Remove backpressure debug warning

In cases where backpressure signals are being pathologically
ignored, the additional warning becomes too spammy to be useful.
Given that it's often out of the users control (as in the case
of a worker using next.js which suffers from this), the warning
becomes unhelpful additional noise. Just remove it.

Author: jasnell

src/workerd/api/streams/internal.c++

@@ -980,29 +980,6 @@ void WritableStreamInternalController::increaseCurrentWriteBufferSize(
   KJ_IF_SOME(highWaterMark, maybeHighWaterMark) {
     int64_t amount = highWaterMark - currentWriteBufferSize;
     updateBackpressure(js, amount <= 0);
-    // If the current buffer size is greater than or equal to double the high water mark,
-    // let's emit a warning about excessive backpressure.
-    // TODO(later): For the standard stream, we use a variable multiplier if the highWaterMark
-    // is < 10 because the default high water mark is 1 and we don't want to emit the warning
-    // too often. For internal streams, tho, there is no default high water mark and the user
-    // would have to provide one... and since these are always bytes it would make sense
-    // for the user to specify a larger value here in the typical case... so I decided to go with
-    // the fixed 2x multiplier. However, I can make this variable too if folks feel the consistency
-    // is important.
-    if (warnAboutExcessiveBackpressure && (currentWriteBufferSize >= 2 * highWaterMark)) {
-      excessiveBackpressureWarningCount++;
-      auto warning = kj::str("A WritableStream is experiencing excessive backpressure. "
-                             "The current write buffer size is ",
-          currentWriteBufferSize,
-          " bytes, which is greater than or equal to double the high water mark "
-          "of ",
-          highWaterMark,
-          " bytes. Streams that consistently exceed the "
-          "configured high water mark may cause excessive memory usage. ",
-          "(Count ", excessiveBackpressureWarningCount, ")");
-      js.logWarning(warning);
-      warnAboutExcessiveBackpressure = false;
-    }
   }
 }
 
@@ -1028,7 +1005,6 @@ void WritableStreamInternalController::updateBackpressure(jsg::Lock& js, bool ba
     }
 
     // When backpressure is updated and is false, we resolve the ready promise on the writer
-    warnAboutExcessiveBackpressure = true;
     maybeResolvePromise(js, writerLock.getReadyFulfiller());
   }
 }

src/workerd/api/streams/internal.h

@@ -276,8 +276,6 @@ class WritableStreamInternalController: public WritableStreamController {
   kj::Maybe<kj::Own<PendingAbort>> maybePendingAbort;
 
   uint64_t currentWriteBufferSize = 0;
-  bool warnAboutExcessiveBackpressure = true;
-  size_t excessiveBackpressureWarningCount = 0;
 
   // The highWaterMark is the total amount of data currently buffered in
   // the controller waiting to be flushed out to the underlying WritableStreamSink.

src/workerd/api/streams/standard.c++

@@ -1492,30 +1492,6 @@ void WritableImpl<Self>::updateBackpressure(jsg::Lock& js) {
   KJ_ASSERT(!isCloseQueuedOrInFlight());
   bool bp = getDesiredSize() < 0;
 
-  // We use a variable multiplier here in order to prevent the warning from being too
-  // spammy in the default case. The default high water mark for a standard writable stream
-  // is 1, which means we'd end up emitting a warning every time the buffer size is greater
-  // than 2, which is not very helpful. Instead, for any highWaterMark < 10, we'll configure
-  // a multiplier of 10, and for any highWaterMark >= 10, we'll configure a multiplier of 2.
-  // This is fairly arbitrary and may need to be tuned further.
-  int warningMultiplier = highWaterMark <= 10 ? 10 : 2;
-
-  if (flags.warnAboutExcessiveBackpressure &&
-      (amountBuffered >= warningMultiplier * highWaterMark)) {
-    excessiveBackpressureWarningCount++;
-    auto warning = kj::str("A WritableStream is experiencing excessive backpressure. "
-                           "The current write buffer size is ",
-        amountBuffered, ", which is greater than or equal to ", warningMultiplier,
-        " times the high water mark of ", highWaterMark,
-        ". Streams that consistently exceed the configured high water ",
-        "mark may cause excessive memory usage. ", "(Count ", excessiveBackpressureWarningCount,
-        ")");
-    js.logWarning(warning);
-    flags.warnAboutExcessiveBackpressure = false;
-  }
-
-  if (!bp) flags.warnAboutExcessiveBackpressure = true;
-
   if (bp != flags.backpressure) {
     flags.backpressure = bp;
     KJ_IF_SOME(owner, tryGetOwner()) {

src/workerd/api/streams/standard.h

@@ -374,7 +374,6 @@ class WritableImpl {
 
   size_t highWaterMark = 1;
   size_t amountBuffered = 0;
-  size_t excessiveBackpressureWarningCount = 0;
 
   // `writeRequests` is often going to be empty in common usage patterns, in which case std::list
   // is more memory efficient than a std::deque, for example.
@@ -389,7 +388,6 @@ class WritableImpl {
     uint8_t started : 1 = 0;
     uint8_t starting : 1 = 0;
     uint8_t backpressure : 1 = 0;
-    uint8_t warnAboutExcessiveBackpressure : 1 = 1;
   };
   Flags flags{};