### Threads

#### Application's calling thread

The application-layer must block on writing I/O. We can't return from a write until we've pushed its bytes onto the socket. Otherwise, if the write fails we are unable to deliver its IOException to the application. We would have told the application layer that the write succeeded, but it didn't!

### What is "Mounting" { #what-is-mounting }

"Mounting" means adding a complete "independent" application in a specific path, that then takes care of handling all the sub-paths.

This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

application/mac-binhex40       hqx              # Macintosh binhexed archives
application/mspowerpoint       ppt              # Microsoft Powerpoint
application/msword             doc              # Microsoft Word
application/octet-stream       bin exe ani      # Binary File
application/oda                oda
application/pagemaker          pm5 pt5 pm       # PageMaker
application/pdf                pdf              # Adobe Acrobat

        // Add a sequence instead of APPLICATION tagged object
        DERSequence wrongTag = new DERSequence(new ASN1Encodable[] { new ASN1Integer(5) });
        innerContent.write(wrongTag.getEncoded());

        byte[] content = innerContent.toByteArray();

        // Create GSS-API wrapper
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        baos.write(0x60); // APPLICATION 0
        baos.write(content.length);

     <span style="background-color:#007166"><font color="#D3D7CF"> INFO </font></span>  Waiting for application startup.
     <span style="background-color:#007166"><font color="#D3D7CF"> INFO </font></span>  Waiting for application startup.
     <span style="background-color:#007166"><font color="#D3D7CF"> INFO </font></span>  Waiting for application startup.

'’žÉ§MetaSys ¼X-Minio-Internal-actual-sizeÄ 141250§MetaUsr‚¤etagÙ"51fe09d68bacc8c5a68a-1¬content-type¸application/octet-streamÎöa‰ 10/xl.meta XL2 Æ b ¨Versions‘‚¤Type ¥V2ObjÞ ¢IDÄ ¤DDirÄ ÔLã°ê8EÒŸˆ”Ù Sé6¦EcAlgo £EcM £EcN §EcBSizeÒ §EcIndex ¦EcDistš ¨CSumAlgo ¨PartNums‘ ©PartETags‘ ©PartSizes‘Ò 'ªPartASizes‘Ò '¤SizeÒ 'Â¥MTimeÓ ¿W '’žÉ§MetaSys ¼X-Minio-Internal-actual-sizeÄ 141250§MetaUsr‚¬content-type¸application/octet-stream¤etagÙ"51fe09d68bacc8c5a68a-1Îøù{~ 2/xl.meta XL2 Æ b ¨Versions‘‚¤Type ¥V2ObjÞ ¢IDÄ...

		<postConstruct name="addRule">
			<arg>"mimeType"</arg>
			<!-- Supported MIME type -->
			<arg>
  "(application/xml"
+ "|application/xhtml+xml"
+ "|application/rdf+xml"
+ "|application/pdf"
+ "|application/x-freemind"
+ "|application/lha"
+ "|application/x-lha"
+ "|application/x-lha-compressed"
+ "|text/xml"
+ "|text/xml-external-parsed-entity"
+ "|text/html)"
			</arg>
		</postConstruct>

    }

    public void test_add_overwrite() {
        fileTypeHelper.add("application/pdf", "pdf");
        assertEquals("pdf", fileTypeHelper.get("application/pdf"));

        fileTypeHelper.add("application/pdf", "document");
        assertEquals("document", fileTypeHelper.get("application/pdf"));
    }

    public void test_add_withNullMimetype() {
        fileTypeHelper.add(null, "test");

# Lifespan Events { #lifespan-events }

You can define logic (code) that should be executed before the application **starts up**. This means that this code will be executed **once**, **before** the application **starts receiving requests**.

The same way, you can define logic (code) that should be executed when the application is **shutting down**. In this case, this code will be executed **once**, **after** having handled possibly **many requests**.

For some types of applications you might want to add dependencies to the whole application.

Similar to the way you can [add `dependencies` to the *path operation decorators*](dependencies-in-path-operation-decorators.md){.internal-link target=_blank}, you can add them to the `FastAPI` application.

In that case, they will be applied to all the *path operations* in the application:

{* ../../docs_src/dependencies/tutorial012_an_py39.py hl[16] *}