Mariadb sharding

OK, flights.flight is sharded but basically only has one chunk so far, and hence all current data is on one shard and so all writes can only go to one shard - you will need more before the collection can be balanced across multiple shards. Unless you pre-split (something like this) or use a hashed shard key (which you are not) then the mongos process is what is responsible for automatically splitting the chunks.

It will attempt the first split after it has seen writes of approximately 20% of the max chunk size (default is 64MiB, so 20% is ~13MiB). It looks like this has not yet happened, or has failed for some reason in your case.

It should be noted that although the mongos will track all the writes, it will lose its "history" if restarted. It should also be noted that the config servers must be up and working for any splits to happen. Check the mongos logs for any evidence of split failures or similar.

If you want to kick start things manually, just pick two (or more) reasonable split points and use the splitAt() command to break up your current single chunk. You can then wait for the balancer to move things, or you can move them manually with the moveChunk() command. You can find examples of this in the answer to the question I linked above.

In order for data to be distributed across multiple shards, you need to have multiple chunks for a given sharded collection. A chunk is a contiguous range of shard key values representing approximately 64 megabytes of data by default.

Chunk ranges are normally created automatically based on observation of the shard key values and size of documents being inserted through mongos. When documents are added to a chunk range which is approaching the maximum chunk size, mongos will trigger a chunk split which will try to create smaller logical chunks for balancing.

Currently all data in your sharded testDB.testdata collection is covered by a single chunk on shard0000 (aka your Shard1 server):

    testDB.testData
        shard key: { "name" : 1 }
        chunks:
            shard0000   1
        { "name" : { "$minKey" : 1 } } -->> { "name" : { "$maxKey" : 1 } } on : shard0000 Timestamp(1, 0) 

Using Object.bsonsize() in the mongo shell to determine document size, your sample document in the question is about 43 bytes in BSON. With only 10,000 documents you would not be close to reaching the 64 megabytes of data required to trigger any chunk splits. Something closer to 1.5 million documents of that size would be required.

You will also need to ensure the values for your chosen shard key have reasonable uniqueness. A poor shard key (i.e. with many common values) can lead to indivisible jumbo chunks that cannot be further split.

If you just want to test how sharding works you could:

• insert larger (or more) test documents
• lower the chunk size from the default of 64MB
• pre-split an empty collection before inserting data