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| <pre><span class="sourceLineNo">001</span>/*<a name="line.1"></a> |
| <span class="sourceLineNo">002</span> * Licensed to the Apache Software Foundation (ASF) under one<a name="line.2"></a> |
| <span class="sourceLineNo">003</span> * or more contributor license agreements. See the NOTICE file<a name="line.3"></a> |
| <span class="sourceLineNo">004</span> * distributed with this work for additional information<a name="line.4"></a> |
| <span class="sourceLineNo">005</span> * regarding copyright ownership. The ASF licenses this file<a name="line.5"></a> |
| <span class="sourceLineNo">006</span> * to you under the Apache License, Version 2.0 (the<a name="line.6"></a> |
| <span class="sourceLineNo">007</span> * "License"); you may not use this file except in compliance<a name="line.7"></a> |
| <span class="sourceLineNo">008</span> * with the License. You may obtain a copy of the License at<a name="line.8"></a> |
| <span class="sourceLineNo">009</span> *<a name="line.9"></a> |
| <span class="sourceLineNo">010</span> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.10"></a> |
| <span class="sourceLineNo">011</span> *<a name="line.11"></a> |
| <span class="sourceLineNo">012</span> * Unless required by applicable law or agreed to in writing, software<a name="line.12"></a> |
| <span class="sourceLineNo">013</span> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.13"></a> |
| <span class="sourceLineNo">014</span> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.14"></a> |
| <span class="sourceLineNo">015</span> * See the License for the specific language governing permissions and<a name="line.15"></a> |
| <span class="sourceLineNo">016</span> * limitations under the License.<a name="line.16"></a> |
| <span class="sourceLineNo">017</span> */<a name="line.17"></a> |
| <span class="sourceLineNo">018</span>package org.apache.hadoop.hbase.wal;<a name="line.18"></a> |
| <span class="sourceLineNo">019</span><a name="line.19"></a> |
| <span class="sourceLineNo">020</span>import java.io.Closeable;<a name="line.20"></a> |
| <span class="sourceLineNo">021</span>import java.io.IOException;<a name="line.21"></a> |
| <span class="sourceLineNo">022</span>import org.apache.hadoop.hbase.wal.WAL.Entry;<a name="line.22"></a> |
| <span class="sourceLineNo">023</span>import org.apache.yetus.audience.InterfaceAudience;<a name="line.23"></a> |
| <span class="sourceLineNo">024</span><a name="line.24"></a> |
| <span class="sourceLineNo">025</span>/**<a name="line.25"></a> |
| <span class="sourceLineNo">026</span> * A WAL reader which is designed for be able to tailing the WAL file which is currently being<a name="line.26"></a> |
| <span class="sourceLineNo">027</span> * written. It adds support<a name="line.27"></a> |
| <span class="sourceLineNo">028</span> */<a name="line.28"></a> |
| <span class="sourceLineNo">029</span>@InterfaceAudience.Private<a name="line.29"></a> |
| <span class="sourceLineNo">030</span>public interface WALTailingReader extends Closeable {<a name="line.30"></a> |
| <span class="sourceLineNo">031</span><a name="line.31"></a> |
| <span class="sourceLineNo">032</span> enum State {<a name="line.32"></a> |
| <span class="sourceLineNo">033</span> /** This means we read an Entry without any error */<a name="line.33"></a> |
| <span class="sourceLineNo">034</span> NORMAL,<a name="line.34"></a> |
| <span class="sourceLineNo">035</span> /**<a name="line.35"></a> |
| <span class="sourceLineNo">036</span> * This means the WAL file has a trailer and we have reached it, which means we have finished<a name="line.36"></a> |
| <span class="sourceLineNo">037</span> * reading this file normally<a name="line.37"></a> |
| <span class="sourceLineNo">038</span> */<a name="line.38"></a> |
| <span class="sourceLineNo">039</span> EOF_WITH_TRAILER,<a name="line.39"></a> |
| <span class="sourceLineNo">040</span> /**<a name="line.40"></a> |
| <span class="sourceLineNo">041</span> * This means we meet an error so the upper layer need to reset to read again<a name="line.41"></a> |
| <span class="sourceLineNo">042</span> */<a name="line.42"></a> |
| <span class="sourceLineNo">043</span> ERROR_AND_RESET,<a name="line.43"></a> |
| <span class="sourceLineNo">044</span> /**<a name="line.44"></a> |
| <span class="sourceLineNo">045</span> * Mostly the same with the above {@link #ERROR_AND_RESET}, the difference is that here we also<a name="line.45"></a> |
| <span class="sourceLineNo">046</span> * mess up the compression dictionary when reading data, so the upper layer should also clear<a name="line.46"></a> |
| <span class="sourceLineNo">047</span> * the compression context when reseting, which means when calling resetTo method, we need to<a name="line.47"></a> |
| <span class="sourceLineNo">048</span> * skip to the position instead of just seek to, which will impact performance.<a name="line.48"></a> |
| <span class="sourceLineNo">049</span> */<a name="line.49"></a> |
| <span class="sourceLineNo">050</span> ERROR_AND_RESET_COMPRESSION,<a name="line.50"></a> |
| <span class="sourceLineNo">051</span> /**<a name="line.51"></a> |
| <span class="sourceLineNo">052</span> * This means we reach the EOF and the upper layer need to reset to see if there is more data.<a name="line.52"></a> |
| <span class="sourceLineNo">053</span> * Notice that this does not mean that there is necessarily more data, the upper layer should<a name="line.53"></a> |
| <span class="sourceLineNo">054</span> * determine whether they need to reset and read again.<a name="line.54"></a> |
| <span class="sourceLineNo">055</span> */<a name="line.55"></a> |
| <span class="sourceLineNo">056</span> EOF_AND_RESET,<a name="line.56"></a> |
| <span class="sourceLineNo">057</span> /**<a name="line.57"></a> |
| <span class="sourceLineNo">058</span> * Mostly the same with the above {@link #EOF_AND_RESET}, the difference is that here we also<a name="line.58"></a> |
| <span class="sourceLineNo">059</span> * mess up the compression dictionary when reading data, so the upper layer should also clear<a name="line.59"></a> |
| <span class="sourceLineNo">060</span> * the compression context when reseting, which means when calling resetTo method, we need to<a name="line.60"></a> |
| <span class="sourceLineNo">061</span> * skip to the position instead of just seek to, which will impact performance. The<a name="line.61"></a> |
| <span class="sourceLineNo">062</span> * implementation should try its best to not fall into this situation.<a name="line.62"></a> |
| <span class="sourceLineNo">063</span> */<a name="line.63"></a> |
| <span class="sourceLineNo">064</span> EOF_AND_RESET_COMPRESSION;<a name="line.64"></a> |
| <span class="sourceLineNo">065</span><a name="line.65"></a> |
| <span class="sourceLineNo">066</span> /**<a name="line.66"></a> |
| <span class="sourceLineNo">067</span> * A dummy result for returning, as except {@link NORMAL}, for other state we do not need to<a name="line.67"></a> |
| <span class="sourceLineNo">068</span> * provide fields other than state in the returned {@link Result}.<a name="line.68"></a> |
| <span class="sourceLineNo">069</span> */<a name="line.69"></a> |
| <span class="sourceLineNo">070</span> private Result result = new Result(this, null, -1);<a name="line.70"></a> |
| <span class="sourceLineNo">071</span><a name="line.71"></a> |
| <span class="sourceLineNo">072</span> public Result getResult() {<a name="line.72"></a> |
| <span class="sourceLineNo">073</span> return result;<a name="line.73"></a> |
| <span class="sourceLineNo">074</span> }<a name="line.74"></a> |
| <span class="sourceLineNo">075</span><a name="line.75"></a> |
| <span class="sourceLineNo">076</span> public boolean resetCompression() {<a name="line.76"></a> |
| <span class="sourceLineNo">077</span> return this == ERROR_AND_RESET_COMPRESSION || this == EOF_AND_RESET_COMPRESSION;<a name="line.77"></a> |
| <span class="sourceLineNo">078</span> }<a name="line.78"></a> |
| <span class="sourceLineNo">079</span><a name="line.79"></a> |
| <span class="sourceLineNo">080</span> public boolean eof() {<a name="line.80"></a> |
| <span class="sourceLineNo">081</span> return this == EOF_AND_RESET || this == EOF_AND_RESET_COMPRESSION || this == EOF_WITH_TRAILER;<a name="line.81"></a> |
| <span class="sourceLineNo">082</span> }<a name="line.82"></a> |
| <span class="sourceLineNo">083</span> }<a name="line.83"></a> |
| <span class="sourceLineNo">084</span><a name="line.84"></a> |
| <span class="sourceLineNo">085</span> final class Result {<a name="line.85"></a> |
| <span class="sourceLineNo">086</span><a name="line.86"></a> |
| <span class="sourceLineNo">087</span> private final State state;<a name="line.87"></a> |
| <span class="sourceLineNo">088</span> private final Entry entry;<a name="line.88"></a> |
| <span class="sourceLineNo">089</span> private final long entryEndPos;<a name="line.89"></a> |
| <span class="sourceLineNo">090</span><a name="line.90"></a> |
| <span class="sourceLineNo">091</span> public Result(State state, Entry entry, long entryEndPos) {<a name="line.91"></a> |
| <span class="sourceLineNo">092</span> this.state = state;<a name="line.92"></a> |
| <span class="sourceLineNo">093</span> this.entry = entry;<a name="line.93"></a> |
| <span class="sourceLineNo">094</span> this.entryEndPos = entryEndPos;<a name="line.94"></a> |
| <span class="sourceLineNo">095</span> }<a name="line.95"></a> |
| <span class="sourceLineNo">096</span><a name="line.96"></a> |
| <span class="sourceLineNo">097</span> public State getState() {<a name="line.97"></a> |
| <span class="sourceLineNo">098</span> return state;<a name="line.98"></a> |
| <span class="sourceLineNo">099</span> }<a name="line.99"></a> |
| <span class="sourceLineNo">100</span><a name="line.100"></a> |
| <span class="sourceLineNo">101</span> public Entry getEntry() {<a name="line.101"></a> |
| <span class="sourceLineNo">102</span> return entry;<a name="line.102"></a> |
| <span class="sourceLineNo">103</span> }<a name="line.103"></a> |
| <span class="sourceLineNo">104</span><a name="line.104"></a> |
| <span class="sourceLineNo">105</span> public long getEntryEndPos() {<a name="line.105"></a> |
| <span class="sourceLineNo">106</span> return entryEndPos;<a name="line.106"></a> |
| <span class="sourceLineNo">107</span> }<a name="line.107"></a> |
| <span class="sourceLineNo">108</span> }<a name="line.108"></a> |
| <span class="sourceLineNo">109</span><a name="line.109"></a> |
| <span class="sourceLineNo">110</span> /**<a name="line.110"></a> |
| <span class="sourceLineNo">111</span> * Read the next entry and make sure the position after reading does not go beyond the given<a name="line.111"></a> |
| <span class="sourceLineNo">112</span> * {@code limit}.<a name="line.112"></a> |
| <span class="sourceLineNo">113</span> * <p/><a name="line.113"></a> |
| <span class="sourceLineNo">114</span> * Notice that we will not throw any checked exception out, all the states are represented by the<a name="line.114"></a> |
| <span class="sourceLineNo">115</span> * return value. Of course we will log the exceptions out. The reason why we do this is that, for<a name="line.115"></a> |
| <span class="sourceLineNo">116</span> * tailing a WAL file which is currently being written, we will hit EOFException many times, so it<a name="line.116"></a> |
| <span class="sourceLineNo">117</span> * should not be considered as an 'exception' and also, creating an Exception is a bit expensive.<a name="line.117"></a> |
| <span class="sourceLineNo">118</span> * @param limit the position limit. See HBASE-14004 for more details about why we need this<a name="line.118"></a> |
| <span class="sourceLineNo">119</span> * limitation. -1 means no limit.<a name="line.119"></a> |
| <span class="sourceLineNo">120</span> */<a name="line.120"></a> |
| <span class="sourceLineNo">121</span> Result next(long limit);<a name="line.121"></a> |
| <span class="sourceLineNo">122</span><a name="line.122"></a> |
| <span class="sourceLineNo">123</span> /**<a name="line.123"></a> |
| <span class="sourceLineNo">124</span> * Get the current reading position.<a name="line.124"></a> |
| <span class="sourceLineNo">125</span> */<a name="line.125"></a> |
| <span class="sourceLineNo">126</span> long getPosition() throws IOException;<a name="line.126"></a> |
| <span class="sourceLineNo">127</span><a name="line.127"></a> |
| <span class="sourceLineNo">128</span> /**<a name="line.128"></a> |
| <span class="sourceLineNo">129</span> * Reopen the reader to see if there is new data arrives, and also seek(or skip) to the given<a name="line.129"></a> |
| <span class="sourceLineNo">130</span> * position.<a name="line.130"></a> |
| <span class="sourceLineNo">131</span> * <p/><a name="line.131"></a> |
| <span class="sourceLineNo">132</span> * If you want to read from the beginning instead of a given position, please pass -1 as<a name="line.132"></a> |
| <span class="sourceLineNo">133</span> * {@code position}, then the reader will locate to the first entry. Notice that, since we have a<a name="line.133"></a> |
| <span class="sourceLineNo">134</span> * magic header and a pb header, the first WAL entry is not located at position 0, so passing 0<a name="line.134"></a> |
| <span class="sourceLineNo">135</span> * will cause trouble.<a name="line.135"></a> |
| <span class="sourceLineNo">136</span> * @param position the position we want to start reading from after resetting, or -1 if<a name="line.136"></a> |
| <span class="sourceLineNo">137</span> * you want to start reading from the beginning.<a name="line.137"></a> |
| <span class="sourceLineNo">138</span> * @param resetCompression whether we also need to clear the compression context. If {@code true},<a name="line.138"></a> |
| <span class="sourceLineNo">139</span> * we will use skip instead of seek after resetting.<a name="line.139"></a> |
| <span class="sourceLineNo">140</span> */<a name="line.140"></a> |
| <span class="sourceLineNo">141</span> void resetTo(long position, boolean resetCompression) throws IOException;<a name="line.141"></a> |
| <span class="sourceLineNo">142</span><a name="line.142"></a> |
| <span class="sourceLineNo">143</span> /**<a name="line.143"></a> |
| <span class="sourceLineNo">144</span> * Override to remove the 'throws IOException' as we are just a reader.<a name="line.144"></a> |
| <span class="sourceLineNo">145</span> */<a name="line.145"></a> |
| <span class="sourceLineNo">146</span> @Override<a name="line.146"></a> |
| <span class="sourceLineNo">147</span> void close();<a name="line.147"></a> |
| <span class="sourceLineNo">148</span>}<a name="line.148"></a> |
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| </pre> |
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