A request came in the other day asking if it was possible to make a Dodeca view’s connection dynamic/selectable by the user. For example, say you are rotating through cubes every month that are essentially the same outline but just have different data. You might have the January cube, the February cube, and so on. This is a somewhat unorthodox, but certainly not unique design approach that I have seen over the years. Among other things, this approach can help keep a cube very manageable/fast when an organization’s data needs and processes might otherwise require an entirely new dimension or other dimensional shenanigans in order to facilitate the necessary reporting, planning, and forecasting activities.
To start, since connection objects in Dodeca are centrally managed it is certainly possible to just update the connection details as needed and point to the proper cube. But in this case we need a little more power. Can we let the user choose the connection for their own Dodeca view? Absolutely. I’ll show you how in this article. Continue Reading…
I blogged quite some time ago about using JNDI to configure database connections in Dodeca. As I mentioned then, JNDI can bring some useful improvements to your configuration, management, security, and administration of your environment versus how you might be configuring normal JDBC connections. To be clear, this isn’t because JNDI connections are inherently better from a performance standpoint, it’s just that it might be a cleaner solution in various ways.
My original blog post looked at configuring a pretty typical MySQL connection in JNDI. As I have worked with this in the last few months, I have run into a few issues with the configuration as it related to connection timeout issues. I was occasionally getting some timeout issues like this:
MySQL connection timeout when configured with JNDI
Helpfully enough (or perhaps unhelpfully) the error message itself reports that perhaps the autoReconnect=true setting would be of help. I’ve actually used that setting in the past and it seemed to help things out. But as it turns out, that setting is deprecated and should not be used. There are some alternative techniques that can/should be used to ensure the program gets a valid connection back.
One common technique is to specify a “validation query”. This is often something like
SELECT 1 or
SELECT 1 FROM DUAL depending on the particular database technology being used. You can use
SELECT 1 for MySQL. What this essentially means is that before returning a connection via JNDI to the Java servlet to do things with, the connection pool manager is going to run the validation query to ensure that it is indeed a valid connection (able to connect, doesn’t error out, and so on.
Interestingly enough, MySQL in particular has added an optimization for this use case such that you can give it a sort of fake query (code:
/* ping */) and it’s slightly more optimized than the overhead involved with a SELECT 1.
Together with this optimized test query, some additional attributes on the JNDI configuration (
removedAbandoned, I’ve updated the overall JNDI configuration and it seems to be much more robust. Here’s the new connection JNDI code from my Tomcat context.xml:
<Resource name="jdbc/dodeca_sample" auth="Container" type="javax.sql.DataSource" username="dodeca" password="password" driverClassName="com.mysql.jdbc.Driver" url="jdbc:mysql://localhost/dodeca_sample?noDatetimeStringSync=true" maxActive="100" maxIdle="30" maxWait="10000" removeAbandoned="true" removeAbandonedTimeout="20" logAbandoned="true" validationQuery="/* ping */" testWhileIdle="true" testOnBorrow="true" testOnReturn="false" />
<ResourceLink name="jdbc/dodeca_sample" global="jdbc/dodeca_sample" type="javax.sql.DataSource"/>
I wanted to punch up a Dodeca view the other day by putting a little zebra striping on some relational data. Although having built-in support for this is on my wishlist, for now a simple workbook script (WBS) gets the job done. This is also alternatively called “greenbar”… depending on what decade you were born in.
The technique itself is pretty simple. You can accomplish this in a few ways in Dodeca (as with everything), so here’s one way to go. First, when the view is opened, we have a workbook script to set a color index (that’s the first step in the following screenshot). In this case I am setting a very light grey to be color Index 2.
In the next step (the one that actually does the striping), I have defined a simple method that applies to a range named “Address” and just paint every other row depending on if it’s even or not. I’m just using the formula
=MOD(@CRow(), 2) = 0, which is a normal Excel function (modulus), and a workbook script function (
@CRow()) that returns the current row number being processed. If it’s even, then the cell should be painted. If not, nothing happens. So if you wanted two different colors you’d just add a new color set step and a new SetFill method that applied to odd rows.
Here’s a screenshot of the full WBS:
Dodeca WBS Zebra Striping Example