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Handle SQLITE_BUSY errors gracefully 

This allows other applications (e.g. minetestmapper) to interrogate
the database while minetest is running, without causing an almost
certain minetest crash.
This commit is contained in:
Rogier 2015-12-23 11:38:50 +01:00 committed by est31
parent 848b050a56
commit c6bb6f99d1
2 changed files with 64 additions and 0 deletions
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60
src/database-sqlite3.cpp
View File

@ -31,10 +31,19 @@ SQLite format specification:
#include "filesys.h"
#include "exceptions.h"
#include "settings.h"
#include "porting.h"
#include "util/string.h"
#include <cassert>
// When to print messages when the database is being held locked by another process
// Note: I've seen occasional delays of over 250ms while running minetestmapper.
#define BUSY_INFO_TRESHOLD 100 // Print first informational message after 100ms.
#define BUSY_WARNING_TRESHOLD 250 // Print warning message after 250ms. Lag is increased.
#define BUSY_ERROR_TRESHOLD 1000 // Print error message after 1000ms. Significant lag.
#define BUSY_FATAL_TRESHOLD 3000 // Allow SQLITE_BUSY to be returned, which will cause a minetest crash.
#define BUSY_ERROR_INTERVAL 10000 // Safety net: report again every 10 seconds
#define SQLRES(s, r) \
if ((s) != (r)) { \
@ -56,6 +65,51 @@ SQLite format specification:
sqlite3_errmsg(m_database)); \
}
int Database_SQLite3::busyHandler(void *data, int count)
{
s64 &first_time = reinterpret_cast<s64 *>(data)[0];
s64 &prev_time = reinterpret_cast<s64 *>(data)[1];
s64 cur_time = getTimeMs();
if (count == 0) {
first_time = cur_time;
prev_time = first_time;
} else {
while (cur_time < prev_time)
cur_time += s64(1)<<32;
}
if (cur_time - first_time < BUSY_INFO_TRESHOLD) {
; // do nothing
} else if (cur_time - first_time >= BUSY_INFO_TRESHOLD &&
prev_time - first_time < BUSY_INFO_TRESHOLD) {
infostream << "SQLite3 database has been locked for "
<< cur_time - first_time << " ms." << std::endl;
} else if (cur_time - first_time >= BUSY_WARNING_TRESHOLD &&
prev_time - first_time < BUSY_WARNING_TRESHOLD) {
warningstream << "Sqlite3 database has been locked for "
<< cur_time - first_time << " ms." << std::endl;
} else if (cur_time - first_time >= BUSY_ERROR_TRESHOLD &&
prev_time - first_time < BUSY_ERROR_TRESHOLD) {
errorstream << "SQLite3 database has been locked for "
<< cur_time - first_time << " ms; this causes lag." << std::endl;
} else if (cur_time - first_time >= BUSY_FATAL_TRESHOLD &&
prev_time - first_time < BUSY_FATAL_TRESHOLD) {
errorstream << "Sqlite3 database has been locked for "
<< cur_time - first_time << " ms - giving up!" << std::endl;
} else if ((cur_time - first_time) / BUSY_ERROR_INTERVAL !=
(prev_time - first_time) / BUSY_ERROR_INTERVAL) {
// Safety net: keep reporting every BUSY_ERROR_INTERVAL
errorstream << "SQLite3 database has been locked for "
<< (cur_time - first_time) / 1000 << " seconds!" << std::endl;
}
prev_time = cur_time;
// Make sqlite transaction fail if delay exceeds BUSY_FATAL_TRESHOLD
return cur_time - first_time < BUSY_FATAL_TRESHOLD;
}
Database_SQLite3::Database_SQLite3(const std::string &savedir) :
m_initialized(false),
@ -107,6 +161,12 @@ void Database_SQLite3::openDatabase()
throw FileNotGoodException("Cannot open database file");
}
if (sqlite3_busy_handler(m_database, sqlite3BusyHandler, busy_handler_data) != SQLITE_OK) {
errorstream << "SQLite3 database failed to set busy handler: "
<< sqlite3_errmsg(m_database) << std::endl;
throw FileNotGoodException("Failed to set busy handler for sqlite connection");
}
if (needs_create) {
createDatabase();
}

4
src/database-sqlite3.h
View File

@ -63,6 +63,10 @@ private:
sqlite3_stmt *m_stmt_delete;
sqlite3_stmt *m_stmt_begin;
sqlite3_stmt *m_stmt_end;
s64 m_busy_handler_data[2];
static int busyHandler(void *data, int count);
};
#endif