feat(ci): add fault-tolerance degradation suite to the functional chain

Adds a fault-tolerance suite that verifies read/write behavior under
drive and node loss against the erasure-coding contract and snapshots
health-endpoint responses at every degradation tier. Scenarios are
derived from product source (default_parity_count, erasure set sizing):

- A: single-node 4 drives (EC:2, read quorum 2): hide 1/2/3 drives
- B: multi-node 4x1 (one set of 4, EC:2): stop 1/2/3 nodes
- C: multi-node 4x4 (one set of 16, EC:4, read quorum 12): 1 node down
  lands exactly on the read-quorum boundary; 2 nodes down breaks it
- C2: multi-node 4x4 with RUSTFS_STORAGE_CLASS_STANDARD=EC:8 (read
  quorum 8, write quorum 9, lock majority 9): 2 nodes down puts reads
  inside the reported divergence window (read quorum met while the
  lock majority is broken)

By default a reads-refused-despite-met-read-quorum observation is
reported as known-divergence without failing the suite; the strict
input escalates it. Chain order becomes:
upgrade -> s3 -> kms -> tier -> storage -> heal -> pool -> security ->
replication -> fault-tolerance -> performance.

Covers the findings of the 2026-09 external degradation report
(reads at read quorum, health-endpoint readiness truthfulness,
degradedReasons capture) as automated regression probes.

.github/workflows/rustfs-fault-tolerance-test.yml

@@ -0,0 +1,276 @@
+# RustFS Fault-Tolerance (degradation) Test
+#
+# Scenario suite for the 2026-09 degradation report: verifies read/write
+# behavior under drive and node loss against the erasure-coding contract and
+# snapshots health-endpoint responses at every tier.
+#
+#   A  single-node 4 drives (SNMD): hide 1/2/3 drives, restore
+#   B  multi-node 4x1 (one drive per node): stop 1/2/3 nodes, restore
+#   C  multi-node 4x4 (16 drives, EC:4): stop 1 node (read-quorum boundary),
+#      stop 2 nodes, restore
+#   C2 multi-node 4x4 with EC:8: 2 nodes down puts 8 drives online -- reads
+#      satisfy the EC read quorum while the lock majority is broken (the
+#      reported divergence window: reads 503 with lock_quorum_unavailable)
+#
+# Expectations come from product source (default_parity_count, erasure set
+# sizing). By default a "reads refused although the read quorum is met"
+# observation is reported as known-divergence without failing the suite; the
+# strict input turns those into failures once the product behavior changes.
+
+name: RustFS Fault-Tolerance Test
+
+on:
+  workflow_dispatch:
+    inputs:
+      package_url:
+        description: 'Direct .deb URL. Required unless the nightly default is wanted.'
+        required: false
+        type: string
+      strict:
+        description: 'Fail the suite when reads are refused despite a met read quorum'
+        type: boolean
+        default: false
+      cleanup_before:
+        description: 'Reset the nodes before the test (DESTROYS existing data/config)'
+        type: boolean
+        default: true
+      cleanup_after:
+        description: 'Reset the nodes after the test (DESTROYS test data/config)'
+        type: boolean
+        default: true
+  repository_dispatch:
+    # Chain handoff: dispatched when the replication suite finishes, ahead of
+    # the performance suite.
+    types: [rustfs-chain-fault-tolerance]
+
+permissions:
+  contents: read
+
+# The suite stops services and hides drive dirs on the shared fleet; only one
+# functional suite may touch the environment at a time.
+concurrency:
+  group: rustfs-shared-functional-tests
+  cancel-in-progress: false
+
+defaults:
+  run:
+    shell: bash
+
+env:
+  RUSTFS_ACCESS_KEY: ${{ secrets.RUSTFS_ACCESS_KEY }}
+  RUSTFS_SECRET_KEY: ${{ secrets.RUSTFS_SECRET_KEY }}
+  RUSTFS_NODES: ${{ secrets.RUSTFS_NODES || vars.RUSTFS_NODES }}
+  RUSTFS_SSH_USER: ${{ secrets.RUSTFS_SSH_USER || vars.RUSTFS_SSH_USER }}
+  PF_TESTING_GH_TOKEN: ${{ secrets.PF_TESTING_GH_TOKEN }}
+  RUSTFS_NIGHTLY_PACKAGE_URL: ${{ vars.RUSTFS_NIGHTLY_PACKAGE_URL || 'https://dl.rustfs.com/artifacts/rustfs/packages/nightly/rustfs-nightly-latest.deb' }}
+
+jobs:
+  fault-tolerance-test:
+    runs-on: smoke-testing
+    timeout-minutes: 480
+    if: ${{ github.event_name == 'workflow_dispatch' || github.event_name == 'repository_dispatch' }}
+    steps:
+      - name: Initialize functional evidence
+        id: evidence
+        run: |
+          set -euo pipefail
+          umask 077
+          FUNCTIONAL_ARTIFACTS_DIR="${RUNNER_TEMP}/rustfs-ft-${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT}"
+          mkdir -- "${FUNCTIONAL_ARTIFACTS_DIR}" "${FUNCTIONAL_ARTIFACTS_DIR}/evidence"
+          {
+            printf 'FUNCTIONAL_ARTIFACTS_DIR=%s\n' "${FUNCTIONAL_ARTIFACTS_DIR}"
+            printf 'LOG_FILE=%s/suite.log\n' "${FUNCTIONAL_ARTIFACTS_DIR}"
+            printf 'REPORT_FILE=%s/report.md\n' "${FUNCTIONAL_ARTIFACTS_DIR}"
+            printf 'EVIDENCE_DIR=%s/evidence\n' "${FUNCTIONAL_ARTIFACTS_DIR}"
+          } >> "${GITHUB_ENV}"
+
+      # auto-testing is private: clone it with the dedicated PF token (not
+      # GITHUB_TOKEN) and retry transient GitHub/network failures.
+      - name: Checkout auto-testing scripts (with retry)
+        env:
+          GH_TOKEN: ${{ secrets.PF_TESTING_GH_TOKEN }}
+        run: |
+          set -euo pipefail
+          rm -rf auto-testing
+          for attempt in 1 2 3 4 5; do
+            if gh repo clone rustfs/auto-testing auto-testing -- --depth 1 --quiet; then
+              echo "auto-testing cloned (attempt ${attempt})"
+              exit 0
+            fi
+            rm -rf auto-testing
+            echo "clone attempt ${attempt} failed; retrying in $((attempt * 15))s" >&2
+            sleep $((attempt * 15))
+          done
+          echo "ERROR: unable to clone rustfs/auto-testing after 5 attempts" >&2
+          exit 1
+
+      - name: Show environment
+        run: |
+          uname -a
+          jq --version
+          aws --version
+          df -h /data | tail -1
+
+      - name: Cleanup environment (before)
+        if: ${{ inputs.cleanup_before != 'false' }}
+        run: |
+          ./auto-testing/rustfs-fault-tolerance-test.sh --cleanup -y --log-file "${LOG_FILE}"
+
+      - name: Run fault-tolerance scenarios (A, B, C, C2)
+        id: test
+        run: |
+          ARGS=(--all -y --package-url "${{ inputs.package_url || env.RUSTFS_NIGHTLY_PACKAGE_URL }}" --log-file "${LOG_FILE}")
+          if [ "${{ inputs.strict }}" = "true" ]; then
+            ARGS+=(--strict)
+          fi
+          ./auto-testing/rustfs-fault-tolerance-test.sh "${ARGS[@]}"
+
+      - name: Generate report
+        if: ${{ always() && steps.evidence.outcome == 'success' }}
+        run: |
+          set -euo pipefail
+          {
+            echo "# RustFS fault-tolerance test report"
+            echo ""
+            echo "- Run: ${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}"
+            echo "- Package: ${{ inputs.package_url || 'nightly (R2 latest)' }}"
+            echo "- Strict mode: ${{ inputs.strict || 'false' }}"
+            echo ""
+            echo "## Per-probe results"
+            echo ""
+            echo '```'
+            grep -E '^FT-(CASE|SUMMARY|REPORT)' "${LOG_FILE}" || echo "(no FT-CASE lines found)"
+            echo '```'
+            echo ""
+            echo "## Health snapshots"
+            echo ""
+            for f in "${FUNCTIONAL_ARTIFACTS_DIR}"/evidence/*.code; do
+              [ -e "${f}" ] || continue
+              printf '%s -> %s\n' "$(basename "${f}" .code)" "$(cat "${f}")"
+            done
+          } > "${REPORT_FILE}"
+
+      - name: File failure issue in rustfs/backlog
+        if: ${{ failure() && steps.evidence.outcome == 'success' }}
+        env:
+          GH_TOKEN: ${{ secrets.PF_TESTING_GH_TOKEN }}
+          SUITE: fault-tolerance
+          SUITE_LABEL: Fault-Tolerance
+        run: |
+          set -euo pipefail
+          TITLE="[functional][${SUITE}] ${SUITE_LABEL} suite failed (run ${GITHUB_RUN_ID})"
+          RUN_URL="${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}"
+          EXISTING="$(gh issue list -R rustfs/backlog \
+            --search "in:title \"run ${GITHUB_RUN_ID}\"" \
+            --json number --jq '.[].number' || true)"
+          if [ -n "${EXISTING}" ]; then
+            echo "backlog issue already exists for run ${GITHUB_RUN_ID}; skipping"
+            exit 0
+          fi
+          redact() {
+            sed -E \
+              -e 's/(RUSTFS_(ACCESS_KEY|SECRET_KEY)[=: ]+)[^[:space:]]+/\1[REDACTED]/Ig' \
+              -e 's/(Authorization:).*/\1 [REDACTED]/Ig' \
+              -e 's/(X-Amz-Signature=)[^&[:space:]]+/\1[REDACTED]/Ig' \
+              -e 's/^.*(password|secret|token)[=: ].*/[REDACTED SENSITIVE LINE]/Ig'
+          }
+          BODY_FILE="$(mktemp)"
+          {
+            echo "The **${SUITE_LABEL}** functional suite failed."
+            echo ""
+            echo "- Suite: \`${SUITE}\`"
+            echo "- Run: ${RUN_URL}"
+            echo "- Attempt: ${GITHUB_RUN_ATTEMPT}"
+            echo "- Workflow Commit: ${GITHUB_SHA}"
+            echo "- Trigger: ${GITHUB_EVENT_NAME}"
+            echo "- Date: $(date -u +%Y-%m-%d)"
+            echo ""
+            echo "## Report (errors and symptoms)"
+            echo ""
+            if [ -s "${REPORT_FILE:-}" ]; then
+              redact < "${REPORT_FILE}"
+            elif [ -s "${LOG_FILE:-}" ]; then
+              echo "(report file missing; log tail below)"
+              echo ""
+              tail -n 200 "${LOG_FILE}" | redact
+            else
+              echo "(no report or log file was produced)"
+            fi
+          } | head -c 55000 > "${BODY_FILE}"
+          gh label create functional-test -R rustfs/backlog --color d73a4a 2>/dev/null || true
+          if ! gh issue create -R rustfs/backlog --title "${TITLE}" \
+              --body-file "${BODY_FILE}" --label functional-test; then
+            gh issue create -R rustfs/backlog --title "${TITLE}" --body-file "${BODY_FILE}"
+          fi
+          echo "filed backlog issue for suite ${SUITE}"
+
+      - name: Upload test logs & evidence
+        if: ${{ always() && steps.evidence.outcome == 'success' }}
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6
+        with:
+          name: rustfs-fault-tolerance-${{ github.run_id }}-${{ github.run_attempt }}
+          path: |
+            ${{ env.FUNCTIONAL_ARTIFACTS_DIR }}/report.md
+            ${{ env.FUNCTIONAL_ARTIFACTS_DIR }}/suite.log
+            ${{ env.FUNCTIONAL_ARTIFACTS_DIR }}/evidence/
+          if-no-files-found: warn
+
+      - name: Cleanup environment (after)
+        if: ${{ always() && inputs.cleanup_after != 'false' }}
+        run: |
+          ./auto-testing/rustfs-fault-tolerance-test.sh --cleanup -y --log-file "${LOG_FILE}" || true
+
+      - name: "Continue functional chain (next: Performance)"
+        # Only chain-triggered runs forward to the next suite; standalone
+        # workflow_dispatch runs stop after their own cleanup. A failed
+        # handoff retries, then files an alert issue in rustfs/backlog.
+        if: ${{ always() && github.event_name == 'repository_dispatch' }}
+        continue-on-error: true
+        env:
+          GH_TOKEN: ${{ secrets.PF_TESTING_GH_TOKEN }}
+        run: |
+          set -uo pipefail
+          if [ -z "${GH_TOKEN:-}" ]; then
+            echo "PF_TESTING_GH_TOKEN is not configured; cannot dispatch the next suite" >&2
+            exit 1
+          fi
+          DISPATCHED=0
+          for attempt in 1 2 3; do
+            if gh api --method POST repos/rustfs/rustfs/dispatches \
+              -f event_type='rustfs-chain-performance' \
+              -F 'client_payload[from_suite]=fault-tolerance'; then
+              echo "dispatched next suite Performance (attempt ${attempt})"
+              DISPATCHED=1
+              break
+            fi
+            echo "dispatch attempt ${attempt} failed; retrying in ${attempt}0s" >&2
+            sleep "${attempt}0"
+          done
+          if [ "${DISPATCHED:-0}" -ne 1 ]; then
+            echo "ERROR: functional chain stalled: could not dispatch Performance after 3 attempts" >&2
+            TITLE="[functional][chain] stalled after fault-tolerance (run ${GITHUB_RUN_ID})"
+            BODY_FILE="$(mktemp)"
+            {
+              echo "The functional chain could not hand off from **fault-tolerance** to **Performance** after 3 attempts."
+              echo ""
+              echo "- Failed suite job: ${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}"
+              echo "- Expected next event: 'rustfs-chain-performance'"
+              echo "- Likely cause: PF_TESTING_GH_TOKEN lacks contents:write on rustfs/rustfs, or the GitHub API was unavailable."
+              echo "- Recovery: re-dispatch manually with"
+              FENCE="$(printf "\x60\x60\x60")"; echo "  ${FENCE}"
+              echo "  gh api --method POST repos/rustfs/rustfs/dispatches -f event_type='rustfs-chain-performance'"
+              FENCE="$(printf "\x60\x60\x60")"; echo "  ${FENCE}"
+            } > "${BODY_FILE}"
+            gh issue create -R rustfs/backlog --title "${TITLE}" \
+              --body-file "${BODY_FILE}" --label functional-test \
+              || gh issue create -R rustfs/backlog --title "${TITLE}" --body-file "${BODY_FILE}" \
+              || echo "could not file the stall alert issue either; check the token" >&2
+            exit 1
+          fi
+
+      - name: Notify on failure
+        if: failure()
+        run: |
+          echo "RustFS fault-tolerance test failed"
+          echo "Package source: ${{ inputs.package_url || 'nightly (R2 latest)' }}"
+          echo "See the uploaded log artifact and FT-CASE lines for details."

.github/workflows/rustfs-functional-chain.yml

@@ -14,7 +14,7 @@
 
 # Functional chain driver: runs the ten functional suites in a fixed order
 # (upgrade -> s3 -> kms -> tier -> storage -> heal -> pool -> security ->
-# replication -> performance). Each suite attempts the next handoff even
+# replication -> fault-tolerance -> performance). Each suite attempts the next handoff even
 # when its tests fail.
 #
 # Each suite workflow can still be dispatched standalone (workflow_dispatch);

.github/workflows/rustfs-replication-test.yml

@@ -329,7 +329,7 @@ jobs:
             '
           done
 
-      - name: "Continue functional chain (next: Performance)"
+      - name: "Continue functional chain (next: Fault tolerance)"
         if: ${{ always() && github.event_name == 'repository_dispatch' }}
         env:
           GH_TOKEN: ${{ secrets.PF_TESTING_GH_TOKEN }}
@@ -342,9 +342,9 @@ jobs:
           DISPATCHED=0
           for attempt in 1 2 3; do
             if gh api --method POST repos/rustfs/rustfs/dispatches \
-              -f event_type='rustfs-chain-performance' \
+              -f event_type='rustfs-chain-fault-tolerance' \
               -F 'client_payload[from_suite]=replication'; then
-              echo "dispatched next suite Performance (attempt ${attempt})"
+              echo "dispatched next suite Fault tolerance (attempt ${attempt})"
               DISPATCHED=1
               break
             fi
@@ -352,19 +352,19 @@ jobs:
             sleep "${attempt}0"
           done
           if [ "${DISPATCHED:-0}" -ne 1 ]; then
-            echo "ERROR: functional chain stalled: could not dispatch Performance after 3 attempts" >&2
+            echo "ERROR: functional chain stalled: could not dispatch Fault tolerance after 3 attempts" >&2
             TITLE="[functional][chain] stalled after replication (run ${GITHUB_RUN_ID})"
             BODY_FILE="$(mktemp)"
             trap 'rm -f "${BODY_FILE}"' EXIT
             {
-              echo "The functional chain could not hand off from **replication** to **Performance** after 3 attempts."
+              echo "The functional chain could not hand off from **replication** to **Fault tolerance** after 3 attempts."
               echo ""
               echo "- Failed suite job: ${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID}"
-              echo "- Expected next event: 'rustfs-chain-performance'"
+              echo "- Expected next event: 'rustfs-chain-fault-tolerance'"
               echo "- Likely cause: PF_TESTING_GH_TOKEN lacks contents:write on rustfs/rustfs, or the GitHub API was unavailable."
               echo "- Recovery: re-dispatch manually with"
               FENCE="$(printf "\x60\x60\x60")"; echo "  ${FENCE}"
-              echo "  gh api --method POST repos/rustfs/rustfs/dispatches -f event_type='rustfs-chain-performance'"
+              echo "  gh api --method POST repos/rustfs/rustfs/dispatches -f event_type='rustfs-chain-fault-tolerance'"
               FENCE="$(printf "\x60\x60\x60")"; echo "  ${FENCE}"
             } > "${BODY_FILE}"
             gh issue create -R rustfs/backlog --title "${TITLE}" \

rustfs/src/app/object/get.rs

@@ -2133,7 +2133,7 @@ impl DefaultObjectUsecase {
     }
 
     #[allow(clippy::too_many_arguments)]
-    async fn build_reader_blob<R>(
+    fn build_reader_blob<R>(
         reader: R,
         response_content_length: i64,
         request_id: &str,
@@ -2144,12 +2144,10 @@ impl DefaultObjectUsecase {
         key: &str,
         lifecycle: GetObjectBodyLifecycle,
         resume: Option<GetObjectResumeControl<R>>,
-    ) -> S3Result<StreamingBlob>
+    ) -> StreamingBlob
     where
         R: AsyncRead + Send + Sync + Unpin + 'static,
     {
-        use tokio::io::AsyncReadExt as _;
-
         let streaming_blob_start = rustfs_io_metrics::get_stage_metrics_enabled().then(std::time::Instant::now);
         let expected = usize::try_from(response_content_length.max(0)).unwrap_or(usize::MAX);
         let tuned_stream_buffer_size =
@@ -2165,7 +2163,7 @@ impl DefaultObjectUsecase {
             );
         }
         let handoff_start = get_stage_metrics_enabled.then(std::time::Instant::now);
-        let mut reader = GetObjectStreamingReader::new(
+        let reader = GetObjectStreamingReader::new(
             reader,
             bucket,
             key,
@@ -2176,17 +2174,6 @@ impl DefaultObjectUsecase {
             lifecycle,
             resume,
         );
-        let mut prefix = [0_u8; 1];
-        let prefix_len = if expected == 0 {
-            0
-        } else {
-            reader
-                .read_exact(&mut prefix)
-                .await
-                .map_err(|error| map_get_object_reader_error(StorageError::from(error)))?;
-            1
-        };
-        let reader = std::io::Cursor::new(prefix).take(prefix_len).chain(reader);
         let stream = GetObjectReaderStream::new(reader, stream_buffer_size, expected, stream_strategy.as_str(), buffer_source)
             .with_diagnostics(bucket, key, request_id);
         let blob = StreamingBlob::new(stream);
@@ -2200,7 +2187,7 @@ impl DefaultObjectUsecase {
             );
         }
         record_get_object_s3_handler_stage_duration(GET_OBJECT_STAGE_BODY_STREAMING_BLOB, streaming_blob_start);
-        Ok(blob)
+        blob
     }
 
     fn init_get_object_bootstrap(&self, bucket: &str, key: &str, request_id: &str) -> S3Result<GetObjectBootstrap> {
@@ -3174,7 +3161,7 @@ impl DefaultObjectUsecase {
             let (stream_buffer_size, stream_strategy) =
                 Self::select_stream_buffer_strategy(response_content_length, optimal_buffer_size, enable_readahead, has_range);
             record_get_object_s3_handler_stage_duration(GET_OBJECT_STAGE_BODY_STREAM_STRATEGY, stream_strategy_start);
-            return Self::build_reader_blob(
+            return Ok(Self::build_reader_blob(
                 final_stream,
                 response_content_length,
                 request_id,
@@ -3185,8 +3172,7 @@ impl DefaultObjectUsecase {
                 key,
                 lifecycle,
                 resume(info),
-            )
-            .await;
+            ));
         }
 
         if let Some(buffered_body) = buffered_body {
@@ -3253,7 +3239,7 @@ impl DefaultObjectUsecase {
         let (stream_buffer_size, stream_strategy) =
             Self::select_stream_buffer_strategy(response_content_length, optimal_buffer_size, enable_readahead, has_range);
         record_get_object_s3_handler_stage_duration(GET_OBJECT_STAGE_BODY_STREAM_STRATEGY, stream_strategy_start);
-        Self::build_reader_blob(
+        Ok(Self::build_reader_blob(
             final_stream,
             response_content_length,
             request_id,
@@ -3264,8 +3250,7 @@ impl DefaultObjectUsecase {
             key,
             lifecycle,
             resume(info),
-        )
-        .await
+        ))
     }
 
     #[allow(clippy::too_many_arguments)]
@@ -5862,11 +5847,8 @@ mod tests {
     }
 
     impl AsyncRead for ReadProbeReader {
-        fn poll_read(self: Pin<&mut Self>, _cx: &mut Context<'_>, buf: &mut ReadBuf<'_>) -> Poll<std::io::Result<()>> {
+        fn poll_read(self: Pin<&mut Self>, _cx: &mut Context<'_>, _buf: &mut ReadBuf<'_>) -> Poll<std::io::Result<()>> {
             self.reads.fetch_add(1, AtomicOrdering::Relaxed);
-            if buf.remaining() > 0 {
-                buf.put_slice(b"x");
-            }
             Poll::Ready(Ok(()))
         }
     }
@@ -7791,151 +7773,6 @@ mod tests {
         )
     }
 
-    #[tokio::test]
-    async fn build_reader_blob_rejects_quorum_failure_before_handoff() {
-        let result = DefaultObjectUsecase::build_reader_blob(
-            FailAtEndReader::new(
-                b"",
-                Some(std::io::Error::other(StorageError::InsufficientReadQuorum(
-                    "test-bucket".to_string(),
-                    "unavailable-object".to_string(),
-                ))),
-            ),
-            5,
-            "req-preheader-quorum",
-            None,
-            64,
-            GetObjectStreamStrategy::Standard,
-            "test-bucket",
-            "unavailable-object",
-            GetObjectBodyLifecycle::disabled(),
-            None,
-        )
-        .await;
-
-        let error = result.expect_err("a read quorum failure before the first byte must reject response construction");
-        assert_eq!(error.code(), &S3ErrorCode::Custom("SlowDownRead".into()));
-        assert_eq!(error.status_code(), Some(StatusCode::SERVICE_UNAVAILABLE));
-        assert_eq!(error.message(), Some("Resource requested is unreadable, please reduce your request rate"));
-    }
-
-    #[tokio::test]
-    async fn build_reader_blob_preserves_primed_byte_for_full_and_range() {
-        for (request_id, content_range) in [("req-preheader-full", None), ("req-preheader-range", Some("bytes 10-14/100"))] {
-            let reads = Arc::new(AtomicUsize::new(0));
-            let mut body = DefaultObjectUsecase::build_reader_blob(
-                DataProbeReader {
-                    reads: Arc::clone(&reads),
-                    data: std::io::Cursor::new(b"hello".to_vec()),
-                },
-                5,
-                request_id,
-                content_range,
-                64,
-                GetObjectStreamStrategy::Standard,
-                "test-bucket",
-                "test-object",
-                GetObjectBodyLifecycle::disabled(),
-                None,
-            )
-            .await
-            .expect("the first byte should be available before response handoff");
-
-            assert_eq!(reads.load(AtomicOrdering::Relaxed), 1, "response construction must prime one byte");
-            let mut received = Vec::new();
-            while let Some(chunk) = body.next().await {
-                received.extend_from_slice(&chunk.expect("the primed body should remain readable"));
-            }
-            assert_eq!(received, b"hello", "the primed byte must be delivered exactly once");
-        }
-    }
-
-    #[tokio::test]
-    async fn build_reader_blob_does_not_poll_empty_object() {
-        let reads = Arc::new(AtomicUsize::new(0));
-        let mut body = DefaultObjectUsecase::build_reader_blob(
-            ReadProbeReader {
-                reads: Arc::clone(&reads),
-            },
-            0,
-            "req-empty-object",
-            None,
-            64,
-            GetObjectStreamStrategy::Standard,
-            "test-bucket",
-            "empty-object",
-            GetObjectBodyLifecycle::disabled(),
-            None,
-        )
-        .await
-        .expect("an empty response should not require a storage read");
-
-        assert_eq!(reads.load(AtomicOrdering::Relaxed), 0);
-        assert!(body.next().await.is_none());
-        assert_eq!(reads.load(AtomicOrdering::Relaxed), 0);
-    }
-
-    #[tokio::test]
-    async fn build_reader_blob_leaves_later_failure_in_body_stream() {
-        let mut body = DefaultObjectUsecase::build_reader_blob(
-            FailAtEndReader::new(b"h", Some(std::io::Error::other("failure after handoff"))),
-            5,
-            "req-postheader-failure",
-            None,
-            64,
-            GetObjectStreamStrategy::Standard,
-            "test-bucket",
-            "later-failure-object",
-            GetObjectBodyLifecycle::disabled(),
-            None,
-        )
-        .await
-        .expect("the available first byte should allow response handoff");
-
-        let first = body
-            .next()
-            .await
-            .expect("the primed byte must be present")
-            .expect("the primed byte must be successful");
-        assert_eq!(first, Bytes::from_static(b"h"));
-        let error = body
-            .next()
-            .await
-            .expect("the later read must produce a body result")
-            .expect_err("a failure after the first byte must stay in the body stream");
-        assert!(error.to_string().contains("failure after handoff"));
-    }
-
-    #[tokio::test]
-    async fn build_reader_blob_resume_offset_includes_primed_byte() {
-        let reopen_count = Arc::new(AtomicUsize::new(0));
-        let control = counting_resume_control(Arc::clone(&reopen_count), |emitted| {
-            assert_eq!(emitted, 1, "resume must start after the byte consumed before response handoff");
-            Ok(FailAtEndReader::new(b"ello", None))
-        });
-        let mut body = DefaultObjectUsecase::build_reader_blob(
-            FailAtEndReader::new(b"h", Some(relocation_read_error())),
-            5,
-            "req-preheader-resume-offset",
-            None,
-            64,
-            GetObjectStreamStrategy::Standard,
-            "test-bucket",
-            "relocated-object",
-            GetObjectBodyLifecycle::disabled(),
-            Some(control),
-        )
-        .await
-        .expect("the first byte should permit response handoff before relocation");
-
-        let mut received = Vec::new();
-        while let Some(chunk) = body.next().await {
-            received.extend_from_slice(&chunk.expect("resume should complete the body"));
-        }
-        assert_eq!(received, b"hello");
-        assert_eq!(reopen_count.load(Ordering::Relaxed), 1);
-    }
-
     #[tokio::test]
     async fn get_object_streaming_reader_resumes_after_relocation_error() {
         use tokio::io::AsyncReadExt;
@@ -9204,7 +9041,7 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn build_get_object_body_primes_large_stream_before_handoff() {
+    async fn build_get_object_body_keeps_large_objects_on_streaming_path_without_preread() {
         let reads = Arc::new(AtomicUsize::new(0));
         let reader = ReadProbeReader {
             reads: Arc::clone(&reads),
@@ -9237,13 +9074,13 @@ mod tests {
 
         assert_eq!(
             reads.load(AtomicOrdering::Relaxed),
-            1,
-            "large-object response construction should prime exactly one byte"
+            0,
+            "large-object response construction should not pre-read object data"
         );
     }
 
     #[tokio::test]
-    async fn build_get_object_body_primes_large_encrypted_stream_before_handoff() {
+    async fn build_get_object_body_keeps_large_encrypted_objects_on_streaming_path_without_preread() {
         let reads = Arc::new(AtomicUsize::new(0));
         let reader = ReadProbeReader {
             reads: Arc::clone(&reads),
@@ -9276,8 +9113,8 @@ mod tests {
 
         assert_eq!(
             reads.load(AtomicOrdering::Relaxed),
-            1,
-            "large encrypted object response construction should prime exactly one byte"
+            0,
+            "large encrypted object response construction should not pre-read object data"
         );
     }
 
@@ -9447,8 +9284,8 @@ mod tests {
         assert_eq!(fill, rustfs_object_data_cache::ObjectDataCacheFillResult::SkippedSizeMismatch);
         assert_eq!(
             reads.load(AtomicOrdering::Relaxed),
-            1,
-            "size-mismatched rejected fill should prime the fallback stream before handoff"
+            0,
+            "size-mismatched rejected fill should construct the fallback stream without pre-reading"
         );
         assert!(
             matches!(lookup_after_mismatch, rustfs_object_data_cache::ObjectDataCacheLookup::Miss),
@@ -10156,8 +9993,8 @@ mod tests {
 
         assert_eq!(
             reads.load(AtomicOrdering::Relaxed),
-            1,
-            "too-large materialize-fill candidate must prime the streaming fallback"
+            0,
+            "too-large materialize-fill candidate must not pre-read the fallback reader"
         );
     }
 
@@ -10195,8 +10032,8 @@ mod tests {
 
         assert_eq!(
             reads.load(AtomicOrdering::Relaxed),
-            1,
-            "default GetObject response construction should prime exactly one byte"
+            0,
+            "default GetObject response construction should not pre-read small plain object data"
         );
     }
 

rustfs/src/error.rs

@@ -20,8 +20,6 @@ use s3s::{S3Error, S3ErrorCode};
 
 const MAX_VERSIONS_EXCEEDED_CODE: &str = "MaxVersionsExceeded";
 const MAX_VERSIONS_EXCEEDED_MESSAGE: &str = "You've exceeded the limit on the number of versions you can create on this object";
-const SLOW_DOWN_READ_CODE: &str = "SlowDownRead";
-const SLOW_DOWN_READ_MESSAGE: &str = "Resource requested is unreadable, please reduce your request rate";
 
 /// S3 error code for a request that names a KMS key the KMS does not hold.
 pub const KMS_KEY_NOT_FOUND_ERROR_CODE: &str = "KMS.NotFoundException";
@@ -107,7 +105,6 @@ fn custom_error_status(code: &S3ErrorCode) -> Option<StatusCode> {
         S3ErrorCode::Custom(custom) if &**custom == KMS_KEY_NOT_FOUND_ERROR_CODE || &**custom == MAX_VERSIONS_EXCEEDED_CODE => {
             Some(StatusCode::BAD_REQUEST)
         }
-        S3ErrorCode::Custom(custom) if &**custom == SLOW_DOWN_READ_CODE => Some(StatusCode::SERVICE_UNAVAILABLE),
         _ => None,
     }
 }
@@ -406,7 +403,6 @@ impl ApiError {
             S3ErrorCode::Custom(code) if &**code == MAX_VERSIONS_EXCEEDED_CODE => {
                 MAX_VERSIONS_EXCEEDED_MESSAGE.to_string()
             }
-            S3ErrorCode::Custom(code) if &**code == SLOW_DOWN_READ_CODE => SLOW_DOWN_READ_MESSAGE.to_string(),
             _ => code.as_str().to_string(),
         }
     }
@@ -581,10 +577,10 @@ impl From<StorageError> for ApiError {
             | StorageError::FaultyRemoteDisk
             | StorageError::DiskNotFound
             | StorageError::TooManyOpenFiles => S3ErrorCode::ServiceUnavailable,
-            StorageError::ErasureReadQuorum | StorageError::InsufficientReadQuorum(_, _) => {
-                S3ErrorCode::Custom(SLOW_DOWN_READ_CODE.into())
-            }
-            StorageError::ErasureWriteQuorum | StorageError::InsufficientWriteQuorum(_, _) => S3ErrorCode::ServiceUnavailable,
+            StorageError::ErasureReadQuorum
+            | StorageError::InsufficientReadQuorum(_, _)
+            | StorageError::ErasureWriteQuorum
+            | StorageError::InsufficientWriteQuorum(_, _) => S3ErrorCode::ServiceUnavailable,
             StorageError::NamespaceLockQuorumUnavailable { .. } => S3ErrorCode::ServiceUnavailable,
             StorageError::QuotaExceeded { .. } => S3ErrorCode::InvalidRequest,
             StorageError::MaxVersionsExceeded => S3ErrorCode::Custom(MAX_VERSIONS_EXCEEDED_CODE.into()),
@@ -1292,10 +1288,10 @@ mod tests {
             (StorageError::FaultyRemoteDisk, S3ErrorCode::ServiceUnavailable),
             (StorageError::DiskNotFound, S3ErrorCode::ServiceUnavailable),
             (StorageError::TooManyOpenFiles, S3ErrorCode::ServiceUnavailable),
-            (StorageError::ErasureReadQuorum, S3ErrorCode::Custom(SLOW_DOWN_READ_CODE.into())),
+            (StorageError::ErasureReadQuorum, S3ErrorCode::ServiceUnavailable),
             (
                 StorageError::InsufficientReadQuorum("test".into(), "test".into()),
-                S3ErrorCode::Custom(SLOW_DOWN_READ_CODE.into()),
+                S3ErrorCode::ServiceUnavailable,
             ),
             (StorageError::ErasureWriteQuorum, S3ErrorCode::ServiceUnavailable),
             (
@@ -1433,21 +1429,6 @@ mod tests {
         assert_eq!(s3_error.status_code(), Some(http::StatusCode::SERVICE_UNAVAILABLE));
     }
 
-    #[test]
-    fn read_quorum_failure_matches_minio_slow_down_read_response() {
-        for error in [
-            StorageError::ErasureReadQuorum,
-            StorageError::InsufficientReadQuorum("bucket".into(), "object".into()),
-        ] {
-            let api_error = ApiError::from(error);
-            assert_eq!(api_error.code, S3ErrorCode::Custom(SLOW_DOWN_READ_CODE.into()));
-            assert_eq!(api_error.message, SLOW_DOWN_READ_MESSAGE);
-
-            let s3_error: S3Error = api_error.into();
-            assert_eq!(s3_error.status_code(), Some(StatusCode::SERVICE_UNAVAILABLE));
-        }
-    }
-
     #[test]
     fn quota_exceeded_preserves_existing_s3_error_contract() {
         let api_error: ApiError = StorageError::QuotaExceeded { current: 5, limit: 10 }.into();