From 0b934194ba96170b945f28c9ed296e43e6788b8d Mon Sep 17 00:00:00 2001
From: Stefan Larimore <gef@meta.com>
Date: Wed, 15 Jan 2025 19:32:22 -0800
Subject: [PATCH] Introduce conditional XLOGF_EVERY_<>_OR macros

Summary:
Continuing where garrettd in D48244354 left off. My project has a need for this new behavior (see reference to this diff in D67725319).

I decided to "refactor" some comments for the XX_EVERY_N macros to de-dup a bit.

Reviewed By: yfeldblum

Differential Revision: D67739158

fbshipit-source-id: bc94414177de6cf2df4c4e23b7f33bfb43ae8c49
---
 folly/logging/test/XlogTest.cpp | 25 +++++++++++++++++++++++
 folly/logging/xlog.h            | 36 +++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)

diff --git a/folly/logging/test/XlogTest.cpp b/folly/logging/test/XlogTest.cpp
index af308a2809a..7e74d1986dd 100644
--- a/folly/logging/test/XlogTest.cpp
+++ b/folly/logging/test/XlogTest.cpp
@@ -400,6 +400,24 @@ TEST_F(XlogTest, rateLimiting) {
           "msg 0", "msg 8", "msg 16", "msg 24", "msg 32", "msg 40", "msg 48"));
   handler->clearMessages();
 
+  // Test XLOGF_EVERY_N_OR
+  for (size_t n = 0; n < 10; ++n) {
+    bool shouldLog = n % 2 == 0;
+    XLOGF_EVERY_N_OR(DBG1, shouldLog, 2, "msg {}", n);
+  }
+  EXPECT_THAT(
+      handler->getMessageValues(),
+      ElementsAre(
+          "msg 0",
+          "msg 1",
+          "msg 2",
+          "msg 4",
+          "msg 5",
+          "msg 6",
+          "msg 8",
+          "msg 9"));
+  handler->clearMessages();
+
   // Test XLOG_EVERY_N_EXACT
   for (size_t n = 0; n < 50; ++n) {
     XLOG_EVERY_N_EXACT(DBG1, 7, "msg ", n);
@@ -481,6 +499,7 @@ TEST_F(XlogTest, rateLimiting) {
     XLOG_EVERY_MS_IF(DBG1, shouldLog, 100, "int arg conditional ", n);
     XLOGF_EVERY_MS_IF(DBG1, shouldLog, 100, "int fmt arg conditional {}", n);
     XLOG_EVERY_MS_OR(DBG1, shouldLog, 100, "int arg conditional or ", n);
+    XLOGF_EVERY_MS_OR(DBG1, shouldLog, 100, "int fmt arg conditional or {}", n);
 
     // Sleep for 100ms between iterations 5 and 6
     if (n == 5) {
@@ -502,13 +521,16 @@ TEST_F(XlogTest, rateLimiting) {
           "1x ms arg 0",
           "3x s arg 0",
           "int arg conditional or 0",
+          "int fmt arg conditional or 0",
           "2x int arg 1",
           "3x s arg 1",
           "3x s arg 2",
           "int arg conditional 2",
           "int fmt arg conditional 2",
           "int arg conditional or 2",
+          "int fmt arg conditional or 2",
           "int arg conditional or 4",
+          "int fmt arg conditional or 4",
           "int arg 6",
           "ms arg 6",
           "fmt arg 6",
@@ -520,9 +542,12 @@ TEST_F(XlogTest, rateLimiting) {
           "int arg conditional 6",
           "int fmt arg conditional 6",
           "int arg conditional or 6",
+          "int fmt arg conditional or 6",
           "2x int arg 7",
           "int arg conditional or 7",
+          "int fmt arg conditional or 7",
           "int arg conditional or 8",
+          "int fmt arg conditional or 8",
       }));
   handler->clearMessages();
 
diff --git a/folly/logging/xlog.h b/folly/logging/xlog.h
index fdf3b63db15..c4f28d64e44 100644
--- a/folly/logging/xlog.h
+++ b/folly/logging/xlog.h
@@ -205,6 +205,25 @@ static_assert(
 #define XLOGF_EVERY_MS(level, ms, fmt, ...) \
   XLOGF_EVERY_MS_IF(level, true, ms, fmt, ##__VA_ARGS__)
 
+/**
+ * Similar to XLOGF(...) except log a message if the specified condition
+ * predicate evaluates to true or every @param ms milliseconds
+ *
+ * Note that this is threadsafe.
+ */
+#define XLOGF_EVERY_MS_OR(level, cond, ms, fmt, ...)                         \
+  XLOGF_IF(                                                                  \
+      level,                                                                 \
+      (cond) ||                                                              \
+          [__folly_detail_xlog_ms = ms] {                                    \
+            static ::folly::logging::IntervalRateLimiter                     \
+                folly_detail_xlog_limiter(                                   \
+                    1, ::std::chrono::milliseconds(__folly_detail_xlog_ms)); \
+            return folly_detail_xlog_limiter.check();                        \
+          }(),                                                               \
+      fmt,                                                                   \
+      ##__VA_ARGS__)
+
 namespace folly {
 namespace detail {
 
@@ -305,6 +324,23 @@ FOLLY_EXPORT FOLLY_ALWAYS_INLINE bool xlogEveryNImpl(size_t n) {
       fmt,                                                                    \
       ##__VA_ARGS__)
 
+/**
+ * Similar to XLOGF(...) except it logs a message if the condition predicate
+ * evalutes to true or approximately every @param n invocations
+ *
+ * See concurrency discussion for XLOG_EVERY_N which applies here as well.
+ */
+#define XLOGF_EVERY_N_OR(level, cond, n, fmt, ...)                            \
+  XLOGF_IF(                                                                   \
+      level,                                                                  \
+      (cond) ||                                                               \
+          [&] {                                                               \
+            struct folly_detail_xlog_tag {};                                  \
+            return ::folly::detail::xlogEveryNImpl<folly_detail_xlog_tag>(n); \
+          }(),                                                                \
+      fmt,                                                                    \
+      ##__VA_ARGS__)
+
 namespace folly {
 namespace detail {