GLITE Tutorial

Advanced gLite: Distributed Applications (2)

R-GMA may be used by the jobs to inform themselves about their respective contact addresses.

Create a RGMA table Contacts to hold for each communication partner id its contact address addr:
```
  rgma -c 'create table Contacts  
    (id INTEGER PRIMARY KEY, addr VARCHAR(99))'
```
Put scripts publish.sh and query.sh into the input sandbox of each job:
```
  InputSandbox = { ..., "publish.sh", "query.sh" }
```
When a job starts execution, it publishes (after binding to a free port) its contact information in table Contacts:
```
  /bin/sh publish.sh id hostname:port
```
Each job may query the contact address of communication partner id from table Contacts:
```
  /bin/sh query.sh id 
```
(Repeat query, if address has not yet been published).

The same principle may be applied in a more sophisticated form within programs by the use of the R-GMA API.

  # publish.sh: publish <id> and <contact>
  #!/bin/sh
  if [ $# -ne 2 ]; then exit 127; fi
  $RGMA_HOME/bin/rgma<<EOF
  set producer latest
  set producer lrp 24 hours
  insert into Contacts values ($1, "$2")
  EOF
  exit 0

  # query.sh: query for <id> and print <addr>
  #!/bin/sh
  if [ $# -ne 1 ]; then exit 127; fi
  $RGMA_HOME/bin/rgma<<EOF | tail -n4 | head -n1  
    | awk '{print $2}' | awk -F, '{print $1}'
  set output csv
  select addr from Contacts where id=$1
  EOF
  exit 0

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