Github user amansinha100 commented on a diff in the pull request:
https://github.com/apache/drill/pull/653#discussion_r88404356
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/Metadata.java
---
@@ -495,31 +499,75 @@ private ParquetFileMetadata_v3
getParquetFileMetadata_v3(ParquetTableMetadata_v3
* @param p
* @throws IOException
*/
- private void writeFile(ParquetTableMetadata_v3 parquetTableMetadata,
Path p) throws IOException {
+ private void writeFile(ParquetTableMetadata_v3 parquetTableMetadata,
String path) throws IOException {
JsonFactory jsonFactory = new JsonFactory();
jsonFactory.configure(Feature.AUTO_CLOSE_TARGET, false);
jsonFactory.configure(JsonParser.Feature.AUTO_CLOSE_SOURCE, false);
ObjectMapper mapper = new ObjectMapper(jsonFactory);
SimpleModule module = new SimpleModule();
module.addSerializer(ColumnMetadata_v3.class, new
ColumnMetadata_v3.Serializer());
mapper.registerModule(module);
- FSDataOutputStream os = fs.create(p);
+
+ // If multiple clients are updating metadata cache file concurrently,
the cache file
+ // can get corrupted. To prevent this, write to a unique temporary
file and then do
+ // atomic rename.
+ UUID randomUUID = UUID.randomUUID();
--- End diff --
Is there a way to get the global queryId created by the Foreman ? The name
of the temp file would best be associated with the queryId. If that is not
possible (I am not sure if the query context is accessible easily from here),
at the very least we should re-use the UUID for both the METADATA_FILENAME and
METADATA_DIRECTORIES_FILENAME . It is not a correctness issue but will avoid
confusion.
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