievedbound to this job, or query execution may have been stoppedan empty map is returned.<br/>

==asyncjob:stopfinished==

|-valign="top"| width='120' | '''SignaturesSignature'''|{{Func|async<pre>job:stop|finished( $id as xs:string|empty-sequence()}}as xs:boolean</pre>|-valign="top"

|Cancels Indicates if the execution evaluation of a query an already running job with the specified query {{Code|$id}}has finished. As the IDs of finished jobs will usually be discarded, unless caching is enabled, or drops the query result if it has already been executedfunction will also return <code>true</code> for unknown jobs.|-| '''Errors'''|{{Error|unknown|#Errors}} * <code>false</code> indicates that the supplied query id job ID is unknown: The query result may already have been retrievedscheduled, queued, or query execution may have been stoppedcurrently running.* <code>true<br/code>will be returned if the job has either finished, or if the ID is unknown (because the IDs of all finished jobs will not be cached).

==asyncjob:idsservices==

|-valign="top"| width='120' | '''SignaturesSignature'''|{{Func|async:ids||xs<pre>job:stringservices() as element(job)*}}</pre>|-valign="top"

|Returns the ids a list of all queries that are either being executed asynchronously, or jobs that have been executed and the results of which have been cachedpersistently registered as [[#Services|Services]].|-valign="top"| '''ExamplesErrors'''|* <code>async:ids() ! async:stop({{Error|services|#Errors}} Registered services cannot be parsed.)<br/code> stops and invalidates all asynchronous queries and results.

|-valign="top"|{{Code|unexpectedoptions}}| An unexpected error occurred while running a query or function in a separate threadThe specified options are conflicting.|-valign="top"|{{Code|out-of-rangeid}}| The supplied option specified ID is out of rangeinvalid or has already been assigned.|-valign="top"|{{Code|updatingoverflow}}| A Too many queries or query is expected to be non-updating, but it performs updatesresults are queued.|-valign="top"|{{Code|non-updatingrange}}| A query specified time or duration is expected to be updating, but it does not perform updates.|-|{{Code|unknown}}| The supplied query id is unknown or not available anymoreout of range.|-valign="top"|{{Code|is-running}}