From 2b076c4b17e735b37bdeb65351fededcc54d07ed Mon Sep 17 00:00:00 2001
From: Jun Wu <quark@fb.com>
Date: Fri, 20 Sep 2019 17:43:59 -0700
Subject: [PATCH] blackbox: preserve session_id when replacing singleton

Summary:
The current API replaces `session_id` when the global blackbox switched
from in-memory to on-disk. It should preserve the session id.

Reviewed By: singhsrb

Differential Revision: D17429691

fbshipit-source-id: d37811c3d7622c4f86615c41bce40f4e479eabd2
---
 lib/blackbox/src/blackbox.rs  | 2 +-
 lib/blackbox/src/singleton.rs | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/blackbox/src/blackbox.rs b/lib/blackbox/src/blackbox.rs
index d8d028281e..031fed63ce 100644
--- a/lib/blackbox/src/blackbox.rs
+++ b/lib/blackbox/src/blackbox.rs
@@ -26,7 +26,7 @@ pub struct Blackbox {
     opts: BlackboxOptions,
 
     // An ID that can be "grouped by" to figure everything about a session.
-    session_id: u64,
+    pub(crate) session_id: u64,
 
     // The on-disk files are considered bad (ex. no permissions, or no disk space)
     // and further write attempts will be ignored.
diff --git a/lib/blackbox/src/singleton.rs b/lib/blackbox/src/singleton.rs
index 7fbdebe776..fe31a55392 100644
--- a/lib/blackbox/src/singleton.rs
+++ b/lib/blackbox/src/singleton.rs
@@ -20,6 +20,8 @@ lazy_static! {
 
 /// Replace the global [`Blackbox`] instance.
 ///
+/// The session ID of the old blackbox will be reused.
+///
 /// If [`log`] was called, their side effects will be re-applied to the
 /// specified blackbox.
 pub fn init(mut blackbox: Blackbox) {
@@ -34,6 +36,7 @@ pub fn init(mut blackbox: Blackbox) {
             }
         }
     }
+    blackbox.session_id = old_blackbox.session_id;
 
     *singleton.deref_mut() = blackbox;
 }