| /* |
| * 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. |
| */ |
| package org.apache.cassandra.service.reads; |
| |
| import org.apache.cassandra.exceptions.ConfigurationException; |
| import org.apache.cassandra.metrics.SnapshottingTimer; |
| import org.apache.cassandra.schema.TableParams; |
| |
| public interface SpeculativeRetryPolicy |
| { |
| public enum Kind |
| { |
| NEVER, FIXED, PERCENTILE, HYBRID, ALWAYS |
| } |
| |
| /** |
| * Calculate the delay in microseconds after which speculation takes place |
| * |
| * @param latency snapshot of coordinator latencies (in microseconds) |
| * @param existingValue existing speculation threshold (in microseconds) |
| * @return speculation delay (in microseconds). |
| */ |
| long calculateThreshold(SnapshottingTimer latency, long existingValue); |
| |
| Kind kind(); |
| |
| public static SpeculativeRetryPolicy fromString(String str) |
| { |
| if (AlwaysSpeculativeRetryPolicy.stringMatches(str)) |
| return AlwaysSpeculativeRetryPolicy.INSTANCE; |
| |
| if (NeverSpeculativeRetryPolicy.stringMatches(str)) |
| return NeverSpeculativeRetryPolicy.INSTANCE; |
| |
| if (PercentileSpeculativeRetryPolicy.stringMatches(str)) |
| return PercentileSpeculativeRetryPolicy.fromString(str); |
| |
| if (FixedSpeculativeRetryPolicy.stringMatches(str)) |
| return FixedSpeculativeRetryPolicy.fromString(str); |
| |
| if (HybridSpeculativeRetryPolicy.stringMatches(str)) |
| return HybridSpeculativeRetryPolicy.fromString(str); |
| |
| throw new ConfigurationException(String.format("Invalid value %s for option '%s'", str, TableParams.Option.SPECULATIVE_RETRY)); |
| } |
| } |