Merge "Add experiment flag for DNS query global limiter" am: 7299cab99f am: a3e650899e

Original change: https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/2071247

Change-Id: I22b771876ed17d2bc307b5a90f19e3876ec6e6af
Ignore-AOSP-First: this is an automerge
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>

2 files changed, 13 insertions, 7 deletions

diff --git a/Experiments.h b/Experiments.h
index 2511012e..209a208e 100644
--- a/Experiments.h
+++ b/Experiments.h
@@ -68,6 +68,7 @@ class Experiments {
             "doh_idle_timeout_ms",
             "doh_session_resumption",
             "mdns_resolution",
+            "max_queries_global",
     };
     // This value is used in updateInternal as the default value if any flags can't be found.
     static constexpr int kFlagIntDefault = INT_MIN;
diff --git a/OperationLimiter.h b/OperationLimiter.h
index 1fa1bf23..332157a7 100644
--- a/OperationLimiter.h
+++ b/OperationLimiter.h
@@ -23,6 +23,8 @@
 #include <android-base/logging.h>
 #include <android-base/thread_annotations.h>
 
+#include "Experiments.h"
+
 namespace android {
 namespace netdutils {
 
@@ -43,8 +45,7 @@ namespace netdutils {
 template <typename KeyType>
 class OperationLimiter {
   public:
-    OperationLimiter(int limitPerKey, int globalLimit = INT_MAX)
-        : mLimitPerKey(limitPerKey), mGlobalLimit(globalLimit) {}
+    OperationLimiter(int limitPerKey) : mLimitPerKey(limitPerKey) {}
 
     ~OperationLimiter() {
         DCHECK(mCounters.empty()) << "Destroying OperationLimiter with active operations";
@@ -57,15 +58,22 @@ class OperationLimiter {
     // finish(key).
     bool start(KeyType key) EXCLUDES(mMutex) {
         std::lock_guard lock(mMutex);
-
-        if (mGlobalCounter >= mGlobalLimit) {
+        int globalLimit =
+                android::net::Experiments::getInstance()->getFlag("max_queries_global", INT_MAX);
+        if (globalLimit < mLimitPerKey) {
+            LOG(ERROR) << "Misconfiguration on max_queries_global " << globalLimit;
+            globalLimit = INT_MAX;
+        }
+        if (mGlobalCounter >= globalLimit) {
             // Oh, no!
+            LOG(ERROR) << "Query from " << key << " denied due to global limit: " << globalLimit;
             return false;
         }
 
         auto& cnt = mCounters[key];  // operator[] creates new entries as needed.
         if (cnt >= mLimitPerKey) {
             // Oh, no!
+            LOG(ERROR) << "Query from " << key << " denied due to limit: " << mLimitPerKey;
             return false;
         }
 
@@ -109,9 +117,6 @@ class OperationLimiter {
 
     // Maximum number of outstanding queries from a single key.
     const int mLimitPerKey;
-
-    // Maximum number of outstanding queries, globally.
-    const int mGlobalLimit;
 };
 
 }  // namespace netdutils