prepare for "check connectivity" api

* Cmd now has more generic "name" property and optional "portNumber"
* add CmdType CHECK_CONNECTIVITY
* add a simple one-shot PeerCheck utility
* add CheckCompletionHandler that handles a Cmd with type CHECK_CONNECTIVITY
* dummy in handleCmd for now

9 files changed, 186 insertions, 8 deletions

diff --git a/configd/src/apps/sentinel/CMakeLists.txt b/configd/src/apps/sentinel/CMakeLists.txt
index f6b4c3a2184..d67a41f2a75 100644
--- a/configd/src/apps/sentinel/CMakeLists.txt
+++ b/configd/src/apps/sentinel/CMakeLists.txt
@@ -1,6 +1,7 @@
 # Copyright 2017 Yahoo Holdings. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 vespa_add_executable(configd_config-sentinel_app
     SOURCES
+    check-completion-handler.cpp
     cmdq.cpp
     config-owner.cpp
     env.cpp
@@ -8,11 +9,13 @@ vespa_add_executable(configd_config-sentinel_app
     manager.cpp
     metrics.cpp
     output-connection.cpp
+    peer-check.cpp
     rpchooks.cpp
     rpcserver.cpp
     sentinel.cpp
     service.cpp
     state-api.cpp
+    status-callback.cpp
     OUTPUT_NAME vespa-config-sentinel
     INSTALL sbin
     DEPENDS
diff --git a/configd/src/apps/sentinel/check-completion-handler.cpp b/configd/src/apps/sentinel/check-completion-handler.cpp
new file mode 100644
index 00000000000..f854a85d297
--- /dev/null
+++ b/configd/src/apps/sentinel/check-completion-handler.cpp
@@ -0,0 +1,31 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "check-completion-handler.h"
+#include <vespa/log/log.h>
+LOG_SETUP(".check-completion-handler");
+
+namespace config::sentinel {
+
+void CheckCompletionHandler::create(Cmd::UP request, FRT_Supervisor &orb) {
+    LOG_ASSERT(request->type() == Cmd::CHECK_CONNECTIVITY);
+    // will delete itself on completion:
+    new CheckCompletionHandler(std::move(request), orb);
+}
+
+CheckCompletionHandler::CheckCompletionHandler(Cmd::UP request, FRT_Supervisor &orb)
+  : _parentRequest(std::move(request))
+{
+    const std::string & host = _parentRequest->name();
+    int port = _parentRequest->portNumber();
+    _peerCheck = std::make_unique<PeerCheck>(*this, host, port, orb);
+    
+}
+
+CheckCompletionHandler::~CheckCompletionHandler() = default;
+
+void CheckCompletionHandler::returnStatus(bool ok) {
+    _parentRequest->retValue(ok ? "ok" : "bad");
+    delete this;
+}
+
+}
diff --git a/configd/src/apps/sentinel/check-completion-handler.h b/configd/src/apps/sentinel/check-completion-handler.h
new file mode 100644
index 00000000000..ae43799dd54
--- /dev/null
+++ b/configd/src/apps/sentinel/check-completion-handler.h
@@ -0,0 +1,27 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include "status-callback.h"
+#include "peer-check.h"
+#include "cmdq.h"
+
+namespace config::sentinel {
+
+/**
+ * Handles a checkConnectivity request by making an outgoing
+ * ping request.  When the ping finishes, fills an answer
+ * into the parent request and deletes itself.
+ **/
+class CheckCompletionHandler : public StatusCallback {
+public:
+    static void create(Cmd::UP request, FRT_Supervisor &orb);
+    virtual ~CheckCompletionHandler();
+    void returnStatus(bool ok) override;
+private:
+    CheckCompletionHandler(Cmd::UP request, FRT_Supervisor &orb);
+    Cmd::UP _parentRequest;
+    std::unique_ptr<PeerCheck> _peerCheck;
+};
+
+}
diff --git a/configd/src/apps/sentinel/cmdq.h b/configd/src/apps/sentinel/cmdq.h
index 105d5f29b60..38c95967d70 100644
--- a/configd/src/apps/sentinel/cmdq.h
+++ b/configd/src/apps/sentinel/cmdq.h
@@ -5,6 +5,7 @@
 #include <memory>
 #include <mutex>
 #include <vector>
+#include <string>
 
 class FRT_RPCRequest;
 
@@ -13,14 +14,16 @@ namespace config::sentinel {
 class Cmd {
 public:
     using UP = std::unique_ptr<Cmd>;
-    enum CmdType { LIST, RESTART, START, STOP };
+    enum CmdType { LIST, RESTART, START, STOP, CHECK_CONNECTIVITY };
 
-    Cmd(FRT_RPCRequest *req, CmdType cmdType, const char *service = "")
-      : _req(req), _cmdType(cmdType), _serviceName(service)
+    Cmd(FRT_RPCRequest *req, CmdType cmdType, std::string name = "", int portnum = 0)
+      : _req(req), _cmdType(cmdType), _name(name), _port(portnum)
     {}
 
     CmdType type() const { return _cmdType; }
-    const char *serviceName() const { return _serviceName; }
+    // the service name or host name:
+    const std::string & name() const { return _name; }
+    int portNumber() const { return _port; }
 
     void retError(const char *errorString) const;
     void retValue(const char *valueString) const;
@@ -29,7 +32,8 @@ public:
 private:
     FRT_RPCRequest *_req;
     CmdType _cmdType;
-    const char *_serviceName;
+    std::string _name;
+    int _port;
 };
 
 class CommandQueue
diff --git a/configd/src/apps/sentinel/manager.cpp b/configd/src/apps/sentinel/manager.cpp
index 80dd2a3fda8..6f8bf69cb83 100644
--- a/configd/src/apps/sentinel/manager.cpp
+++ b/configd/src/apps/sentinel/manager.cpp
@@ -271,7 +271,7 @@ Manager::handleCmd(const Cmd& cmd)
         break;
     case Cmd::RESTART:
         {
-            Service *service = serviceByName(cmd.serviceName());
+            Service *service = serviceByName(cmd.name());
             if (service == nullptr) {
                 cmd.retError("Cannot find named service");
                 return;
@@ -287,7 +287,7 @@ Manager::handleCmd(const Cmd& cmd)
         break;
     case Cmd::START:
         {
-            Service *service = serviceByName(cmd.serviceName());
+            Service *service = serviceByName(cmd.name());
             if (service == nullptr) {
                 cmd.retError("Cannot find named service");
                 return;
@@ -301,7 +301,7 @@ Manager::handleCmd(const Cmd& cmd)
         break;
     case Cmd::STOP:
         {
-            Service *service = serviceByName(cmd.serviceName());
+            Service *service = serviceByName(cmd.name());
             if (service == nullptr) {
                 cmd.retError("Cannot find named service");
                 return;
@@ -312,6 +312,10 @@ Manager::handleCmd(const Cmd& cmd)
             }
         }
         break;
+    case Cmd::CHECK_CONNECTIVITY:
+        // XXX placeholder:
+        cmd.retValue("unknown");
+        break;
     }
 }
 
diff --git a/configd/src/apps/sentinel/peer-check.cpp b/configd/src/apps/sentinel/peer-check.cpp
new file mode 100644
index 00000000000..6aef1443ef2
--- /dev/null
+++ b/configd/src/apps/sentinel/peer-check.cpp
@@ -0,0 +1,51 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "peer-check.h"
+#include <vespa/vespalib/util/stringfmt.h>
+#include <vespa/log/log.h>
+
+LOG_SETUP(".peer-check");
+
+using vespalib::make_string_short::fmt;
+
+namespace config::sentinel {
+
+PeerCheck::PeerCheck(StatusCallback &callback, const std::string &host, int port, FRT_Supervisor &orb)
+  : _callback(callback),
+    _hostname(host),
+    _portnum(port),
+    _target(nullptr),
+    _req(nullptr)
+{
+    auto spec = fmt("tcp/%s:%d", _hostname.c_str(), _portnum);
+    _target = orb.GetTarget(spec.c_str());
+    _req = orb.AllocRPCRequest();
+    _req->SetMethodName("frt.rpc.ping");
+    _target->InvokeAsync(_req, 0.500, this);
+}
+
+PeerCheck::~PeerCheck() {
+    if (_req != nullptr) {
+        _req->Abort();
+    }
+}
+
+void PeerCheck::RequestDone(FRT_RPCRequest *req) {
+    LOG_ASSERT(req == _req);
+    bool statusOk = false;
+    if (req->IsError()) {
+        LOG(warning, "error on ping to %s [port %d]: %s (%d)", _hostname.c_str(), _portnum,
+            req->GetErrorMessage(), req->GetErrorCode());
+    } else {
+        LOG(info, "OK ping to %s [port %d]", _hostname.c_str(), _portnum);
+        statusOk = true;
+    }
+    _req->SubRef();
+    _req = nullptr;
+    _target->SubRef();
+    _target = nullptr;
+    // Note: will delete this object, so must be called as final step:
+    _callback.returnStatus(statusOk);
+}
+
+}
diff --git a/configd/src/apps/sentinel/peer-check.h b/configd/src/apps/sentinel/peer-check.h
new file mode 100644
index 00000000000..658375a8d7b
--- /dev/null
+++ b/configd/src/apps/sentinel/peer-check.h
@@ -0,0 +1,37 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+#include "status-callback.h"
+#include <string>
+#include <vespa/fnet/task.h>
+#include <vespa/fnet/frt/invoker.h>
+#include <vespa/fnet/frt/rpcrequest.h>
+#include <vespa/fnet/frt/supervisor.h>
+#include <vespa/fnet/frt/target.h>
+
+namespace config::sentinel {
+
+class PeerCheck : public FRT_IRequestWait
+{
+public:
+    PeerCheck(StatusCallback &callback, const std::string &host, int portnum, FRT_Supervisor &orb);
+    ~PeerCheck();
+
+    PeerCheck(const PeerCheck &) = delete;
+    PeerCheck(PeerCheck &&) = delete;
+    PeerCheck& operator= (const PeerCheck &) = delete;
+    PeerCheck& operator= (PeerCheck &&) = delete;
+
+    /** from FRT_IRequestWait **/
+    void RequestDone(FRT_RPCRequest *req) override;
+
+private:
+    StatusCallback &_callback;
+    std::string     _hostname;
+    int             _portnum;
+    FRT_Target     *_target;
+    FRT_RPCRequest *_req;
+};
+
+}
diff --git a/configd/src/apps/sentinel/status-callback.cpp b/configd/src/apps/sentinel/status-callback.cpp
new file mode 100644
index 00000000000..9bd820c9f39
--- /dev/null
+++ b/configd/src/apps/sentinel/status-callback.cpp
@@ -0,0 +1,8 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#include "status-callback.h"
+namespace config::sentinel {
+
+StatusCallback::~StatusCallback() = default;
+
+}
diff --git a/configd/src/apps/sentinel/status-callback.h b/configd/src/apps/sentinel/status-callback.h
new file mode 100644
index 00000000000..53a3185623b
--- /dev/null
+++ b/configd/src/apps/sentinel/status-callback.h
@@ -0,0 +1,13 @@
+// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+
+#pragma once
+
+namespace config::sentinel {
+
+/** very simple callback API with "ok" or "not ok" status only */
+struct StatusCallback {
+    virtual void returnStatus(bool ok) = 0;
+    virtual ~StatusCallback();
+};
+
+}