pp108 : Managing Application Packages in a Primary Distributed Setup

Managing Application Packages in a Primary Distributed Setup
This topic provides an overview of managing the application packages in a Primary-Distributed setup.

In a Primary-Distributed setup, two or more installations of Process Platform share the same directory service (OpenText CARS) and distribute the load of service requests among themselves. This setup is preferred in high availability required environments. It installs only the runtime environment required for the service containers to be configured and executed on a system. This kind of setup is useful for load balancing.

You must ensure to keep the Primary-Distributed cluster setup consistent while managing the application packages. This means that all the packages of a specific version and their dependent packages must be deployed in all the nodes of the cluster. The runtime behavior of the distributed setup is improper if the consistency is not maintained.

Deploying application packages in a Primary-Distributed setup

  1. Open Application Deployer.
  2. Click New to view the list of the application packages to be deployed.
  3. Right-click the selected application packages and select Deploy. The Application Deployer wizard appears displaying the Application Packages and their Dependencies dialog box.
  4. Click Next to continue. The Application Signature Verification Status page is displayed.
    Note: This page is displayed only if one or more applications fail the signature verification. If the status of an application appears tampered or unsigned, to proceed with the deployment, select the Allow to Proceed option. Ensure that the security permissions to deploy are set to Prompt or Allow.
    If the signature verification fails with the error message 'File not found', then one of the following must be ensured:
    • The application package is uploaded in the primary computer.
    • The security permissions to deploy are set to Prompt or Allow.
      Note: If you are not allowed to deploy the application, contact the system administrator and obtain a relevant signed application.
  5. Click Next to continue. If the Show Impact Analysis option is selected in the Applications and their Dependencies dialog box, the Impact Analysis of Selected Applications dialog box is displayed. It provides information about the artifact and the impact (Create, Update, Move, Rename, and Delete) the deploy operation has on the artifact.
    The impact provides an overview of which artifacts will be deployed on the primary node and secondary node respectively.
  6. Click Next to continue. A list of the nodes configured in the Primary-Distributed setup is displayed.
  7. Select the nodes on which you want to deploy the application packages and click Next.
    An Applications Summary page appears displaying the list of the nodes on which the application will be deployed.
  8. Refer to Application summary for more detailed actions to complete the deployment.

Cluster summary view

Sometimes, an application package may fail to deploy on a node of the Primary-Distributed setup (cluster) and succeed on the other node. It is also possible that while upgrading an application package to an higher version, one of the nodes in a cluster might not be available. This forces the package to get into an inconsistent situation. While it is important to have a consistent deployment of application packages in a cluster, having a clear overview of the consistent deployment becomes even more apparent. 

To have a clear overview of the cluster setup, Process Platform, provides "Cluster summary" view. This view will help the system administrators to have a clear view of the packages, it's versions and the status of the deployment across the cluster. The cluster wide status of the packages will be calculated by summarizing the status of a package on all the available nodes of the cluster. 

Looking at this view, the administrators can decide if any further actions needs to be performed to bring the cluster setup to consistent state. One can define "filters" to short list set of packages with specific status.

Types of status

The cluster wide status of  the packages is explained below with a 3-node cluster setup.

Deployed: An application package will be in "Deployed" status in a cluster only when the package with same version is successfully deployed in all the available 3 nodes.
Partial: An application package will be in "Partial" state when the package of same version is deployed successfully in 2 of the 3 available nodes and is yet to deployed in the 3rd available node.
  • A package successfully deployed in all the 3 available nodes can still get into partial state when the package is undeployed from one of the available node. This may happen when some of the nodes are not available during undeployment
  • After successfully deploying a package of same version in a 2-node cluster, a package can get the partial status when a new node is added because package might not be deployed yet in the newly added node.
Incomplete:  An application package will be in 'Incomplete' state in a cluster when:
  • The deployment or upgrade of a package fails on one of the available node.
  • An higher or lower version of an application package is deployed in one of the available node.

Viewing Cluster Summary View

  1. Open Application Deployer.
  2. Switch to Summary tab, which is located at left bottom of the page.
  3. By default Shared space type is selected.
  4. Select Show All or Show selected options:
    1. To filter a set of packages, click on the zoom button adjacent to Show Selected radio button. A modal dialog with a list of packages will be displayed. You can also filter Platform packages from the selected list.
    2. To view cluster status of all the packages, click on Show All radio button. This option will also include all platform packages.

    Note: you an also filter the set of packages based on their cluster status as explained above. Select one or more filters (Deployed, Partial and Incomplete) check boxes to filter packages with the matching cluster status. By default, Partial and Incomplete check boxes will be selected.

  5. Click View Summary, to view the details of the selected packages. A tabular view of the packages with version and status details will be shown.
  6. The Status column in the Summary view will display cluster status of the selected packages from all the available nodes.
  7. Each column in the grid, represents a available node in the cluster. Each cell element displays the version of the package deployed on that node.
    1. If a package is in incomplete state in a node, then the cell value of that package will be labeled with Incomplete status along with it's version.
    2. If a package is yet to be deployed in a available node, the cell value of that node for that package will be marked as 'x' 
    3. If a package in a node is having different version of a package compared to other nodes in the cluster, then the cell value will show the version of the package highlighted with red color.

    You can use the column chooser option to show/hide a set of nodes from the tabular view to quickly compare packages across set of selected nodes.

Exceptions and and recommendations

The following table lists the exceptions and recommendations for managing application packages in a Primary-Distributed setup:

Deploying an incomplete package on a new node

Problem Description

A package is in an incomplete state in a node of a cluster. If the same package is being deployed on an another node and goes to an incomplete state, revert of such a package does not work.

Use case
  1. Deploy a package A in a node 'N1' of a cluster. If this package deployment fails for a valid reason such as if the required service container is not started or the database connection timed out, and so on, based on the 'Revert on failure' option selected, the package is in ‘Incomplete’ state.
  2. Deploy the same package A on a different node 'N2' of the cluster. If this package also goes to the incomplete state,
    reverting the package from both the nodes does not succeed.

Recommendation

If there is a package in an incomplete state on a node, do not deploy the same package of the same or higher version on another node until the issue is addressed on the former node.

Undeploying a base package from a node when the dependent package is deployed in an Organization space

Problem Description

A base package 'A' is deployed in the Shared space on both the nodes N1 and N2 of a two-node cluster. The dependent package 'B' is deployed in an Organization space on node N

1. In this scenario, if the base package 'A' is being undeployed from the other node N2, the undeployment does not succeed.

Use case
  1. Deploy a package A in the Shared space on both the nodes N1 and N2 of a two-node cluster.
  2. Deploy a dependent package B in the Organization space only on node N1.
  3. Undeploy the base package A from node N2. The undeployment does not succeed.

Recommendation

This issue occurs since the dependent package B is not deployed on both the nodes. Hence, it is recommended to undeploy package B from node N1 and then undeploy the base package A from node N2.

Displaying an incorrect version in a cluster in the All Organization view

Problem Description

The 'All Organizations' view shows the incorrect package version as deployed for a specific organization.

Use case
  1. Deploy package A with version 1.0 in the Organization space X on both the nodes N1 and N2 of a two-node cluster.
  2. Upgrade with version 2.0 in the same Organization space X on node N1. The deployment fails and goes to an incomplete state.
  3. Click the All Organizations view and select organization X. It displays version 2.0 as the deployed version though it is in an incomplete state.

Recommendation

Fixing the reason for the upgrade failure on node N1 shows the correct version.

'File not found' error occurring at the Signature Verification step during deployment in a cluster

Problem Description

An application package fails at the Signature Verification step while deploying it in a cluster. This occurs when the package to be deployed is uploaded on to one of the distributed computers. During validation, since the signature verification is done on the primary computer, the system searches for the application package on the primary computer.

Use case
  1. Upload the unsigned package A with version 1.0 on one of the distributed nodes N1. The package will be listed in the New list.
  2. Select the package and deploy it.
  3. The Signature Verification step fails, displaying the 'File not found' error.

Recommendation

If Code Signing settings are set to 'Prompt' or 'Disallow' in Security Administration and signature verification is required, it is recommended to create the Security Administration service container on the distributed node.