In this article, we’ll build a highly available IRIS configuration using Kubernetes Deployments with distributed persistent storage instead of the “traditional” IRIS mirror pair. This deployment would be able to tolerate infrastructure-related failures, such as node, storage and Availability Zone failures. The described approach greatly reduces the complexity of the deployment at the expense of slightly extended RTO.

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I've created a scheduled task that dumps HL7 messages to flat files. It uses the OutputToLibraryStream() method of EnsLib.HL7.Message. I'd like to be able to run it on a mirror member host whether it's primary or backup.

When run against a database that's mounted read-only, it works fine. However, when I attempt to run it against a mirror backup database, I get the following error:

#5002: Cache error: <PROTECT>%LoadData+7^EnsLib.HL7.Message.1

Tracing that back to the source, I find:

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Mirroring 101

Caché mirroring is a reliable, inexpensive, and easy to implement high availability and disaster recovery solution for Caché and Ensemble-based applications. Mirroring provides automatic failover under a broad range of planned and unplanned outage scenarios, with application recovery time typically limited to seconds. Logical data replication eliminates storage as a single point of failure and a source of data corruption. Upgrades can be executed with little or no downtime.

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We are trying to script a High Availability Shutdown/Start script in case we need to fail over to one of our other servers we can be back up within mins. Is there a way to configure the startup procedure to Automatically Stop/Start the JDBC server when shutting down or starting up cache? is there an auto setting we can change?


Scott Roth

The Ohio State University Wexner Medical Center

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++ Update: August 1, 2018

The use of the InterSystems Virtual IP (VIP) address built-in to Caché database mirroring has certain limitations. In particular, it can only be used when mirror members reside the same network subnet. When multiple data centers are used, network subnets are not often “stretched” beyond the physical data center due to added network complexity (more detailed discussion here). For similar reasons, Virtual IP is often not usable when the database is hosted in the cloud.

Network traffic management appliances such as load balancers (physical or virtual) can be used to achieve the same level of transparency, presenting a single address to the client applications or devices. The network traffic manager automatically redirects clients to the current mirror primary’s real IP address. The automation is intended to meet the needs of both HA failover and DR promotion following a disaster. 

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In System Administration | Configuration |  System Configuration | Journal Settings there is a check box for Freeze on error.

From reading the documentation, it sounds like the choice to freeze on error is one of system availability vs system integrity.

Curious to know whether Ensemble users choose to freeze on error or not.

If you have a best practice recommendation based upon your experience or knowledge, that would be helpful information too.

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Jon Astle · Nov 9, 2017
Detecting and managing failover

I have Ensemble/Healthshare running in a production environment which is setup with a mirror failover and an arbiter sitting between them.

In the event of a failover we have a number of connections that need stopping/monitoring and starting in a certain order.

Is there a programmatic way we can detect the failover and stop certain services and operations immediately and then start them up again in the required order, checking their connection state before starting the next connection.

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Mirror Outage Procedures

Caché mirroring is a reliable, inexpensive and easy to implement high availability and disaster recovery solution for Caché and Ensemble-based applications. This article provides an overview of recommended procedures for dealing with a variety of planned and unplanned mirror outage scenarios.

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