public async Task WriteTransferEventsForMakerDAOToAzureStorage()
{
// Load config
// - this will contain the secrets and connection strings we don't want to hard code
var config = TestConfiguration.LoadConfig();
string azureStorageConnectionString = config["AzureStorageConnectionString"];
// Create a proxy for the blockchain
var web3 = new Web3.Web3(TestConfiguration.BlockchainUrls.Infura.Mainnet);
// Create an Azure Table Storage Factory
// - The factory communicates with Azure to create and get different tables
var tableStorageFactory = new AzureTablesSubscriberRepositoryFactory(azureStorageConnectionString);
// Create a Handler for a Table
// - It wraps a table repository
// - This is where we're going to put the matching event logs
// - we're supplying a table prefix
// - the actual table name would be "<prefix>TransactionLogs")
// - this allows us to have different tables for different types of event logs
// - the handler implements ILogHandler
// - ILogHandler is a really simple interface to implement if you wish to customise the storage
var storageHandlerForLogs = await tableStorageFactory.GetLogRepositoryHandlerAsync(tablePrefix : "makerdaotransfersstorage");
// Create an event subscription specifically for ERC20 Transfers
// - Passing in the maker dao address to ensure only logs with a matching address are processed
// - There is an option to pass an implementation of IEventHandlerHistoryRepository in to the constructor
// - This would record history for each event handler and is used to prevent duplication
var eventSubscription = new EventSubscription <TransferEventDto>(
contractAddressesToMatch: new[] { MAKER_CONTRACT_ADDRESS });
// Assign the storage handler to the event subscription
// - Matching events will be passed to the handler
// - internally the handler passes the events to the repository layer which writes them to Azure
eventSubscription.AddStorageHandler(storageHandlerForLogs);
// Azure storage setup
// - this example reads and writes block progress to an Azure storage table
// - to avoid collision with other samples we provide a prefix
var storageCloudSetup = new CloudTableSetup(azureStorageConnectionString, prefix: $"makerdaotransfersstorage");
// Create a progress repository
// - It stores and retrieves the most recent block processed
var blockProgressRepo = storageCloudSetup.CreateBlockProgressRepository();
// Create a progress service
// - This uses the progress repo to dictate what blocks to process next
// - The MIN_BLOCK_NUMBER dictates the starting point if the progress repo is empty or has fallen too far behind
var progressService = new BlockProgressService(web3, MIN_BLOCK_NUMBER, blockProgressRepo);
// Create a filter
// - This is essentially the query that is sent to the chain when retrieving logs
// - It is OPTIONAL - without it, all logs in the block range are requested
// - The filter is invoked before any event subscriptions evaluate the logs
// - The subscriptions are free to implement their own matching logic
// - In this sample we're only interested in MakerDAO logs
// - Therefore it makes sense to restrict the number of logs to retrieve from the chain
var makerAddressFilter = new NewFilterInput()
{
Address = new[] { MAKER_CONTRACT_ADDRESS }
};
// Create a log processor
// - This uses the blockchainProxy to get the logs
// - It sends each log to the event subscriptions to indicate if the logs matches the subscription criteria
// - It then allocates matching logs to separate batches per event subscription
var logProcessor = new BlockRangeLogsProcessor(web3, new[] { eventSubscription }, makerAddressFilter);
// Create a batch log processor service
// - It uses the progress service to calculates the block range to progress
// - It then invokes the log processor - passing in the range to process
// - It updates progress via the progress service
var batchProcessorService = new LogsProcessor(logProcessor, progressService, MAX_BLOCKS_PER_BATCH);
// execute
try
{
// Optional cancellation token
// - Useful for cancelling long running processing operations
var ctx = new System.Threading.CancellationTokenSource();
// instruct the service to get and process the next range of blocks
// when the rangeProcessed is null - it means there was nothing to process
var rangeProcessed = await batchProcessorService.ProcessOnceAsync(ctx.Token);
// ensure we have processed the expected number of events
// the event subscription has state which can record running totals across many processing batches
Assert.Equal(11, eventSubscription.State.GetInt("EventsHandled"));
// get the row count from azure storage
// the querying on storage is limited
// the TransactionHash is the partitionkey and the rowkey is the LogIndex
// this allows us to query by tx hash
var logRepositoryHandler = storageHandlerForLogs as TransactionLogRepositoryHandler;
var repository = logRepositoryHandler.TransactionLogRepository as TransactionLogRepository;
var expectedTransactionHashes = new[]
{
"0x8d58abc578f5e321f2e6b7c0637ccc60fbf62b39b120691cbf19ff201f5069b0",
"0x0bee561ac6bafb59bcc4c48fc4c1225aaedbab3e8089acea420140aafa47f3e5",
"0x6fc82b076fa7088581a80869cb9c7a08d7f8e897670a9f67e39139b39246da7e",
"0xdc2ee28db35ed5dbbc9e18a7d6bdbacb6e6633a9fce1ecda99ea7e1cf4bc8c72",
"0xcd2fea48c84468f70c9a44c4ffd7b26064a2add8b72937edf593634d2501c1f6",
"0x3acf887420887148222aab1d25d4d4893794e505ef276cc4cb6a48fffc6cb381",
"0x96129f905589b2a95c26276aa7e8708a12381ddec50485d6684c4abf9a5a1d00"
};
List <TransactionLog> logsFromRepo = new List <TransactionLog>();
foreach (var txHash in expectedTransactionHashes)
{
logsFromRepo.AddRange(await repository.GetManyAsync(txHash));
}
Assert.Equal(11, logsFromRepo.Count);
}
finally
{
// delete any data from Azure
await storageCloudSetup.GetCountersTable().DeleteIfExistsAsync();
await tableStorageFactory.DeleteTablesAsync();
}
}