Real-time conditions data distribution for the Online data processing of the ALICE experiment

A pair of java classes were developed for this project: the Sender and the MulticastReceiver.
These entities are using the Blob class to store complete data objects. These objects will be sent via multicast mesages from the Central repository to the Multicast receivers programs that run on the EPNs (Event Processing Node).

A Blob object has two important fields that store useful information: metadata and payload.
Because a typical Blob size is around 2 MB (which is far more than the maximum payload size of UDP packets - 64KB) I had to use a fragmentation and reassembling mechanism.
The FragmentedBlob class stores partial content from a Blob: either metadata, either data, depending on the Packet Type field. This object is serialized using the following structure and sent in the local network using a DatagramSocket:

FragmentOffset = start index of this fragment payload in the Blob
PacketType(Flags) = Indicates what kind of payload does this fragment carry
UUID = Universally Unique IDentifier, also used as ETag in the REST API
BlobP ayloadLength = the total length of the Blob’s payload or Blob’s metadata
KeyLength = the length of the key associated with the current Blob
BlobP ayloadchecksum = the checksum of the payload or metadata
Key = the key content with size x
Payload = the Blob’s (partial) metadata or payload with size y

Requirements:
#todo

Compile:

(Create .jar files)
cd package
./package.sh

Clean: (removes .jar files too)
make clean

Generate documentation:
make doc

Running

Increase the receiver buffer size:
sudo ./kernel_configuration.sh
cd package
(Compile)

• the receiver:

./runReceiver

• the sender:

export MAX_PAYLOAD_SIZE=1400
./runSender.sh