The objective of this project is to implement a multithreaded web server “myhttpd” in C/C++ on a UNIX-based platform.
###SYNOPSIS: To run this program:
myhttpd [−d] [−h] [−l file] [−p port] [−r dir] [−t time] [−n threadnum] [−s sched]
myhttpd is a simple web server. It binds to a given port on the given address and waits for incoming HTTP/1.0 requests. It serves content from the given directory. That is,any requests for documents is resolved relative to this directory (the document root – by default,the directory where the server is running).
- −d : Enter debugging mode. Without this option, the web server should run as a daemon process in the background.
- −h : Print a usage summary with all options and exit.
- −l file : Log all requests to the given file. See LOGGING for details.
- −p port : Listen on the given port. If not provided, myhttpd will listen on port 8080.
- −r dir : Set the root directory for the http server to dir.
- −t time : Set the queuing time to time seconds. The default is 60 seconds.
- −n threadnum : Set number of threads waiting ready in the execution thread pool to threadnum. The default should is 4 execution threads.
- −s sched : Set the scheduling policy. It can be either FCFS or SJF. The default will be FCFS.
myhttpd speaks a simplified version of HTTP/1.0: it responds to GET and HEAD requests according to RFC1945. When a connection is made, myhttpd will respond with the appropriate HTTP/1.0 status code and the following headers:
- Date : The current timestamp in GMT.
- Server : A string identifying this server and version.
- Last-Modified : The timestamp in GMT of the file’s last modification date.
- Content-Type : text/html or image/gif
- Content-Length : The size in bytes of the data returned.
If the request type was a GET, then it will subsequently return the data of the requested file. After serving the request, the connection is terminated. The HEAD request will only return the metadata but not actual content.
If the request was for a directory and the directory does not contain a file named "index.html", then myhttpd will generate a directory index, listing the contents of the directory in alphanumeric order. Files starting with a "." are ignored.
If the request begins with a ‘~’, then the following string up to the first slash is translated into that user’s myhttpd directory (ie / home//myhttpd/).
By default, myhttpd does not do any logging. If explicitly enabled via the −l flag, myhttpd will log every request in a slight variation of Apache’s so-called "common" format:
’%a %t %t %r %>s %b’
all in a single line per request. That is, it will log:
- %a : The remote IP address.
- %t : The time the request was received by the queuing thread (in GMT).
- %t : The time the request was assigned to an execution thread by the scheduler (in GMT).
- %r : The (quoted) first line of the request.
- %s : The status of the request.
- %b : Size of the response in bytes. i.e, "Content-Length".
Example:
127.0.0.1 - [19/Sep/2011:13:55:36 -0600] [19/Sep/2011:13:58:21 -0600] "GET /index.html HTTP/1.0" 200 326
The server will consist of 2+n threads. A pool of n threads will be always ready for executing/serving incoming requests (n x execution threads). The number n is given as a parameter when you start the server (using option: -n threadnum). One thread will be responsible for listening to incoming HTTP requests and inserting them in a ready queue (1 x queuing thread). Another thread will be responsible for choosing a request from the ready queue and scheduling it to one of the execution threads (1 x scheduling thread).
The queuing thread will be continuously listening to the port p for incoming http requests. As soon as a new http request comes to the myhttpd server, it will be inserted into the ready queue. For the first t seconds after the server is started, there will be no execution and all requests will wait in the ready queue.
The scheduling policy to be used will be set via the [–s sched] option when myhttpd server is first started. The available policies are First Come First Serve (FCFS) and Shortest Job First (SJF). When SJF scheduling policy is selected, you can use the file size information as the job length for scheduling purposes, assuming serving larger files will take longer. The schedulerthread will choose one of the requests in the ready queue according to the scheduling policyselected. The request will then be assigned to one of the available execution threads for service. There will be no scheduling done during the first t seconds after the myhttpd server is started. This time period will be used to accumulate some requests in the ready queue.
To make sure that we protect the ready queue and other shared data structures across multiple threads to prevent race conditions. Mutex locks have been implemented for the same.