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<h1 class="topictitle1">How Does FunctionGraph Implement Domain Name Resolution?</h1>
<div id="body0000001275571889"><p id="functiongraph_03_0839__p111601850324">FunctionGraph cannot directly resolve private DNS domain names. To resolve them, call DNS APIs and perform the following steps.</p>
<div class="section" id="functiongraph_03_0839__section723623122912"><h4 class="sectiontitle">Resolving a Private DNS Domain Name with an Event Function</h4><p id="functiongraph_03_0839__p0241289307">Ensure that a VPC and private DNS domain name have been created before performing the following steps:</p>
<ol id="functiongraph_03_0839__ol4140750144620"><li id="functiongraph_03_0839__li114055054619">Associate a VPC with the private domain name and add record sets.<p id="functiongraph_03_0839__p1654932474217"><a name="functiongraph_03_0839__li114055054619"></a><a name="li114055054619"></a>Log in to the DNS console and associate a VPC with the private domain name.</p>
<div class="fignone" id="functiongraph_03_0839__fig14690103117243"><span class="figcap"><b>Figure 1 </b>Associating a VPC with the private domain name</span><br><span><img id="functiongraph_03_0839__image9690331102414" src="en-us_image_0000002250724973.png" title="Click to enlarge" class="imgResize"></span></div>
<p id="functiongraph_03_0839__p1123416214332">Click the domain name, and add a type A record set.</p>
<div class="fignone" id="functiongraph_03_0839__fig1544424002811"><span class="figcap"><b>Figure 2 </b>Adding a record set</span><br><span><img id="functiongraph_03_0839__image1044414019281" src="en-us_image_0000002250645069.png" title="Click to enlarge" class="imgResize"></span></div>
</li><li id="functiongraph_03_0839__li614065010467"><a name="functiongraph_03_0839__li614065010467"></a><a name="li614065010467"></a>Create a function.<p id="functiongraph_03_0839__p07135361550"><a name="functiongraph_03_0839__li614065010467"></a><a name="li614065010467"></a>Create a function whose runtime is Python 2.7. The following is sample code.</p>
<pre class="screen" id="functiongraph_03_0839__screen045452051412"># -*- coding:utf-8 -*-
import json
import os
def handler(event, context):
     os.system("curl -iv www.test.com")</pre>
</li><li id="functiongraph_03_0839__li1714025011466"><a name="functiongraph_03_0839__li1714025011466"></a><a name="li1714025011466"></a>Configure an agency with DNS and VPC permissions for the function.<p id="functiongraph_03_0839__p1798711118189"><a name="functiongraph_03_0839__li1714025011466"></a><a name="li1714025011466"></a>Log in to the IAM console, and configure an agency with the <strong id="functiongraph_03_0839__b52141631182916">DNS ReadOnlyAccess</strong> and <strong id="functiongraph_03_0839__b1462543616295">VPC Administrator</strong> permissions for FunctionGraph. </p>
<div class="fignone" id="functiongraph_03_0839__fig137075651315"><span class="figcap"><b>Figure 3 </b>Creating an agency with DNS and VPC permissions</span><br><span><img id="functiongraph_03_0839__image117075661310" src="en-us_image_0000002269988645.png" title="Click to enlarge" class="imgResize"></span></div>
<div class="note" id="functiongraph_03_0839__note2047524523718"><img src="public_sys-resources/note_3.0-en-us.png"><span class="notetitle"> </span><div class="notebody"><p id="functiongraph_03_0839__p247544533717">You need to configure the permission to read DNS resource data because the function needs to obtain such data when resolving a domain name. Otherwise, the following error message is displayed, indicating that the DNS resource data failed to be obtained.</p>
<pre class="screen" id="functiongraph_03_0839__screen310853124016">2020/08/20 10:37:12 GMT+08:00  Start invoke request 'a2f105b4-2e72-4fda-94a5-86d3837e961d', version: latest
<strong id="functiongraph_03_0839__b484310381414">[GET /v2/zones/{zone_id}/recordsets] failed, response: {"code":"DNS.1802","message":"Policy doesn't allow dns:recordset:list to be performed."}</strong>
2020/08/20 10:37:13 GMT+08:00  Finish invoke request 'a2f105b4-2e72-4fda-94a5-86d3837e961d', duration: 1030.072ms, billing duration: 1100ms, memory used: 77.039MB.</pre>
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</li><li id="functiongraph_03_0839__li151411550134619">Configure the function.<p id="functiongraph_03_0839__p14239125822310"><a name="functiongraph_03_0839__li151411550134619"></a><a name="li151411550134619"></a>On the details page of the function created in <a href="#functiongraph_03_0839__li614065010467">step 2</a>, click the <strong id="functiongraph_03_0839__b1323612113218">Configuration</strong> tab and configure the following settings:</p>
<ol type="a" id="functiongraph_03_0839__ol1146511522414"><li id="functiongraph_03_0839__li13466657243">For <strong id="functiongraph_03_0839__b1454723833811">Permissions</strong>, select the agency created in <a href="#functiongraph_03_0839__li1714025011466">step 3</a>.</li><li id="functiongraph_03_0839__li1619781714245">Enable VPC access and select the created VPC, subnet, and domain name.</li></ol>
<div class="fignone" id="functiongraph_03_0839__fig9673104713339"><span class="figcap"><b>Figure 4 </b>Configuring the function</span><br><span><img id="functiongraph_03_0839__image136742047103314" src="en-us_image_0000002250645081.png" title="Click to enlarge" class="imgResize"></span></div>
</li><li id="functiongraph_03_0839__li2014195074618">Check the execution result.<p id="functiongraph_03_0839__p11382139132911"><a name="functiongraph_03_0839__li2014195074618"></a><a name="li2014195074618"></a>All configured IPv4 domain names can be resolved.</p>
<div class="fignone" id="functiongraph_03_0839__fig10783957192912"><span class="figcap"><b>Figure 5 </b>Executing the function</span><br><span><img id="functiongraph_03_0839__image191549363299" src="en-us_image_0000002215725106.png" title="Click to enlarge" class="imgResize"></span></div>
</li></ol>
<div class="note" id="functiongraph_03_0839__note1695220317132"><img src="public_sys-resources/note_3.0-en-us.png"><span class="notetitle"> </span><div class="notebody"><p id="functiongraph_03_0839__p10953831121312">Changes to the IP addresses corresponding to the VPC domain names you configure will take effect in 10 minutes.</p>
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<div class="section" id="functiongraph_03_0839__section157058495714"><h4 class="sectiontitle">Resolving a Private DNS Domain Name with a Container Image–based Function</h4><ol id="functiongraph_03_0839__ol1881444185819"><li id="functiongraph_03_0839__li381434116587">Obtain a private domain name and zone ID.<p id="functiongraph_03_0839__p1078915413574"><a name="functiongraph_03_0839__li381434116587"></a><a name="li381434116587"></a>This procedure uses a domain name with a record set as an example.</p>
<ol type="a" id="functiongraph_03_0839__ol1579018417579"><li id="functiongraph_03_0839__li187905410573">Log in to the DNS console.</li><li id="functiongraph_03_0839__li179908192214">Obtain a zone ID.<p id="functiongraph_03_0839__p3605917173819"><a name="functiongraph_03_0839__li179908192214"></a><a name="li179908192214"></a>Click <span><img id="functiongraph_03_0839__image1160131743813" src="en-us_image_0000002248343474.png"></span>, and select <strong id="functiongraph_03_0839__b175173261409">Domain Name</strong> in the search box to obtain a zone ID.</p>
</li><li id="functiongraph_03_0839__li27901446579">Obtain the private domain name corresponding to a recording set.<p id="functiongraph_03_0839__p1079019410578"><a name="functiongraph_03_0839__li27901446579"></a><a name="li27901446579"></a>Click the domain name to go to the record set list, and select a record set.</p>
</li></ol>
</li></ol><ol start="2" id="functiongraph_03_0839__ol1886674214412"><li id="functiongraph_03_0839__li5866742446">Compile the resolution logic.<p id="functiongraph_03_0839__p179134115711"><a name="functiongraph_03_0839__li5866742446"></a><a name="li5866742446"></a>Use  to debug the API used to <a href="https://docs.otc.t-systems.com/domain-name-service/api-ref/apis/record_set_management/querying_record_sets_in_a_zone.html#dns-api-64004" target="_blank" rel="noopener noreferrer">query record sets in a zone</a>.</p>
<ul id="functiongraph_03_0839__ul81891233102017"><li id="functiongraph_03_0839__li13189103311203">Set <strong id="functiongraph_03_0839__b153075491429">zone_id</strong> to the zone ID obtained in the preceding step, and click <strong id="functiongraph_03_0839__b430794919421">Debug</strong>. The IP address of the private domain name is displayed in the response body.</li><li id="functiongraph_03_0839__li12621282118">Switch to the <strong id="functiongraph_03_0839__b13966105864215">Sample Code</strong> tab to obtain the complete code. For details about the dependencies, click <strong id="functiongraph_03_0839__b79672587423">View SDK Details</strong>.</li></ul>
</li></ol>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="functiongraph_03_0110_00.html">General FAQs</a></div>
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