From 318fe6941a95397d4e7243132319f3519f14c78a Mon Sep 17 00:00:00 2001
From: Peter Dillinger <peterd@fb.com>
Date: Tue, 24 Aug 2021 17:45:01 -0700
Subject: [PATCH] Add port::GetProcessID() (#8693)

Summary:
Useful in some places for object uniqueness across processes.
Currently used for generating a host-wide identifier of Cache objects
but expected to be used soon in some unique id generation code.

`int64_t` is chosen for return type because POSIX uses signed integer type,
usually `int`, for `pid_t` and Windows uses `DWORD`, which is `uint32_t`.

Future work: avoid copy-pasted declarations in port_*.h, perhaps with
port_common.h always included from port.h

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8693

Test Plan: manual for now

Reviewed By: ajkr, anand1976

Differential Revision: D30492876

Pulled By: pdillinger

fbshipit-source-id: 39fc2788623cc9f4787866bdb67a4d183dde7eef
---
 db/internal_stats.cc | 4 +++-
 port/port_posix.cc   | 2 ++
 port/port_posix.h    | 2 ++
 port/win/port_win.cc | 2 ++
 port/win/port_win.h  | 2 ++
 5 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/db/internal_stats.cc b/db/internal_stats.cc
index a91883975..abe4b6607 100644
--- a/db/internal_stats.cc
+++ b/db/internal_stats.cc
@@ -23,6 +23,7 @@
 #include "cache/cache_entry_stats.h"
 #include "db/column_family.h"
 #include "db/db_impl/db_impl.h"
+#include "port/port.h"
 #include "rocksdb/system_clock.h"
 #include "rocksdb/table.h"
 #include "table/block_based/cachable_entry.h"
@@ -602,7 +603,8 @@ void InternalStats::CacheEntryRoleStats::BeginCollection(
   ++collection_count;
   role_map_ = CopyCacheDeleterRoleMap();
   std::ostringstream str;
-  str << cache->Name() << "@" << static_cast<void*>(cache);
+  str << cache->Name() << "@" << static_cast<void*>(cache) << "#"
+      << port::GetProcessID();
   cache_id = str.str();
   cache_capacity = cache->GetCapacity();
 }
diff --git a/port/port_posix.cc b/port/port_posix.cc
index 112984de2..57f19e33d 100644
--- a/port/port_posix.cc
+++ b/port/port_posix.cc
@@ -263,6 +263,8 @@ void SetCpuPriority(ThreadId id, CpuPriority priority) {
 #endif
 }
 
+int64_t GetProcessID() { return getpid(); }
+
 }  // namespace port
 }  // namespace ROCKSDB_NAMESPACE
 
diff --git a/port/port_posix.h b/port/port_posix.h
index 90f131e13..fa23f9c33 100644
--- a/port/port_posix.h
+++ b/port/port_posix.h
@@ -219,5 +219,7 @@ using ThreadId = pid_t;
 
 extern void SetCpuPriority(ThreadId id, CpuPriority priority);
 
+int64_t GetProcessID();
+
 } // namespace port
 }  // namespace ROCKSDB_NAMESPACE
diff --git a/port/win/port_win.cc b/port/win/port_win.cc
index bd7b55f42..b28a44895 100644
--- a/port/win/port_win.cc
+++ b/port/win/port_win.cc
@@ -277,6 +277,8 @@ void SetCpuPriority(ThreadId id, CpuPriority priority) {
   (void)priority;
 }
 
+int64_t GetProcessID() { return GetCurrentProcessId(); }
+
 }  // namespace port
 }  // namespace ROCKSDB_NAMESPACE
 
diff --git a/port/win/port_win.h b/port/win/port_win.h
index a6a6de278..7de9b61c5 100644
--- a/port/win/port_win.h
+++ b/port/win/port_win.h
@@ -347,6 +347,8 @@ using ThreadId = int;
 
 extern void SetCpuPriority(ThreadId id, CpuPriority priority);
 
+int64_t GetProcessID();
+
 }  // namespace port