From 52e702a66e34e2a53e005bec3e22b5d198c09139 Mon Sep 17 00:00:00 2001
From: achains <achains@yandex-team.com>
Date: Fri, 24 Apr 2026 14:29:22 +0300
Subject: YT-26179: lazy read request
 commit_hash:a3758715df7ff97a0a471492dd907f949744e4d7

---
 yt/cpp/mapreduce/client/client_reader.cpp | 37 ++++++++++++++++++++++++++++---
 1 file changed, 34 insertions(+), 3 deletions(-)

(limited to 'yt/cpp/mapreduce/client/client_reader.cpp')

diff --git a/yt/cpp/mapreduce/client/client_reader.cpp b/yt/cpp/mapreduce/client/client_reader.cpp
index 0bbc6fa1322..f60bf8b8547 100644
--- a/yt/cpp/mapreduce/client/client_reader.cpp
+++ b/yt/cpp/mapreduce/client/client_reader.cpp
@@ -76,7 +76,6 @@ TClientReader::TClientReader(
     }
 
     TransformYPath();
-    CreateRequest();
 }
 
 bool TClientReader::Retry(
@@ -131,16 +130,25 @@ void TClientReader::ResetRetries()
 
 void TClientReader::Abort()
 {
-    Input_->Abort();
+    auto g = Guard(Lock_);
+    AbortRequested_ = true;
+    if (Input_) {
+        Input_->Abort();
+    }
 }
 
 bool TClientReader::IsAborted() const
 {
+    auto g = Guard(Lock_);
+    if (!Input_) {
+        return AbortRequested_;
+    }
     return Input_->IsAborted();
 }
 
 size_t TClientReader::DoRead(void* buf, size_t len)
 {
+    EnsureInitialized();
     return Input_->Read(buf, len);
 }
 
@@ -193,11 +201,34 @@ void TClientReader::CreateRequest(const TMaybe<ui32>& rangeIndex, const TMaybe<u
         ranges->begin()->LowerLimit(TReadLimit().RowIndex(*rowIndex));
     }
 
-    Input_ = NDetail::RequestWithRetry<std::unique_ptr<IAbortableInputStream>>(
+    auto newInput = NDetail::RequestWithRetry<std::unique_ptr<IAbortableInputStream>>(
         CurrentRequestRetryPolicy_,
         [this, &transactionId] (TMutationId /*mutationId*/) {
             return RawClient_->ReadTable(transactionId, Path_, Format_, Options_);
         });
+
+    auto g = Guard(Lock_);
+    // NB: Abort could've been called while we are waiting for newInput
+    if (AbortRequested_) {
+        newInput->Abort();
+    }
+
+    Input_ = std::move(newInput);
+}
+
+void TClientReader::EnsureInitialized()
+{
+    if (Input_) {
+        return;
+    }
+
+    {
+        auto g = Guard(Lock_);
+        if (AbortRequested_) {
+            ythrow TInputStreamAbortedError() << "Stream was aborted";
+        }
+    }
+    CreateRequest();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-- 
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