#### Project Information
* Repository: https://github.com/holgern/beem
* Project Name: Beem
* Publisher: @holger80

A [GitHub issue](https://github.com/holgern/beem/issues/69) was created and the bug was confirmed and fixed by the PO.

#### Expected behavior
`Blockchain.stream(threading=True)` should use threads to fetch several blocks in parallel. Each block should be fetched once from the RPC node.

#### Actual behavior
`Blockchain.stream(threading=True)` requests blocks twice from the RPC node, if those block don't contain operations or only virtual operations. This limits the benefits from the parallel threads.

#### How to reproduce
```python
from beem.blockchain import Blockchain
b = Blockchain()
for op in b.stream(start=2500000, stop=2500010, threading=True):
    continue
```

Plus printf-debugging:
```patch
index 5cb196c..2e19545 100644
--- a/beemapi/steemnoderpc.py
+++ b/beemapi/steemnoderpc.py
@@ -53,6 +53,7 @@ class SteemNodeRPC(GrapheneRPC):
             :raises ValueError: if the server does not respond in proper JSON format
             :raises RPCError: if the server returns an error
         """
+        print(payload)
         if self.url is None:
             raise except
```

Output:
```
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 1}
{'method': 'call', 'params': ['database_api', 'get_dynamic_global_properties', []], 'jsonrpc': '2.0', 'id': 2}
{'method': 'call', 'params': ['database_api', 'get_feed_history', []], 'jsonrpc': '2.0', 'id': 3}
{'method': 'call', 'params': ['database_api', 'get_feed_history', []], 'jsonrpc': '2.0', 'id': 4}
{'method': 'call', 'params': ['database_api', 'get_next_scheduled_hardfork', []], 'jsonrpc': '2.0', 'id': 5}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 6}
{'method': 'call', 'params': ['database_api', 'get_witness_schedule', []], 'jsonrpc': '2.0', 'id': 7}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 8}
{'method': 'call', 'params': ['database_api', 'get_reward_fund', ['post']], 'jsonrpc': '2.0', 'id': 9}
{'method': 'call', 'params': ['database_api', 'get_dynamic_global_properties', []], 'jsonrpc': '2.0', 'id': 10}
{'method': 'call', 'params': [None, 'get_block', [25031061]], 'jsonrpc': '2.0', 'id': 11}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 1}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 1}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 1}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 1}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 1}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 1}
{'method': 'call', 'params': ['database_api', 'get_config', []], 'jsonrpc': '2.0', 'id': 1}
{'method': 'call', 'params': [None, 'get_block', [2500000]], 'jsonrpc': '2.0', 'id': 12}
{'method': 'call', 'params': [None, 'get_block', [2500001]], 'jsonrpc': '2.0', 'id': 2}
{'method': 'call', 'params': [None, 'get_block', [2500002]], 'jsonrpc': '2.0', 'id': 2}
{'method': 'call', 'params': [None, 'get_block', [2500003]], 'jsonrpc': '2.0', 'id': 2}
{'method': 'call', 'params': [None, 'get_block', [2500004]], 'jsonrpc': '2.0', 'id': 2}
{'method': 'call', 'params': [None, 'get_block', [2500005]], 'jsonrpc': '2.0', 'id': 2}
{'method': 'call', 'params': [None, 'get_block', [2500006]], 'jsonrpc': '2.0', 'id': 2}
{'method': 'call', 'params': [None, 'get_block', [2500007]], 'jsonrpc': '2.0', 'id': 2}
{'method': 'call', 'params': [None, 'get_block', [2500000]], 'jsonrpc': '2.0', 'id': 13}
{'method': 'call', 'params': [None, 'get_block', [2500003]], 'jsonrpc': '2.0', 'id': 14}
{'method': 'call', 'params': [None, 'get_block', [2500004]], 'jsonrpc': '2.0', 'id': 15}
{'method': 'call', 'params': [None, 'get_block', [2500005]], 'jsonrpc': '2.0', 'id': 16}
{'method': 'call', 'params': [None, 'get_block', [2500007]], 'jsonrpc': '2.0', 'id': 17}
{'method': 'call', 'params': [None, 'get_block', [2500008]], 'jsonrpc': '2.0', 'id': 18}
{'method': 'call', 'params': [None, 'get_block', [2500009]], 'jsonrpc': '2.0', 'id': 3}
{'method': 'call', 'params': [None, 'get_block', [2500010]], 'jsonrpc': '2.0', 'id': 3}
{'method': 'call', 'params': [None, 'get_block', [2500008]], 'jsonrpc': '2.0', 'id': 19}
{'method': 'call', 'params': [None, 'get_block', [2500009]], 'jsonrpc': '2.0', 'id': 20}
{'method': 'call', 'params': [None, 'get_block', [2500010]], 'jsonrpc': '2.0', 'id': 21}
```

8 of the 11 blocks are fetched twice: 2500000, 2500003, 2500004, 2500005, 2500007, 2500008, 2500009, 2500010. Those blocks contain no operations.

---

The reason was confirmed to be here:
https://github.com/holgern/beem/blob/78281e724248b44724f985f8b57f936558d0d769/beem/blockchain.py#L463
with `len(b.operations) == 0`, the block is treated as if it was never fetched from the chain.

The check for `len(b.operations) == 0` was removed by the PO.

#### Environment
```
# beempy --version
beempy, version 0.19.53
# python --version
Python 3.6.6
```

#### GitHub Account
https://github.com/crokkon