mirror of https://github.com/BOINC/boinc.git
233 lines
7.3 KiB
PHP
233 lines
7.3 KiB
PHP
<?
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require_once("docutil.php");
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page_head("Back end programs");
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echo "
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<p>
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A project back end consists of a set of programs,
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some of which have project- or application-specific parts.
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<p>
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<table border=1 cellpadding=8>
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<tr>
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<th>Component</th>
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<th>BOINC-supplied part</th>
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<th>project-supplied part</th>
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</tr>
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<tr>
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<td valign=top>
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<b>Work generator</b>: generates work units and the corresponding input files.
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</td>
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<td valign=top>
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Interfaces for creating workunits.
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</td>
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<td valign=top>
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Programs or scripts that generate input files,
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install them on data servers, and call the BOINC interface functions.
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</td></tr>
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<tr>
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<td valign=top><b>Transitioner</b>:
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Handles various state transitions of workunits and results,
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such as timeouts.
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Generates results for workunits as needed.
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</td>
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<td valign=top>A program <b>transitioner</b>.</td>
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<td valign=top>None</td>
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</tr>
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<tr>
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<td valign=top><b>Result validation and accounting</b>:
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compare redundant results; select a <b>canonical result</b>
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representing the correct output,
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and a <b>canonical credit</b> granted to users and hosts
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that return the correct output.</td>
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<td valign=top>A program, <b>validate</b>,
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that contains the basic logic for validation.</td>
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<td valign=top>An application-specific function, linked with <b>validate</b>,
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that compares sets of redundant results.</td>
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</tr>
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<tr>
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<td valign=top><b>Assimilator</b>:
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handles workunits that are 'completed':
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that is, that have a canonical result or for which
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an error condition has occurred.
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Handling a successfully completed result might involve
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record results in a database and perhaps generating more work.</td>
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<td valign=top>
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A program <b>assimilator</b> that contains the
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basic logic for assimilation.
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</td>
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<td valign=top>
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A handler function that assimilates a workunit,
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either by processing its canonical result
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or handling an error return.
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</td>
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</tr>
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<tr>
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<td valign=top><b>File deleter</b>: delete input and output files
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when they are no longer needed.</td>
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<td valign=top>A program <b>file_deleter</b>.</td>
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<td valign=top>None.</td>
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</tr>
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</table>
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<h3>Work generator</h3>
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<p>
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<pre>
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for each wu created
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wu.transition_time = now
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</pre>
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<h3>scheduler</h3>
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<pre>
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when send a result
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result.report_deadline = now + wu.delay_bound
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wu.transition_time = min(wu.transition_time, result.report_deadline)
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when receive a result
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if client error
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result.outcome = client_error
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result.validate_state = INVALID
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else
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result.outcome = success
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result.server_state = OVER
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wu.transition_time = now
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when a result falls off the bottom of infeasible queue
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result.server_state = OVER
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result.outcome = COULDNT_SEND
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wu.transition_time = now
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</pre>
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<h3>Transitioner</h3>
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<p>
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<pre>
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// gets run when either
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// - a result becomes done (via timeout or client reply)
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// - the WU error mask is set (e.g. by validater)
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// - assimilation is finished
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for each WU with now > transition_time:
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// check for timed-out results
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for each result of WU
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if result.server_state = in_progress and now > result.report_deadline
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result.server_state = OVER
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result.outcome = NO_REPLY
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// trigger validation if needed
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K = # of SUCCESS results
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if K >= M
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if any result is server_state OVER, outcome SUCCESS, validate_state INIT
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wu.need_validate = true
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// check for WU error conditions
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if any result has outcome couldnt_send
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error_mask |= couldnt_send
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K = # results with outcome = client_error
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if K > A
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error_mask |= too_many_error_results
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// Note: check on # of success results is done in validator
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K = total # results
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if K > B
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error_mask |= too_many_total_results
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// if no WU errors, generate new results if needed
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if error_mask == 0
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K = # results w/ server_state = unsent or in_progress
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L = N - K
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generate L new results
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// if WU errors, clean up unsent results
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// and trigger assimilation if needed
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if error_mask
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for all results server_state = unsent
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server_state = over
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outcome = didnt_need
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if wu.assimilate_state == init
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wu.assimilate_state = ready
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// if WU is assimilated, trigger deletion of files
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if wu.assimilated_state = DONE
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// trigger input file deletion if needed
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if all results are OVER
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wu.file_delete_state = ready
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// outputs of error results can be deleted immediately;
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// outputs of successful results can be deleted when validated
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for results of WU
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if canonical result and not all results OVER
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continue
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if outcome = CLIENT_ERROR or (SUCCESS and (VALID or INVALID))
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if file_delete_state = INIT
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result.file_delete_state = READY
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// get next result timeout if any
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transition_time = MAX_INT
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if any results are IN_PROGRESS
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transition_time = min(result.report_deadline)
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</pre>
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<h3>Validator</h3>
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<p>
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BOINC supplies a utility program <b>validate</b>
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to perform validation and credit-granting.
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This program must be linked with two project-specific functions:
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<pre>
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int check_set(vector<RESULT> results, int& canonicalid, double& credit);
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int check_pair(RESULT& r1, RESULT& r2, bool& match);
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</pre>
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<b>check_set()</b> takes a set of results.
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If there is sufficient agreement,
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it selects one of them as the canonical result
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(returning its ID) and also decides what credit should
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be granted for correct results for this workunit.
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<p>
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<b>check_pair()</b> compares two results and returns match=true
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if they agree.
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<p>
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The file <b>validate_test.C</b> contains an example
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implementation of check_set() and check_pair().
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<pre>
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for each WU w/ need_validate true
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if have canonical result
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for each result w/ validate_state INIT and outcome SUCCESS
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// possible that we've already deleted canonical output files
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if canonical_result.file_delete_state = DONE
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validate_state = INVALID
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else
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if matches canonical, grant credit
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validate_state = VALID or INVALID
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need_to_handle_over_results = true
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else
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S = set of results w/ outcome SUCCESS
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if consensus(S)
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set canonical_result
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set success results as VALID or INVALID
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grant credit
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need_to_handle_over_results = true
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wu.assimilate_state = READY
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for all results server_state UNSENT
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server_state = OVER
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outcome = DIDNT_NEED
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else
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if # of successful results > C
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wu.error_mask |= too_many_success_result
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need_to_handle_over_results = true
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if need_to_handle_over_results:
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wu.transition_time = now
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</pre>
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<h3>Assimilator</h3>
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<pre>
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for each WU with assimilate_state = READY
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call project-specific handler function
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wu.assimilate_state = done
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wu.transition_time = now
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</pre>
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";
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page_tail();
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?>
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