Remote Images Retrieval With Splunk Using Custom Command “getimage.py”
Every once in a while my customers ask for a functionality that is not natively supported by Splunk. Out of the box Splunk is a very capable platform, however, there are certain tasks Splunk is not designed for. But that never stops a Splunker from finding a solution! The use-case I am about to discuss in this blog is an example of that: The customer owns large chain of pharmacies across the country, the bulk of the stores transactions end up in Hadoop Data Lake; the customer wants to use Hunk/Splunk to visualize and analyze the massive amount of information collected, which is something Hunk can do easily. The challenge came about when I was asked if Splunk could show RX TIFF images (doctor’s hand written prescription) along side the patient’s records. I was presented with the following criteria:
- Retrieve patient’s records from Hadoop and marry them to RX image residing on an imaging server(s).
- The imaging server(s) is running Apache tomcat.
- RX Images are stored in TIFF format (but sometime can be in different format)
- Must be able to handle billion of images and accommodate error conditions (ex: file not found, failed communication, …etc.)
The Hadoop part was easy with Hunk. After all that’s what we do best! But dealing with images retrieval required a little more work. Initially I thought, I can use the workflow built-in Splunk to retrieve remote URLs http://docs.splunk.com/Documentation/Splunk/6.3.3/Knowledge/CreateworkflowactionsinSplunkWeb
But I soon discovered that simple approach would not help solve the following problems:
- Images are stored in TIFF format and most browsers don’t support it (with the exception of Safari).
- We need to process (download) large amounts of image files from multiple image servers. Therefore, performance and error handling are critical.
- Retrieved images need to be annotated for added information.
- Retrieved images may need to be resized before displaying (if larger than certain size).
To address those challenges I turned to the power of custom search commands. Splunk Enterprise lets you implement custom search command for extending SPL (Search Processing Language). I wrote a search command called getimage.py that will satisfy all of the above requirements. To demonstrate the usage of this custom command I also created a little app the can be found here https://github.com/mhassan2/rx_image_review_app/tree/master/rx_image_review_app
How does it work?
The script will accept two arguments <fieldname> <url>. The first argument is the field name that contains the image name in raw data. The second argument is the remote imaging server URL (without the destination file name). I used the image_file field name to retrieve the file from the remote imaging server(s)
source=”patients.records” | getimage image_file http://10.211.55.3/icons | table Patient_Name, Prescription, image_file, new_image, wget_result, link, cached_image
The script uses the infamous wget command https://www.gnu.org/software/wget/ to download images. Once retrieved, we use “convert” command from a well-known image manipulation package called ImageMagick http://www.imagemagick.org/script/binary-releases.php
The “convert” command (not to be confused with Splunk own convert command) is used to transform images format from TIFF to JPG (or PNG) then add any required annotation or resizing. Additionally, the script utilizes a caching mechanism to minimize the impact on the network. So if an image is retrieved repeatedly (within a pre-configured time value), it will be fetched from the cache directory (residing on Splunk Search Head). The getimage.py script will append several fields to the search results. Most of these fields are used for troubleshooting. Depending on how the dashboard xml is written you may want to use the “link” field or “new_image” field.
Here is a list of fields injected into the search output:
- [rc_wget]: The output of wget command
- [rc_convert]: The output of ImageMagick’s convert command
- [new_image]: The converted image name
- [image_size]: Size of newly converted image (shows up when cached only)
- [file_loc]: *Experimental* location new image URI (using file:///)
- [link]: URL of the new converted image on the Search Head
- [cached_imaged]: Indicate if image is served from local cache or not
- [wget_result]: A cleaned up version of wget output
- [app_shortcut_url]: location of all cached images for xml use (dashboard)
How to test it?
From the command line:
- Setup a VM running apache server (my test VM IP is 10.211.55.3).
- Install ImageMagick on your Search Head (we’re interested in convert command only).
- Install wget on your Search Head.
- Copy sample images (found in the apps sample_images directory) to /var/www/icons/ directory on apache server (default apache configurations for icons).
- Modify getimage.conf to match your environment.
- The shipped app rx_image_review_app should have the required files to make the script work (command.conf, authorize.conf).
- Verify that you are able to retrieve images manually using wget. Run this on the Search Head: wget –timeout=2 –tries=1 –no-use-server-timestamps http://10.211.55.3/icons/rx_sample1.tif
- Verify that you are able to use convert command (part of ImageMagick). Run this on the Search Head: /opt/ImageMagic/bin/convert rx_sample1.tif rx_sample1.jpg
From the app UI:
- Manually import patients.records (under sample_logs) into Splunk. Make sure you use CSV source type to get a quick field extraction; otherwise you will have to manually extract the fields.
- Verify that the log import was successful using Splunk UI. The most important field to us is “image_file”.
- To test connectivity, kill httpd on the image server then try refreshing your dashboard.
- To test 404 file not found error, remove one of the sample files from the image server; refresh your browser.
- To test 403 forbidden error (which mostly means permission issues), change perms to 600 on a sample file on the image server then try to connect again.
- To test handling of different image types, convert an image to any of the 100’s of types the ImageMagick supports on the image server then refresh your dashboard.
- A log file to track activity is created in: /opt/splunk/var/log/splunk/getimage.log
This is how the sample file (patients.records) will look like without getimage.py:
Here is an example of how the output will look like using getimage command:
Using the built-in dashboard (RX Images Retrieval with icons):
As you can see the script added an additional field called “link” which is a link to the location of the image on the Search Head.
- Can handle images without file name extension.
- Can convert over a 100 major image file formats (ImageMagick).
- Built-in caching (can be turned off).
- Cached files do not linger around forever. There is a cleaning mechanism.
- Dynamically handles many caching conditions scenarios.
- Multiple configurable parameters (set in a config file) for agile deployment.
- Can handle network connection failures, 404 File not found, and 403 Forbidden errors.
- Images are annotated before displaying (Image name, cached condition, and/or error conditions).
- The script produces multiple fields that can be used for troubleshooting.
What else can you do with this script?
I wrote this custom command and created a showcase app in order to solve a specific problem for my customer. I am sure there are a lot more use-cases around images with Splunk. So feel free to borrow whatever you need in order to solve your problem. I attempted to document as much as possible of the code with the intention that someone is going to read, dissect, and/or reverse engineer it.
Here is a list of functionality improvements you can add:
- Remove dependency on shell commands (wget, convert) and use equivalent python modules (this may require additional packages imported into Splunk’s shipped python (PIL and WGET libraries).
- Add more annotation to the images to communicate precise/detailed messages to users.
- In high volume retrieval scenarios, you can download images in bulk to speed up the response time.
The App (rx_image_review_app):
A simple app was created to demonstrate how getimage.py could be used. This app is shipped with sample data and sample images. I borrowed some of the xml and java script code (Table Icon Set-rangemap) from Splunk 6.x Dashboard Examples app https://splunkbase.splunk.com/app/1603/
I used the rangemap icons to quickly visualize the status of communication with the imaging server.
Here are the relevant directories from the main app directory rx_image_review_app:
- appserver/static/cache all retrieved images are deposited here.
- bin location of python script and configuration files
- /default/data/ui/view all dashboards xml documents
- sample_log sample input data patients.records
- sample_images sample images (need to copy to your imaging server)
- default authorize.conf and command.conf must have for script to work. Please note web.conf is for testing (turn of splunkweb caching)