phet commented on code in PR #3715:
URL: https://github.com/apache/gobblin/pull/3715#discussion_r1263168291
##########
gobblin-runtime/src/main/java/org/apache/gobblin/runtime/api/MysqlMultiActiveLeaseArbiter.java:
##########
@@ -155,19 +163,26 @@ public MysqlMultiActiveLeaseArbiter(Config config) throws
IOException {
} catch (SQLException e) {
throw new IOException("Table creation failure for " +
leaseArbiterTableName, e);
}
+ initializeConstantsTable();
+
+ log.info("MysqlMultiActiveLeaseArbiter initialized");
+ }
+
+ // Initialize Constants table if needed and insert row into it if one does
not exist
+ private void initializeConstantsTable() throws IOException {
String createConstantsStatement =
String.format(CREATE_CONSTANTS_TABLE_STATEMENT, this.constantsTableName);
withPreparedStatement(createConstantsStatement, createStatement ->
createStatement.executeUpdate(), true);
- int count = withPreparedStatement(String.format(GET_ROW_COUNT_STATEMENT,
this.constantsTableName), getStatement -> {
+ Optional<Integer> count =
withPreparedStatement(String.format(GET_ROW_COUNT_STATEMENT,
this.constantsTableName), getStatement -> {
ResultSet resultSet = getStatement.executeQuery();
if (resultSet.next()) {
- return resultSet.getInt(1);
+ return Optional.of(resultSet.getInt(1));
}
- return -1;
+ return Optional.absent();
}, true);
// Only insert epsilon and linger values from config if this table does
not contain pre-existing values.
- if (count == 0) {
+ if (count.isPresent() && count.get() == 0) {
Review Comment:
with multiple participants, use of "check, then set" is error-prone. e.g.
two or more rows could be inserted.
the algo requires there to only ever be *exactly one*. as this is
essential, add a primary key field that should only ever have one value (== 1).
every INSERT should hard-code that PK value. to seamlessly handle both
first-time init, or instead update when the config settings have changed,
utilize `INSERT... ON DUPLICATE KEY UPDATE`. see:
https://stackoverflow.com/a/1361368
*EVERY PARTICIPANT* would then "upsert" when it starts up, where the most
recent value wins, clobbering the former. even so, due to all participants
having uniform config, in general, no actual overwriting happens with most
updates.
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