Monday, July 20, 2015

Bluemix: Simple cron-like service for my Python code

Schedule background tasks in Bluemix
This morning I had some time to fiddle around with Bluemix and Python. I wanted to test out creating a cron-like service, i.e., something that runs in the background and kicks off tasks with given intervals or at a given time. For Python there exists a package "schedule" that is easy to set up and use. So how do you create a background service in Bluemix?

The trick is in the file manifest.yml and the Cloudfoundry documentation has all the needed details (Bluemix is built on this open standard). The attribute "no-route" is set to true, indicating that this is not a Web application and we don't need a subdomain name. In addition the attribute "command" is set to invoke the Python interpreter with my script as parameter. Basically, this starts my background task:

 applications:  
 - name: hltimer  
  memory: 256M  
  instances: 1  
  no-route: true  
  command: python mytimer.py  
  path: .  


The cron-like service script is pretty simple. It uses the "schedule" package to set up recurring jobs. I tested it with the Twilio API to send me SMS at given timestamps. You can also use it to scrape webpages in given intervals, kick off feed aggregators, read out sensors and update databases like Cloudant or DB2, and more. See this Github repository for the full source.

 import schedule  
 import time 

 def job():  
 #put the task to execute here  

 def anotherJob():  
 #another task can be defined here  

 schedule.every(10).minutes.do(job)  
 schedule.every().day.at("10:30").do(anotherJob)  

while True:  
   schedule.run_pending()  
   time.sleep(1)  

Friday, July 17, 2015

DB2 Encryption: Some rotation before the weekend

Some bits on encryption...
Some while ago I wrote about DB2 encryption and how to rotate the master key. Well, today I rotated the master key again and looked at the metadata before and after the key rotation. I started with an encrypted database that I created some months ago.

The first step was to obtain the encryption information, i.e., metadata about the encrypted database. This can be done in two ways: Either using the utility db2pd or by calling the table function ADMIN_GET_ENCRYPTION_INFO.

Wednesday, July 1, 2015

DB2 Battle: Optimization Profile vs. Statement Concentrator (Part 3)

db2expln output - statement concentrator active
In February I had fiddled with optimization profiles and REOPT working against the statement concentrator (part 2 is here). Today I wanted to give an interesting (hopefully) update. The tool db2expln can be used to describe the access plan for static and dynamic SQL statements. It works in a different way than db2exfmt and visual explain (part of tools like Data Studio and IBM Data Server Manager). Thus, I was eager to see whether it could help to find out whether my optimization profile was applied.


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