Docker Service Inspection Filtering & Template Engine under Swarm Mode

Go programming language has really helped in shaping Docker as a powerful software and enabling fast development for distributed systems. It has been helping developers and operations team to quickly construct programs and tools for Cloud computing environment. Go offers built-in support for JSON  (JavaScript Object Notation) encoding and decoding, including to and from built-in and custom data types.

golang

 

In last 1 year, Docker Swarm Mode has matured enough to become production-ready. The Orchestration platform is quite stable with numerous features like Logging, Secrets Management, Security Scanning, improvement over Scheduling, networking etc. making it more simple to use and scale-out in just few liner commands. With the introduction of new APIs like swarm, node, volume plugins, services etc., Swarm Mode brings dozens of features to control every aspect of swarm cluster sitting on the master node. But when you start building services in the range of 100s & 1000s and that too distributed across another 100s and 1000s of nodes, there arise a need of quick and handy way of filtering the output, especially when you are interested to capture one specific data out of the whole cluster-wide configuration. Here comes ‘a filtering flag’ as a rescue.

swarm11

The filtering flag (-f or --filter) format is a key=value pair which is actually a very powerful weapon for developers & system administrators.If you have ever played around with Docker CLI, you must have used docker inspect command to get metadata on a container/ image. Using it with -f provides you more specific information like IP address, network etc. There are numerous guide on how to use filters with standalone host holding the Docker images but I found lack of guides talking about Swarm Mode filters.

Under this blog post, I have prepared a quick list of consolidated filtering commands and outputs in tabular format for Swarm Mode Cluster(shown below).

I have 3 node Swarm Mode cluster running on one of my Google Cloud Engine. Let us first create a simple wordpress application as shown below:

 

swarm-1

 

We will create a simple wordpress service as shown:

master==>docker service create –env WORDPRESS_DB_HOST=wordpressdb1 –env WORDPRESS_DB_PASSWORD=collab123 –network collabnet –replicas 4 –name wordpressapp –publish 80:80/tcp wordpress:latest

Below is the tabular list of commands and outputs which talks about various filtering mode for docker service inspect command:

 

Inspecting the “wordpress” service:

[wpsm_comparison_table id="3" class=""]

To retrieve the network information for specific service:

[wpsm_comparison_table id="6" class=""]

To list out the port which wordpress is using for specific service:

[wpsm_comparison_table id="7" class=""]

To list out the protocol detail for specific service:

[wpsm_comparison_table id="8" class=""]

To list out the type of Published port:

[wpsm_comparison_table id="9" class=""]

To verify if its DNS RR or Virtual IP(VIP) based for specific service:

[wpsm_comparison_table id="10" class=""]

 

To list out the type of Published port for specific service:

[wpsm_comparison_table id="11" class=""]

To list out the replication factor for a specific service:

[wpsm_comparison_table id="12" class=""]

To list out the environmental variable passed for specific service:

[wpsm_comparison_table id="13" class=""]

To list out the image detail for specific service:

[wpsm_comparison_table id="14" class=""]

To list out the complete networking details for specific service:

[wpsm_comparison_table id="15" class=""]

To list out detailed consolidated  meta data information for the specific service::

[wpsm_comparison_table id="4" class=""]
 
To list out further detailed information of the service :

[wpsm_comparison_table id="5" class=""]

Let us create another service called “wordpressdb1” which is actually a database service under Docker Swarm Mode:

$docker service create –replicas 1 –name wordpressdb1 –network collabnet –env MYSQL_ROOT_PASSWORD=collab123 –env MYSQL_DATABASE=wordpress mysql:latest

Inspecting the service “collabdb1”:

[wpsm_comparison_table id="16" class=""]

Displaying the output in human-friendly way:

[wpsm_comparison_table id="17" class=""]

To list out the VIPs details for specific service:

[wpsm_comparison_table id="18" class=""]

Retrieving the last StatusUpdate details:

[wpsm_comparison_table id="19" class=""]

I have plans to add more examples during the course of time based on experience and exploration. I hope you will find it handy.

 

 
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