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kavehahmadi60meta-codesync[bot]
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Add EdenFS mount health check helper
Summary: Add a standalone helper that checks running EdenFS mounts against the kernel mount table and .eden access. Return structured daemon mount-health reasons without wiring the helper into periodic daemon emission yet. Reviewed By: muirdm Differential Revision: D108200400 fbshipit-source-id: bce81388d37ddcd2a54783c674c1495efa973d75
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‎eden/fs/utils/BUCK‎

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@@ -335,3 +335,17 @@ cpp_library(
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],
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exported_deps = ["//folly:expected"],
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)
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cpp_library(
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name = "mount_health_check",
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srcs = ["MountHealthCheck.cpp"],
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headers = ["MountHealthCheck.h"],
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deps = [
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":mount_info_table",
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"//eden/common/utils:fsdetect",
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"//folly:string",
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"//folly/logging:logging",
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"//folly/portability:sys_stat",
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"//folly/portability:unistd",
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],
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)

‎eden/fs/utils/MountHealthCheck.cpp‎

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/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2.
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*/
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#include "eden/fs/utils/MountHealthCheck.h"
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#include <atomic>
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#include <cerrno>
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#include <optional>
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#include <string>
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#include <folly/String.h>
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#include <folly/logging/xlog.h>
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#include <folly/portability/SysStat.h>
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#include <folly/portability/Unistd.h>
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#ifdef __linux__
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#include "eden/common/utils/FSDetect.h"
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#include "eden/fs/utils/MountInfoTable.h"
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#endif
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namespace facebook::eden {
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namespace {
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bool isNotConnectedErrno(int err) {
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return err == ENOTCONN || err == ENXIO;
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}
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#ifdef __linux__
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bool isEdenMountInfo(
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const std::string& mountSource,
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const std::string& fsType) {
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return is_edenfs_fs_type(mountSource) || is_edenfs_fs_type(fsType) ||
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fsType == "fuse.edenfs";
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}
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#endif
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std::optional<int> lstatError(const std::string& path) {
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struct stat st{};
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if (lstat(path.c_str(), &st) == 0) {
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return std::nullopt;
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}
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return errno;
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}
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std::optional<EdenMountHealthCheckIssue> issueForPathAccessError(
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const std::string& path,
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int err) {
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if (isNotConnectedErrno(err)) {
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return EdenMountHealthCheckIssue{
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EdenMountHealthIssueReason::DaemonRunningMountNotConnected,
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path + ": " + folly::errnoStr(err)};
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}
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if (err == ETIMEDOUT) {
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return EdenMountHealthCheckIssue{
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EdenMountHealthIssueReason::DaemonRunningMountTimedOut,
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path + ": " + folly::errnoStr(err)};
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}
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XLOGF(
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WARN,
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"Unexpected EdenFS mount health check lstat error for {}: {}",
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path,
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folly::errnoStr(err));
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return EdenMountHealthCheckIssue{
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EdenMountHealthIssueReason::DaemonRunningMountAccessError,
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path + ": " + folly::errnoStr(err)};
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}
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std::optional<bool> hasEdenMountInKernelMountTable(
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const std::string& mountPath) {
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#ifdef __linux__
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MountInfoOptions options;
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options.includeMountSource = true;
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auto result = getMountInfoForPath(mountPath.c_str(), options);
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if (result.hasError()) {
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XLOGF(
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WARN,
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"Failed to read kernel mount table for {}: {}",
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mountPath,
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folly::errnoStr(result.error()));
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// The mount table check is inconclusive. Continue with the .eden probes
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// instead of reporting a mount-health issue from the failed lookup itself.
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return std::nullopt;
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}
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const auto& mountInfo = result.value();
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if (!mountInfo.has_value()) {
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return false;
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}
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return isEdenMountInfo(mountInfo->mountSource, mountInfo->fsType);
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#else
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(void)mountPath;
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return true;
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#endif
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}
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std::string makeExpectedMissingPath(const std::string& mountPath) {
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// Use a fresh negative lookup path each time so kernel/FUSE negative-entry
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// caching does not hide whether EdenFS can answer a lookup now.
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static std::atomic<uint64_t> nextHealthCheckPathId{0};
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auto id = nextHealthCheckPathId.fetch_add(1, std::memory_order_relaxed);
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return mountPath + "/.eden/edenfs-mount-health-" + std::to_string(id);
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}
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} // namespace
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std::string_view edenMountHealthIssueReasonString(
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EdenMountHealthIssueReason reason) {
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switch (reason) {
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case EdenMountHealthIssueReason::DaemonRunningKernelMountMissing:
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return "daemon_running_kernel_mount_missing";
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case EdenMountHealthIssueReason::DaemonRunningDotEdenMissing:
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return "daemon_running_dot_eden_missing";
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case EdenMountHealthIssueReason::DaemonRunningMountNotConnected:
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return "daemon_running_mount_not_connected";
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case EdenMountHealthIssueReason::DaemonRunningMountTimedOut:
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return "daemon_running_mount_timed_out";
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case EdenMountHealthIssueReason::DaemonRunningMountAccessError:
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return "daemon_running_mount_access_error";
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}
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return "unknown";
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}
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std::optional<EdenMountHealthCheckIssue> checkRunningEdenMountHealth(
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const std::string& mountPath) {
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auto hasKernelMount = hasEdenMountInKernelMountTable(mountPath);
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if (hasKernelMount.has_value() && !hasKernelMount.value()) {
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return EdenMountHealthCheckIssue{
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EdenMountHealthIssueReason::DaemonRunningKernelMountMissing,
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"EdenFS mount is missing from the kernel mount table"};
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}
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// If the mount table lookup failed, keep going. The path probes below can
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// still identify a disconnected, missing, or hanging Eden mount.
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auto dotEdenPath = mountPath + "/.eden";
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auto dotEdenError = lstatError(dotEdenPath);
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if (dotEdenError.has_value()) {
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auto err = dotEdenError.value();
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if (err == ENOENT) {
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return EdenMountHealthCheckIssue{
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EdenMountHealthIssueReason::DaemonRunningDotEdenMissing,
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dotEdenPath + ": " + folly::errnoStr(err)};
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}
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return issueForPathAccessError(dotEdenPath, err);
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}
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// Since .eden was readable, probe a child path that should not exist. A
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// healthy mount should answer ENOENT; disconnected or hanging mounts can
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// surface as ENOTCONN/ENXIO/ETIMEDOUT.
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auto expectedMissingPath = makeExpectedMissingPath(mountPath);
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auto expectedMissingError = lstatError(expectedMissingPath);
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if (!expectedMissingError.has_value()) {
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// The probe path unexpectedly exists, so this check is inconclusive.
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return std::nullopt;
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}
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auto err = expectedMissingError.value();
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if (err == ENOENT) {
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// The mount handled lookup normally and reported the probe path missing.
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return std::nullopt;
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}
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return issueForPathAccessError(expectedMissingPath, err);
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}
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} // namespace facebook::eden

‎eden/fs/utils/MountHealthCheck.h‎

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/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2.
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*/
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#pragma once
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#include <optional>
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#include <string>
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#include <string_view>
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namespace facebook::eden {
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enum class EdenMountHealthIssueReason {
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DaemonRunningKernelMountMissing,
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DaemonRunningDotEdenMissing,
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DaemonRunningMountNotConnected,
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DaemonRunningMountTimedOut,
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DaemonRunningMountAccessError,
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};
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std::string_view edenMountHealthIssueReasonString(
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EdenMountHealthIssueReason reason);
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struct EdenMountHealthCheckIssue {
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EdenMountHealthIssueReason reason;
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std::string error;
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};
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// Checks a daemon-reported RUNNING mount against the kernel mount table and
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// lightweight .eden path probes. Returns an issue only when the mount is
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// clearly missing, disconnected, timing out, or returning path access errors.
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std::optional<EdenMountHealthCheckIssue> checkRunningEdenMountHealth(
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const std::string& mountPath);
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} // namespace facebook::eden

‎eden/fs/utils/test/BUCK‎

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load("@fbcode_macros//build_defs:cpp_benchmark.bzl", "cpp_benchmark")
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load("@fbcode_macros//build_defs:cpp_unittest.bzl", "cpp_unittest")
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load("@fbsource//tools/build_defs/testinfra:network_access_utils.bzl", "network_access_utils")
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oncall("scm_client_infra")
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],
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)
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cpp_unittest(
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name = "mount_health_check_test",
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srcs = ["MountHealthCheckTest.cpp"],
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network_access = network_access_utils.none(),
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supports_static_listing = False,
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deps = [
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"//eden/fs/utils:mount_health_check",
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"//folly/portability:gtest",
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],
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)
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cpp_benchmark(
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name = "bench",
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srcs = [

‎eden/fs/utils/test/MountHealthCheckTest.cpp‎

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/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This software may be used and distributed according to the terms of the
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* GNU General Public License version 2.
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*/
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#include "eden/fs/utils/MountHealthCheck.h"
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#include <folly/portability/GTest.h>
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namespace facebook::eden {
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namespace {
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#ifdef __linux__
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TEST(MountHealthCheckTest, reportsMissingKernelMountForNonEdenMount) {
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auto issue = checkRunningEdenMountHealth("/");
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ASSERT_TRUE(issue.has_value());
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EXPECT_EQ(
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EdenMountHealthIssueReason::DaemonRunningKernelMountMissing,
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issue->reason);
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}
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#endif
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TEST(MountHealthCheckTest, reasonStringsMatchTelemetryContract) {
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EXPECT_EQ(
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"daemon_running_kernel_mount_missing",
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edenMountHealthIssueReasonString(
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EdenMountHealthIssueReason::DaemonRunningKernelMountMissing));
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EXPECT_EQ(
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"daemon_running_dot_eden_missing",
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edenMountHealthIssueReasonString(
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EdenMountHealthIssueReason::DaemonRunningDotEdenMissing));
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EXPECT_EQ(
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"daemon_running_mount_not_connected",
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edenMountHealthIssueReasonString(
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EdenMountHealthIssueReason::DaemonRunningMountNotConnected));
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EXPECT_EQ(
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"daemon_running_mount_timed_out",
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edenMountHealthIssueReasonString(
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EdenMountHealthIssueReason::DaemonRunningMountTimedOut));
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EXPECT_EQ(
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"daemon_running_mount_access_error",
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edenMountHealthIssueReasonString(
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EdenMountHealthIssueReason::DaemonRunningMountAccessError));
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}
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} // namespace
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} // namespace facebook::eden

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