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5.4. QAD GRID WORKER 131
2. This request triggers another stored procedure that performs the following
steps:
� If there exists a request within the last five minutes containing
the same key or the same IP address the whole request is canceled.
This is done to prevent abusive generation of worker accounts which
might result in high load on the server.
� A new database account is created with randomly generated user
name and password.
� A new public/private key pair for asymmetric RSA encryption is
generated.
� A new certificate is created that is based on the MD5 digest of
a combination of the requesting worker’s service id and the just
generated public key for this worker.
� A new table entry is created that contains these information (DB
account, key pair, certificate) and is encrypted by the 2048bit key
the worker sent at initialization as binary array. This entry is identified
by the request id the server sent back to the worker.
3. The worker fetches this information by database query, decrypts it and
splits it back to the single components. These are then stored at the
worker’s host.
4. A new worker entry is created into the worker table of the platform
server.
5. The worker is now registered and can log into the QAD Grid system
with these credentials.
At later logins the worker simply authenticates using these credentials and
announces itself at the Grid. This announcement includes a unique identification
key that is created when a worker starts up and used to identify each
worker, e.g. for status updates.
5.4.3 Status Messages
Since the workers and client machines are not directly controlled by the Grid
(as opposed to a cluster) the Grid needs to get messages from the clients
to get information about their status. This is by updates to a status table
that contains a record for each client currently registered at the Grid. These
updates are sent every 5-300 seconds by the workers and contain the following
informations:
State: The state a worker is in is actually a text string. This string can be set
during computations and can e.g. contain progress information or state
changes during algorithm execution. It is mainly intended for humans
to get information about the actual worker condition.
Local load: This measures (estimates) the load of the host system the worker
is running on, caused by foreign processes. We define load as the time
needed by the operating system to give control once to each other process