问题描述
我有一个Oozie工作流程，其中包含一个Pig动作，生成一个零件文件作为输出
/user/wf_user/app_dir/output/part-v003-o000-r-00100
Pig操作之后，有一个fs操作，该操作将生成完成标志文件并将part-v003-o000-r-00100移至alert_message（用于重命名），然后更改文件路径{{ 1}}，以使后续的工作流程操作均可访问该文件。
此后，有一个决策控制节点来检查文件/user/wf_user/app_dir/output/alert_message是否存在并且大小大于零。仅当大小不为零时，才会通过电子邮件发送警报消息。
但是，即使文件存在且大小不为零，决策条件也始终返回false，从而永远不会将警报消息通过电子邮件发送给通知用户。
/user/wf_user/app_dir/output/alert_message以下是相关工作流程操作的摘录
<switch xmlns="uri:oozie:workflow:0.4">
<case to="message_pref_alert">false</case>
<default to="success_email" />
</switch>
注意：我尚未将 <action name='generate_preftable_pref_count_report' cred="hcatauth,athensauth">
<pig>
<prepare>
<delete path="${flag_dir}"></delete>
</prepare>
<script>generate_diffcount_w_perc_mktg_prefs.pig</script>
<param>today=${today}</param>
<param>prev_date=${prev_date}</param>
<param>lake_tahoe_dump=${lake_tahoe_dump}</param>
<param>current_pref_snapshot=${current_pref_snapshot}</param>
<param>preference_user=${preference_user}</param>
<param>pref_count_report=${pref_count_report}</param>
<param>flag_dir=${flag_dir}</param>
<file>${common_lib}/elephant-bird-pig.jar#elephant-bird-pig.jar</file>
<file>${common_lib}/elephant-bird-core.jar#elephant-bird-core.jar</file>
<file>${common_lib}/elephant-bird-hadoop-compat.jar#elephant-bird-hadoop-compat.jar</file>
</pig>
<ok to="fs-create-report-flag-and-alert" />
<error to="failure_email" />
</action>
<action name="fs-create-report-flag-and-alert">
<fs>
<chmod path='${flag_dir}' permissions='-rwxrwxrwx' dir-files='true'/>
<delete path='${flag_dir}/report_generated_${prev_date}'/>
<touchz path='${flag_dir}/report_generated_${today}'/>
<move source='${flag_dir}/part*' target='${alert_message_file}' />
<chmod path='${alert_message_file}' permissions='-rwxrwxrwx' dir-files='true'/>
</fs>
<ok to="if_alert_prefs_present"/>
<error to="failure_email"/>
</action>
<decision name="if_alert_prefs_present">
<switch>
<case to="message_pref_alert">${(fs:exists('${alert_message_file}')) and (fs:fileSize('${alert_message_file}') gt 0 )}</case>
<default to="success_email"/>
</switch>
</decision>
<action name="message_pref_alert">
<email xmlns="uri:oozie:email-action:0.1">
<to>${notify_to}</to>
<subject>PrefTable-PrefCount-Update-${today} : Pref Count Alert</subject>
<body>In today's pref counts,the pref count difference >= 5% for some sub/unsub preferences. Please check the below file for sub/unsub details.
${alert_message_file}
For further details on count and percentage difference,please check the hive table ${pref_count_report} .
</body>
</email>
<ok to="success_email"/>
<error to="failure_email"/>
</action>
设置为工作流配置属性，而仅在如下所示的协调器属性文件中进行了设置。
${alert_message_file}还研究了关于同一主题的其他类似SO讨论： How to check whether the file exist in HDFS location,using oozie?
解决方法
通过${alert_message_file}作为工作流配置属性来解决错误。实际上，变量Alert_message_file（在属性中定义）是不可访问的，除非它通过工作流通过配置属性传递，否则将出现“变量无法解析”错误。
在workflow.xml中
<configuration>
<property>
...
</property>
<property>
<name>alert_message_file</name>
<value>${alert_message_file}</value>
</property>
</configuration>
然后按如下所示更改决策节点
<decision name="if_alert_prefs_present">
<switch>
<case to="message_pref_alert">${(fs:exists(wf:conf('alert_message_file'))) and (fs:fileSize(wf:conf('alert_message_file')) gt 0 )}</case>
<default to="success_email"/>
</switch>
</decision>