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Posted to commits@hbase.apache.org by mi...@apache.org on 2016/08/29 15:33:00 UTC
[10/52] [partial] hbase-site git commit: Published site at
950d547dae684155020edb879a343bee1bf18e97.
http://git-wip-us.apache.org/repos/asf/hbase-site/blob/45a663dd/devapidocs/src-html/org/apache/hadoop/hbase/master/snapshot/SnapshotFileCache.SnapshotDirectoryInfo.html
----------------------------------------------------------------------
diff --git a/devapidocs/src-html/org/apache/hadoop/hbase/master/snapshot/SnapshotFileCache.SnapshotDirectoryInfo.html b/devapidocs/src-html/org/apache/hadoop/hbase/master/snapshot/SnapshotFileCache.SnapshotDirectoryInfo.html
index ac4f63e..9ec3893 100644
--- a/devapidocs/src-html/org/apache/hadoop/hbase/master/snapshot/SnapshotFileCache.SnapshotDirectoryInfo.html
+++ b/devapidocs/src-html/org/apache/hadoop/hbase/master/snapshot/SnapshotFileCache.SnapshotDirectoryInfo.html
@@ -35,358 +35,366 @@
<span class="sourceLineNo">027</span>import java.util.Set;<a name="line.27"></a>
<span class="sourceLineNo">028</span>import java.util.Timer;<a name="line.28"></a>
<span class="sourceLineNo">029</span>import java.util.TimerTask;<a name="line.29"></a>
-<span class="sourceLineNo">030</span><a name="line.30"></a>
-<span class="sourceLineNo">031</span>import com.google.common.annotations.VisibleForTesting;<a name="line.31"></a>
-<span class="sourceLineNo">032</span>import com.google.common.collect.Lists;<a name="line.32"></a>
-<span class="sourceLineNo">033</span>import org.apache.commons.logging.Log;<a name="line.33"></a>
-<span class="sourceLineNo">034</span>import org.apache.commons.logging.LogFactory;<a name="line.34"></a>
-<span class="sourceLineNo">035</span>import org.apache.hadoop.hbase.classification.InterfaceAudience;<a name="line.35"></a>
-<span class="sourceLineNo">036</span>import org.apache.hadoop.hbase.classification.InterfaceStability;<a name="line.36"></a>
-<span class="sourceLineNo">037</span>import org.apache.hadoop.conf.Configuration;<a name="line.37"></a>
-<span class="sourceLineNo">038</span>import org.apache.hadoop.fs.FileStatus;<a name="line.38"></a>
-<span class="sourceLineNo">039</span>import org.apache.hadoop.fs.FileSystem;<a name="line.39"></a>
-<span class="sourceLineNo">040</span>import org.apache.hadoop.fs.Path;<a name="line.40"></a>
-<span class="sourceLineNo">041</span>import org.apache.hadoop.hbase.Stoppable;<a name="line.41"></a>
-<span class="sourceLineNo">042</span>import org.apache.hadoop.hbase.snapshot.CorruptedSnapshotException;<a name="line.42"></a>
-<span class="sourceLineNo">043</span>import org.apache.hadoop.hbase.snapshot.SnapshotDescriptionUtils;<a name="line.43"></a>
-<span class="sourceLineNo">044</span>import org.apache.hadoop.hbase.util.FSUtils;<a name="line.44"></a>
-<span class="sourceLineNo">045</span><a name="line.45"></a>
-<span class="sourceLineNo">046</span>/**<a name="line.46"></a>
-<span class="sourceLineNo">047</span> * Intelligently keep track of all the files for all the snapshots.<a name="line.47"></a>
-<span class="sourceLineNo">048</span> * <p><a name="line.48"></a>
-<span class="sourceLineNo">049</span> * A cache of files is kept to avoid querying the {@link FileSystem} frequently. If there is a cache<a name="line.49"></a>
-<span class="sourceLineNo">050</span> * miss the directory modification time is used to ensure that we don't rescan directories that we<a name="line.50"></a>
-<span class="sourceLineNo">051</span> * already have in cache. We only check the modification times of the snapshot directories<a name="line.51"></a>
-<span class="sourceLineNo">052</span> * (/hbase/.snapshot/[snapshot_name]) to determine if the files need to be loaded into the cache.<a name="line.52"></a>
-<span class="sourceLineNo">053</span> * <p><a name="line.53"></a>
-<span class="sourceLineNo">054</span> * New snapshots will be added to the cache and deleted snapshots will be removed when we refresh<a name="line.54"></a>
-<span class="sourceLineNo">055</span> * the cache. If the files underneath a snapshot directory are changed, but not the snapshot itself,<a name="line.55"></a>
-<span class="sourceLineNo">056</span> * we will ignore updates to that snapshot's files.<a name="line.56"></a>
-<span class="sourceLineNo">057</span> * <p><a name="line.57"></a>
-<span class="sourceLineNo">058</span> * This is sufficient because each snapshot has its own directory and is added via an atomic rename<a name="line.58"></a>
-<span class="sourceLineNo">059</span> * <i>once</i>, when the snapshot is created. We don't need to worry about the data in the snapshot<a name="line.59"></a>
-<span class="sourceLineNo">060</span> * being run.<a name="line.60"></a>
-<span class="sourceLineNo">061</span> * <p><a name="line.61"></a>
-<span class="sourceLineNo">062</span> * Further, the cache is periodically refreshed ensure that files in snapshots that were deleted are<a name="line.62"></a>
-<span class="sourceLineNo">063</span> * also removed from the cache.<a name="line.63"></a>
-<span class="sourceLineNo">064</span> * <p><a name="line.64"></a>
-<span class="sourceLineNo">065</span> * A {@link SnapshotFileCache.SnapshotFileInspector} must be passed when creating <tt>this</tt> to<a name="line.65"></a>
-<span class="sourceLineNo">066</span> * allow extraction of files under /hbase/.snapshot/[snapshot name] directory, for each snapshot.<a name="line.66"></a>
-<span class="sourceLineNo">067</span> * This allows you to only cache files under, for instance, all the logs in the .logs directory or<a name="line.67"></a>
-<span class="sourceLineNo">068</span> * all the files under all the regions.<a name="line.68"></a>
-<span class="sourceLineNo">069</span> * <p><a name="line.69"></a>
-<span class="sourceLineNo">070</span> * <tt>this</tt> also considers all running snapshots (those under /hbase/.snapshot/.tmp) as valid<a name="line.70"></a>
-<span class="sourceLineNo">071</span> * snapshots and will attempt to cache files from those snapshots as well.<a name="line.71"></a>
-<span class="sourceLineNo">072</span> * <p><a name="line.72"></a>
-<span class="sourceLineNo">073</span> * Queries about a given file are thread-safe with respect to multiple queries and cache refreshes.<a name="line.73"></a>
-<span class="sourceLineNo">074</span> */<a name="line.74"></a>
-<span class="sourceLineNo">075</span>@InterfaceAudience.Private<a name="line.75"></a>
-<span class="sourceLineNo">076</span>@InterfaceStability.Evolving<a name="line.76"></a>
-<span class="sourceLineNo">077</span>public class SnapshotFileCache implements Stoppable {<a name="line.77"></a>
-<span class="sourceLineNo">078</span> interface SnapshotFileInspector {<a name="line.78"></a>
-<span class="sourceLineNo">079</span> /**<a name="line.79"></a>
-<span class="sourceLineNo">080</span> * Returns a collection of file names needed by the snapshot.<a name="line.80"></a>
-<span class="sourceLineNo">081</span> * @param snapshotDir {@link Path} to the snapshot directory to scan.<a name="line.81"></a>
-<span class="sourceLineNo">082</span> * @return the collection of file names needed by the snapshot.<a name="line.82"></a>
-<span class="sourceLineNo">083</span> */<a name="line.83"></a>
-<span class="sourceLineNo">084</span> Collection<String> filesUnderSnapshot(final Path snapshotDir) throws IOException;<a name="line.84"></a>
-<span class="sourceLineNo">085</span> }<a name="line.85"></a>
-<span class="sourceLineNo">086</span><a name="line.86"></a>
-<span class="sourceLineNo">087</span> private static final Log LOG = LogFactory.getLog(SnapshotFileCache.class);<a name="line.87"></a>
-<span class="sourceLineNo">088</span> private volatile boolean stop = false;<a name="line.88"></a>
-<span class="sourceLineNo">089</span> private final FileSystem fs;<a name="line.89"></a>
-<span class="sourceLineNo">090</span> private final SnapshotFileInspector fileInspector;<a name="line.90"></a>
-<span class="sourceLineNo">091</span> private final Path snapshotDir;<a name="line.91"></a>
-<span class="sourceLineNo">092</span> private final Set<String> cache = new HashSet<String>();<a name="line.92"></a>
-<span class="sourceLineNo">093</span> /**<a name="line.93"></a>
-<span class="sourceLineNo">094</span> * This is a helper map of information about the snapshot directories so we don't need to rescan<a name="line.94"></a>
-<span class="sourceLineNo">095</span> * them if they haven't changed since the last time we looked.<a name="line.95"></a>
-<span class="sourceLineNo">096</span> */<a name="line.96"></a>
-<span class="sourceLineNo">097</span> private final Map<String, SnapshotDirectoryInfo> snapshots =<a name="line.97"></a>
-<span class="sourceLineNo">098</span> new HashMap<String, SnapshotDirectoryInfo>();<a name="line.98"></a>
-<span class="sourceLineNo">099</span> private final Timer refreshTimer;<a name="line.99"></a>
-<span class="sourceLineNo">100</span><a name="line.100"></a>
-<span class="sourceLineNo">101</span> private long lastModifiedTime = Long.MIN_VALUE;<a name="line.101"></a>
-<span class="sourceLineNo">102</span><a name="line.102"></a>
-<span class="sourceLineNo">103</span> /**<a name="line.103"></a>
-<span class="sourceLineNo">104</span> * Create a snapshot file cache for all snapshots under the specified [root]/.snapshot on the<a name="line.104"></a>
-<span class="sourceLineNo">105</span> * filesystem.<a name="line.105"></a>
-<span class="sourceLineNo">106</span> * <p><a name="line.106"></a>
-<span class="sourceLineNo">107</span> * Immediately loads the file cache.<a name="line.107"></a>
-<span class="sourceLineNo">108</span> * @param conf to extract the configured {@link FileSystem} where the snapshots are stored and<a name="line.108"></a>
-<span class="sourceLineNo">109</span> * hbase root directory<a name="line.109"></a>
-<span class="sourceLineNo">110</span> * @param cacheRefreshPeriod frequency (ms) with which the cache should be refreshed<a name="line.110"></a>
-<span class="sourceLineNo">111</span> * @param refreshThreadName name of the cache refresh thread<a name="line.111"></a>
-<span class="sourceLineNo">112</span> * @param inspectSnapshotFiles Filter to apply to each snapshot to extract the files.<a name="line.112"></a>
-<span class="sourceLineNo">113</span> * @throws IOException if the {@link FileSystem} or root directory cannot be loaded<a name="line.113"></a>
-<span class="sourceLineNo">114</span> */<a name="line.114"></a>
-<span class="sourceLineNo">115</span> public SnapshotFileCache(Configuration conf, long cacheRefreshPeriod, String refreshThreadName,<a name="line.115"></a>
-<span class="sourceLineNo">116</span> SnapshotFileInspector inspectSnapshotFiles) throws IOException {<a name="line.116"></a>
-<span class="sourceLineNo">117</span> this(FSUtils.getCurrentFileSystem(conf), FSUtils.getRootDir(conf), 0, cacheRefreshPeriod,<a name="line.117"></a>
-<span class="sourceLineNo">118</span> refreshThreadName, inspectSnapshotFiles);<a name="line.118"></a>
-<span class="sourceLineNo">119</span> }<a name="line.119"></a>
-<span class="sourceLineNo">120</span><a name="line.120"></a>
-<span class="sourceLineNo">121</span> /**<a name="line.121"></a>
-<span class="sourceLineNo">122</span> * Create a snapshot file cache for all snapshots under the specified [root]/.snapshot on the<a name="line.122"></a>
-<span class="sourceLineNo">123</span> * filesystem<a name="line.123"></a>
-<span class="sourceLineNo">124</span> * @param fs {@link FileSystem} where the snapshots are stored<a name="line.124"></a>
-<span class="sourceLineNo">125</span> * @param rootDir hbase root directory<a name="line.125"></a>
-<span class="sourceLineNo">126</span> * @param cacheRefreshPeriod period (ms) with which the cache should be refreshed<a name="line.126"></a>
-<span class="sourceLineNo">127</span> * @param cacheRefreshDelay amount of time to wait for the cache to be refreshed<a name="line.127"></a>
-<span class="sourceLineNo">128</span> * @param refreshThreadName name of the cache refresh thread<a name="line.128"></a>
-<span class="sourceLineNo">129</span> * @param inspectSnapshotFiles Filter to apply to each snapshot to extract the files.<a name="line.129"></a>
-<span class="sourceLineNo">130</span> */<a name="line.130"></a>
-<span class="sourceLineNo">131</span> public SnapshotFileCache(FileSystem fs, Path rootDir, long cacheRefreshPeriod,<a name="line.131"></a>
-<span class="sourceLineNo">132</span> long cacheRefreshDelay, String refreshThreadName, SnapshotFileInspector inspectSnapshotFiles) {<a name="line.132"></a>
-<span class="sourceLineNo">133</span> this.fs = fs;<a name="line.133"></a>
-<span class="sourceLineNo">134</span> this.fileInspector = inspectSnapshotFiles;<a name="line.134"></a>
-<span class="sourceLineNo">135</span> this.snapshotDir = SnapshotDescriptionUtils.getSnapshotsDir(rootDir);<a name="line.135"></a>
-<span class="sourceLineNo">136</span> // periodically refresh the file cache to make sure we aren't superfluously saving files.<a name="line.136"></a>
-<span class="sourceLineNo">137</span> this.refreshTimer = new Timer(refreshThreadName, true);<a name="line.137"></a>
-<span class="sourceLineNo">138</span> this.refreshTimer.scheduleAtFixedRate(new RefreshCacheTask(), cacheRefreshDelay,<a name="line.138"></a>
-<span class="sourceLineNo">139</span> cacheRefreshPeriod);<a name="line.139"></a>
-<span class="sourceLineNo">140</span> }<a name="line.140"></a>
-<span class="sourceLineNo">141</span><a name="line.141"></a>
-<span class="sourceLineNo">142</span> /**<a name="line.142"></a>
-<span class="sourceLineNo">143</span> * Trigger a cache refresh, even if its before the next cache refresh. Does not affect pending<a name="line.143"></a>
-<span class="sourceLineNo">144</span> * cache refreshes.<a name="line.144"></a>
-<span class="sourceLineNo">145</span> * <p><a name="line.145"></a>
-<span class="sourceLineNo">146</span> * Blocks until the cache is refreshed.<a name="line.146"></a>
-<span class="sourceLineNo">147</span> * <p><a name="line.147"></a>
-<span class="sourceLineNo">148</span> * Exposed for TESTING.<a name="line.148"></a>
-<span class="sourceLineNo">149</span> */<a name="line.149"></a>
-<span class="sourceLineNo">150</span> public void triggerCacheRefreshForTesting() {<a name="line.150"></a>
-<span class="sourceLineNo">151</span> try {<a name="line.151"></a>
-<span class="sourceLineNo">152</span> SnapshotFileCache.this.refreshCache();<a name="line.152"></a>
-<span class="sourceLineNo">153</span> } catch (IOException e) {<a name="line.153"></a>
-<span class="sourceLineNo">154</span> LOG.warn("Failed to refresh snapshot hfile cache!", e);<a name="line.154"></a>
-<span class="sourceLineNo">155</span> }<a name="line.155"></a>
-<span class="sourceLineNo">156</span> LOG.debug("Current cache:" + cache);<a name="line.156"></a>
-<span class="sourceLineNo">157</span> }<a name="line.157"></a>
-<span class="sourceLineNo">158</span><a name="line.158"></a>
-<span class="sourceLineNo">159</span> /**<a name="line.159"></a>
-<span class="sourceLineNo">160</span> * Check to see if any of the passed file names is contained in any of the snapshots.<a name="line.160"></a>
-<span class="sourceLineNo">161</span> * First checks an in-memory cache of the files to keep. If its not in the cache, then the cache<a name="line.161"></a>
-<span class="sourceLineNo">162</span> * is refreshed and the cache checked again for that file.<a name="line.162"></a>
-<span class="sourceLineNo">163</span> * This ensures that we never return files that exist.<a name="line.163"></a>
-<span class="sourceLineNo">164</span> * <p><a name="line.164"></a>
-<span class="sourceLineNo">165</span> * Note this may lead to periodic false positives for the file being referenced. Periodically, the<a name="line.165"></a>
-<span class="sourceLineNo">166</span> * cache is refreshed even if there are no requests to ensure that the false negatives get removed<a name="line.166"></a>
-<span class="sourceLineNo">167</span> * eventually. For instance, suppose you have a file in the snapshot and it gets loaded into the<a name="line.167"></a>
-<span class="sourceLineNo">168</span> * cache. Then at some point later that snapshot is deleted. If the cache has not been refreshed<a name="line.168"></a>
-<span class="sourceLineNo">169</span> * at that point, cache will still think the file system contains that file and return<a name="line.169"></a>
-<span class="sourceLineNo">170</span> * <tt>true</tt>, even if it is no longer present (false positive). However, if the file never was<a name="line.170"></a>
-<span class="sourceLineNo">171</span> * on the filesystem, we will never find it and always return <tt>false</tt>.<a name="line.171"></a>
-<span class="sourceLineNo">172</span> * @param files file to check, NOTE: Relies that files are loaded from hdfs before method<a name="line.172"></a>
-<span class="sourceLineNo">173</span> * is called (NOT LAZY)<a name="line.173"></a>
-<span class="sourceLineNo">174</span> * @return <tt>unReferencedFiles</tt> the collection of files that do not have snapshot references<a name="line.174"></a>
-<span class="sourceLineNo">175</span> * @throws IOException if there is an unexpected error reaching the filesystem.<a name="line.175"></a>
-<span class="sourceLineNo">176</span> */<a name="line.176"></a>
-<span class="sourceLineNo">177</span> // XXX this is inefficient to synchronize on the method, when what we really need to guard against<a name="line.177"></a>
-<span class="sourceLineNo">178</span> // is an illegal access to the cache. Really we could do a mutex-guarded pointer swap on the<a name="line.178"></a>
-<span class="sourceLineNo">179</span> // cache, but that seems overkill at the moment and isn't necessarily a bottleneck.<a name="line.179"></a>
-<span class="sourceLineNo">180</span> public synchronized Iterable<FileStatus> getUnreferencedFiles(Iterable<FileStatus> files)<a name="line.180"></a>
-<span class="sourceLineNo">181</span> throws IOException {<a name="line.181"></a>
-<span class="sourceLineNo">182</span> List<FileStatus> unReferencedFiles = Lists.newArrayList();<a name="line.182"></a>
-<span class="sourceLineNo">183</span> List<String> snapshotsInProgress = null;<a name="line.183"></a>
-<span class="sourceLineNo">184</span> boolean refreshed = false;<a name="line.184"></a>
-<span class="sourceLineNo">185</span> for (FileStatus file : files) {<a name="line.185"></a>
-<span class="sourceLineNo">186</span> String fileName = file.getPath().getName();<a name="line.186"></a>
-<span class="sourceLineNo">187</span> if (!refreshed && !cache.contains(fileName)) {<a name="line.187"></a>
-<span class="sourceLineNo">188</span> refreshCache();<a name="line.188"></a>
-<span class="sourceLineNo">189</span> refreshed = true;<a name="line.189"></a>
-<span class="sourceLineNo">190</span> }<a name="line.190"></a>
-<span class="sourceLineNo">191</span> if (cache.contains(fileName)) {<a name="line.191"></a>
-<span class="sourceLineNo">192</span> continue;<a name="line.192"></a>
-<span class="sourceLineNo">193</span> }<a name="line.193"></a>
-<span class="sourceLineNo">194</span> if (snapshotsInProgress == null) {<a name="line.194"></a>
-<span class="sourceLineNo">195</span> snapshotsInProgress = getSnapshotsInProgress();<a name="line.195"></a>
-<span class="sourceLineNo">196</span> }<a name="line.196"></a>
-<span class="sourceLineNo">197</span> if (snapshotsInProgress.contains(fileName)) {<a name="line.197"></a>
-<span class="sourceLineNo">198</span> continue;<a name="line.198"></a>
-<span class="sourceLineNo">199</span> }<a name="line.199"></a>
-<span class="sourceLineNo">200</span> unReferencedFiles.add(file);<a name="line.200"></a>
-<span class="sourceLineNo">201</span> }<a name="line.201"></a>
-<span class="sourceLineNo">202</span> return unReferencedFiles;<a name="line.202"></a>
-<span class="sourceLineNo">203</span> }<a name="line.203"></a>
-<span class="sourceLineNo">204</span><a name="line.204"></a>
-<span class="sourceLineNo">205</span> private synchronized void refreshCache() throws IOException {<a name="line.205"></a>
-<span class="sourceLineNo">206</span> long lastTimestamp = Long.MAX_VALUE;<a name="line.206"></a>
-<span class="sourceLineNo">207</span> boolean hasChanges = false;<a name="line.207"></a>
-<span class="sourceLineNo">208</span><a name="line.208"></a>
-<span class="sourceLineNo">209</span> // get the status of the snapshots directory and check if it is has changes<a name="line.209"></a>
-<span class="sourceLineNo">210</span> try {<a name="line.210"></a>
-<span class="sourceLineNo">211</span> FileStatus dirStatus = fs.getFileStatus(snapshotDir);<a name="line.211"></a>
-<span class="sourceLineNo">212</span> lastTimestamp = dirStatus.getModificationTime();<a name="line.212"></a>
-<span class="sourceLineNo">213</span> hasChanges |= (lastTimestamp >= lastModifiedTime);<a name="line.213"></a>
-<span class="sourceLineNo">214</span> } catch (FileNotFoundException e) {<a name="line.214"></a>
-<span class="sourceLineNo">215</span> if (this.cache.size() > 0) {<a name="line.215"></a>
-<span class="sourceLineNo">216</span> LOG.error("Snapshot directory: " + snapshotDir + " doesn't exist");<a name="line.216"></a>
-<span class="sourceLineNo">217</span> }<a name="line.217"></a>
-<span class="sourceLineNo">218</span> return;<a name="line.218"></a>
-<span class="sourceLineNo">219</span> }<a name="line.219"></a>
-<span class="sourceLineNo">220</span><a name="line.220"></a>
-<span class="sourceLineNo">221</span> // get the status of the snapshots temporary directory and check if it has changes<a name="line.221"></a>
-<span class="sourceLineNo">222</span> // The top-level directory timestamp is not updated, so we have to check the inner-level.<a name="line.222"></a>
-<span class="sourceLineNo">223</span> try {<a name="line.223"></a>
-<span class="sourceLineNo">224</span> Path snapshotTmpDir = new Path(snapshotDir, SnapshotDescriptionUtils.SNAPSHOT_TMP_DIR_NAME);<a name="line.224"></a>
-<span class="sourceLineNo">225</span> FileStatus tempDirStatus = fs.getFileStatus(snapshotTmpDir);<a name="line.225"></a>
-<span class="sourceLineNo">226</span> lastTimestamp = Math.min(lastTimestamp, tempDirStatus.getModificationTime());<a name="line.226"></a>
-<span class="sourceLineNo">227</span> hasChanges |= (lastTimestamp >= lastModifiedTime);<a name="line.227"></a>
-<span class="sourceLineNo">228</span> if (!hasChanges) {<a name="line.228"></a>
-<span class="sourceLineNo">229</span> FileStatus[] tmpSnapshots = FSUtils.listStatus(fs, snapshotDir);<a name="line.229"></a>
-<span class="sourceLineNo">230</span> if (tmpSnapshots != null) {<a name="line.230"></a>
-<span class="sourceLineNo">231</span> for (FileStatus dirStatus: tmpSnapshots) {<a name="line.231"></a>
-<span class="sourceLineNo">232</span> lastTimestamp = Math.min(lastTimestamp, dirStatus.getModificationTime());<a name="line.232"></a>
-<span class="sourceLineNo">233</span> }<a name="line.233"></a>
-<span class="sourceLineNo">234</span> hasChanges |= (lastTimestamp >= lastModifiedTime);<a name="line.234"></a>
-<span class="sourceLineNo">235</span> }<a name="line.235"></a>
-<span class="sourceLineNo">236</span> }<a name="line.236"></a>
-<span class="sourceLineNo">237</span> } catch (FileNotFoundException e) {<a name="line.237"></a>
-<span class="sourceLineNo">238</span> // Nothing todo, if the tmp dir is empty<a name="line.238"></a>
-<span class="sourceLineNo">239</span> }<a name="line.239"></a>
-<span class="sourceLineNo">240</span><a name="line.240"></a>
-<span class="sourceLineNo">241</span> // if the snapshot directory wasn't modified since we last check, we are done<a name="line.241"></a>
-<span class="sourceLineNo">242</span> if (!hasChanges) {<a name="line.242"></a>
-<span class="sourceLineNo">243</span> return;<a name="line.243"></a>
-<span class="sourceLineNo">244</span> }<a name="line.244"></a>
-<span class="sourceLineNo">245</span><a name="line.245"></a>
-<span class="sourceLineNo">246</span> // directory was modified, so we need to reload our cache<a name="line.246"></a>
-<span class="sourceLineNo">247</span> // there could be a slight race here where we miss the cache, check the directory modification<a name="line.247"></a>
-<span class="sourceLineNo">248</span> // time, then someone updates the directory, causing us to not scan the directory again.<a name="line.248"></a>
-<span class="sourceLineNo">249</span> // However, snapshot directories are only created once, so this isn't an issue.<a name="line.249"></a>
-<span class="sourceLineNo">250</span><a name="line.250"></a>
-<span class="sourceLineNo">251</span> // 1. update the modified time<a name="line.251"></a>
-<span class="sourceLineNo">252</span> this.lastModifiedTime = lastTimestamp;<a name="line.252"></a>
-<span class="sourceLineNo">253</span><a name="line.253"></a>
-<span class="sourceLineNo">254</span> // 2.clear the cache<a name="line.254"></a>
-<span class="sourceLineNo">255</span> this.cache.clear();<a name="line.255"></a>
-<span class="sourceLineNo">256</span> Map<String, SnapshotDirectoryInfo> known = new HashMap<String, SnapshotDirectoryInfo>();<a name="line.256"></a>
-<span class="sourceLineNo">257</span><a name="line.257"></a>
-<span class="sourceLineNo">258</span> // 3. check each of the snapshot directories<a name="line.258"></a>
-<span class="sourceLineNo">259</span> FileStatus[] snapshots = FSUtils.listStatus(fs, snapshotDir);<a name="line.259"></a>
-<span class="sourceLineNo">260</span> if (snapshots == null) {<a name="line.260"></a>
-<span class="sourceLineNo">261</span> // remove all the remembered snapshots because we don't have any left<a name="line.261"></a>
-<span class="sourceLineNo">262</span> if (LOG.isDebugEnabled() && this.snapshots.size() > 0) {<a name="line.262"></a>
-<span class="sourceLineNo">263</span> LOG.debug("No snapshots on-disk, cache empty");<a name="line.263"></a>
-<span class="sourceLineNo">264</span> }<a name="line.264"></a>
-<span class="sourceLineNo">265</span> this.snapshots.clear();<a name="line.265"></a>
-<span class="sourceLineNo">266</span> return;<a name="line.266"></a>
-<span class="sourceLineNo">267</span> }<a name="line.267"></a>
-<span class="sourceLineNo">268</span><a name="line.268"></a>
-<span class="sourceLineNo">269</span> // 3.1 iterate through the on-disk snapshots<a name="line.269"></a>
-<span class="sourceLineNo">270</span> for (FileStatus snapshot : snapshots) {<a name="line.270"></a>
-<span class="sourceLineNo">271</span> String name = snapshot.getPath().getName();<a name="line.271"></a>
-<span class="sourceLineNo">272</span> // its not the tmp dir,<a name="line.272"></a>
-<span class="sourceLineNo">273</span> if (!name.equals(SnapshotDescriptionUtils.SNAPSHOT_TMP_DIR_NAME)) {<a name="line.273"></a>
-<span class="sourceLineNo">274</span> SnapshotDirectoryInfo files = this.snapshots.remove(name);<a name="line.274"></a>
-<span class="sourceLineNo">275</span> // 3.1.1 if we don't know about the snapshot or its been modified, we need to update the<a name="line.275"></a>
-<span class="sourceLineNo">276</span> // files the latter could occur where I create a snapshot, then delete it, and then make a<a name="line.276"></a>
-<span class="sourceLineNo">277</span> // new snapshot with the same name. We will need to update the cache the information from<a name="line.277"></a>
-<span class="sourceLineNo">278</span> // that new snapshot, even though it has the same name as the files referenced have<a name="line.278"></a>
-<span class="sourceLineNo">279</span> // probably changed.<a name="line.279"></a>
-<span class="sourceLineNo">280</span> if (files == null || files.hasBeenModified(snapshot.getModificationTime())) {<a name="line.280"></a>
-<span class="sourceLineNo">281</span> // get all files for the snapshot and create a new info<a name="line.281"></a>
-<span class="sourceLineNo">282</span> Collection<String> storedFiles = fileInspector.filesUnderSnapshot(snapshot.getPath());<a name="line.282"></a>
-<span class="sourceLineNo">283</span> files = new SnapshotDirectoryInfo(snapshot.getModificationTime(), storedFiles);<a name="line.283"></a>
-<span class="sourceLineNo">284</span> }<a name="line.284"></a>
-<span class="sourceLineNo">285</span> // 3.2 add all the files to cache<a name="line.285"></a>
-<span class="sourceLineNo">286</span> this.cache.addAll(files.getFiles());<a name="line.286"></a>
-<span class="sourceLineNo">287</span> known.put(name, files);<a name="line.287"></a>
-<span class="sourceLineNo">288</span> }<a name="line.288"></a>
-<span class="sourceLineNo">289</span> }<a name="line.289"></a>
-<span class="sourceLineNo">290</span><a name="line.290"></a>
-<span class="sourceLineNo">291</span> // 4. set the snapshots we are tracking<a name="line.291"></a>
-<span class="sourceLineNo">292</span> this.snapshots.clear();<a name="line.292"></a>
-<span class="sourceLineNo">293</span> this.snapshots.putAll(known);<a name="line.293"></a>
-<span class="sourceLineNo">294</span> }<a name="line.294"></a>
-<span class="sourceLineNo">295</span> <a name="line.295"></a>
-<span class="sourceLineNo">296</span> @VisibleForTesting List<String> getSnapshotsInProgress() throws IOException {<a name="line.296"></a>
-<span class="sourceLineNo">297</span> List<String> snapshotInProgress = Lists.newArrayList();<a name="line.297"></a>
-<span class="sourceLineNo">298</span> // only add those files to the cache, but not to the known snapshots<a name="line.298"></a>
-<span class="sourceLineNo">299</span> Path snapshotTmpDir = new Path(snapshotDir, SnapshotDescriptionUtils.SNAPSHOT_TMP_DIR_NAME);<a name="line.299"></a>
-<span class="sourceLineNo">300</span> // only add those files to the cache, but not to the known snapshots<a name="line.300"></a>
-<span class="sourceLineNo">301</span> FileStatus[] running = FSUtils.listStatus(fs, snapshotTmpDir);<a name="line.301"></a>
-<span class="sourceLineNo">302</span> if (running != null) {<a name="line.302"></a>
-<span class="sourceLineNo">303</span> for (FileStatus run : running) {<a name="line.303"></a>
-<span class="sourceLineNo">304</span> try {<a name="line.304"></a>
-<span class="sourceLineNo">305</span> snapshotInProgress.addAll(fileInspector.filesUnderSnapshot(run.getPath()));<a name="line.305"></a>
-<span class="sourceLineNo">306</span> } catch (CorruptedSnapshotException e) {<a name="line.306"></a>
-<span class="sourceLineNo">307</span> // See HBASE-16464<a name="line.307"></a>
-<span class="sourceLineNo">308</span> if (e.getCause() instanceof FileNotFoundException) {<a name="line.308"></a>
-<span class="sourceLineNo">309</span> // If the snapshot is not in progress, we will delete it<a name="line.309"></a>
-<span class="sourceLineNo">310</span> if (!fs.exists(new Path(run.getPath(),<a name="line.310"></a>
-<span class="sourceLineNo">311</span> SnapshotDescriptionUtils.SNAPSHOT_IN_PROGRESS))) {<a name="line.311"></a>
-<span class="sourceLineNo">312</span> fs.delete(run.getPath(), true);<a name="line.312"></a>
-<span class="sourceLineNo">313</span> LOG.warn("delete the " + run.getPath() + " due to exception:", e.getCause());<a name="line.313"></a>
-<span class="sourceLineNo">314</span> }<a name="line.314"></a>
-<span class="sourceLineNo">315</span> } else {<a name="line.315"></a>
-<span class="sourceLineNo">316</span> throw e;<a name="line.316"></a>
-<span class="sourceLineNo">317</span> }<a name="line.317"></a>
-<span class="sourceLineNo">318</span> }<a name="line.318"></a>
-<span class="sourceLineNo">319</span> }<a name="line.319"></a>
-<span class="sourceLineNo">320</span> }<a name="line.320"></a>
-<span class="sourceLineNo">321</span> return snapshotInProgress;<a name="line.321"></a>
-<span class="sourceLineNo">322</span> }<a name="line.322"></a>
-<span class="sourceLineNo">323</span><a name="line.323"></a>
-<span class="sourceLineNo">324</span> /**<a name="line.324"></a>
-<span class="sourceLineNo">325</span> * Simple helper task that just periodically attempts to refresh the cache<a name="line.325"></a>
-<span class="sourceLineNo">326</span> */<a name="line.326"></a>
-<span class="sourceLineNo">327</span> public class RefreshCacheTask extends TimerTask {<a name="line.327"></a>
-<span class="sourceLineNo">328</span> @Override<a name="line.328"></a>
-<span class="sourceLineNo">329</span> public void run() {<a name="line.329"></a>
-<span class="sourceLineNo">330</span> try {<a name="line.330"></a>
-<span class="sourceLineNo">331</span> SnapshotFileCache.this.refreshCache();<a name="line.331"></a>
-<span class="sourceLineNo">332</span> } catch (IOException e) {<a name="line.332"></a>
-<span class="sourceLineNo">333</span> LOG.warn("Failed to refresh snapshot hfile cache!", e);<a name="line.333"></a>
-<span class="sourceLineNo">334</span> }<a name="line.334"></a>
-<span class="sourceLineNo">335</span> }<a name="line.335"></a>
-<span class="sourceLineNo">336</span> }<a name="line.336"></a>
-<span class="sourceLineNo">337</span><a name="line.337"></a>
-<span class="sourceLineNo">338</span> @Override<a name="line.338"></a>
-<span class="sourceLineNo">339</span> public void stop(String why) {<a name="line.339"></a>
-<span class="sourceLineNo">340</span> if (!this.stop) {<a name="line.340"></a>
-<span class="sourceLineNo">341</span> this.stop = true;<a name="line.341"></a>
-<span class="sourceLineNo">342</span> this.refreshTimer.cancel();<a name="line.342"></a>
+<span class="sourceLineNo">030</span>import java.util.concurrent.locks.ReentrantLock;<a name="line.30"></a>
+<span class="sourceLineNo">031</span><a name="line.31"></a>
+<span class="sourceLineNo">032</span>import com.google.common.annotations.VisibleForTesting;<a name="line.32"></a>
+<span class="sourceLineNo">033</span>import com.google.common.collect.Lists;<a name="line.33"></a>
+<span class="sourceLineNo">034</span>import org.apache.commons.logging.Log;<a name="line.34"></a>
+<span class="sourceLineNo">035</span>import org.apache.commons.logging.LogFactory;<a name="line.35"></a>
+<span class="sourceLineNo">036</span>import org.apache.hadoop.hbase.classification.InterfaceAudience;<a name="line.36"></a>
+<span class="sourceLineNo">037</span>import org.apache.hadoop.hbase.classification.InterfaceStability;<a name="line.37"></a>
+<span class="sourceLineNo">038</span>import org.apache.hadoop.conf.Configuration;<a name="line.38"></a>
+<span class="sourceLineNo">039</span>import org.apache.hadoop.fs.FileStatus;<a name="line.39"></a>
+<span class="sourceLineNo">040</span>import org.apache.hadoop.fs.FileSystem;<a name="line.40"></a>
+<span class="sourceLineNo">041</span>import org.apache.hadoop.fs.Path;<a name="line.41"></a>
+<span class="sourceLineNo">042</span>import org.apache.hadoop.hbase.Stoppable;<a name="line.42"></a>
+<span class="sourceLineNo">043</span>import org.apache.hadoop.hbase.snapshot.CorruptedSnapshotException;<a name="line.43"></a>
+<span class="sourceLineNo">044</span>import org.apache.hadoop.hbase.snapshot.SnapshotDescriptionUtils;<a name="line.44"></a>
+<span class="sourceLineNo">045</span>import org.apache.hadoop.hbase.util.FSUtils;<a name="line.45"></a>
+<span class="sourceLineNo">046</span><a name="line.46"></a>
+<span class="sourceLineNo">047</span>/**<a name="line.47"></a>
+<span class="sourceLineNo">048</span> * Intelligently keep track of all the files for all the snapshots.<a name="line.48"></a>
+<span class="sourceLineNo">049</span> * <p><a name="line.49"></a>
+<span class="sourceLineNo">050</span> * A cache of files is kept to avoid querying the {@link FileSystem} frequently. If there is a cache<a name="line.50"></a>
+<span class="sourceLineNo">051</span> * miss the directory modification time is used to ensure that we don't rescan directories that we<a name="line.51"></a>
+<span class="sourceLineNo">052</span> * already have in cache. We only check the modification times of the snapshot directories<a name="line.52"></a>
+<span class="sourceLineNo">053</span> * (/hbase/.snapshot/[snapshot_name]) to determine if the files need to be loaded into the cache.<a name="line.53"></a>
+<span class="sourceLineNo">054</span> * <p><a name="line.54"></a>
+<span class="sourceLineNo">055</span> * New snapshots will be added to the cache and deleted snapshots will be removed when we refresh<a name="line.55"></a>
+<span class="sourceLineNo">056</span> * the cache. If the files underneath a snapshot directory are changed, but not the snapshot itself,<a name="line.56"></a>
+<span class="sourceLineNo">057</span> * we will ignore updates to that snapshot's files.<a name="line.57"></a>
+<span class="sourceLineNo">058</span> * <p><a name="line.58"></a>
+<span class="sourceLineNo">059</span> * This is sufficient because each snapshot has its own directory and is added via an atomic rename<a name="line.59"></a>
+<span class="sourceLineNo">060</span> * <i>once</i>, when the snapshot is created. We don't need to worry about the data in the snapshot<a name="line.60"></a>
+<span class="sourceLineNo">061</span> * being run.<a name="line.61"></a>
+<span class="sourceLineNo">062</span> * <p><a name="line.62"></a>
+<span class="sourceLineNo">063</span> * Further, the cache is periodically refreshed ensure that files in snapshots that were deleted are<a name="line.63"></a>
+<span class="sourceLineNo">064</span> * also removed from the cache.<a name="line.64"></a>
+<span class="sourceLineNo">065</span> * <p><a name="line.65"></a>
+<span class="sourceLineNo">066</span> * A {@link SnapshotFileCache.SnapshotFileInspector} must be passed when creating <tt>this</tt> to<a name="line.66"></a>
+<span class="sourceLineNo">067</span> * allow extraction of files under /hbase/.snapshot/[snapshot name] directory, for each snapshot.<a name="line.67"></a>
+<span class="sourceLineNo">068</span> * This allows you to only cache files under, for instance, all the logs in the .logs directory or<a name="line.68"></a>
+<span class="sourceLineNo">069</span> * all the files under all the regions.<a name="line.69"></a>
+<span class="sourceLineNo">070</span> * <p><a name="line.70"></a>
+<span class="sourceLineNo">071</span> * <tt>this</tt> also considers all running snapshots (those under /hbase/.snapshot/.tmp) as valid<a name="line.71"></a>
+<span class="sourceLineNo">072</span> * snapshots and will attempt to cache files from those snapshots as well.<a name="line.72"></a>
+<span class="sourceLineNo">073</span> * <p><a name="line.73"></a>
+<span class="sourceLineNo">074</span> * Queries about a given file are thread-safe with respect to multiple queries and cache refreshes.<a name="line.74"></a>
+<span class="sourceLineNo">075</span> */<a name="line.75"></a>
+<span class="sourceLineNo">076</span>@InterfaceAudience.Private<a name="line.76"></a>
+<span class="sourceLineNo">077</span>@InterfaceStability.Evolving<a name="line.77"></a>
+<span class="sourceLineNo">078</span>public class SnapshotFileCache implements Stoppable {<a name="line.78"></a>
+<span class="sourceLineNo">079</span> interface SnapshotFileInspector {<a name="line.79"></a>
+<span class="sourceLineNo">080</span> /**<a name="line.80"></a>
+<span class="sourceLineNo">081</span> * Returns a collection of file names needed by the snapshot.<a name="line.81"></a>
+<span class="sourceLineNo">082</span> * @param snapshotDir {@link Path} to the snapshot directory to scan.<a name="line.82"></a>
+<span class="sourceLineNo">083</span> * @return the collection of file names needed by the snapshot.<a name="line.83"></a>
+<span class="sourceLineNo">084</span> */<a name="line.84"></a>
+<span class="sourceLineNo">085</span> Collection<String> filesUnderSnapshot(final Path snapshotDir) throws IOException;<a name="line.85"></a>
+<span class="sourceLineNo">086</span> }<a name="line.86"></a>
+<span class="sourceLineNo">087</span><a name="line.87"></a>
+<span class="sourceLineNo">088</span> private static final Log LOG = LogFactory.getLog(SnapshotFileCache.class);<a name="line.88"></a>
+<span class="sourceLineNo">089</span> private volatile boolean stop = false;<a name="line.89"></a>
+<span class="sourceLineNo">090</span> private final FileSystem fs;<a name="line.90"></a>
+<span class="sourceLineNo">091</span> private final SnapshotFileInspector fileInspector;<a name="line.91"></a>
+<span class="sourceLineNo">092</span> private final Path snapshotDir;<a name="line.92"></a>
+<span class="sourceLineNo">093</span> private final Set<String> cache = new HashSet<String>();<a name="line.93"></a>
+<span class="sourceLineNo">094</span> /**<a name="line.94"></a>
+<span class="sourceLineNo">095</span> * This is a helper map of information about the snapshot directories so we don't need to rescan<a name="line.95"></a>
+<span class="sourceLineNo">096</span> * them if they haven't changed since the last time we looked.<a name="line.96"></a>
+<span class="sourceLineNo">097</span> */<a name="line.97"></a>
+<span class="sourceLineNo">098</span> private final Map<String, SnapshotDirectoryInfo> snapshots =<a name="line.98"></a>
+<span class="sourceLineNo">099</span> new HashMap<String, SnapshotDirectoryInfo>();<a name="line.99"></a>
+<span class="sourceLineNo">100</span> private final Timer refreshTimer;<a name="line.100"></a>
+<span class="sourceLineNo">101</span><a name="line.101"></a>
+<span class="sourceLineNo">102</span> private long lastModifiedTime = Long.MIN_VALUE;<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> * Create a snapshot file cache for all snapshots under the specified [root]/.snapshot on the<a name="line.105"></a>
+<span class="sourceLineNo">106</span> * filesystem.<a name="line.106"></a>
+<span class="sourceLineNo">107</span> * <p><a name="line.107"></a>
+<span class="sourceLineNo">108</span> * Immediately loads the file cache.<a name="line.108"></a>
+<span class="sourceLineNo">109</span> * @param conf to extract the configured {@link FileSystem} where the snapshots are stored and<a name="line.109"></a>
+<span class="sourceLineNo">110</span> * hbase root directory<a name="line.110"></a>
+<span class="sourceLineNo">111</span> * @param cacheRefreshPeriod frequency (ms) with which the cache should be refreshed<a name="line.111"></a>
+<span class="sourceLineNo">112</span> * @param refreshThreadName name of the cache refresh thread<a name="line.112"></a>
+<span class="sourceLineNo">113</span> * @param inspectSnapshotFiles Filter to apply to each snapshot to extract the files.<a name="line.113"></a>
+<span class="sourceLineNo">114</span> * @throws IOException if the {@link FileSystem} or root directory cannot be loaded<a name="line.114"></a>
+<span class="sourceLineNo">115</span> */<a name="line.115"></a>
+<span class="sourceLineNo">116</span> public SnapshotFileCache(Configuration conf, long cacheRefreshPeriod, String refreshThreadName,<a name="line.116"></a>
+<span class="sourceLineNo">117</span> SnapshotFileInspector inspectSnapshotFiles) throws IOException {<a name="line.117"></a>
+<span class="sourceLineNo">118</span> this(FSUtils.getCurrentFileSystem(conf), FSUtils.getRootDir(conf), 0, cacheRefreshPeriod,<a name="line.118"></a>
+<span class="sourceLineNo">119</span> refreshThreadName, inspectSnapshotFiles);<a name="line.119"></a>
+<span class="sourceLineNo">120</span> }<a name="line.120"></a>
+<span class="sourceLineNo">121</span><a name="line.121"></a>
+<span class="sourceLineNo">122</span> /**<a name="line.122"></a>
+<span class="sourceLineNo">123</span> * Create a snapshot file cache for all snapshots under the specified [root]/.snapshot on the<a name="line.123"></a>
+<span class="sourceLineNo">124</span> * filesystem<a name="line.124"></a>
+<span class="sourceLineNo">125</span> * @param fs {@link FileSystem} where the snapshots are stored<a name="line.125"></a>
+<span class="sourceLineNo">126</span> * @param rootDir hbase root directory<a name="line.126"></a>
+<span class="sourceLineNo">127</span> * @param cacheRefreshPeriod period (ms) with which the cache should be refreshed<a name="line.127"></a>
+<span class="sourceLineNo">128</span> * @param cacheRefreshDelay amount of time to wait for the cache to be refreshed<a name="line.128"></a>
+<span class="sourceLineNo">129</span> * @param refreshThreadName name of the cache refresh thread<a name="line.129"></a>
+<span class="sourceLineNo">130</span> * @param inspectSnapshotFiles Filter to apply to each snapshot to extract the files.<a name="line.130"></a>
+<span class="sourceLineNo">131</span> */<a name="line.131"></a>
+<span class="sourceLineNo">132</span> public SnapshotFileCache(FileSystem fs, Path rootDir, long cacheRefreshPeriod,<a name="line.132"></a>
+<span class="sourceLineNo">133</span> long cacheRefreshDelay, String refreshThreadName, SnapshotFileInspector inspectSnapshotFiles) {<a name="line.133"></a>
+<span class="sourceLineNo">134</span> this.fs = fs;<a name="line.134"></a>
+<span class="sourceLineNo">135</span> this.fileInspector = inspectSnapshotFiles;<a name="line.135"></a>
+<span class="sourceLineNo">136</span> this.snapshotDir = SnapshotDescriptionUtils.getSnapshotsDir(rootDir);<a name="line.136"></a>
+<span class="sourceLineNo">137</span> // periodically refresh the file cache to make sure we aren't superfluously saving files.<a name="line.137"></a>
+<span class="sourceLineNo">138</span> this.refreshTimer = new Timer(refreshThreadName, true);<a name="line.138"></a>
+<span class="sourceLineNo">139</span> this.refreshTimer.scheduleAtFixedRate(new RefreshCacheTask(), cacheRefreshDelay,<a name="line.139"></a>
+<span class="sourceLineNo">140</span> cacheRefreshPeriod);<a name="line.140"></a>
+<span class="sourceLineNo">141</span> }<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> * Trigger a cache refresh, even if its before the next cache refresh. Does not affect pending<a name="line.144"></a>
+<span class="sourceLineNo">145</span> * cache refreshes.<a name="line.145"></a>
+<span class="sourceLineNo">146</span> * <p><a name="line.146"></a>
+<span class="sourceLineNo">147</span> * Blocks until the cache is refreshed.<a name="line.147"></a>
+<span class="sourceLineNo">148</span> * <p><a name="line.148"></a>
+<span class="sourceLineNo">149</span> * Exposed for TESTING.<a name="line.149"></a>
+<span class="sourceLineNo">150</span> */<a name="line.150"></a>
+<span class="sourceLineNo">151</span> public void triggerCacheRefreshForTesting() {<a name="line.151"></a>
+<span class="sourceLineNo">152</span> try {<a name="line.152"></a>
+<span class="sourceLineNo">153</span> SnapshotFileCache.this.refreshCache();<a name="line.153"></a>
+<span class="sourceLineNo">154</span> } catch (IOException e) {<a name="line.154"></a>
+<span class="sourceLineNo">155</span> LOG.warn("Failed to refresh snapshot hfile cache!", e);<a name="line.155"></a>
+<span class="sourceLineNo">156</span> }<a name="line.156"></a>
+<span class="sourceLineNo">157</span> LOG.debug("Current cache:" + cache);<a name="line.157"></a>
+<span class="sourceLineNo">158</span> }<a name="line.158"></a>
+<span class="sourceLineNo">159</span><a name="line.159"></a>
+<span class="sourceLineNo">160</span> /**<a name="line.160"></a>
+<span class="sourceLineNo">161</span> * Check to see if any of the passed file names is contained in any of the snapshots.<a name="line.161"></a>
+<span class="sourceLineNo">162</span> * First checks an in-memory cache of the files to keep. If its not in the cache, then the cache<a name="line.162"></a>
+<span class="sourceLineNo">163</span> * is refreshed and the cache checked again for that file.<a name="line.163"></a>
+<span class="sourceLineNo">164</span> * This ensures that we never return files that exist.<a name="line.164"></a>
+<span class="sourceLineNo">165</span> * <p><a name="line.165"></a>
+<span class="sourceLineNo">166</span> * Note this may lead to periodic false positives for the file being referenced. Periodically, the<a name="line.166"></a>
+<span class="sourceLineNo">167</span> * cache is refreshed even if there are no requests to ensure that the false negatives get removed<a name="line.167"></a>
+<span class="sourceLineNo">168</span> * eventually. For instance, suppose you have a file in the snapshot and it gets loaded into the<a name="line.168"></a>
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+<span class="sourceLineNo">170</span> * at that point, cache will still think the file system contains that file and return<a name="line.170"></a>
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