public async Task TestDelayStoreWithExponentialBackoffRetry()
{
// Simulates the DB on the server:
var innerStore = new InMemoryKeyValueStore();
// Simulates the connection to the server:
var simulatedRemoteConnection = new MockDekayKeyValueStore().WithFallbackStore(innerStore);
var requestRetry = new RetryKeyValueStore(simulatedRemoteConnection, maxNrOfRetries: 5);
var outerStore = new InMemoryKeyValueStore().WithFallbackStore(requestRetry);
var key1 = "key1";
var value1 = "value1";
var key2 = "key2";
var value2 = "value2";
var fallback2 = "fallback2";
{
var delayedSetTask = outerStore.Set(key1, value1);
Assert.Equal(value1, await outerStore.Get(key1, "")); // The outer store already has the update
Assert.NotEqual(value1, await innerStore.Get(key1, "")); // The inner store did not get the update yet
// After waiting for set to fully finish the inner store has the update too:
await delayedSetTask;
Assert.Equal(value1, await innerStore.Get(key1, ""));
}
// Now simulate that the remote DB/server never can be reached:
simulatedRemoteConnection.throwTimeoutError = true;
{
var timeoutErrorCounter = 0;
// In the retry listen to any error if the wrapped store:
requestRetry.onError = (e) => {
Assert.IsType <TimeoutException>(e); // thrown by the simulatedRemoteConnection
timeoutErrorCounter++;
};
var delayedSetTask = outerStore.Set(key2, value2);
Assert.Equal(value2, await outerStore.Get(key2, fallback2)); // In the outer store the value was set
Assert.False(await innerStore.ContainsKey(key2)); // The inner store never got the update
// The delayedSetTask was canceled after 5 retries:
await Assert.ThrowsAsync <OperationCanceledException>(async() => await delayedSetTask);
// There will be 5 TimeoutException in the simulatedRemoteConnection:
Assert.Equal(requestRetry.maxNrOfRetries, timeoutErrorCounter);
}
}
public async Task ExampleUsage3()
{
// Simulate the DB on the server
var simulatedDb = new InMemoryKeyValueStore();
// Simulate the connection (with a delay) to the server:
var simulatedRemoteConnection = new MockDelayKeyValueStore(simulatedDb);
// The connection to the server is wrapped by a automatic retry for failing requests:
var requestRetry = new RetryKeyValueStore(simulatedRemoteConnection, maxNrOfRetries: 5);
// Any errors in the inner layers like connection errors, DB errors are catched by default:
var errorHandler = new ExceptionWrapperKeyValueStore(requestRetry);
// The outer store is a local in memory cache and the main point of contact:
var outerStore = new InMemoryKeyValueStore().WithFallbackStore(errorHandler);
var key1 = "key1";
var value1 = "value1";
var fallback1 = "fallback1";
await outerStore.Set(key1, value1);
Assert.Equal(value1, await outerStore.Get(key1, fallback1));
Assert.Equal(value1, await simulatedDb.Get(key1, fallback1));
// Simmulate connection problems to the remote DB:
simulatedRemoteConnection.throwTimeoutError = true;
var key2 = "key2";
var value2 = "value2";
var fallback2 = "fallback2";
// Awaiting a set will take some time since there will be 5 retries:
await outerStore.Set(key2, value2);
// The outer store has the set value cached:
Assert.Equal(value2, await outerStore.Get(key2, fallback2));
// But the request never reached the simulated DB:
Assert.False(await simulatedDb.ContainsKey(key2));
}
