JSON to SSTable tool out-of-memory failure

Question

json2sstable tool supplied with Cassandra 1.2.15 fails with out-of-memory error. Back in 2011 a similar issue was reported as bug and fixed: https://issues.apache.org/jira/browse/CASSANDRA-2189

Either I am missing some steps in the tool configuration/usage or the bug has re-emerged. Please point out what I am missing.

Repro steps:

1) Cassandra 1.2.15, one table with varchar key and one varchar column filled with random uuids, 6x10^6 records.

2) JSON file generated with sstable2json tool (~1G).

3) Cassandra restarted with new configuration (new data/cache/commit dirs, new partitioner)

4) Keyspace re-created

5) json2sstable fails after several minutes of processing:

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
    at java.util.Arrays.copyOfRange(Arrays.java:2694)
    at java.lang.String.<init>(String.java:203)
    at org.codehaus.jackson.util.TextBuffer.contentsAsString(TextBuffer.java:350)
    at org.codehaus.jackson.impl.Utf8StreamParser.getText(Utf8StreamParser.java:278)
    at org.codehaus.jackson.map.deser.std.UntypedObjectDeserializer.deserialize(UntypedObjectDeserializer.java:59)
    at org.codehaus.jackson.map.deser.std.UntypedObjectDeserializer.mapArray(UntypedObjectDeserializer.java:165)
    at org.codehaus.jackson.map.deser.std.UntypedObjectDeserializer.deserialize(UntypedObjectDeserializer.java:51)
    at org.codehaus.jackson.map.deser.std.UntypedObjectDeserializer.mapArray(UntypedObjectDeserializer.java:165)
    at org.codehaus.jackson.map.deser.std.UntypedObjectDeserializer.deserialize(UntypedObjectDeserializer.java:51)
    at org.codehaus.jackson.map.deser.std.UntypedObjectDeserializer.mapObject(UntypedObjectDeserializer.java:204)
    at org.codehaus.jackson.map.deser.std.UntypedObjectDeserializer.deserialize(UntypedObjectDeserializer.java:47)
    at org.codehaus.jackson.map.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:104)
    at org.codehaus.jackson.map.deser.std.ObjectArrayDeserializer.deserialize(ObjectArrayDeserializer.java:18)
    at org.codehaus.jackson.map.ObjectMapper._readValue(ObjectMapper.java:2695)
    at org.codehaus.jackson.map.ObjectMapper.readValue(ObjectMapper.java:1294)
    at org.codehaus.jackson.JsonParser.readValueAs(JsonParser.java:1368)
    at org.apache.cassandra.tools.SSTableImport.importUnsorted(SSTableImport.java:344)
    at org.apache.cassandra.tools.SSTableImport.importJson(SSTableImport.java:328)
    at org.apache.cassandra.tools.SSTableImport.main(SSTableImport.java:547)

Answer 1

From json2sstable source code, the tool loads all the records from json file into memory and sorts records by keys:

        private int importUnsorted(String jsonFile, ColumnFamily columnFamily, String ssTablePath, IPartitioner<?> partitioner) throws IOException
        {
            int importedKeys = 0;
            long start = System.currentTimeMillis();

            JsonParser parser = getParser(jsonFile);

            Object[] data = parser.readValueAs(new TypeReference<Object[]>(){});

            keyCountToImport = (keyCountToImport == null) ? data.length : keyCountToImport;
            SSTableWriter writer = new SSTableWriter(ssTablePath, keyCountToImport);

            System.out.printf("Importing %s keys...%n", keyCountToImport);

            // sort by dk representation, but hold onto the hex version
            SortedMap<DecoratedKey,Map<?, ?>> decoratedKeys = new TreeMap<DecoratedKey,Map<?, ?>>();

            for (Object row : data)
            {
                Map<?,?> rowAsMap = (Map<?, ?>)row;
                decoratedKeys.put(partitioner.decorateKey( hexToBytes((String)rowAsMap.get("key"))), rowAsMap);
....

According to Jonathan Elis' comment in CASSANDRA-2322 issue the behavior is by design.

Thus json2sstable is not very well suited for importing production size data to Cassandra. The tool is likely to crash on large datasets.