>>> [!note] Migrated issue <!-- Drupal.org comment --> <!-- Migrated from issue #3613619. --> Reported by: [das-peter](https://www.drupal.org/user/762870) Related to !116 !107 >>> <h3 id="summary-problem-motivation">Problem/Motivation</h3> <p>&#9888;&#65039;Code has been generated using LLM support. It has had some review cycles by a grumpy free range dev.&#9888;&#65039;</p> <p>I've had some similar issues as described in <a href="https://www.drupal.org/project/graphql_compose/issues/3477239">https://www.drupal.org/project/graphql_compose/issues/3477239</a> and <a href="https://www.drupal.org/project/graphql_compose/issues/3541422">https://www.drupal.org/project/graphql_compose/issues/3541422</a><br> However, I use <code>graphql_core_schema</code> not <code>graphql_compose</code> so these issues seemed to point towards a more central caching issue.</p> <p>I've started digging trough the code and got suspicious of the cache handling around <code>\Drupal\graphql\Plugin\GraphQL\Schema\SdlSchemaPluginBase</code> because it handles multiple cache items and processes stuff conditionally.<br> In a cache that can have (single item) random evictions like memcache and / or redis this is often problematic.</p> <p>I've pointed an LLM towards the suspected problem and it came up with the following mechanism:</p> <blockquote><p> <code>getSchema()</code> in graphql's SdlSchemaPluginBase.php:119 builds the schema from four independent cache entries &mdash; schema:, extension:, schema_extension:, full: &mdash; and <code>CoreComposableSchema</code> has a hidden dependency between two of them:</p> <ul> <li><code>$this-&gt;generatedTypes</code> is written in exactly one place: CoreComposableSchema.php:172, inside <code>getSchemaDefinition()</code>.</li> <li><code>getSchemaDefinition()</code> only runs when the <code>schema</code> cache misses (CoreComposableSchema.php:308).</li> <li><code>getExtensionDocument()</code> reads it at CoreComposableSchema.php:341:<br> <code>$extension-&gt;getTypeExtensionDefinition($this-&gt;generatedTypes ?? [])</code>.</li> </ul> <p> So if <code>schema</code> is warm while <code>extension</code> (or <code>full</code>) is cold &mdash; which is precisely what a volatile/evicting backend produces &mdash; every TypeAwareSchemaExtensionInterface gets an empty type list and bails</p> <div class="codeblock"> <pre><span style="color: #000000"><span style="color: #0000BB">&lt;?php<br>&nbsp; </span><span style="color: #FF8000">// ImageExtension::getTypeExtensionDefinition()<br>&nbsp; </span><span style="color: #007700">if (!</span><span style="color: #0000BB">in_array</span><span style="color: #007700">(</span><span style="color: #DD0000">'FieldItemTypeImage'</span><span style="color: #007700">, </span><span style="color: #0000BB">$types</span><span style="color: #007700">)) {<br>&nbsp;&nbsp;&nbsp; return </span><span style="color: #DD0000">''</span><span style="color: #007700">;&nbsp;&nbsp; </span><span style="color: #FF8000">// &lt;- $types is [] because generatedTypes was never computed<br>&nbsp; </span><span style="color: #007700">}<br></span><span style="color: #0000BB">?&gt;</span></span></pre></div> </blockquote> <p>From this I was able to concoct the below reproduction steps to verify this was indeed a valid problem.</p> <h4 id="summary-steps-reproduce">Steps to reproduce</h4> <ol> <li>Configure graphql server with some additional schemas from either graphql_compose or graphql_core_schema</li> <li>Ensure you're not running in development mode and that AST caching is enabled. <br>This also should trigger <code>assumeValid</code> to be true.</li> <li>Prepare a GraphQl Query that uses one of the query additions from graphql_compose or graphql_core_schema</li> <li>Execute the GraphQl Query</li> <li>Delete the following AST cache entries e.g. via drush:<br> <pre>ddev drush ev "\Drupal::getContainer()-&gt;get('cache.graphql.ast')-&gt;deleteMultiple([<br>&nbsp;&nbsp;&nbsp; 'extension:core_composable:general:en',<br>&nbsp;&nbsp;&nbsp; 'full:core_composable:general:en',<br>&nbsp; ]);"</pre></li> <li>Execute the GraphQl Query again: Should lead to broken query, either missing type error OR simply missing result properties of that type. <strong>This will not recover!</strong></li> <li>Clear all graphql caches: <code>ddev drush ev "\Drupal::getContainer()-&gt;get('cache.graphql.ast')-&gt;deleteAll();"</code></li> <li>Execute the GraphQl Query again - all fine again</li> </ol> <h3 id="summary-proposed-resolution">Proposed resolution</h3> <p>Generally speaking a cache relying on multiple items has to expect that single items are lost - due to the ephemeral nature of caching - and be able to detect and recover from such a situation.</p> <h3 id="summary-remaining-tasks">Remaining tasks</h3> <ol> <li>&#10003; Write tests to verify behavior</li> <li>Write fix - &#9888;&#65039;Current code has been generated using LLM support. It has had some review cycles by a grumpy free range dev.&#9888;&#65039;</li> <li>Review</li> <li>Merge</li> <li>Profit</li> </ol> <h3 id="summary-ui-changes">User interface changes</h3> <p>None.</p> <h3 id="summary-api-changes">API changes</h3> <p>None.</p> <h3 id="summary-data-model-changes">Data model changes</h3> <p>None.</p> > Related issue: [Issue #3477239](https://www.drupal.org/node/3477239) > Related issue: [Issue #3541422](https://www.drupal.org/node/3541422)