Transcript 4_Checking_the_Server

Checking the Server
Location of Server Files on the
Virtual Machine
• On your virtual machine:
– We’ll use the root directory of the shrew/hyrax checkout
often and refer to it as $prefix
– The value of $prefix on you VM is
/home/opendap/src/hyrax-1.9
– The Tomcat servlet engine is in $prefix/tomcat
– The BES, data handlers and related source files are in
$prefix/src. The BES has been built and installed in
$prefix/{bin,lib,…}
– The OLFS web archive file is
$prefix/tomcat/webapps/opendap.war
– BES: bes.conf, found at $prefix/etc/bes/bes.conf
– OLFS: olfs.xml and catalog.xml, found at
$prefix/tomcat/content/opendap
Background: Starting the
Server
• Start the BES (back-end data
processing component)
• Use bescmdln to verify it’s working
• Start Tomcat: This automatically starts
all installed servlets
– Servlets are installed by copying the .war
file to the servlet’s webapps directory
• Verify it’s working using a web browser
Start the BES
Verify the BES is running
Start Tomcat & the OLFS
•
Typical steps:
– Unpack the olfs jar-file
– Copy the opendap.war file to Tomcat’s
webapps directory
– Start Tomcat
•
Since all but the last step has been
done already, start Tomcat:
–
/usr/local/javadev/apache-tomcat5.5.12/bin/startup.sh
…terminal view
Verify Tomcat is running
http://localhost:8080
…and Hyrax
http://localhost:8080/opendap
Troubleshooting
• The getdap command line client
– Can request any of the DAP response
objects
– Can act as a simple, generic web client
• When even getdap cannot diagnose a
problem, use telnet!
Troubleshooting with getdap
• Use getdap to get
– The DAS, DDS, Data, DDX
– Version information
• Use telnet to view the raw HTTP
response
• If the server times out too quickly, use
expect to control telnet
Use the ‘-a’ option to get a DAS response
Also provide a valid URL
http://localhost:8080/opendap/data/nc/fnoc1.nc
Use the ‘-d’ option to get a DDS response
…or drop the -d option and append the ‘.dds’ suffix
Use the ‘-D’ (data) and ‘-c’ (constraint)
options to get a data response.
A constraint expression with just one
variable. We got this from the DDS above
This constraint is asking for the values of
‘time’ between indexes 2 and 6 (every
second value).
Appending the string ‘version’ to the server
root name requests version information. It
comes back in an XML document.
Telnet reveals all
• Use telnet to pass HTTP commands directly to the
‘opendap’ web application
• Open the connection using the host name and port
number
• Use the ‘GET’ command, the pathname part of the
URL including the DAP request extension and
‘HTTP/1.1’ or ‘HTTP/1.0’
• Often you will need to supply a ‘Host: <name>’
header
• A blank line.
Connect to the Tomcat or Apache server
GET <pathname> HTTP/1.1 (or 1.0) - hit
return quickly!
Host: header is important for a virtual server
Here’s the payoff - we can see all of the
headers set by both the web app and
the server, plus the response. Be cautious
with data responses because they are
binary and will mess up your terminal
session. Note the HTTP 1.1 chunking
counts (c5 and 0)