Hibernate MySql Connection timeout

I noticed that a web application deployed on tomcat application server kept throwing JDBC exceptions after every couple of days. So I guessed that it must be a problem with mysql database connection timing out. I did quick search on the issue and found this article explaining the problem. You need to switch from the default Hibernate connection pooling to one of the production grade database connection pooling technology and set appropriate timeout settings.

You will also need to create a c3p0.properties file containing following values;

# a good mysql test query
c3p0.preferredTestQuery=SELECT 1
c3p0.testConnectionOnCheckout=true

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Creating no-reply@domain.com account in Postfix

If you wanted to send emails to users but did not want to receive any replies to the email, you would need to setup a no-reply@domain.com email account. These kind of email ids are useful when sending emails containing forgotten passwords or activation code. Below are the steps for creating such account in Postfix. 1. Identify the file containing alias for Postfix First, make sure the following line in the ALIAS DATABASE section of the /etc/postfix/main.cf is NOT commented out: alias_maps = hash:/etc/aliases 2. Create an alias that redirects messages to /dev/null Edit /etc/aliases and add following entry devnull: /dev/null 3. Create a virtual email id Edit /etc/postfix/virtual and add following entry no-reply@domain.com devnull 4. refresh postfix alias and postfix cache Execute following commands. (You may require root privileges) > newaliases > postfix reload

jupyter notebook execution error: "http://localhost:8889/tree?token=xxx" doesn’t understand the “open location” message

I got this error when I tried to launch jupyter notebook on a mac. It is not a fatal error. I could still go to browser directly and copy/paste the url manually. The error indicates that when the command automatically tried to launch a browser, it couldn't find the default browser in jupyter configuration file. The easy fix is to specify the browser. Here are the steps to do so; 1. Open ~/.jupyter/jupyter_notebook_config.py in an editor. If the file does not exist then you can create a default config file by typing the following command; jupyter notebook --generate-config 2. Search for a word "browser" to locate a following line. #c.NotebookApp.browser = '' By default it is commented. You can uncomment it and use one of the following values depending on your browser preference. # set default browser to chrome c.NotebookApp.browser = 'chrome' ...

Firefox 401 - Unauthorized: Access is denied due to invalid credentials

I was getting this error in Firefox when I tried loading our company intranet site. Chrome was able to log me in fine. I found a solution on Mozilla support forum. See the image below for a fix. Set the value to true and then try loading the page again. That fixed the problem for me. Next time I visited the site it prompted me to enter username and password.

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