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13782b8ba8 docs: add perf section to developer docs (James O'Beirne) 58180b5fd4 tests: add utility to easily profile node performance with perf (James O'Beirne) Pull request description: Adds a context manager to easily (and selectively) profile node performance during functional test execution using `perf`. While writing some tests, I encountered some odd bitcoind slowness. I wrote up a utility (`TestNode.profile_with_perf`) that generates performance diagnostics for a node by running `perf` during the execution of a particular region of test code. `perf` usage is detailed in the excellent (and sadly unmerged) https://github.com/bitcoin/bitcoin/pull/12649; all due props to @eklitzke. ### Example ```python with node.profile_with_perf("large-msgs"): for i in range(200): node.p2p.send_message(some_large_msg) node.p2p.sync_with_ping() ``` This generates a perf data file in the test node's datadir (`/tmp/testtxmpod0y/node0/node-0-TestName-large-msgs.perf.data`). Running `perf report` generates nice output about where the node spent most of its time while running that part of the test: ```bash $ perf report -i /tmp/testtxmpod0y/node0/node-0-TestName-large-msgs.perf.data --stdio \ | c++filt \ | less # To display the perf.data header info, please use --header/--header-only options. # # # Total Lost Samples: 0 # # Samples: 135 of event 'cycles:pp' # Event count (approx.): 1458205679493582 # # Children Self Command Shared Object Symbol # ........ ........ ............... ................... ........................................................................................................................................................................................................................................................................ # 70.14% 0.00% bitcoin-net bitcoind [.] CNode::ReceiveMsgBytes(char const*, unsigned int, bool&) | ---CNode::ReceiveMsgBytes(char const*, unsigned int, bool&) 70.14% 0.00% bitcoin-net bitcoind [.] CNetMessage::readData(char const*, unsigned int) | ---CNetMessage::readData(char const*, unsigned int) CNode::ReceiveMsgBytes(char const*, unsigned int, bool&) 35.52% 0.00% bitcoin-net bitcoind [.] std::vector<char, zero_after_free_allocator<char> >::_M_fill_insert(__gnu_cxx::__normal_iterator<char*, std::vector<char, zero_after_free_allocator<char> > >, unsigned long, char const&) | ---std::vector<char, zero_after_free_allocator<char> >::_M_fill_insert(__gnu_cxx::__normal_iterator<char*, std::vector<char, zero_after_free_allocator<char> > >, unsigned long, char const&) CNetMessage::readData(char const*, unsigned int) CNode::ReceiveMsgBytes(char const*, unsigned int, bool&) ... ``` Tree-SHA512: 9ac4ceaa88818d5eca00994e8e3c8ad42ae019550d6583972a0a4f7b0c4f61032e3d0c476b4ae58756bc5eb8f8015a19a7fc26c095bd588f31d49a37ed0c6b3e
158 lines
7.2 KiB
Markdown
158 lines
7.2 KiB
Markdown
# Functional tests
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### Writing Functional Tests
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#### Example test
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The [example_test.py](example_test.py) is a heavily commented example of a test case that uses both
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the RPC and P2P interfaces. If you are writing your first test, copy that file
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and modify to fit your needs.
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#### Coverage
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Running `test_runner.py` with the `--coverage` argument tracks which RPCs are
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called by the tests and prints a report of uncovered RPCs in the summary. This
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can be used (along with the `--extended` argument) to find out which RPCs we
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don't have test cases for.
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#### Style guidelines
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- Where possible, try to adhere to [PEP-8 guidelines](https://www.python.org/dev/peps/pep-0008/)
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- Use a python linter like flake8 before submitting PRs to catch common style
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nits (eg trailing whitespace, unused imports, etc)
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- The oldest supported Python version is specified in [doc/dependencies.md](/doc/dependencies.md).
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Consider using [pyenv](https://github.com/pyenv/pyenv), which checks [.python-version](/.python-version),
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to prevent accidentally introducing modern syntax from an unsupported Python version.
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The Travis linter also checks this, but [possibly not in all cases](https://github.com/bitcoin/bitcoin/pull/14884#discussion_r239585126).
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- See [the python lint script](/test/lint/lint-python.sh) that checks for violations that
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could lead to bugs and issues in the test code.
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- Avoid wildcard imports
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- Use a module-level docstring to describe what the test is testing, and how it
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is testing it.
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- When subclassing the BitcoinTestFramwork, place overrides for the
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`set_test_params()`, `add_options()` and `setup_xxxx()` methods at the top of
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the subclass, then locally-defined helper methods, then the `run_test()` method.
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- Use `'{}'.format(x)` for string formatting, not `'%s' % x`.
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#### Naming guidelines
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- Name the test `<area>_test.py`, where area can be one of the following:
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- `feature` for tests for full features that aren't wallet/mining/mempool, eg `feature_rbf.py`
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- `interface` for tests for other interfaces (REST, ZMQ, etc), eg `interface_rest.py`
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- `mempool` for tests for mempool behaviour, eg `mempool_reorg.py`
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- `mining` for tests for mining features, eg `mining_prioritisetransaction.py`
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- `p2p` for tests that explicitly test the p2p interface, eg `p2p_disconnect_ban.py`
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- `rpc` for tests for individual RPC methods or features, eg `rpc_listtransactions.py`
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- `wallet` for tests for wallet features, eg `wallet_keypool.py`
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- use an underscore to separate words
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- exception: for tests for specific RPCs or command line options which don't include underscores, name the test after the exact RPC or argument name, eg `rpc_decodescript.py`, not `rpc_decode_script.py`
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- Don't use the redundant word `test` in the name, eg `interface_zmq.py`, not `interface_zmq_test.py`
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#### General test-writing advice
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- Set `self.num_nodes` to the minimum number of nodes necessary for the test.
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Having additional unrequired nodes adds to the execution time of the test as
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well as memory/CPU/disk requirements (which is important when running tests in
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parallel or on Travis).
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- Avoid stop-starting the nodes multiple times during the test if possible. A
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stop-start takes several seconds, so doing it several times blows up the
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runtime of the test.
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- Set the `self.setup_clean_chain` variable in `set_test_params()` to control whether
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or not to use the cached data directories. The cached data directories
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contain a 200-block pre-mined blockchain and wallets for four nodes. Each node
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has 25 mature blocks (25x500=12500 DASH) in its wallet.
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- When calling RPCs with lots of arguments, consider using named keyword
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arguments instead of positional arguments to make the intent of the call
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clear to readers.
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- Many of the core test framework classes such as `CBlock` and `CTransaction`
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don't allow new attributes to be added to their objects at runtime like
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typical Python objects allow. This helps prevent unpredictable side effects
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from typographical errors or usage of the objects outside of their intended
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purpose.
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#### RPC and P2P definitions
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Test writers may find it helpful to refer to the definitions for the RPC and
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P2P messages. These can be found in the following source files:
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- `/src/rpc/*` for RPCs
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- `/src/wallet/rpc*` for wallet RPCs
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- `ProcessMessage()` in `/src/net_processing.cpp` for parsing P2P messages
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#### Using the P2P interface
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- `messages.py` contains all the definitions for objects that pass
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over the network (`CBlock`, `CTransaction`, etc, along with the network-level
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wrappers for them, `msg_block`, `msg_tx`, etc).
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- P2P tests have two threads. One thread handles all network communication
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with the dashd(s) being tested in a callback-based event loop; the other
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implements the test logic.
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- `P2PConnection` is the class used to connect to a dashd. `P2PInterface`
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contains the higher level logic for processing P2P payloads and connecting to
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the Bitcoin Core node application logic. For custom behaviour, subclass the
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P2PInterface object and override the callback methods.
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- Can be used to write tests where specific P2P protocol behavior is tested.
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Examples tests are `p2p_unrequested_blocks.py`, `p2p_compactblocks.py`.
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### test-framework modules
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#### [test_framework/authproxy.py](test_framework/authproxy.py)
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Taken from the [python-bitcoinrpc repository](https://github.com/jgarzik/python-bitcoinrpc).
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#### [test_framework/test_framework.py](test_framework/test_framework.py)
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Base class for functional tests.
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#### [test_framework/util.py](test_framework/util.py)
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Generally useful functions.
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#### [test_framework/mininode.py](test_framework/mininode.py)
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Basic code to support P2P connectivity to a dashd.
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#### [test_framework/script.py](test_framework/script.py)
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Utilities for manipulating transaction scripts (originally from python-bitcoinlib)
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#### [test_framework/key.py](test_framework/key.py)
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Wrapper around OpenSSL EC_Key (originally from python-bitcoinlib)
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#### [test_framework/bignum.py](test_framework/bignum.py)
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Helpers for script.py
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#### [test_framework/blocktools.py](test_framework/blocktools.py)
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Helper functions for creating blocks and transactions.
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### Benchmarking with perf
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An easy way to profile node performance during functional tests is provided
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for Linux platforms using `perf`.
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Perf will sample the running node and will generate profile data in the node's
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datadir. The profile data can then be presented using `perf report` or a graphical
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tool like [hotspot](https://github.com/KDAB/hotspot).
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There are two ways of invoking perf: one is to use the `--perf` flag when
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running tests, which will profile each node during the entire test run: perf
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begins to profile when the node starts and ends when it shuts down. The other
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way is the use the `profile_with_perf` context manager, e.g.
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```python
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with node.profile_with_perf("send-big-msgs"):
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# Perform activity on the node you're interested in profiling, e.g.:
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for _ in range(10000):
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node.p2p.send_message(some_large_message)
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```
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To see useful textual output, run
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```sh
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perf report -i /path/to/datadir/send-big-msgs.perf.data.xxxx --stdio | c++filt | less
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```
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#### See also:
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- [Installing perf](https://askubuntu.com/q/50145)
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- [Perf examples](http://www.brendangregg.com/perf.html)
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- [Hotspot](https://github.com/KDAB/hotspot): a GUI for perf output analysis
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