Add transaction tests and documentations

Signed-off-by: Tao He <sighingnow@gmail.com>

.github/workflows/build-test.yml

@@ -172,6 +172,9 @@ jobs:
           echo "Run the etcd watcher test ........................."
           ./build/bin/WatcherTest
 
+          echo "Run the etcd transaction test ........................."
+          ./build/bin/TransactionTest
+
           echo "Run the etcd election test ........................."
           ./build/bin/ElectionTest
 

README.md

@@ -734,6 +734,35 @@ is constructed.
 Without handler, the internal state can be checked via `KeepAlive::Check()` and it will rethrow
 the async exception when there are errors during keeping the lease alive.
 
+### Etcd transactions
+
+Etcd v3's [Transaction APIs](https://etcd.io/docs/v3.4/learning/api/#transaction) is supported via the
+`etcdv3::Transaction` interfaces. A set of convenient APIs are use to add operations to a transaction, e.g.,
+
+```cpp
+  etcdv3::Transaction txn;
+  txn.setup_put("/test/x1", "1");
+  txn.setup_put("/test/x2", "2");
+  txn.setup_put("/test/x3", "3");
+  etcd::Response resp = etcd.txn(txn).get();
+```
+
+Transactions in etcd supports set a set of comparison targets to specify the condition of transaction, e.g.,
+
+```cpp
+  etcdv3::Transaction txn;
+
+  // setup the conditions
+  txn.reset_key("/test/x1");
+  txn.init_compare("1", etcdv3::CompareResult::EQUAL, etcdv3::CompareTarget::VALUE);
+
+  txn.reset_key("/test/x2");
+  txn.init_compare("2", etcdv3::CompareResult::EQUAL, etcdv3::CompareTarget::VALUE);
+```
+
+See full example of the usages of transaction APIs, please refer to [./tst/TransactionTest.cpp](./tst/TransactionTest.cpp),
+for full list of the transaction operation APIs, see [./etcd/v3/Transaction.hpp](./etcd/v3/Transaction.hpp).
+
 ### Election API
 
 Etcd v3's [election APIs](https://github.com/etcd-io/etcd/blob/main/server/etcdserver/api/v3election/v3electionpb/v3election.proto)

tst/TransactionTest.cpp

@@ -0,0 +1,89 @@
+#define CATCH_CONFIG_MAIN
+#include <catch.hpp>
+
+#include <chrono>
+#include <iostream>
+#include <thread>
+
+#include "etcd/Client.hpp"
+#include "etcd/v3/Transaction.hpp"
+
+
+TEST_CASE("setup")
+{
+  etcd::Client etcd("http://127.0.0.1:2379");
+  etcd.rmdir("/test", true).wait();
+}
+
+TEST_CASE("add a new key")
+{
+  etcd::Client etcd("http://127.0.0.1:2379");
+  etcd.rmdir("/test", true).wait();
+
+  // do some put using txn
+  {
+    etcdv3::Transaction txn;
+    txn.setup_put("/test/x1", "1");
+    txn.setup_put("/test/x2", "2");
+    txn.setup_put("/test/x3", "3");
+    etcd::Response resp = etcd.txn(txn).get();
+    REQUIRE(0 == resp.error_code());
+  }
+
+  // check the value
+  {
+    etcd::Response resp = etcd.get("/test/x1").get();
+    REQUIRE(0 == resp.error_code());
+    CHECK(resp.value().as_string() == "1");
+
+    resp = etcd.get("/test/x2").get();
+    REQUIRE(0 == resp.error_code());
+    CHECK(resp.value().as_string() == "2");
+
+    resp = etcd.get("/test/x3").get();
+    REQUIRE(0 == resp.error_code());
+    CHECK(resp.value().as_string() == "3");
+  }
+
+  // do some put and delete using txn
+  {
+    etcdv3::Transaction txn;
+    
+    // setup the conditions
+    txn.reset_key("/test/x1");
+    txn.init_compare("1", etcdv3::CompareResult::EQUAL, etcdv3::CompareTarget::VALUE);
+
+    txn.reset_key("/test/x2");
+    txn.init_compare("2", etcdv3::CompareResult::EQUAL, etcdv3::CompareTarget::VALUE);
+
+    txn.setup_put("/test/x1", "111");
+    txn.setup_delete("/test/x2");
+    txn.setup_delete("/test/x3");
+    txn.setup_put("/test/x4", "4");
+    etcd::Response resp = etcd.txn(txn).get();
+    REQUIRE(0 == resp.error_code());
+  }
+
+  // check the value
+  {
+    etcd::Response resp = etcd.get("/test/x1").get();
+    REQUIRE(0 == resp.error_code());
+    CHECK(resp.value().as_string() == "111");
+
+    resp = etcd.get("/test/x2").get();
+    REQUIRE(etcdv3::ERROR_KEY_NOT_FOUND == resp.error_code());
+
+    resp = etcd.get("/test/x3").get();
+    REQUIRE(etcdv3::ERROR_KEY_NOT_FOUND == resp.error_code());
+
+    resp = etcd.get("/test/x4").get();
+    REQUIRE(0 == resp.error_code());
+    CHECK(resp.value().as_string() == "4");
+  }
+}
+
+TEST_CASE("cleanup")
+{
+  etcd::Client etcd("http://127.0.0.1:2379");
+  REQUIRE(0 == etcd.rmdir("/test", true).get().error_code());
+}