damccorm commented on code in PR #41069:
URL: https://github.com/apache/beam/pull/41069#discussion_r4512695854
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sdks/java/io/iceberg/src/main/java/org/apache/beam/sdk/io/iceberg/RecordWriterManager.java:
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@@ -345,12 +346,14 @@ private Table loadOrCreateTable(IcebergDestination
destination, Schema dataSchem
// Create namespace if it does not exist yet
if (!namespace.isEmpty() && catalog instanceof SupportsNamespaces) {
SupportsNamespaces supportsNamespaces = (SupportsNamespaces) catalog;
- if (!supportsNamespaces.namespaceExists(namespace)) {
- try {
- supportsNamespaces.createNamespace(namespace);
- LOG.info("Created new namespace '{}'.", namespace);
- } catch (AlreadyExistsException ignored) {
- // race condition: another worker already created this namespace
+ synchronized (NAMESPACE_LOCK) {
Review Comment:
It should not have a meaningful runtime impact because `loadOrCreateTable`
is only invoked as the cache-miss loader inside
`TableCache.getAndRefreshIfStale(catalogConfig, identifier, () ->
loadOrCreateTable(...))` (`RecordWriterManager.java:323`).
`TableCache.TABLES` is a process-wide Guava cache (`expireAfterAccess(1,
TimeUnit.HOURS)`) that already synchronizes per `(catalogConfig,
tableIdentifier)` on initial table load, and subsequent periodic refreshes
(`DEFAULT_REFRESH_INTERVAL = 2m`) call `table.refresh()` directly without
calling `loadOrCreateTable`. Thus `NAMESPACE_LOCK` is only entered once per
cold table-cache miss per unique table identifier on a worker (when multiple
threads simultaneously cold-load *different* tables in the same new namespace).
That said, we can make this even lighter-weight by using double-checked
locking (`if (!supportsNamespaces.namespaceExists(namespace)) { synchronized
(NAMESPACE_LOCK) { if (!supportsNamespaces.namespaceExists(namespace)) { ... }
} }`) so existing namespaces don't acquire the lock at all, or by also catching
`RuntimeException` with `Duplicate`/`AlreadyExists` from
`BigQueryMetastoreCatalog`. Happy to update to double-checked locking if that
sounds good!
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