consul package and basic client added (#716)

* this adds a consul package which can be used to fetch a consul binary
* it also adds a `ConsulProcess` helper which can be used to spawn and manage a consul service instance
* zencore dependencies brought across:
   - `except_fmt.h` for easer generation of formatted exception messages
   - `process.h/cpp` changes (adds `Kill` operation and process group support on Windows)
   - `string.h` changes to allow generic use of `WideToUtf8()`

1 files changed, 140 insertions, 0 deletions

diff --git a/src/zenutil/consul/consul.cpp b/src/zenutil/consul/consul.cpp
new file mode 100644
index 000000000..6ddebf97a
--- /dev/null
+++ b/src/zenutil/consul/consul.cpp
@@ -0,0 +1,140 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include <zenutil/consul.h>
+
+#include <zencore/except_fmt.h>
+#include <zencore/fmtutils.h>
+#include <zencore/logging.h>
+#include <zencore/process.h>
+#include <zencore/string.h>
+#include <zencore/timer.h>
+
+#include <fmt/format.h>
+
+namespace zen::consul {
+
+//////////////////////////////////////////////////////////////////////////
+
+struct ConsulProcess::Impl
+{
+	Impl(std::string_view BaseUri) : m_HttpClient(BaseUri) {}
+	~Impl() = default;
+
+	void SpawnConsulAgent()
+	{
+		if (m_ProcessHandle.IsValid())
+		{
+			return;
+		}
+
+		CreateProcOptions Options;
+		Options.Flags |= CreateProcOptions::Flag_Windows_NewProcessGroup;
+
+		CreateProcResult Result = CreateProc("consul" ZEN_EXE_SUFFIX_LITERAL, "consul" ZEN_EXE_SUFFIX_LITERAL " agent -dev", Options);
+
+		if (Result)
+		{
+			m_ProcessHandle.Initialize(Result);
+
+			Stopwatch Timer;
+
+			// Poll to check when the agent is ready
+
+			do
+			{
+				Sleep(100);
+				HttpClient::Response Resp = m_HttpClient.Get("v1/status/leader");
+				if (Resp)
+				{
+					ZEN_INFO("Consul agent started successfully (waited {})", NiceTimeSpanMs(Timer.GetElapsedTimeMs()));
+
+					return;
+				}
+			} while (Timer.GetElapsedTimeMs() < 10000);
+		}
+
+		// Report failure!
+
+		ZEN_WARN("Consul agent failed to start within timeout period");
+	}
+
+	void StopConsulAgent()
+	{
+		if (!m_ProcessHandle.IsValid())
+		{
+			return;
+		}
+
+		// This waits for the process to exit and also resets the handle
+		m_ProcessHandle.Kill();
+	}
+
+private:
+	ProcessHandle m_ProcessHandle;
+	HttpClient	  m_HttpClient;
+};
+
+ConsulProcess::ConsulProcess() : m_Impl(std::make_unique<Impl>("http://localhost:8500/"))
+{
+}
+
+ConsulProcess::~ConsulProcess()
+{
+}
+
+void
+ConsulProcess::SpawnConsulAgent()
+{
+	m_Impl->SpawnConsulAgent();
+}
+
+void
+ConsulProcess::StopConsulAgent()
+{
+	m_Impl->StopConsulAgent();
+}
+
+//////////////////////////////////////////////////////////////////////////
+
+ConsulClient::ConsulClient(std::string_view BaseUri) : m_HttpClient(BaseUri)
+{
+}
+
+ConsulClient::~ConsulClient()
+{
+}
+
+void
+ConsulClient::SetKeyValue(std::string_view Key, std::string_view Value)
+{
+	IoBuffer			 ValueBuffer = IoBufferBuilder::MakeFromMemory(MakeMemoryView(Value));
+	HttpClient::Response Result =
+		m_HttpClient.Put(fmt::format("v1/kv/{}", Key), ValueBuffer, {{"Content-Type", "text/plain"}, {"Accept", "application/json"}});
+	if (!Result)
+	{
+		throw runtime_error("ConsulClient::SetKeyValue() failed to set key '{}' ({})", Key, Result.ErrorMessage(""));
+	}
+}
+
+std::string
+ConsulClient::GetKeyValue(std::string_view Key)
+{
+	HttpClient::Response Result = m_HttpClient.Get(fmt::format("v1/kv/{}?raw", Key));
+	if (!Result)
+	{
+		throw runtime_error("ConsulClient::GetKeyValue() failed to get key '{}' ({})", Key, Result.ErrorMessage(""));
+	}
+	return Result.ToText();
+}
+
+void
+ConsulClient::DeleteKey(std::string_view Key)
+{
+	HttpClient::Response Result = m_HttpClient.Delete(fmt::format("v1/kv/{}", Key));
+	if (!Result)
+	{
+		throw runtime_error("ConsulClient::DeleteKey() failed to delete key '{}' ({})", Key, Result.ErrorMessage(""));
+	}
+}
+
+}  // namespace zen::consul