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docs: collect refreshed mongo-ops wiki site (API-correct overhaul, v0.1.5)

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Vishesh 'ironeagle' Bangotra
2026-09-14 13:46:11 +05:30
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mongo-ops/03_use_cases/03_transactions/index.html
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@@ -457,7 +457,7 @@
<span class="md-ellipsis">
02 components
Core Components
</span>
@@ -575,6 +575,8 @@
<input class="md-nav__toggle md-toggle" type="checkbox" id="__toc">
<label class="md-nav__link md-nav__link--active" for="__toc">
@@ -607,6 +609,8 @@
<label class="md-nav__title" for="__toc">
<span class="md-nav__icon md-icon"></span>
@@ -615,9 +619,36 @@
<ul class="md-nav__list" data-md-component="toc" data-md-scrollfix>
<li class="md-nav__item">
<a href="#use-case-3-transaction-support-for-multi-document-operations" class="md-nav__link">
<a href="#whats-new" class="md-nav__link">
<span class="md-ellipsis">
Use Case 3: Transaction Support for Multi-Document Operations
📦 What's New?
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#example" class="md-nav__link">
<span class="md-ellipsis">
🚀 Example
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#tips" class="md-nav__link">
<span class="md-ellipsis">
💡 Tips
</span>
</a>
</li>
<li class="md-nav__item">
<a href="#related" class="md-nav__link">
<span class="md-ellipsis">
Related
</span>
</a>
@@ -1004,71 +1035,129 @@
<h1>Transactions</h1>
<h3 id="use-case-3-transaction-support-for-multi-document-operations">Use Case 3: Transaction Support for Multi-Document Operations</h3>
<p><strong>Scenario:</strong> Order processing system that updates inventory and creates order atomically.</p>
<div class="language-python highlight"><span class="filename">Python</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="kn">from</span><span class="w"> </span><span class="nn">mongo_ops</span><span class="w"> </span><span class="kn">import</span> <span class="n">BaseDocument</span><span class="p">,</span> <span class="n">BaseRepository</span><span class="p">,</span> <span class="n">TransactionManager</span>
<h1 id="use-case-3-transaction-support-for-multi-document-operations">Use Case 3: Transaction Support for Multi-Document Operations</h1>
<p><strong>Scenario:</strong> Order processing must update inventory and create an order <strong>atomically</strong>. Any failure rolls both back.</p>
<hr />
<h2 id="whats-new">📦 What's New?</h2>
<table>
<thead>
<tr>
<th>Component</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td><code>TransactionManager.start_session</code></td>
<td>Async context manager yielding a session with an active transaction.</td>
</tr>
<tr>
<td><code>session=</code> kwarg</td>
<td>Pass to every <code>insert_one</code> / <code>update_one</code> / <code>find_one</code> inside the block.</td>
</tr>
</tbody>
</table>
<hr />
<h2 id="example">🚀 Example</h2>
<div class="language-python highlight"><span class="filename">Python</span><pre><span></span><code><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><span class="kn">from</span><span class="w"> </span><span class="nn">contextlib</span><span class="w"> </span><span class="kn">import</span> <span class="n">asynccontextmanager</span>
<a id="__codelineno-0-2" name="__codelineno-0-2" href="#__codelineno-0-2"></a><span class="kn">from</span><span class="w"> </span><span class="nn">datetime</span><span class="w"> </span><span class="kn">import</span> <span class="n">datetime</span>
<a id="__codelineno-0-3" name="__codelineno-0-3" href="#__codelineno-0-3"></a><span class="kn">from</span><span class="w"> </span><span class="nn">typing</span><span class="w"> </span><span class="kn">import</span> <span class="n">List</span>
<a id="__codelineno-0-4" name="__codelineno-0-4" href="#__codelineno-0-4"></a><span class="kn">from</span><span class="w"> </span><span class="nn">pydantic</span><span class="w"> </span><span class="kn">import</span> <span class="n">Field</span>
<a id="__codelineno-0-5" name="__codelineno-0-5" href="#__codelineno-0-5"></a>
<a id="__codelineno-0-6" name="__codelineno-0-6" href="#__codelineno-0-6"></a><span class="k">class</span><span class="w"> </span><span class="nc">Order</span><span class="p">(</span><span class="n">BaseDocument</span><span class="p">):</span>
<a id="__codelineno-0-7" name="__codelineno-0-7" href="#__codelineno-0-7"></a> <span class="n">user_id</span><span class="p">:</span> <span class="nb">str</span>
<a id="__codelineno-0-8" name="__codelineno-0-8" href="#__codelineno-0-8"></a> <span class="n">items</span><span class="p">:</span> <span class="n">List</span><span class="p">[</span><span class="nb">dict</span><span class="p">]</span> <span class="c1"># [{&quot;product_id&quot;: &quot;...&quot;, &quot;quantity&quot;: 2}]</span>
<a id="__codelineno-0-9" name="__codelineno-0-9" href="#__codelineno-0-9"></a> <span class="n">total_amount</span><span class="p">:</span> <span class="nb">float</span>
<a id="__codelineno-0-10" name="__codelineno-0-10" href="#__codelineno-0-10"></a> <span class="n">status</span><span class="p">:</span> <span class="nb">str</span> <span class="o">=</span> <span class="s2">&quot;pending&quot;</span>
<a id="__codelineno-0-11" name="__codelineno-0-11" href="#__codelineno-0-11"></a>
<a id="__codelineno-0-12" name="__codelineno-0-12" href="#__codelineno-0-12"></a><span class="k">class</span><span class="w"> </span><span class="nc">OrderRepository</span><span class="p">(</span><span class="n">BaseRepository</span><span class="p">[</span><span class="n">Order</span><span class="p">]):</span>
<a id="__codelineno-0-13" name="__codelineno-0-13" href="#__codelineno-0-13"></a> <span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<a id="__codelineno-0-14" name="__codelineno-0-14" href="#__codelineno-0-14"></a> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">(</span><span class="s2">&quot;orders&quot;</span><span class="p">,</span> <span class="n">Order</span><span class="p">)</span>
<a id="__codelineno-0-3" name="__codelineno-0-3" href="#__codelineno-0-3"></a>
<a id="__codelineno-0-4" name="__codelineno-0-4" href="#__codelineno-0-4"></a><span class="kn">from</span><span class="w"> </span><span class="nn">bson</span><span class="w"> </span><span class="kn">import</span> <span class="n">ObjectId</span>
<a id="__codelineno-0-5" name="__codelineno-0-5" href="#__codelineno-0-5"></a><span class="kn">from</span><span class="w"> </span><span class="nn">fastapi</span><span class="w"> </span><span class="kn">import</span> <span class="n">FastAPI</span><span class="p">,</span> <span class="n">HTTPException</span>
<a id="__codelineno-0-6" name="__codelineno-0-6" href="#__codelineno-0-6"></a><span class="kn">from</span><span class="w"> </span><span class="nn">mongo_ops</span><span class="w"> </span><span class="kn">import</span> <span class="n">BaseDocument</span><span class="p">,</span> <span class="n">BaseRepository</span><span class="p">,</span> <span class="n">MongoConnectionManager</span><span class="p">,</span> <span class="n">TransactionManager</span>
<a id="__codelineno-0-7" name="__codelineno-0-7" href="#__codelineno-0-7"></a>
<a id="__codelineno-0-8" name="__codelineno-0-8" href="#__codelineno-0-8"></a>
<a id="__codelineno-0-9" name="__codelineno-0-9" href="#__codelineno-0-9"></a><span class="k">class</span><span class="w"> </span><span class="nc">Order</span><span class="p">(</span><span class="n">BaseDocument</span><span class="p">):</span>
<a id="__codelineno-0-10" name="__codelineno-0-10" href="#__codelineno-0-10"></a> <span class="n">user_id</span><span class="p">:</span> <span class="nb">str</span>
<a id="__codelineno-0-11" name="__codelineno-0-11" href="#__codelineno-0-11"></a> <span class="n">items</span><span class="p">:</span> <span class="nb">list</span><span class="p">[</span><span class="nb">dict</span><span class="p">]</span> <span class="c1"># [{&quot;product_id&quot;: &quot;...&quot;, &quot;quantity&quot;: 2}]</span>
<a id="__codelineno-0-12" name="__codelineno-0-12" href="#__codelineno-0-12"></a> <span class="n">total_amount</span><span class="p">:</span> <span class="nb">float</span> <span class="o">=</span> <span class="mf">0.0</span>
<a id="__codelineno-0-13" name="__codelineno-0-13" href="#__codelineno-0-13"></a> <span class="n">status</span><span class="p">:</span> <span class="nb">str</span> <span class="o">=</span> <span class="s2">&quot;pending&quot;</span>
<a id="__codelineno-0-14" name="__codelineno-0-14" href="#__codelineno-0-14"></a>
<a id="__codelineno-0-15" name="__codelineno-0-15" href="#__codelineno-0-15"></a>
<a id="__codelineno-0-16" name="__codelineno-0-16" href="#__codelineno-0-16"></a><span class="k">class</span><span class="w"> </span><span class="nc">OrderService</span><span class="p">:</span>
<a id="__codelineno-0-17" name="__codelineno-0-17" href="#__codelineno-0-17"></a> <span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">order_repo</span><span class="p">:</span> <span class="n">OrderRepository</span><span class="p">,</span> <span class="n">product_repo</span><span class="p">:</span> <span class="n">ProductRepository</span><span class="p">):</span>
<a id="__codelineno-0-18" name="__codelineno-0-18" href="#__codelineno-0-18"></a> <span class="bp">self</span><span class="o">.</span><span class="n">order_repo</span> <span class="o">=</span> <span class="n">order_repo</span>
<a id="__codelineno-0-19" name="__codelineno-0-19" href="#__codelineno-0-19"></a> <span class="bp">self</span><span class="o">.</span><span class="n">product_repo</span> <span class="o">=</span> <span class="n">product_repo</span>
<a id="__codelineno-0-16" name="__codelineno-0-16" href="#__codelineno-0-16"></a><span class="k">class</span><span class="w"> </span><span class="nc">Inventory</span><span class="p">(</span><span class="n">BaseDocument</span><span class="p">):</span>
<a id="__codelineno-0-17" name="__codelineno-0-17" href="#__codelineno-0-17"></a> <span class="n">product_id</span><span class="p">:</span> <span class="n">ObjectId</span> <span class="o">=</span> <span class="kc">None</span>
<a id="__codelineno-0-18" name="__codelineno-0-18" href="#__codelineno-0-18"></a> <span class="n">quantity</span><span class="p">:</span> <span class="nb">int</span> <span class="o">=</span> <span class="mi">0</span>
<a id="__codelineno-0-19" name="__codelineno-0-19" href="#__codelineno-0-19"></a>
<a id="__codelineno-0-20" name="__codelineno-0-20" href="#__codelineno-0-20"></a>
<a id="__codelineno-0-21" name="__codelineno-0-21" href="#__codelineno-0-21"></a> <span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">create_order_with_inventory_update</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">order</span><span class="p">:</span> <span class="n">Order</span><span class="p">)</span> <span class="o">-&gt;</span> <span class="n">Order</span><span class="p">:</span>
<a id="__codelineno-0-22" name="__codelineno-0-22" href="#__codelineno-0-22"></a><span class="w"> </span><span class="sd">&quot;&quot;&quot;Create order and update inventory atomically&quot;&quot;&quot;</span>
<a id="__codelineno-0-23" name="__codelineno-0-23" href="#__codelineno-0-23"></a>
<a id="__codelineno-0-24" name="__codelineno-0-24" href="#__codelineno-0-24"></a> <span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">create_order_transaction</span><span class="p">(</span><span class="n">session</span><span class="p">):</span>
<a id="__codelineno-0-25" name="__codelineno-0-25" href="#__codelineno-0-25"></a> <span class="c1"># Insert order</span>
<a id="__codelineno-0-26" name="__codelineno-0-26" href="#__codelineno-0-26"></a> <span class="n">order_doc</span> <span class="o">=</span> <span class="n">order</span><span class="o">.</span><span class="n">model_dump</span><span class="p">(</span><span class="n">exclude</span><span class="o">=</span><span class="p">{</span><span class="s2">&quot;id&quot;</span><span class="p">},</span> <span class="n">exclude_none</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
<a id="__codelineno-0-27" name="__codelineno-0-27" href="#__codelineno-0-27"></a> <span class="n">order_doc</span><span class="p">[</span><span class="s2">&quot;created_at&quot;</span><span class="p">]</span> <span class="o">=</span> <span class="n">datetime</span><span class="o">.</span><span class="n">utcnow</span><span class="p">()</span>
<a id="__codelineno-0-28" name="__codelineno-0-28" href="#__codelineno-0-28"></a> <span class="n">order_doc</span><span class="p">[</span><span class="s2">&quot;updated_at&quot;</span><span class="p">]</span> <span class="o">=</span> <span class="n">datetime</span><span class="o">.</span><span class="n">utcnow</span><span class="p">()</span>
<a id="__codelineno-0-29" name="__codelineno-0-29" href="#__codelineno-0-29"></a> <span class="n">result</span> <span class="o">=</span> <span class="k">await</span> <span class="bp">self</span><span class="o">.</span><span class="n">order_repo</span><span class="o">.</span><span class="n">collection</span><span class="o">.</span><span class="n">insert_one</span><span class="p">(</span><span class="n">order_doc</span><span class="p">,</span> <span class="n">session</span><span class="o">=</span><span class="n">session</span><span class="p">)</span>
<a id="__codelineno-0-21" name="__codelineno-0-21" href="#__codelineno-0-21"></a><span class="k">class</span><span class="w"> </span><span class="nc">OrderRepository</span><span class="p">(</span><span class="n">BaseRepository</span><span class="p">[</span><span class="n">Order</span><span class="p">]):</span>
<a id="__codelineno-0-22" name="__codelineno-0-22" href="#__codelineno-0-22"></a> <span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<a id="__codelineno-0-23" name="__codelineno-0-23" href="#__codelineno-0-23"></a> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">(</span><span class="s2">&quot;orders&quot;</span><span class="p">,</span> <span class="n">Order</span><span class="p">)</span>
<a id="__codelineno-0-24" name="__codelineno-0-24" href="#__codelineno-0-24"></a>
<a id="__codelineno-0-25" name="__codelineno-0-25" href="#__codelineno-0-25"></a>
<a id="__codelineno-0-26" name="__codelineno-0-26" href="#__codelineno-0-26"></a><span class="k">class</span><span class="w"> </span><span class="nc">InventoryRepository</span><span class="p">(</span><span class="n">BaseRepository</span><span class="p">[</span><span class="n">Inventory</span><span class="p">]):</span>
<a id="__codelineno-0-27" name="__codelineno-0-27" href="#__codelineno-0-27"></a> <span class="k">def</span><span class="w"> </span><span class="fm">__init__</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<a id="__codelineno-0-28" name="__codelineno-0-28" href="#__codelineno-0-28"></a> <span class="nb">super</span><span class="p">()</span><span class="o">.</span><span class="fm">__init__</span><span class="p">(</span><span class="s2">&quot;inventory&quot;</span><span class="p">,</span> <span class="n">Inventory</span><span class="p">)</span>
<a id="__codelineno-0-29" name="__codelineno-0-29" href="#__codelineno-0-29"></a>
<a id="__codelineno-0-30" name="__codelineno-0-30" href="#__codelineno-0-30"></a>
<a id="__codelineno-0-31" name="__codelineno-0-31" href="#__codelineno-0-31"></a> <span class="c1"># Update inventory for each item</span>
<a id="__codelineno-0-32" name="__codelineno-0-32" href="#__codelineno-0-32"></a> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">order</span><span class="o">.</span><span class="n">items</span><span class="p">:</span>
<a id="__codelineno-0-33" name="__codelineno-0-33" href="#__codelineno-0-33"></a> <span class="k">await</span> <span class="bp">self</span><span class="o">.</span><span class="n">product_repo</span><span class="o">.</span><span class="n">collection</span><span class="o">.</span><span class="n">update_one</span><span class="p">(</span>
<a id="__codelineno-0-34" name="__codelineno-0-34" href="#__codelineno-0-34"></a> <span class="p">{</span><span class="s2">&quot;_id&quot;</span><span class="p">:</span> <span class="n">ObjectId</span><span class="p">(</span><span class="n">item</span><span class="p">[</span><span class="s2">&quot;product_id&quot;</span><span class="p">])},</span>
<a id="__codelineno-0-35" name="__codelineno-0-35" href="#__codelineno-0-35"></a> <span class="p">{</span>
<a id="__codelineno-0-36" name="__codelineno-0-36" href="#__codelineno-0-36"></a> <span class="s2">&quot;$inc&quot;</span><span class="p">:</span> <span class="p">{</span><span class="s2">&quot;quantity&quot;</span><span class="p">:</span> <span class="o">-</span><span class="n">item</span><span class="p">[</span><span class="s2">&quot;quantity&quot;</span><span class="p">]},</span>
<a id="__codelineno-0-37" name="__codelineno-0-37" href="#__codelineno-0-37"></a> <span class="s2">&quot;$set&quot;</span><span class="p">:</span> <span class="p">{</span><span class="s2">&quot;updated_at&quot;</span><span class="p">:</span> <span class="n">datetime</span><span class="o">.</span><span class="n">utcnow</span><span class="p">()}</span>
<a id="__codelineno-0-38" name="__codelineno-0-38" href="#__codelineno-0-38"></a> <span class="p">},</span>
<a id="__codelineno-0-39" name="__codelineno-0-39" href="#__codelineno-0-39"></a> <span class="n">session</span><span class="o">=</span><span class="n">session</span>
<a id="__codelineno-0-40" name="__codelineno-0-40" href="#__codelineno-0-40"></a> <span class="p">)</span>
<a id="__codelineno-0-31" name="__codelineno-0-31" href="#__codelineno-0-31"></a><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">create_order_with_inventory_update</span><span class="p">(</span>
<a id="__codelineno-0-32" name="__codelineno-0-32" href="#__codelineno-0-32"></a> <span class="n">order</span><span class="p">:</span> <span class="n">Order</span><span class="p">,</span>
<a id="__codelineno-0-33" name="__codelineno-0-33" href="#__codelineno-0-33"></a> <span class="n">order_repo</span><span class="p">:</span> <span class="n">OrderRepository</span><span class="p">,</span>
<a id="__codelineno-0-34" name="__codelineno-0-34" href="#__codelineno-0-34"></a> <span class="n">inv_repo</span><span class="p">:</span> <span class="n">InventoryRepository</span><span class="p">,</span>
<a id="__codelineno-0-35" name="__codelineno-0-35" href="#__codelineno-0-35"></a><span class="p">)</span> <span class="o">-&gt;</span> <span class="n">Order</span><span class="p">:</span>
<a id="__codelineno-0-36" name="__codelineno-0-36" href="#__codelineno-0-36"></a> <span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">insert_order</span><span class="p">(</span><span class="n">session</span><span class="p">):</span>
<a id="__codelineno-0-37" name="__codelineno-0-37" href="#__codelineno-0-37"></a> <span class="n">doc</span> <span class="o">=</span> <span class="n">order</span><span class="o">.</span><span class="n">model_dump</span><span class="p">(</span><span class="n">exclude</span><span class="o">=</span><span class="p">{</span><span class="s2">&quot;id&quot;</span><span class="p">},</span> <span class="n">exclude_none</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>
<a id="__codelineno-0-38" name="__codelineno-0-38" href="#__codelineno-0-38"></a> <span class="n">doc</span><span class="p">[</span><span class="s2">&quot;created_at&quot;</span><span class="p">]</span> <span class="o">=</span> <span class="n">doc</span><span class="p">[</span><span class="s2">&quot;updated_at&quot;</span><span class="p">]</span> <span class="o">=</span> <span class="n">datetime</span><span class="o">.</span><span class="n">utcnow</span><span class="p">()</span>
<a id="__codelineno-0-39" name="__codelineno-0-39" href="#__codelineno-0-39"></a> <span class="n">result</span> <span class="o">=</span> <span class="k">await</span> <span class="n">order_repo</span><span class="o">.</span><span class="n">collection</span><span class="o">.</span><span class="n">insert_one</span><span class="p">(</span><span class="n">doc</span><span class="p">,</span> <span class="n">session</span><span class="o">=</span><span class="n">session</span><span class="p">)</span>
<a id="__codelineno-0-40" name="__codelineno-0-40" href="#__codelineno-0-40"></a> <span class="k">return</span> <span class="k">await</span> <span class="n">order_repo</span><span class="o">.</span><span class="n">collection</span><span class="o">.</span><span class="n">find_one</span><span class="p">({</span><span class="s2">&quot;_id&quot;</span><span class="p">:</span> <span class="n">result</span><span class="o">.</span><span class="n">inserted_id</span><span class="p">},</span> <span class="n">session</span><span class="o">=</span><span class="n">session</span><span class="p">)</span>
<a id="__codelineno-0-41" name="__codelineno-0-41" href="#__codelineno-0-41"></a>
<a id="__codelineno-0-42" name="__codelineno-0-42" href="#__codelineno-0-42"></a> <span class="c1"># Fetch created order</span>
<a id="__codelineno-0-43" name="__codelineno-0-43" href="#__codelineno-0-43"></a> <span class="n">created</span> <span class="o">=</span> <span class="k">await</span> <span class="bp">self</span><span class="o">.</span><span class="n">order_repo</span><span class="o">.</span><span class="n">collection</span><span class="o">.</span><span class="n">find_one</span><span class="p">(</span>
<a id="__codelineno-0-44" name="__codelineno-0-44" href="#__codelineno-0-44"></a> <span class="p">{</span><span class="s2">&quot;_id&quot;</span><span class="p">:</span> <span class="n">result</span><span class="o">.</span><span class="n">inserted_id</span><span class="p">},</span>
<a id="__codelineno-0-45" name="__codelineno-0-45" href="#__codelineno-0-45"></a> <span class="n">session</span><span class="o">=</span><span class="n">session</span>
<a id="__codelineno-0-46" name="__codelineno-0-46" href="#__codelineno-0-46"></a> <span class="p">)</span>
<a id="__codelineno-0-47" name="__codelineno-0-47" href="#__codelineno-0-47"></a> <span class="k">return</span> <span class="n">Order</span><span class="p">(</span><span class="o">**</span><span class="n">created</span><span class="p">)</span>
<a id="__codelineno-0-48" name="__codelineno-0-48" href="#__codelineno-0-48"></a>
<a id="__codelineno-0-49" name="__codelineno-0-49" href="#__codelineno-0-49"></a> <span class="c1"># Execute in transaction</span>
<a id="__codelineno-0-50" name="__codelineno-0-50" href="#__codelineno-0-50"></a> <span class="k">async</span> <span class="k">with</span> <span class="n">TransactionManager</span><span class="o">.</span><span class="n">start_session</span><span class="p">()</span> <span class="k">as</span> <span class="n">session</span><span class="p">:</span>
<a id="__codelineno-0-51" name="__codelineno-0-51" href="#__codelineno-0-51"></a> <span class="k">return</span> <span class="k">await</span> <span class="n">create_order_transaction</span><span class="p">(</span><span class="n">session</span><span class="p">)</span>
<a id="__codelineno-0-52" name="__codelineno-0-52" href="#__codelineno-0-52"></a>
<a id="__codelineno-0-53" name="__codelineno-0-53" href="#__codelineno-0-53"></a><span class="c1"># Usage in FastAPI</span>
<a id="__codelineno-0-54" name="__codelineno-0-54" href="#__codelineno-0-54"></a><span class="nd">@app</span><span class="o">.</span><span class="n">post</span><span class="p">(</span><span class="s2">&quot;/orders/&quot;</span><span class="p">,</span> <span class="n">response_model</span><span class="o">=</span><span class="n">Order</span><span class="p">)</span>
<a id="__codelineno-0-55" name="__codelineno-0-55" href="#__codelineno-0-55"></a><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">create_order</span><span class="p">(</span><span class="n">order</span><span class="p">:</span> <span class="n">Order</span><span class="p">):</span>
<a id="__codelineno-0-56" name="__codelineno-0-56" href="#__codelineno-0-56"></a> <span class="n">order_service</span> <span class="o">=</span> <span class="n">OrderService</span><span class="p">(</span><span class="n">order_repo</span><span class="p">,</span> <span class="n">product_repo</span><span class="p">)</span>
<a id="__codelineno-0-57" name="__codelineno-0-57" href="#__codelineno-0-57"></a> <span class="k">try</span><span class="p">:</span>
<a id="__codelineno-0-58" name="__codelineno-0-58" href="#__codelineno-0-58"></a> <span class="k">return</span> <span class="k">await</span> <span class="n">order_service</span><span class="o">.</span><span class="n">create_order_with_inventory_update</span><span class="p">(</span><span class="n">order</span><span class="p">)</span>
<a id="__codelineno-0-59" name="__codelineno-0-59" href="#__codelineno-0-59"></a> <span class="k">except</span> <span class="ne">Exception</span> <span class="k">as</span> <span class="n">e</span><span class="p">:</span>
<a id="__codelineno-0-60" name="__codelineno-0-60" href="#__codelineno-0-60"></a> <span class="k">raise</span> <span class="n">HTTPException</span><span class="p">(</span><span class="n">status_code</span><span class="o">=</span><span class="mi">400</span><span class="p">,</span> <span class="n">detail</span><span class="o">=</span><span class="nb">str</span><span class="p">(</span><span class="n">e</span><span class="p">))</span>
<a id="__codelineno-0-42" name="__codelineno-0-42" href="#__codelineno-0-42"></a> <span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">update_inventory</span><span class="p">(</span><span class="n">session</span><span class="p">):</span>
<a id="__codelineno-0-43" name="__codelineno-0-43" href="#__codelineno-0-43"></a> <span class="k">for</span> <span class="n">item</span> <span class="ow">in</span> <span class="n">order</span><span class="o">.</span><span class="n">items</span><span class="p">:</span>
<a id="__codelineno-0-44" name="__codelineno-0-44" href="#__codelineno-0-44"></a> <span class="k">await</span> <span class="n">inv_repo</span><span class="o">.</span><span class="n">collection</span><span class="o">.</span><span class="n">update_one</span><span class="p">(</span>
<a id="__codelineno-0-45" name="__codelineno-0-45" href="#__codelineno-0-45"></a> <span class="p">{</span><span class="s2">&quot;product_id&quot;</span><span class="p">:</span> <span class="n">ObjectId</span><span class="p">(</span><span class="n">item</span><span class="p">[</span><span class="s2">&quot;product_id&quot;</span><span class="p">])},</span>
<a id="__codelineno-0-46" name="__codelineno-0-46" href="#__codelineno-0-46"></a> <span class="p">{</span>
<a id="__codelineno-0-47" name="__codelineno-0-47" href="#__codelineno-0-47"></a> <span class="s2">&quot;$inc&quot;</span><span class="p">:</span> <span class="p">{</span><span class="s2">&quot;quantity&quot;</span><span class="p">:</span> <span class="o">-</span><span class="n">item</span><span class="p">[</span><span class="s2">&quot;quantity&quot;</span><span class="p">]},</span>
<a id="__codelineno-0-48" name="__codelineno-0-48" href="#__codelineno-0-48"></a> <span class="s2">&quot;$set&quot;</span><span class="p">:</span> <span class="p">{</span><span class="s2">&quot;updated_at&quot;</span><span class="p">:</span> <span class="n">datetime</span><span class="o">.</span><span class="n">utcnow</span><span class="p">()},</span>
<a id="__codelineno-0-49" name="__codelineno-0-49" href="#__codelineno-0-49"></a> <span class="p">},</span>
<a id="__codelineno-0-50" name="__codelineno-0-50" href="#__codelineno-0-50"></a> <span class="n">session</span><span class="o">=</span><span class="n">session</span><span class="p">,</span>
<a id="__codelineno-0-51" name="__codelineno-0-51" href="#__codelineno-0-51"></a> <span class="p">)</span>
<a id="__codelineno-0-52" name="__codelineno-0-52" href="#__codelineno-0-52"></a> <span class="k">return</span> <span class="kc">None</span>
<a id="__codelineno-0-53" name="__codelineno-0-53" href="#__codelineno-0-53"></a>
<a id="__codelineno-0-54" name="__codelineno-0-54" href="#__codelineno-0-54"></a> <span class="k">async</span> <span class="k">with</span> <span class="n">TransactionManager</span><span class="o">.</span><span class="n">start_session</span><span class="p">()</span> <span class="k">as</span> <span class="n">session</span><span class="p">:</span>
<a id="__codelineno-0-55" name="__codelineno-0-55" href="#__codelineno-0-55"></a> <span class="n">created</span> <span class="o">=</span> <span class="k">await</span> <span class="n">insert_order</span><span class="p">(</span><span class="n">session</span><span class="p">)</span>
<a id="__codelineno-0-56" name="__codelineno-0-56" href="#__codelineno-0-56"></a> <span class="k">await</span> <span class="n">update_inventory</span><span class="p">(</span><span class="n">session</span><span class="p">)</span>
<a id="__codelineno-0-57" name="__codelineno-0-57" href="#__codelineno-0-57"></a> <span class="k">return</span> <span class="n">Order</span><span class="p">(</span><span class="o">**</span><span class="n">created</span><span class="p">)</span>
<a id="__codelineno-0-58" name="__codelineno-0-58" href="#__codelineno-0-58"></a>
<a id="__codelineno-0-59" name="__codelineno-0-59" href="#__codelineno-0-59"></a>
<a id="__codelineno-0-60" name="__codelineno-0-60" href="#__codelineno-0-60"></a><span class="c1"># ---------------------------</span>
<a id="__codelineno-0-61" name="__codelineno-0-61" href="#__codelineno-0-61"></a><span class="c1"># FastAPI wiring</span>
<a id="__codelineno-0-62" name="__codelineno-0-62" href="#__codelineno-0-62"></a><span class="c1"># ---------------------------</span>
<a id="__codelineno-0-63" name="__codelineno-0-63" href="#__codelineno-0-63"></a><span class="n">app</span> <span class="o">=</span> <span class="n">FastAPI</span><span class="p">()</span>
<a id="__codelineno-0-64" name="__codelineno-0-64" href="#__codelineno-0-64"></a>
<a id="__codelineno-0-65" name="__codelineno-0-65" href="#__codelineno-0-65"></a><span class="n">order_repo</span> <span class="o">=</span> <span class="n">OrderRepository</span><span class="p">()</span>
<a id="__codelineno-0-66" name="__codelineno-0-66" href="#__codelineno-0-66"></a><span class="n">inv_repo</span> <span class="o">=</span> <span class="n">InventoryRepository</span><span class="p">()</span>
<a id="__codelineno-0-67" name="__codelineno-0-67" href="#__codelineno-0-67"></a>
<a id="__codelineno-0-68" name="__codelineno-0-68" href="#__codelineno-0-68"></a>
<a id="__codelineno-0-69" name="__codelineno-0-69" href="#__codelineno-0-69"></a><span class="nd">@asynccontextmanager</span>
<a id="__codelineno-0-70" name="__codelineno-0-70" href="#__codelineno-0-70"></a><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">lifespan</span><span class="p">(</span><span class="n">_app</span><span class="p">:</span> <span class="n">FastAPI</span><span class="p">):</span>
<a id="__codelineno-0-71" name="__codelineno-0-71" href="#__codelineno-0-71"></a> <span class="k">async</span> <span class="k">with</span> <span class="n">MongoConnectionManager</span><span class="o">.</span><span class="n">lifespan</span><span class="p">(</span>
<a id="__codelineno-0-72" name="__codelineno-0-72" href="#__codelineno-0-72"></a> <span class="n">uri</span><span class="o">=</span><span class="s2">&quot;mongodb://localhost:27017&quot;</span><span class="p">,</span> <span class="n">db_name</span><span class="o">=</span><span class="s2">&quot;shop&quot;</span>
<a id="__codelineno-0-73" name="__codelineno-0-73" href="#__codelineno-0-73"></a> <span class="p">):</span>
<a id="__codelineno-0-74" name="__codelineno-0-74" href="#__codelineno-0-74"></a> <span class="k">yield</span>
<a id="__codelineno-0-75" name="__codelineno-0-75" href="#__codelineno-0-75"></a>
<a id="__codelineno-0-76" name="__codelineno-0-76" href="#__codelineno-0-76"></a>
<a id="__codelineno-0-77" name="__codelineno-0-77" href="#__codelineno-0-77"></a><span class="n">app</span><span class="o">.</span><span class="n">lifespan</span> <span class="o">=</span> <span class="n">lifespan</span>
<a id="__codelineno-0-78" name="__codelineno-0-78" href="#__codelineno-0-78"></a>
<a id="__codelineno-0-79" name="__codelineno-0-79" href="#__codelineno-0-79"></a>
<a id="__codelineno-0-80" name="__codelineno-0-80" href="#__codelineno-0-80"></a><span class="nd">@app</span><span class="o">.</span><span class="n">post</span><span class="p">(</span><span class="s2">&quot;/orders/&quot;</span><span class="p">,</span> <span class="n">response_model</span><span class="o">=</span><span class="n">Order</span><span class="p">)</span>
<a id="__codelineno-0-81" name="__codelineno-0-81" href="#__codelineno-0-81"></a><span class="k">async</span> <span class="k">def</span><span class="w"> </span><span class="nf">create_order</span><span class="p">(</span><span class="n">order</span><span class="p">:</span> <span class="n">Order</span><span class="p">):</span>
<a id="__codelineno-0-82" name="__codelineno-0-82" href="#__codelineno-0-82"></a> <span class="k">try</span><span class="p">:</span>
<a id="__codelineno-0-83" name="__codelineno-0-83" href="#__codelineno-0-83"></a> <span class="k">return</span> <span class="k">await</span> <span class="n">create_order_with_inventory_update</span><span class="p">(</span><span class="n">order</span><span class="p">,</span> <span class="n">order_repo</span><span class="p">,</span> <span class="n">inv_repo</span><span class="p">)</span>
<a id="__codelineno-0-84" name="__codelineno-0-84" href="#__codelineno-0-84"></a> <span class="k">except</span> <span class="ne">Exception</span> <span class="k">as</span> <span class="n">exc</span><span class="p">:</span>
<a id="__codelineno-0-85" name="__codelineno-0-85" href="#__codelineno-0-85"></a> <span class="k">raise</span> <span class="n">HTTPException</span><span class="p">(</span><span class="n">status_code</span><span class="o">=</span><span class="mi">400</span><span class="p">,</span> <span class="n">detail</span><span class="o">=</span><span class="nb">str</span><span class="p">(</span><span class="n">exc</span><span class="p">))</span>
</code></pre></div>
<hr />
<h2 id="tips">💡 Tips</h2>
<ul>
<li>Repositories are created <strong>inside</strong> the lifespan (or a dependency) so the database is connected — see the note in <a href="../01_basic_crud/">use case 01</a>.</li>
<li>Every operation inside the transaction context must receive <code>session=&lt;session&gt;</code> — a missing session silently runs outside the transaction.</li>
<li>MongoDB transactions require a replica set (or the local standalone test server that emulates one).</li>
<li>For a list-of-operations style, see <code>TransactionManager.execute_transaction</code> in <a href="../12_transaction_helper/">use case 12</a>.</li>
</ul>
<hr />
<h2 id="related">Related</h2>
<ul>
<li><a href="../06_multi_model/">06 – Multi-model</a> · <a href="../12_transaction_helper/">12 – Transaction helper</a> · <a href="../../06_error_handling/">Error Handling</a></li>
</ul>