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DatabaseCampaign: avoid table locking

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It is necessary to copy pilot IDs of existing results to a temporary table
before fetching undone jobs from the DB: Otherwise, due to MyISAMs
table-level locking, collect_result_thread() will block in INSERT (SHOW
PROCESSLIST state "Waiting for table level lock") until the (streamed)
pilot query finishes.  As one pilot query follows after the other,
collect_result_thread() may even starve until the memory for the
JobServer's "done" queue runs out, resulting in a crash and the loss of all
queued results.

Change-Id: Ib0ec5fa84db466844b1e9aa0e94142b4d336b022
This commit is contained in:
Horst Schirmeier
2014-02-19 18:51:22 +01:00
parent b094753fde
commit 25a390970a
1 changed files with 19 additions and 2 deletions
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21
src/core/cpn/DatabaseCampaign.cc
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@ -127,14 +127,31 @@ void DatabaseCampaign::collect_result_thread() {
}
bool DatabaseCampaign::run_variant(Database::Variant variant) {
/* Copy pilot IDs of existing results to tmp table: otherwise, due to
* MyISAMs table-level locking, collect_result_thread() will block in
* INSERT (SHOW PROCESSLIST state "Waiting for table level lock") until the
* (streamed) pilot query finishes. As one pilot query follows after the
* other, collect_result_thread() may even starve until the memory for the
* JobServer's "done" queue runs out, resulting in a crash and the loss of
* all queued results. */
db->query("CREATE TEMPORARY TABLE IF NOT EXISTS result_ids (pilot_id INT NOT NULL PRIMARY KEY)");
db->query("TRUNCATE TABLE result_ids");
std::stringstream ss;
ss << "INSERT INTO result_ids "
<< "SELECT r.pilot_id FROM " << db_connect.result_table() << " r "
<< "JOIN fsppilot p ON r.pilot_id = p.id "
<< "WHERE p.fspmethod_id = " << fspmethod_id
<< " AND p.variant_id = " << variant.id;
db->query(ss.str().c_str());
ss.str("");
/* Gather all unfinished jobs */
int experiment_count;
std::string sql_select = "SELECT p.id, p.fspmethod_id, p.variant_id, p.injection_instr, p.injection_instr_absolute, p.data_address, p.data_width ";
std::stringstream ss;
ss << " FROM fsppilot p "
<< " WHERE p.fspmethod_id = " << fspmethod_id
<< " AND p.variant_id = " << variant.id
<< " AND (SELECT COUNT(*) FROM " + db_connect.result_table() + " as r WHERE r.pilot_id = p.id)"
<< " AND (SELECT COUNT(*) FROM result_ids as r WHERE r.pilot_id = p.id)"
<< " < " << expected_number_of_results(variant.variant, variant.benchmark)
<< " ORDER BY p.injection_instr";
std::string sql_body = ss.str();