In Apache, chunked uploads typically refer to the ability to handle HTTP requests with chunked transfer encoding. Chunked transfer encoding is a mechanism used in HTTP to send data in chunks, allowing the sender to transmit a request or response message in parts rather than as a whole.
When it comes to uploading files, especially large ones, chunked uploads can be advantageous. Instead of sending the entire file in one go, the client can break it into smaller chunks and send them separately. This can be useful in scenarios where the client has a slow or unreliable connection, as it allows for more efficient and resilient file uploads.
The technical side of chunked encoding
In Apache, chunked encoding is handled by the Apache core and is typically part of the standard HTTP protocol support. When a client sends an HTTP request with the Transfer-Encoding: chunked header, Apache automatically processes the incoming data in chunks.
Here’s a high-level overview of how chunked uploads work in Apache:
Client Request
The client initiates a file upload by sending an HTTP request to the server. This request includes the Transfer-Encoding: chunked header to indicate that the data will be sent in chunks.
Chunked Data
The client then sends the file data in smaller chunks, each preceded by a line indicating the size of the chunk. This continues until all the data is transmitted. Example:
25
This is the first chunk
1A
and this is the second one
3
end
0In this example, 25, 1A, 3 are hexadecimal values representing the size of each chunk in bytes. The actual data follows each size value.
Server Processing
Apache, being a versatile web server, is capable of handling chunked transfer encoding. It processes the incoming chunks as they arrive, without waiting for the entire payload to be received.
Assembling the File
Apache reassembles the received chunks to reconstruct the complete payload. This is done transparently to the client, and the application or server-side script can access the entire payload as if it were sent in a single piece.
Handling Completion
Once all chunks have been received, the server completes the processing of the request. This may involve passing the data to the appropriate handler, script, or application, depending on the server configuration.
Which applications require chucked uploads?
Chunked uploads can be beneficial in various applications, especially when dealing with large files or in situations where network conditions may be less than ideal. Here are some applications that often benefit from using chunked uploads:
Large File Uploads
Cloud storage Services like Google Drive, Dropbox, or OneDrive often use chunked uploads to allow users to upload large files in parts. This helps in resuming uploads if they are interrupted and is more efficient than trying to upload the entire file in one go.
Content Management platforms that allow users to upload media files, such as videos or high-resolution images, may use chunked uploads to handle large file sizes more effectively.
Resumable Uploads
Online Backup Services that provide online backup often use chunked uploads to allow users to resume large file uploads from where they left off, rather than restarting the upload process.
Some file transfer protocols, like FTP or SFTP, can support chunked uploads, enabling users to resume interrupted transfers.
Unreliable or Slow Networks
Mobile Applications with file upload features may use chunked uploads to handle varying network conditions. This is especially important in scenarios where mobile data connections can be unreliable or slow.
Web applications dealing with large data uploads may benefit from chunked uploads to handle situations where network connectivity is not stable.
Real-time Collaboration
Collaboration Platforms that support real-time collaboration, such as document editing or collaborative design tools, may use chunked uploads to provide a smoother experience for users working on large files.
Media Streaming
When users upload videos to streaming platforms, chunked uploads can help in efficiently processing and encoding the video content on the server side.
APIs and Web Services
APIs that handle file uploads for services like social media platforms or document sharing may implement chunked uploads to enhance performance and reliability.
It’s important to note that the decision to use chunked uploads depends on the specific requirements of the application and the use case. While chunked uploads offer advantages in certain scenarios, not all applications may need this feature, particularly if file sizes are relatively small or network conditions are consistently reliable.
RECOMMENDED READING: How to configure Apache to handle large file uploads?
Server-side Configuration
By default, Apache usually handles chunked encoding automatically when it receives chunked requests. It processes incoming chunks without the need for explicit configuration in most cases.
Enable required modules
But to optimize Apache for efficient chunked request handling, we need to enable a couple of modules:
Verify that the necessary Apache modules are enabled. mod_dav (for WebDAV support) and mod_cgi or mod_cgid (for handling CGI scripts) maybe relevant depending on your specific use case.
So, you will need to include these lines in your Apache configuration to load the required modules.
LoadModule dav_module modules/mod_dav.so
LoadModule dav_fs_module modules/mod_dav_fs.soAdjust timeout
When dealing with chunked uploads in Apache, adjusting timeout settings can be important to accommodate potentially longer upload times, especially in scenarios where users might be working with large files or under slower network conditions. Here are some key timeout directives in Apache that you may consider adjusting:
- Timeout Directive
The Timeout directive sets the maximum time, in seconds, Apache will wait for each request to be completed. If a request exceeds this time, it may be terminated.
Timeout 300This example sets the timeout to 300 seconds (5 minutes). Adjust the value based on the expected duration of chunked uploads.
- KeepAliveTimeout Directive
The KeepAliveTimeout directive sets the maximum time, in seconds, that Apache will wait for the next request when using keep-alive connections. If your clients use keep-alive connections for chunked uploads, consider adjusting this timeout as well.
KeepAliveTimeout 60This example sets the keep-alive timeout to 60 seconds. You may need to adjust it based on the nature of your application.
- RequestReadTimeout Directive
The RequestReadTimeout directive is useful for controlling the timeout for reading the request headers and body. It can be used to set different timeouts for various phases of request processing.
RequestReadTimeout body=300This example sets the timeout for reading the request body (payload) to 300 seconds.
- LimitRequestBody Directive
The LimitRequestBody directive controls the maximum allowed size of an HTTP request body. If you expect large files to be uploaded, ensure that this limit is set appropriately.
LimitRequestBody 0Setting it to 0 means no limit, but you can set a specific value based on your requirements.
Remember to adjust these values according to the specific needs of your application. It’s important to strike a balance between allowing enough time for uploads to complete and preventing excessive resource usage or potential security issues.
After making changes to your Apache configuration, restart or reload the Apache server to apply the new settings: Use these
sudo service apache2 restart
sudo service apache2 reload Client-side Implementation
Implement a client-side script that breaks the file into chunks and sends them sequentially to the server. You can use JavaScript and libraries like Dropzone.js, Resumable.js, or Plupload for this purpose. Here is a basic example using Dropzone.js:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Chunked Upload</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/[email protected]/dist/dropzone.min.css" />
</head>
<body>
<form action="/uploads" class="dropzone"></form>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/dropzone.min.js"></script>
</body>
</html>