Dbxml concurency problems

Question

Hi all,
I have a strange problem.
I have two programs.
One that constantly reads from the database.
the other tries to update a document in the container.
both programs work well when run separately, one at time.
But if both programs run at the same time
the reader crashes with: DbXml::XmlException: Error: DbTxn::commit: DB_RUNRECOVERY: Fatal error, run database recovery
both program open environment with locking, logging and transaction.
reader:
DbEnv env(0);
env.open(env_name.c_str(), DB_INIT_MPOOL|DB_INIT_LOCK|DB_INIT_LOG|DB_INIT_TXN, 0);
XmlManager mgr(&env);
XmlQueryContext context = mgr.createQueryContext(XmlQueryContext::DeadValues, XmlQueryContext::Eager);
for(int x = 0; x < 1000; x++){
try{
XmlTransaction txn = mgr.createTransaction();
XmlContainer c = mgr.openContainer(txn, c_name);
txn.commit();
txn = mgr.createTransaction();
//txn = mgr.createTransaction(DB_TXN_NOWAIT);
XmlQueryExpression qe = mgr.prepare(txn, "collection('method.dbxml')/methods/method[name='TRACE']/status", context);
XmlResults r = qe.execute(txn, context);
DumpResults(r);
}catch(DbXml::XmlException& e){
cerr << "XXX DbXml::XmlException: " << e.what() <<endl;
exit(1);
writer:
DbEnv env(0);
env.set_cachesize(0, 64 * 1024, 1); env.open(path2DbEnv.c_str(),DB_INIT_MPOOL|DB_CREATE|DB_RECOVER|DB_INIT_LOCK|DB_INIT_LOG|DB_INIT_TXN, 0);
try{
XmlTransaction txn_begin = mgr.createTransaction();
XmlContainer container = mgr.openContainer(txn_begin, theContainer);
txn_begin.commit();
XmlTransaction txn = mgr.createTransaction();
XmlQueryContext context = mgr.createQueryContext(XmlQueryContext::LiveValues,XmlQueryContext::Eager);
std::string fullQuery = "collection('" + container.getName() + "')" + path;
string node = buildParamedQuery(fullQuery, search, search_list);
XmlQueryExpression expression = mgr.prepare(txn, fullQuery, context);
XmlResults results = expression.execute(txn, context);
XmlValue value;
XmlUpdateContext uc = mgr.createUpdateContext();
XmlModify modify = mgr.createModify();
modify.addUpdateStep(mgr.prepare(txn, q, context), node_val);
modify.execute(txn, results, context, uc);
txn.commit();
catch(std::exception &e) {
std::cerr << "Document modification failed. ";
std::cerr << e.what() << "\n";
exit( -1 );
}

Answer 1

Hi,
Are both applications sharing the same environment?
If you try deleting the environment and running with the configuration you specified,, do you still see the problem?
What version of Berkeley DB XML are you running?
When you run the writer (which runs recovery) I assume you are not running the reader until recovery completes. Is that true?
Ron