From 77b365c133ed7e0e7378c1dd953e5e4cb3f5eafb Mon Sep 17 00:00:00 2001
From: Metin Cakircali <metin.cakircali@ecmwf.int>
Date: Thu, 16 Jan 2025 15:40:16 +0100
Subject: [PATCH] feat(remoteFDB): add exists to remote store

---
 src/fdb5/remote/client/RemoteStore.cc  | 14 ++++++++++++-
 src/fdb5/remote/server/StoreHandler.cc | 27 ++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/src/fdb5/remote/client/RemoteStore.cc b/src/fdb5/remote/client/RemoteStore.cc
index 8df0bb25e..946862239 100644
--- a/src/fdb5/remote/client/RemoteStore.cc
+++ b/src/fdb5/remote/client/RemoteStore.cc
@@ -244,7 +244,19 @@ eckit::URI RemoteStore::uri() const {
 }
 
 bool RemoteStore::exists() const {
-    return true;
+
+    bool result = false;
+
+    eckit::Buffer       sendBuf(defaultBufferSizeKey);
+    eckit::MemoryStream sms(sendBuf);
+    sms << dbKey_;
+
+    eckit::Buffer recvBuf = controlWriteReadResponse(Message::Exists, generateRequestID(), sendBuf, sms.position());
+
+    eckit::MemoryStream rms(recvBuf);
+    rms >> result;
+
+    return result;
 }
 
 eckit::DataHandle* RemoteStore::retrieve(Field& field) const {
diff --git a/src/fdb5/remote/server/StoreHandler.cc b/src/fdb5/remote/server/StoreHandler.cc
index e11d4e491..c0c290e47 100644
--- a/src/fdb5/remote/server/StoreHandler.cc
+++ b/src/fdb5/remote/server/StoreHandler.cc
@@ -75,6 +75,10 @@ Handled StoreHandler::handleControl(Message message, uint32_t clientID, uint32_t
                 flush(clientID, requestID, payload);
                 return Handled::Yes;
 
+            case Message::Exists:  // given key (payload), check if store exists
+                exists(clientID, requestID, payload);
+                return Handled::Replied;
+
             default: {
                 std::stringstream ss;
                 ss << "ERROR: Unexpected message recieved (" << message << "). ABORTING";
@@ -94,6 +98,8 @@ Handled StoreHandler::handleControl(Message message, uint32_t clientID, uint32_t
     return Handled::No;
 }
 
+//----------------------------------------------------------------------------------------------------------------------
+
 void StoreHandler::read(uint32_t clientID, uint32_t requestID, const eckit::Buffer& payload) {
 
     {
@@ -272,4 +278,25 @@ Store& StoreHandler::store(uint32_t clientID, const Key& dbKey) {
     return *((stores_.emplace(clientID, StoreHelper(!single_, dbKey, config_)).first)->second.store);
 }
 
+void StoreHandler::exists(const uint32_t clientID, const uint32_t requestID, const eckit::Buffer& payload) const {
+
+    ASSERT(payload.size() > 0);
+
+    bool exists = false;
+
+    {
+        eckit::MemoryStream stream(payload);
+        const Key           dbKey(stream);
+        exists = StoreFactory::instance().build(dbKey, config_)->exists();
+    }
+
+    eckit::Buffer       existBuf(5);
+    eckit::MemoryStream stream(existBuf);
+    stream << exists;
+
+    write(Message::Received, true, clientID, requestID, existBuf.data(), stream.position());
+}
+
+//----------------------------------------------------------------------------------------------------------------------
+
 }  // namespace fdb5::remote