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diff --git a/cpp/src/qpid/cluster/WriteEstimate.h b/cpp/src/qpid/cluster/WriteEstimate.h
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+++ b/cpp/src/qpid/cluster/WriteEstimate.h
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+#ifndef QPID_CLUSTER_WRITEESTIMATE_H
+#define QPID_CLUSTER_WRITEESTIMATE_H
+
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * 
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+
+#include "qpid/sys/Mutex.h"
+
+namespace qpid {
+namespace cluster {
+
+/**
+ * Estimate the amount of data that a connection can write between sending
+ * a doOutput notice and re-receiving it.
+ *
+ * The goal is to avoid ever write-idling the connection by sending
+ * the next doOutput request as soon as we've processed the previous
+ * one, such that data generated by the previous request will keep the
+ * writer busy till the next one is delivered.
+ *
+ */
+class WriteEstimate
+{
+  public:
+    WriteEstimate(size_t initial=4096);
+
+    /** About to send a doOutput request.
+     * Update estimation state and return size for next request.
+     */
+    size_t sending(size_t buffered);
+
+    /**
+     * doOutput request just delivered, not yet executed. Update the estimate.
+     * and estimate how much data to request in the next onOutput
+     * request. 0 means don't send an onOutput request.
+     */
+    void delivered(size_t sent, size_t buffered);
+
+  private:
+    bool growing;
+    size_t estimate;
+};
+
+}} // namespace qpid::cluster
+
+#endif  /*!QPID_CLUSTER_WRITEESTIMATE_H*/