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cpp20_streams.cpp
/* Copyright (c) 2018-2022 Marcelo Zimbres Silva (mzimbres@gmail.com)
*
* Distributed under the Boost Software License, Version 1.0. (See
* accompanying file LICENSE.txt)
*/
#include <boost/redis/connection.hpp>
#include <boost/asio/deferred.hpp>
#include <boost/asio/co_spawn.hpp>
#include <boost/asio/detached.hpp>
#include <boost/asio/consign.hpp>
#include <boost/asio/signal_set.hpp>
#include <boost/asio/awaitable.hpp>
#include <iostream>
#if defined(BOOST_ASIO_HAS_CO_AWAIT)
#include <memory>
#include <string>
#include <thread>
#include <vector>
namespace net = boost::asio;
using boost::redis::config;
using boost::redis::generic_response;
using boost::redis::operation;
using boost::redis::request;
using boost::redis::connection;
using signal_set = net::deferred_t::as_default_on_t<net::signal_set>;
auto stream_reader(std::shared_ptr<connection> conn) -> net::awaitable<void>
{
std::string redisStreamKey_;
request req;
generic_response resp;
std::string stream_id{"$"};
std::string const field = "myfield";
for (;;) {
req.push("XREAD", "BLOCK", "0", "STREAMS", "test-topic", stream_id);
co_await conn->async_exec(req, resp, net::deferred);
//std::cout << "Response: ";
//for (auto i = 0UL; i < resp->size(); ++i) {
// std::cout << resp->at(i).value << ", ";
//}
//std::cout << std::endl;
// The following approach was taken in order to be able to
// deal with the responses, as generated by redis in the case
// that there are multiple stream 'records' within a single
// generic_response. The nesting and number of values in
// resp.value() are different, depending on the contents
// of the stream in redis. Uncomment the above commented-out
// code for examples while running the XADD command.
std::size_t item_index = 0;
while (item_index < std::size(resp.value())) {
auto const& val = resp.value().at(item_index).value;
if (field.compare(val) == 0) {
// We've hit a myfield field.
// The streamId is located at item_index - 2
// The payload is located at item_index + 1
stream_id = resp.value().at(item_index - 2).value;
std::cout
<< "StreamId: " << stream_id << ", "
<< "MyField: " << resp.value().at(item_index + 1).value
<< std::endl;
++item_index; // We can increase so we don't read this again
}
++item_index;
}
req.clear();
resp.value().clear();
}
}
// Run this in another terminal:
// redis-cli -r 100000 -i 0.0001 XADD "test-topic" "*" "myfield" "myfieldvalue1"
auto co_main(config cfg) -> net::awaitable<void>
{
auto ex = co_await net::this_coro::executor;
auto conn = std::make_shared<connection>(ex);
net::co_spawn(ex, stream_reader(conn), net::detached);
// Disable health checks.
cfg.health_check_interval = std::chrono::seconds::zero();
conn->async_run(cfg, {}, net::consign(net::detached, conn));
signal_set sig_set(ex, SIGINT, SIGTERM);
co_await sig_set.async_wait();
conn->cancel();
}
#endif // defined(BOOST_ASIO_HAS_CO_AWAIT)
boost::redis::connection
A basic_connection that type erases the executor.
Definition: connection.hpp:339
boost::redis::request
Creates Redis requests.
Definition: request.hpp:46
boost::redis::generic_response
adapter::result< std::vector< resp3::node > > generic_response
A generic response to a request.
Definition: response.hpp:35
boost::redis::operation
operation
Connection operations that can be cancelled.
Definition: operation.hpp:18
boost::redis::config
Configure parameters used by the connection classes.
Definition: config.hpp:30