Changes of Simple Parallel Exec from #8 to #9

Changed lines at line 34
1.1 Error detection/ dealing
- error while connection/authentication (ssh, scp)
- machine dead (for whatever reason)
- programm terminated without success
- programm doesn't return within timeout
- server breaks or gets stopped
1.1 Server
- initialisation: for every slave: try to start client (ssh). If it fails: check ssh connection with dummy ssh command. Success -> copy client to slave using scp and try to start it.
- on http request for configuration: reply client configuration (i.e. what to do on exit)
- on http request for worker executeable: reply with the binary for the right platform
- on http request for new task:  reply with  the next command to execute and all parameters.
- on post: validate result and mark set and collect results
- no more parameter set to process: exit and display statistics.
1.1 Client
- gets via command line: Session ID, command name (path and name of the executeable), md5 checksum of the executeable, server name and port
- register at the server and fetch configuration
- check for the executeable: if not there or the MD5 checksum is wrong: fetch it (for own platform) from the server 
- fetch a task 
- run worker
- check return code: if failed -> Post failture otherwise take the results and post them.
- fetch next task.
- die is there is no more task or the server is not responding.
- different settings for termination: delete executeable (if fetched), delete the client program?
 
1 Protocol
1.1 Configuration
- Request: GET \http://master/config?sessionID=SESSIONID
- Fail (due to wrong session id): 403 (Forbidden)
- Successful Reply: List of Key = Value pairs.
{code:none}
DeleteWorker=Yes/No
DeleteClient=Yes/No
Ping=#
{code}
1.1 Ping (HTTP)
- Ping interval is given in seconds. 0 for no ping.
- Purpose of the ping is that the client realises if the server is stopped or finished or even dead.
- Request: GET \http://master/ping?sessionID=SESSIONID&ticket=TICKET
- Fail due to wrong session id: 403 (Forbidden)
- Successful, but ticket expired (task allready done): 205 Reset Content
- Successful (keep on it!): 204 (No Content)
1.1 Worker
- Request: GET \http://master/worker?sessionID=SESSIONID&name=NAME&platform=PLATFORM
- Fail (due to wrong session id, or wrong name): 403 (Forbidden)
- Fail (due to unsupported platform): 415 Unsupported Media Type
- Success: binary file
1.1 Task
- Request: GET \http://master/task?sessionID=SESSIONID
- Fail (due to wrong session id): 403 (Forbidden)
- Fail (because no task left): 503 Service Unavailable
- Success: 
{code:none}
Ticket=#  (unique number (usually 5 digits))
Timeout=# (in seconds)
CommandLine=commandline
[Input]*
File=filename (or "stdin")
--begin content--
real file content here (binary)
--end content--
[Result]+
Name=resultname
File=filename (or "stdout")
{code}
1.1 Task completed
- Successful: POST \http://master/complete?sessionID=SESSIONID&ticket=TICKET
{code:none}
[Result]+
Name=resultname
--begin content--
file content here (binary)
--end content--
{code}
- Failed: GET \http://master/failed?sessionID=SESSIONID&ticket=TICKET
- Reply Fail due to wrong session id: 403 (Forbidden)
- Reply Otherwise:  200 OK
1 Implementation Details
1.1 Configuation and Files
- Cluster file: list of computers, one per line
- Parameter file: csv file, cells seperated with |, parameter names in the headline and every following line contains one parameter set. All lines have to have the same amount of cells like the headline!
- Specification of worker: Command line: a perl syntax string with parameter Variables for the parameters; Input files: Name of the file and parameter name to write in.
- Result specification: A result consists of a list of name and value pairs. Where name specifies the name of the particular output and value decides where the output comes from. For example output="stdout", outputfile="out.txt".
- Validation function: function template that gets the parameter set and the result of the worker and returns success or not
- Collection function: gets the parameters set and the result of the worker and can do whatever with it (usually print it in a file). 
- NFS aware
1.1 Error detection/ dealing
- error while connection/authentication (ssh, scp)
- machine dead (for whatever reason)
- programm terminated without success
- programm doesn't return within timeout
- server breaks or gets stopped
1.1 Server
- initialisation: for every slave: try to start client (ssh). If it fails: check ssh connection with dummy ssh command. Success -> copy client to slave using scp and try to start it.
- on http request for configuration: reply client configuration (i.e. what to do on exit)
- on http request for worker executeable: reply with the binary for the right platform
- on http request for new task:  reply with  the next command to execute and all parameters.
- on post: validate result and mark set and collect results
- no more parameter set to process: exit and display statistics.
1.1 Client
- gets via command line: Session ID, command name (path and name of the executeable), md5 checksum of the executeable, server name and port
- register at the server and fetch configuration
- check for the executeable: if not there or the MD5 checksum is wrong: fetch it (for own platform) from the server 
- fetch a task 
- run worker
- check return code: if failed -> Post failture otherwise take the results and post them.
- fetch next task.
- die is there is no more task or the server is not responding.
- different settings for termination: delete executeable (if fetched), delete the client program?
 
1 Protocol
1.1 Configuration
- Request: GET \http://master/config?sessionID=SESSIONID
- Fail (due to wrong session id): 403 (Forbidden)
- Successful Reply: List of Key = Value pairs.
{code:none}
DeleteWorker=Yes/No
DeleteClient=Yes/No
Ping=#
{code}
1.1 Ping (HTTP)
- Ping interval is given in seconds. 0 for no ping.
- Purpose of the ping is that the client realises if the server is stopped or finished or even dead.
- Request: GET \http://master/ping?sessionID=SESSIONID&ticket=TICKET
- Fail due to wrong session id: 403 (Forbidden)
- Successful, but ticket expired (task allready done): 205 Reset Content
- Successful (keep on it!): 204 (No Content)
1.1 Worker
- Request: GET \http://master/worker?sessionID=SESSIONID&name=NAME&platform=PLATFORM
- Fail (due to wrong session id, or wrong name): 403 (Forbidden)
- Fail (due to unsupported platform): 415 Unsupported Media Type
- Success: binary file
1.1 Task
- Request: GET \http://master/task?sessionID=SESSIONID
- Fail (due to wrong session id): 403 (Forbidden)
- Fail (because no task left): 503 Service Unavailable
- Success: 
{code:none}
Ticket=#  (unique number (usually 5 digits))
Timeout=# (in seconds)
CommandLine=commandline
[Input]*
File=filename (or "stdin")
--begin content--
real file content here (binary)
--end content--
[Result]+
Name=resultname
File=filename (or "stdout")
{code}
1.1 Task completed
- Successful: POST \http://master/complete?sessionID=SESSIONID&ticket=TICKET
{code:none}
[Result]+
Name=resultname
--begin content--
file content here (binary)
--end content--
{code}
- Failed: GET \http://master/failed?sessionID=SESSIONID&ticket=TICKET
- Reply Fail due to wrong session id: 403 (Forbidden)
- Reply Otherwise:  200 OK
1 Implementation Details
1.1 Configuation and Files
- Cluster file: list of computers, one per line
- Parameter file: csv file, cells seperated with |, parameter names in the headline and every following line contains one parameter set. All lines have to have the same amount of cells like the headline!
- Specification of worker: Command line: a perl syntax string with parameter Variables for the parameters; Input files: Name of the file and parameter name to write in.
- Result specification: A result consists of a list of name and value pairs. Where name specifies the name of the particular output and value decides where the output comes from. For example output="stdout", outputfile="out.txt".
- Validation function: function template that gets the parameter set and the result of the worker and returns success or not
- Collection function: gets the parameters set and the result of the worker and can do whatever with it (usually print it in a file). 
1.1 NFS awareness
The problem is, that if some slaves share files via NFS or another network filesystem it could happen that
different clients overwrite their data. Basically there are three cases:
1. the client is copied
1. the client fetches the worker
1. the worker writes its data to a file.
Solutions:
1. a) start and copy clients in serial (very slow)  b) copy just one client at time, but start in parallel (fast on NFS, slow otherwise)
1. before fetching the worker the client creates a .lock file. The other clients check the existance and wait for the worker. 
1. every worker is started in a speparate directory, given by the session id and the ticket number