THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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Status
Current state: "Under Discussion"
...
Motivation
This is for adding mocks for state stores mock testing support for StateStore, StoreBuilder, StoreSupplier and other store related components which are used in Streams unit testing.
We'd like to use mocks for different types of state stores: KV, window, session - that can be used to record the number of expected put / get calls used in the DSL operator unit testing. These will provide conveniency provide convenience for developers when they are writing unit test for kafka Kafka stream and other related modules.
Public Interfaces
These will be internal classes, so no public API/interface.
Proposed Changes
Describe the new thing you want to do in appropriate detail. This may be fairly extensive and have large subsections of its own. Or it may be a few sentences. Use judgement based on the scope of the change.
For example, in the current streams/TopologyTest.java:
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public class TopologyTest {
private final StoreBuilder storeBuilder = EasyMock.createNiceMock(StoreBuilder.class);
private final KeyValueStoreBuilder globalStoreBuilder = EasyMock.createNiceMock(KeyValueStoreBuilder.class);
private final Topology topology = new Topology();
...
@Test
public void shouldFailIfSinkIsParent() {
topology.addSource("source", "topic-1");
topology.addSink("sink-1", "topic-2", "source");
try {
topology.addSink("sink-2", "topic-3", "sink-1");
fail("Should throw TopologyException for using sink as parent");
} catch (final TopologyException expected) { }
}
@Test(expected = TopologyException.class)
public void shouldNotAllowToAddStateStoreToNonExistingProcessor() {
mockStoreBuilder();
EasyMock.replay(storeBuilder);
topology.addStateStore(storeBuilder, "no-such-processor");
}
@Test
public void shouldNotAllowToAddStateStoreToSource() {
mockStoreBuilder();
EasyMock.replay(storeBuilder);
topology.addSource("source-1", "topic-1");
try {
topology.addStateStore(storeBuilder, "source-1");
fail("Should have thrown TopologyException for adding store to source node");
} catch (final TopologyException expected) { }
}
private void mockStoreBuilder() {
EasyMock.expect(storeBuilder.name()).andReturn("store").anyTimes();
EasyMock.expect(storeBuilder.logConfig()).andReturn(Collections.emptyMap());
EasyMock.expect(storeBuilder.loggingEnabled()).andReturn(false);
}
} |
One of the goal is to replace the in-test vanilla mockStoreBuilder with a more general purpose mockStoreBuilder class, which simplify writing unit test and can be reuse later.
After the improvements, we will replace the easyMock StoreBuilder with our mockStoreBuilder.
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public class TopologyTest {
private final StoreBuilder storeBuilder = EasyMock.createNiceMock(StoreBuilder.class);
private final Topology topology = new Topology();
private final MockStoreFactory mockStoreFactory = new MockStoreFactory<>();
private final KeyValueStoreBuilder keyValueStoreBuilder = mockStoreFactory.createKeyValueStoreBuilder(
Stores.inMemoryKeyValueStore("store"),
Serdes.Bytes(),
Serdes.Bytes(),
false,
Time.System);
...
@Test(expected = TopologyException.class)
public void shouldNotAllowToAddStateStoreToNonExistingProcessor() {
topology.addStateStore(keyValueStoreBuilder, "no-such-processor");
}
} |
Public Interfaces
We add some new classes to a state package (org.apache.kafka.streams.state) under streams/test-utils.
We will provide a MockStoreFactory to generate mock store builders, I will use the KeyValueStoreBuilder I will use the KeyValueStore as an example. Window and Session will have a similar structure.We will provide a MockStoreFactory to generate Mock store builders:
The developers/users can provide their own store as the backend storage, and their own Serde of choice. For example, for simple testing, they can just use an InMemoryKeyValueStore.
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package org.apache.kafka.streams.internals;
public class MockStoreFactory<K, V> {
public final Map<String, StoreBuilder> stateStores = new LinkedHashMap<>();
public MockStoreFactory () {
}
public KeyValueStoreBuilder createKeyValueStoreBuilder(KeyValueBytesStoreSupplier keyValueBytesStoreSupplier,
final Serde<K> keySerde,
final Serde<V> valueSerde,
boolean persistent){
String storeName = keyValueBytesStoreSupplier.name();
stateStores.put(storeName, new MockKeyValueStoreBuilder<>(keyValueBytesStoreSupplier, keySerde, valueSerde, persistent));
return (KeyValueStoreBuilder)stateStores.get(storeName);
}
public WindowStoreBuilder createWindowStoreBuilder(KeyValueBytesStoreSupplier keyValueBytesStoreSupplier,
final Serde<K> keySerde,
final Serde<V> valueSerde,
final Time time){
...
}
public SessionStoreBuilder createSessionStoreBuilder(KeyValueBytesStoreSupplier keyValueBytesStoreSupplier,
final Serde<K> keySerde,
final Serde<V> valueSerde,
final Time time){
...
}
public StoreBuilder getStore(String storeName) {
return stateStores.get(storeName);
}
} |
Each Store builder will have a build method:
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package org.apache.kafka.streams.state; import org.apache.kafka.common.serialization.Serde; import org.apache.kafka.common.utils.Time; import org.apache.kafka.streams.state.internals.KeyValueStoreBuilder; public class MockKeyValueStoreBuilder<K, V> extends KeyValueStoreBuilder<K, V> { private final boolean persistent; private final KeyValueBytesStoreSupplier storeSupplier; final V extends StoreBuilder> { final String storeName; final Serde<K> keySerde; final Serde<V> valueSerde; final Time time; public MockStoreFactory MockKeyValueStoreBuilder(final StringKeyValueBytesStoreSupplier storeNamestoreSupplier, final Serde<K> keySerde, final Serde<V> valueSerde, final boolean persistent, final Time time) { super(storeSupplier, keySerde, valueSerde, time); this.persistent = persistent; this.storeNamestoreSupplier = storeNamestoreSupplier; this.keySerde = keySerde; this.valueSerde = valueSerde; this.time = time; } @Override public MockKeyValueStoreBuilder createKeyValueStoreBuilderKeyValueStore<K, V> build() { return new MockKeyValueStoreBuilder<>MockKeyValueStore<>(storeNamestoreSupplier, keySerde, valueSerde, persistent, time); } } |
Then in the store, we will build a wrapper around the provided backend store. We will capture each get/put/delete call, the user can write tests accordingly. We will also track if the store has been flushed or closed.
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package org.apache.kafka.streams.state; public MockWindowStoreBuilder createWindowStoreBuilder(){ return new MockWindowStoreBuilder<>(storeName, keySerde, valueSerde, time); } public MockSessionStoreBuilder createSessionStoreBuilder() public class MockKeyValueStore<K, V> extends WrappedStateStore<KeyValueStore<Bytes, byte[]>, K, V> implements KeyValueStore<K, V> { // keep a global counter of flushes and a local reference to which store had which // flush, so we can reason about the order in which stores get flushed. private static final AtomicInteger GLOBAL_FLUSH_COUNTER = new AtomicInteger(0); private final AtomicInteger instanceLastFlushCount = new AtomicInteger(-1); public boolean initialized = false; public boolean flushed = false; public boolean closed = true; public String name; public boolean persistent; protected final Time time; final Serde<K> keySerde; final Serde<V> valueSerde; StateSerdes<K, V> serdes; public final List<KeyValue<K, V>> capturedPutCalls = new LinkedList<>(); public final List<KeyValue<K, V>> capturedGetCalls = new LinkedList<>(); public final List<KeyValue<K, V>> capturedDeleteCalls = new LinkedList<>(); public MockKeyValueStore(final KeyValueBytesStoreSupplier keyValueBytesStoreSupplier, final Serde<K> keySerde, final Serde<V> valueSerde, final boolean persistent, final Time time) { super(keyValueBytesStoreSupplier.get()); this.name = keyValueBytesStoreSupplier.name(); this.time = time != null ? time : Time.SYSTEM; this.persistent = persistent; this.keySerde = keySerde; this.valueSerde = valueSerde; } @SuppressWarnings("unchecked") void initStoreSerde(final ProcessorContext context) { return new MockSessionStoreBuilder<>(storeName, keySerde, valueSerde, timeserdes = new StateSerdes<>( ProcessorStateManager.storeChangelogTopic(context.applicationId(), name()), keySerde == null ? (Serde<K>) context.keySerde() : keySerde, valueSerde == null ? (Serde<V>) context.valueSerde() : valueSerde); } @Override public String name() { return name; } @Override public void init(final ProcessorContext context, final StateStore root) { context.register(root, stateRestoreCallback); initialized = true; closed = false; } } |
Each Store builder will have a build method:
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package org.apache.kafka.streams.internals; public class MockKeyValueStoreBuilder<K, V> extends AbstractStoreBuilder<K, V, StateStore> { public MockKeyValueStoreBuilder(final String storeName, @Override public void flush() { instanceLastFlushCount.set(GLOBAL_FLUSH_COUNTER.getAndIncrement()); wrapped().flush(); flushed = true; } public int getLastFlushCount() { return instanceLastFlushCount.get(); } @Override public void close() { wrapped().close(); closed = true; } @Override public boolean persistent() { return persistent; } @Override public boolean isOpen() { return !closed; } public final StateRestoreCallback stateRestoreCallback = new StateRestoreCallback() { @Override public void restore(final byte[] key, final byte[] value) { } }; @Override public void put(final K key, final V value) { capturedPutCalls.add(new KeyValue<>(key, value)); wrapped().put(keyBytes(key), serdes.rawValue(value)); } @Override public V putIfAbsent(final K key, final V value) { final V originalValue = get(key); if (originalValue == null) { put(key, value); capturedPutCalls.add(new KeyValue<>(key, value)); } return originalValue; } @Override public V delete(final Serde<K> keySerde, K key) { V value = outerValue(wrapped().delete(keyBytes(key))); capturedDeleteCalls.add(new KeyValue<>(key, value)); return value; } @Override public void putAll(final List<KeyValue<K, V>> entries) { for (final Serde<V> valueSerde,KeyValue<K, V> entry : entries) { put(entry.key, entry.value); capturedPutCalls.add(entry); } } @Override public V get(final TimeK timekey) { V value = outerValue(wrapped().get(keyBytes(key))); capturedGetCalls.add(new super(storeName, keySerde, valueSerde, timeKeyValue<>(key, value)); return value; } @SuppressWarnings("unchecked") @Override public KeyValueIterator<K,V> range(final K from, final K to) { return new MockKeyValueStore.MockKeyValueIterator( wrapped().range(Bytes.wrap(serdes.rawKey(from)), Bytes.wrap(serdes.rawKey(to)))); } @SuppressWarnings("unchecked") @Override public KeyValueIterator<K,V> KeyValueStore buildall() { return new MockKeyValueStore(name); .MockKeyValueIterator(wrapped().all()); } @Override public long approximateNumEntries() { return wrapped().approximateNumEntries(); } private V outerValue(final byte[] value) { return value != null ? serdes.valueFrom(value) : null; } private Bytes keyBytes(final K key) { return Bytes.wrap(serdes.rawKey(key)); } private class MockKeyValueIterator implements KeyValueIterator<K, V> { private final KeyValueIterator<Bytes, byte[]> iter; .... } } |
Proposed Changes
I proposed to add:
- A MockStoreFactory class to produce mock state store builders.
- A mock StateStoreBuilder class for KV, Session and Window.
- A mock StateStore class for KV, Session and Window with tracking.
Compatibility, Deprecation, and Migration Plan
- What impact (if any) will there be on existing users?
- If we are changing behavior how will we phase out the older behavior?
- If we need special migration tools, describe them here.
- When will we remove the existing behavior?
Rejected Alternatives
...
Until we are refactoring with these new MockStateStores, there shouldn't be any compatibility issues. But the next phase should be refactoring, including:
1) Remove and refactor redundant MockStores (i.e. org.apache.kafka.test.MockKeyValueStore)
2) Examine the current tests (i.e. org.apache.kafka.streams.TopologyTest and refactor the testing code logics with the new MockStateStores.
A discussion that has been brought up is
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Rejected Alternatives
- Using the current EasyMock implementation. There is no strong argument against the current EasyMock implementation, it is easy to use and lightweight. The main argument for this KIP is to write better tests with an in-house mock state store support.