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| <h2 title="Interface FenceMethod" class="title">Interface FenceMethod</h2> |
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| <pre>@InterfaceAudience.Public |
| @InterfaceStability.Unstable |
| public interface <span class="typeNameLabel">FenceMethod</span></pre> |
| <div class="block">A fencing method is a method by which one node can forcibly prevent |
| another node from making continued progress. This might be implemented |
| by killing a process on the other node, by denying the other node's |
| access to shared storage, or by accessing a PDU to cut the other node's |
| power. |
| <p> |
| Since these methods are often vendor- or device-specific, operators |
| may implement this interface in order to achieve fencing. |
| <p> |
| Fencing is configured by the operator as an ordered list of methods to |
| attempt. Each method will be tried in turn, and the next in the list |
| will only be attempted if the previous one fails. See <code>NodeFencer</code> |
| for more information. |
| <p> |
| If an implementation also implements <a href="../../../../org/apache/hadoop/conf/Configurable.html" title="interface in org.apache.hadoop.conf"><code>Configurable</code></a> then its |
| <code>setConf</code> method will be called upon instantiation.</div> |
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| <td class="colFirst"><code>void</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../org/apache/hadoop/ha/FenceMethod.html#checkArgs-java.lang.String-">checkArgs</a></span>(<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</a> args)</code> |
| <div class="block">Verify that the given fencing method's arguments are valid.</div> |
| </td> |
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| <tr id="i1" class="rowColor"> |
| <td class="colFirst"><code>boolean</code></td> |
| <td class="colLast"><code><span class="memberNameLink"><a href="../../../../org/apache/hadoop/ha/FenceMethod.html#tryFence-org.apache.hadoop.ha.HAServiceTarget-java.lang.String-">tryFence</a></span>(<a href="../../../../org/apache/hadoop/ha/HAServiceTarget.html" title="class in org.apache.hadoop.ha">HAServiceTarget</a> target, |
| <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</a> args)</code> |
| <div class="block">Attempt to fence the target node.</div> |
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| <h4>checkArgs</h4> |
| <pre>void checkArgs(<a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</a> args) |
| throws <a href="../../../../org/apache/hadoop/ha/BadFencingConfigurationException.html" title="class in org.apache.hadoop.ha">BadFencingConfigurationException</a></pre> |
| <div class="block">Verify that the given fencing method's arguments are valid.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>args</code> - the arguments provided in the configuration. This may |
| be null if the operator did not configure any arguments.</dd> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="../../../../org/apache/hadoop/ha/BadFencingConfigurationException.html" title="class in org.apache.hadoop.ha">BadFencingConfigurationException</a></code> - if the arguments are invalid</dd> |
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| <h4>tryFence</h4> |
| <pre>boolean tryFence(<a href="../../../../org/apache/hadoop/ha/HAServiceTarget.html" title="class in org.apache.hadoop.ha">HAServiceTarget</a> target, |
| <a href="https://docs.oracle.com/javase/8/docs/api/java/lang/String.html?is-external=true" title="class or interface in java.lang">String</a> args) |
| throws <a href="../../../../org/apache/hadoop/ha/BadFencingConfigurationException.html" title="class in org.apache.hadoop.ha">BadFencingConfigurationException</a></pre> |
| <div class="block">Attempt to fence the target node.</div> |
| <dl> |
| <dt><span class="paramLabel">Parameters:</span></dt> |
| <dd><code>target</code> - the target of the service to fence</dd> |
| <dd><code>args</code> - the configured arguments, which were checked at startup by |
| <a href="../../../../org/apache/hadoop/ha/FenceMethod.html#checkArgs-java.lang.String-"><code>checkArgs(String)</code></a></dd> |
| <dt><span class="returnLabel">Returns:</span></dt> |
| <dd>true if fencing was successful, false if unsuccessful or |
| indeterminate</dd> |
| <dt><span class="throwsLabel">Throws:</span></dt> |
| <dd><code><a href="../../../../org/apache/hadoop/ha/BadFencingConfigurationException.html" title="class in org.apache.hadoop.ha">BadFencingConfigurationException</a></code> - if the configuration was |
| determined to be invalid only at runtime</dd> |
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