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<li class="toctree-l1 current"><a class="current reference internal" href="#">Workflow definition</a><ul>
<li class="toctree-l2"><a class="reference internal" href="#workflow-definition-dig-files">Workflow definition: *.dig files</a></li>
<li class="toctree-l2"><a class="reference internal" href="#is-a-task">“+” is a task</a></li>
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<div class="section" id="workflow-definition">
<h1>Workflow definition<a class="headerlink" href="#workflow-definition" title="Permalink to this headline">¶</a></h1>
<div class="contents local topic" id="contents">
<ul class="simple">
<li><p><a class="reference internal" href="#workflow-definition-dig-files" id="id2">Workflow definition: *.dig files</a></p></li>
<li><p><a class="reference internal" href="#is-a-task" id="id3">“+” is a task</a></p></li>
<li><p><a class="reference internal" href="#operators" id="id4">operators></a></p></li>
<li><p><a class="reference internal" href="#using-variables" id="id5">Using ${variables}</a></p></li>
<li><p><a class="reference internal" href="#calculating-variables" id="id6">Calculating variables</a></p></li>
<li><p><a class="reference internal" href="#defining-variables" id="id7">Defining variables</a></p>
<ul>
<li><p><a class="reference internal" href="#using-export-parameter" id="id8">Using _export: parameter</a></p></li>
<li><p><a class="reference internal" href="#using-api" id="id9">Using API</a></p></li>
<li><p><a class="reference internal" href="#starting-a-session-with-variables" id="id10">Starting a session with variables</a></p></li>
</ul>
</li>
<li><p><a class="reference internal" href="#include-another-file" id="id11">!include another file</a></p></li>
<li><p><a class="reference internal" href="#parallel-execution" id="id12">Parallel execution</a></p></li>
<li><p><a class="reference internal" href="#retrying-failed-tasks-automatically" id="id13">Retrying failed tasks automatically</a></p></li>
<li><p><a class="reference internal" href="#sending-error-notification" id="id14">Sending error notification</a></p></li>
</ul>
</div>
<div class="section" id="workflow-definition-dig-files">
<h2><a class="toc-backref" href="#id2">Workflow definition: *.dig files</a><a class="headerlink" href="#workflow-definition-dig-files" title="Permalink to this headline">¶</a></h2>
<p>A digdag workflow is defined in a file named with <code class="docutils literal notranslate"><span class="pre">.dig</span></code> suffix. Name of the file is name of the workflow.</p>
<p>For example, if you create <code class="docutils literal notranslate"><span class="pre">hello_world</span></code> workflow, you will create <code class="docutils literal notranslate"><span class="pre">hello_world.dig</span></code> file. Contents of the file looks like this:</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">timezone</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">UTC</span>
<span class="nt">+step1</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/shell_sample.sh</span>
<span class="nt">+step2</span><span class="p">:</span>
<span class="nt">py></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks.MyWorkflow.step2</span>
<span class="nt">param1</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">this is param1</span>
<span class="nt">+step3</span><span class="p">:</span>
<span class="nt">rb></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">MyWorkflow.step3</span>
<span class="nt">require</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/ruby_sample.rb</span>
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">timezone</span></code> parameter is used to configure the time zone of the workflow and affects session timestamp variables and scheduling. The default time zone is <code class="docutils literal notranslate"><span class="pre">UTC</span></code>. Some examples of other valid time zones are <code class="docutils literal notranslate"><span class="pre">America/Los_Angeles</span></code>, <code class="docutils literal notranslate"><span class="pre">Europe/Berlin</span></code>, <code class="docutils literal notranslate"><span class="pre">Asia/Tokyo</span></code>, etc.</p>
</div>
<div class="section" id="is-a-task">
<h2><a class="toc-backref" href="#id3">“+” is a task</a><a class="headerlink" href="#is-a-task" title="Permalink to this headline">¶</a></h2>
<p>Key names starting with <code class="docutils literal notranslate"><span class="pre">+</span></code> sign is a task. Tasks run from the top to bottom in order. A task can be nested as a child of another task. In above example, <code class="docutils literal notranslate"><span class="pre">+step2</span></code> runs after <code class="docutils literal notranslate"><span class="pre">+step1</span></code> as a child of <code class="docutils literal notranslate"><span class="pre">+main</span></code> task.</p>
</div>
<div class="section" id="operators">
<h2><a class="toc-backref" href="#id4">operators></a><a class="headerlink" href="#operators" title="Permalink to this headline">¶</a></h2>
<p>A task with <code class="docutils literal notranslate"><span class="pre">type>:</span> <span class="pre">command</span></code> or <code class="docutils literal notranslate"><span class="pre">_type:</span> <span class="pre">NAME</span></code> parameter executes an action. You can choose various kinds of operators such as <a class="reference external" href="operators/sh.html">running shell scripts</a>, <a class="reference external" href="operators/py.html">Python methods</a>, <a class="reference external" href="operators/mail.html">sending email</a>, etc. See <a class="reference external" href="operators.html">Operators</a> page for the list of built-in operators.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Setting <code class="docutils literal notranslate"><span class="pre">foo>:</span> <span class="pre">bar</span></code> parameter is equivalent to setting <code class="docutils literal notranslate"><span class="pre">_type:</span> <span class="pre">foo</span></code> and <code class="docutils literal notranslate"><span class="pre">_command:</span> <span class="pre">bar</span></code> parameters. That is a syntax sugar of setting 2 parameters in 1 line.</p>
</div>
</div>
<div class="section" id="using-variables">
<h2><a class="toc-backref" href="#id5">Using ${variables}</a><a class="headerlink" href="#using-variables" title="Permalink to this headline">¶</a></h2>
<p>Workflow can embed variables using <code class="docutils literal notranslate"><span class="pre">${...}</span></code> syntax. You can use built-in variables or define your own variables.</p>
<p>Here is the list of built-in variables:</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 28%" />
<col style="width: 39%" />
<col style="width: 33%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>Name</p></th>
<th class="head"><p>Description</p></th>
<th class="head"><p>Example</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p><strong>timezone</strong></p></td>
<td><p>Timezone of this workflow</p></td>
<td><p>America/Los_Angeles</p></td>
</tr>
<tr class="row-odd"><td><p><strong>project_id</strong></p></td>
<td><p>The project ID of this workflow</p></td>
<td><p>12345</p></td>
</tr>
<tr class="row-even"><td><p><strong>session_uuid</strong></p></td>
<td><p>Unique UUID of this session</p></td>
<td><p>414a8b9e-b365-4394-916a-f0ed9987bd2b</p></td>
</tr>
<tr class="row-odd"><td><p><strong>session_id</strong></p></td>
<td><p>Integer ID of this session</p></td>
<td><p>2381</p></td>
</tr>
<tr class="row-even"><td><p><strong>session_time</strong></p></td>
<td><p>Time of this session with time zone</p></td>
<td><p>2016-01-30T00:00:00-08:00</p></td>
</tr>
<tr class="row-odd"><td><p><strong>session_date</strong></p></td>
<td><p>Date part of session_time</p></td>
<td><p>2016-01-30</p></td>
</tr>
<tr class="row-even"><td><p><strong>session_date_compact</strong></p></td>
<td><p>Date part of session_time (compact)</p></td>
<td><p>20160130</p></td>
</tr>
<tr class="row-odd"><td><p><strong>session_local_time</strong></p></td>
<td><p>Local time format of session_time</p></td>
<td><p>2016-01-30 00:00:00</p></td>
</tr>
<tr class="row-even"><td><p><strong>session_tz_offset</strong></p></td>
<td><p>Time zone offset part of session_time</p></td>
<td><p>-0800</p></td>
</tr>
<tr class="row-odd"><td><p><strong>session_unixtime</strong></p></td>
<td><p>Seconds since the epoch time</p></td>
<td><p>1454140800</p></td>
</tr>
<tr class="row-even"><td><p><strong>task_name</strong></p></td>
<td><p>Name of this task</p></td>
<td><p>+my_workflow+parent_task+child_task0</p></td>
</tr>
<tr class="row-odd"><td><p><strong>attempt_id</strong></p></td>
<td><p>Integer ID of this attempt</p></td>
<td><p>7</p></td>
</tr>
</tbody>
</table>
<p>If <a class="reference external" href="scheduling_workflow.html">schedule: option is set</a>, <strong>last_session_time</strong> and <strong>next_session_time</strong> are also available as following:</p>
<table class="docutils align-default">
<colgroup>
<col style="width: 41%" />
<col style="width: 30%" />
<col style="width: 30%" />
</colgroup>
<thead>
<tr class="row-odd"><th class="head"><p>Name</p></th>
<th class="head"><p>Example (hourly schedule)</p></th>
<th class="head"><p>Example (daily schedule)</p></th>
</tr>
</thead>
<tbody>
<tr class="row-even"><td><p><strong>last_session_time</strong></p></td>
<td><p>2016-01-29T23:00:00-08:00</p></td>
<td><p>2016-01-29T00:00:00-08:00</p></td>
</tr>
<tr class="row-odd"><td><p><strong>last_session_date</strong></p></td>
<td><p>2016-01-29</p></td>
<td><p>2016-01-29</p></td>
</tr>
<tr class="row-even"><td><p><strong>last_session_date_compact</strong></p></td>
<td><p>20160129</p></td>
<td><p>20160129</p></td>
</tr>
<tr class="row-odd"><td><p><strong>last_session_local_time</strong></p></td>
<td><p>2016-01-29 23:00:00</p></td>
<td><p>2016-01-29 00:00:00</p></td>
</tr>
<tr class="row-even"><td><p><strong>last_session_tz_offset</strong></p></td>
<td><p>-0800</p></td>
<td><p>-0800</p></td>
</tr>
<tr class="row-odd"><td><p><strong>last_session_unixtime</strong></p></td>
<td><p>1454137200</p></td>
<td><p>1454054400</p></td>
</tr>
<tr class="row-even"><td><p><strong>last_executed_session_time</strong></p></td>
<td><p>2016-01-29T23:00:00-08:00</p></td>
<td><p>2016-01-29T00:00:00-08:00</p></td>
</tr>
<tr class="row-odd"><td><p><strong>last_executed_session_unixtime</strong></p></td>
<td><p>1454137200</p></td>
<td><p>1454054400</p></td>
</tr>
<tr class="row-even"><td><p><strong>next_session_time</strong></p></td>
<td><p>2016-01-30T01:00:00-08:00</p></td>
<td><p>2016-01-31T00:00:00-08:00</p></td>
</tr>
<tr class="row-odd"><td><p><strong>next_session_date</strong></p></td>
<td><p>2016-01-30</p></td>
<td><p>2016-01-31</p></td>
</tr>
<tr class="row-even"><td><p><strong>next_session_date_compact</strong></p></td>
<td><p>20160130</p></td>
<td><p>20160131</p></td>
</tr>
<tr class="row-odd"><td><p><strong>next_session_local_time</strong></p></td>
<td><p>2016-01-30 01:00:00</p></td>
<td><p>2016-01-31 00:00:00</p></td>
</tr>
<tr class="row-even"><td><p><strong>next_session_tz_offset</strong></p></td>
<td><p>-0800</p></td>
<td><p>-0800</p></td>
</tr>
<tr class="row-odd"><td><p><strong>next_session_unixtime</strong></p></td>
<td><p>1454144400</p></td>
<td><p>1454227200</p></td>
</tr>
</tbody>
</table>
<p>last_session_time is the timestamp of the last schedule. If the schedule is hourly, it’s the last hour. If the schedule is daily, it’s yesterday. It doesn’t matter whether the last schedule actually ran or not. It’s simply set to the last timestamp calculated from the current session time.
last_executed_session_time variable is the previously executed session time.</p>
</div>
<div class="section" id="calculating-variables">
<h2><a class="toc-backref" href="#id6">Calculating variables</a><a class="headerlink" href="#calculating-variables" title="Permalink to this headline">¶</a></h2>
<p>You can use basic JavaScript scripts in <code class="docutils literal notranslate"><span class="pre">${...}</span></code> syntax to calculate variables.</p>
<p>A common use case is formatting timestamp in different format. Digdag bundles <a class="reference external" href="http://momentjs.com/">Moment.js</a> for time calculation.</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">timezone</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">America/Los_Angeles</span>
<span class="nt">+format_session_time</span><span class="p">:</span>
<span class="c1"># "2016-09-24 00:00:00 -0700"</span>
<span class="nt">echo></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">${moment(session_time).format("YYYY-MM-DD HH:mm:ss Z")}</span>
<span class="nt">+format_in_utc</span><span class="p">:</span>
<span class="c1"># "2016-09-24 07:00:00"</span>
<span class="nt">echo></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">${moment(session_time).utc().format("YYYY-MM-DD HH:mm:ss")}</span>
<span class="nt">+format_tomorrow</span><span class="p">:</span>
<span class="c1"># "September 24, 2016 12:00 AM"</span>
<span class="nt">echo></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">${moment(session_time).add(1, 'days').format("LLL")}</span>
<span class="nt">+get_execution_time</span><span class="p">:</span>
<span class="c1"># "2016-09-24 05:24:49 -0700"</span>
<span class="nt">echo></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">${moment().format("YYYY-MM-DD HH:mm:ss Z")}</span>
</pre></div>
</div>
</div>
<div class="section" id="defining-variables">
<h2><a class="toc-backref" href="#id7">Defining variables</a><a class="headerlink" href="#defining-variables" title="Permalink to this headline">¶</a></h2>
<p>You can define variables in 3 ways:</p>
<ul class="simple">
<li><p>Using <code class="docutils literal notranslate"><span class="pre">_export</span></code> parameter in YAML</p></li>
<li><p>Setting variable programmably using API</p></li>
<li><p>Starting a session with variables</p></li>
</ul>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>You cannot overwrite built-in variables.</p>
</div>
<div class="section" id="using-export-parameter">
<h3><a class="toc-backref" href="#id8">Using _export: parameter</a><a class="headerlink" href="#using-export-parameter" title="Permalink to this headline">¶</a></h3>
<p>In a YAML file, <code class="docutils literal notranslate"><span class="pre">_export:</span></code> directive defines variables. This is useful to load static configurations such as host name of a database.</p>
<p>If a task has <code class="docutils literal notranslate"><span class="pre">_export</span></code> directive, the task and its children can use the variables because it defines variables in a scope. With following example, all tasks can use <code class="docutils literal notranslate"><span class="pre">foo=1</span></code> but only +step1 (and +analyze) can use <code class="docutils literal notranslate"><span class="pre">bar=2</span></code>.</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">_export</span><span class="p">:</span>
<span class="nt">foo</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">1</span>
<span class="nt">+prepare</span><span class="p">:</span>
<span class="nt">py></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks.MyWorkflow.prepare</span>
<span class="nt">+analyze</span><span class="p">:</span>
<span class="nt">_export</span><span class="p">:</span>
<span class="nt">bar</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">2</span>
<span class="nt">+step1</span><span class="p">:</span>
<span class="nt">py></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks.MyWorkflow.analyze_step1</span>
<span class="nt">+dump</span><span class="p">:</span>
<span class="nt">py></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks.MyWorkflow.dump</span>
</pre></div>
</div>
</div>
<div class="section" id="using-api">
<h3><a class="toc-backref" href="#id9">Using API</a><a class="headerlink" href="#using-api" title="Permalink to this headline">¶</a></h3>
<p>You can set variables programmably using language API. For example, Python API provides <code class="docutils literal notranslate"><span class="pre">digdag.env.export</span></code> and <code class="docutils literal notranslate"><span class="pre">digdag.env.store</span></code>:</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">digdag</span>
<span class="k">class</span> <span class="nc">MyWorkflow</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">prepare</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">digdag</span><span class="o">.</span><span class="n">env</span><span class="o">.</span><span class="n">store</span><span class="p">({</span><span class="s2">"my_param"</span><span class="p">:</span> <span class="mi">2</span><span class="p">})</span>
<span class="k">def</span> <span class="nf">analyze</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">my_var</span><span class="p">):</span>
<span class="k">print</span><span class="p">(</span><span class="s2">"my_var should be 2: </span><span class="si">%d</span><span class="s2">"</span> <span class="o">%</span> <span class="n">my_var</span><span class="p">)</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">digdag.env.store(dict)</span></code> stores variables so that all following tasks (including tasks which are not children of the task) can use them.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">import</span> <span class="nn">digdag</span>
<span class="k">class</span> <span class="nc">MyWorkflow</span><span class="p">(</span><span class="nb">object</span><span class="p">):</span>
<span class="k">def</span> <span class="nf">export_and_call_child</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">digdag</span><span class="o">.</span><span class="n">env</span><span class="o">.</span><span class="n">export</span><span class="p">({</span><span class="s2">"my_param"</span><span class="p">:</span> <span class="mi">2</span><span class="p">})</span>
<span class="n">digdag</span><span class="o">.</span><span class="n">env</span><span class="o">.</span><span class="n">add_subtask</span><span class="p">({</span><span class="s1">'_type'</span><span class="p">:</span> <span class="s1">'call'</span><span class="p">,</span> <span class="s1">'_command'</span><span class="p">:</span> <span class="s1">'child1.dig'</span><span class="p">})</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">digdag.env.export(dict)</span></code> is same with “_export” directive in YAML file. It defines variables for their children.</p>
<p>See language API documents for details:</p>
<ul class="simple">
<li><p><a class="reference external" href="python_api.html">Python API</a></p></li>
<li><p><a class="reference external" href="ruby_api.html">Ruby API</a></p></li>
</ul>
</div>
<div class="section" id="starting-a-session-with-variables">
<h3><a class="toc-backref" href="#id10">Starting a session with variables</a><a class="headerlink" href="#starting-a-session-with-variables" title="Permalink to this headline">¶</a></h3>
<p>You can set variables when you start a new workflow session. To set variables, use <code class="docutils literal notranslate"><span class="pre">-p</span> <span class="pre">KEY=VALUE</span></code> multiple times:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> digdag run -p <span class="nv">my_var1</span><span class="o">=</span>foo -p <span class="nv">my_var2</span><span class="o">=</span>abc
</pre></div>
</div>
</div>
</div>
<div class="section" id="include-another-file">
<h2><a class="toc-backref" href="#id11">!include another file</a><a class="headerlink" href="#include-another-file" title="Permalink to this headline">¶</a></h2>
<p>You can divide a YAML file into small files to organize complex workflow. <code class="docutils literal notranslate"><span class="pre">!include</span></code> directive is used to gather those files:</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">_export</span><span class="p">:</span>
<span class="nt">mysql</span><span class="p">:</span>
<span class="nt">!include </span><span class="p">:</span> <span class="s">'config/mysql.dig'</span>
<span class="nt">hive</span><span class="p">:</span>
<span class="nt">!include </span><span class="p">:</span> <span class="s">'config/hive.dig'</span>
<span class="nt">!include </span><span class="p">:</span> <span class="s">'tasks/foo.dig'</span>
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>A whitespace character before <code class="docutils literal notranslate"><span class="pre">:</span></code> is necessary by a limitation to be a valid YAML.</p>
</div>
</div>
<div class="section" id="parallel-execution">
<h2><a class="toc-backref" href="#id12">Parallel execution</a><a class="headerlink" href="#parallel-execution" title="Permalink to this headline">¶</a></h2>
<p>If <code class="docutils literal notranslate"><span class="pre">_parallel:</span> <span class="pre">true</span></code> parameter is set to a group, child tasks in the group run in parallel (grandchildren are not affected):</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">+prepare</span><span class="p">:</span>
<span class="c1"># +data1, +data2, and +data3 run in parallel.</span>
<span class="nt">_parallel</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">true</span>
<span class="nt">+data1</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data1.sh</span>
<span class="nt">+data2</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data2.sh</span>
<span class="nt">+data3</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data3.sh</span>
<span class="nt">+analyze</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/analyze_prepared_data_sets.sh</span>
</pre></div>
</div>
<p>If <code class="docutils literal notranslate"><span class="pre">_parallel:</span> <span class="pre">{limit:</span> <span class="pre">N}</span></code> (N is an integer: 1, 2, 3, …) parameter is set to a group,
child tasks in the group run in parallel is limited to N (grandchildren are not affected):</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">+prepare</span><span class="p">:</span>
<span class="c1"># +data1 and +data2 run in parallel, then +data3 and +data4 run in parallel.</span>
<span class="c1"># (+data1 and +data2 need to be successful.)</span>
<span class="nt">_parallel</span><span class="p">:</span>
<span class="nt">limit</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">2</span>
<span class="nt">+data1</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data1.sh</span>
<span class="nt">+data2</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data2.sh</span>
<span class="nt">+data3</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data3.sh</span>
<span class="nt">+data4</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data4.sh</span>
<span class="nt">+analyze</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/analyze_prepared_data_sets.sh</span>
</pre></div>
</div>
<p>If <code class="docutils literal notranslate"><span class="pre">_background:</span> <span class="pre">true</span></code> parameter is set to a task or group, the task or group run in parallel with previous tasks. Next task wait for the completion of the background task or group.</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">+prepare</span><span class="p">:</span>
<span class="nt">+data1</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data1.sh</span>
<span class="c1"># +data1 and +data2 run in parallel.</span>
<span class="nt">+data2</span><span class="p">:</span>
<span class="nt">_background</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">true</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data2.sh</span>
<span class="c1"># +data3 runs after +data1 and +data2.</span>
<span class="nt">+data3</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/prepare_data3.sh</span>
<span class="nt">+analyze</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/analyze_prepared_data_sets.sh</span>
</pre></div>
</div>
</div>
<div class="section" id="retrying-failed-tasks-automatically">
<h2><a class="toc-backref" href="#id13">Retrying failed tasks automatically</a><a class="headerlink" href="#retrying-failed-tasks-automatically" title="Permalink to this headline">¶</a></h2>
<p>If <code class="docutils literal notranslate"><span class="pre">_retry:</span> <span class="pre">N</span></code> (N is an integer: 1, 2, 3, …) parameter is set to a group, it retries the group from the beginning when one or more children failed.</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">+prepare</span><span class="p">:</span>
<span class="c1"># If +erase_table, +load_data, or +check_loaded_data fail, it retries from</span>
<span class="c1"># +erase_table again.</span>
<span class="nt">_retry</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">3</span>
<span class="nt">+erase_table</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/erase_table.sh</span>
<span class="nt">+load_data</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/load_data.sh</span>
<span class="nt">+check_loaded_data</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/check_loaded_data.sh</span>
<span class="nt">+analyze</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/analyze_prepared_data_sets.sh</span>
</pre></div>
</div>
<p>Tasks also support <code class="docutils literal notranslate"><span class="pre">_retry:</span> <span class="pre">N</span></code> parameter to retry the specific task. Note that some operators don’t support the generic <code class="docutils literal notranslate"><span class="pre">_retry</span></code> option but have their own options to control retrying behavior. Operators that involve external systems may reuse previous results. To ensure an external task is repeated, you may use <code class="docutils literal notranslate"><span class="pre">_retry</span></code> at the group level.</p>
<p>You can set interval to _retry as follows.</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">+prepare</span><span class="p">:</span>
<span class="nt">_retry</span><span class="p">:</span>
<span class="nt">limit</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">3</span>
<span class="nt">interval</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">10</span>
<span class="nt">interval_type</span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">exponential</span>
</pre></div>
</div>
<p><code class="docutils literal notranslate"><span class="pre">limit</span></code> is number of retry.
<code class="docutils literal notranslate"><span class="pre">interval</span></code> is interval time (seconds).
Additionaly you can choose <code class="docutils literal notranslate"><span class="pre">interval_type</span></code> as <code class="docutils literal notranslate"><span class="pre">constant</span></code> or <code class="docutils literal notranslate"><span class="pre">exponential</span></code>.
If you set <code class="docutils literal notranslate"><span class="pre">constant</span></code> (default) , interval time is constant as set by <code class="docutils literal notranslate"><span class="pre">limit</span></code>.
If you set <code class="docutils literal notranslate"><span class="pre">exponential</span></code>, interval time increases with each retry as <code class="docutils literal notranslate"><span class="pre">interval</span> <span class="pre">x</span> <span class="pre">2^(retry_count-1)</span></code>.
In the above example, first retry interval is 10 secs, second is 20 secs, third is 40 secs.</p>
</div>
<div class="section" id="sending-error-notification">
<h2><a class="toc-backref" href="#id14">Sending error notification</a><a class="headerlink" href="#sending-error-notification" title="Permalink to this headline">¶</a></h2>
<p>If an operator configuration is set at <code class="docutils literal notranslate"><span class="pre">_error:</span></code> parameter, the operator runs when the workflow fails.</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="c1"># this task runs when a workflow fails.</span>
<span class="nt">_error</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/runs_when_workflow_failed.sh</span>
<span class="nt">+analyze</span><span class="p">:</span>
<span class="nt">sh></span><span class="p">:</span> <span class="l l-Scalar l-Scalar-Plain">tasks/analyze_prepared_data_sets.sh</span>
</pre></div>
</div>
<p>To send mails, you can use <a class="reference external" href="operators/mail.html">mail> operator</a>.</p>
</div>
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