cron

For those of you who read my previous article (if you have not read it, please do so before proceeding forward), at the very end I showed off a screenshot of a script that I had created for the vCenter Server Appliance (VCSA) which automatically monitors the health of the primary Platform Services Controller (PSC) it is connected to and in the event of a failure, it would automatically repoint and failover to another healthy PSC. The way it accomplishes this is by first deploying two externally replicated PSC's and then associating the VCSA with just the first PSC which we will call our primary/preferred PSC node. Both PSC's are in an Active/Active configuration using a multi-master replication and any changes made in SSO on psc-01 (as shown in the diagram) will automatically be replicated to psc-02.

From a vCenter Server's point of view, it is only get requests serviced by a single PSC, which is psc-01 as shown in the diagram above. Within the VCSA, there is a script which runs a cronjob that will periodically check psc-01's connectivity by performing a simple GET operation on the /websso endpoint. If it is unable to connect, the script will retry for a certain number of times before declaring that the primary/preferred PSC node is no longer available. At this point, the script will automatically re-point the VCSA to the secondary PSC and in a couple of minutes, any users who might have tried to login to the vSphere Web Client will be able login and this happens transparently behind the scenes without any manual interaction. For users that have already logged in to vCenter Server, those sessions will continue to work unless they have timed out, in which case you would need to log back in.

The script is configurable in terms of the number of times to check the PSC for connectivity as well as the amount of time to wait in between each check. In addition, if you have an SMTP server configured on the vCenter Server, you can also specify an email address which the script can send a notification after the failover and alert administrators to the failed PSC node. Although this example is specific to the VCSA, a similar script could be developed on a Windows platform using the same core foundation.

Disclaimer: This script is not officially supported by VMware, it is intended as an example of what can be done with the cmsso-util utility. Use at your own risk.

To setup a similar configuration, you will need to perform the following:

Step 1 - Deploy two External PSCs that are replicated with each other. Ensure you select the "Join an SSO domain in an existing vCenter 6.0 platform services controller" option to setup replication and ensure you are joining the same SSO Site.

Step 2 - Deploy your VCSA and when asked to specify the PSC to connect to, specify the primary/preferred PSC node you had deployed earlier. In my example, this would be psc-01 as seen in the screenshot below.

Step 3 - Download the checkPSCHealth.sh script which can be found here.

Step 4 - SCP the script to your VCSA and store it under /root and then set it to be executable by running the following command:

chmod +x /root/checkPSCHealth.sh

Step 5 - Next, you will need to edit the script and adjust the following variables listed below. They should all be self explanatory and if you do not have an SMTP server setup, you can leave the EMAIL_ADDRESS variable blank.

PRIMARY_PSC - IP/Hostname of Primary PSC
SECONDARY_PSC- IP/Hostname of Secondary PSC (must already be replicating with Primary PSC)
NUMBER_CHECKS- Number of times to check PSC connectivity before failing over (default: 3)
SLEEP_TIME - Number of seconds to wait in between checks (default: 30)
EMAIL_ADDRESS- Email when failover occurs

Step 6 - Lastly, we need to setup a scheduled job using cron. To do so you can run the following command:

crontab -e

Copy the following snippet as shown below into the crontab of the root user account. The first half just covers all the default paths and the expected libraries to perform the operation. I found that without having these paths, you will run into issues calling into the cmsso-util and I figured it was easier to take all the VMware paths from running the env command and just making it available. The very last last line is actually what setups the scheduling and in the example below, it will automatically run the script every 5 minutes. You can setup even more complex rules on how to run the script, for more info, take a look here.

PATH=/sbin:/usr/sbin:/usr/local/sbin:/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin:/usr/games:/usr/lib/mit/bin:/usr/lib/mit/sbin:/usr/java/jre-vmware/bin:/opt/vmware/bin

SHELL=/bin/bash
VMWARE_VAPI_HOME=/usr/lib/vmware-vapi
VMWARE_RUN_FIRSTBOOTS=/bin/run-firstboot-scripts
VMWARE_DATA_DIR=/storage
VMWARE_INSTALL_PARAMETER=/bin/install-parameter
VMWARE_LOG_DIR=/var/log
VMWARE_OPENSSL_BIN=/usr/bin/openssl
VMWARE_TOMCAT=/opt/vmware/vfabric-tc-server-standard/tomcat-7.0.55.A.RELEASE
VMWARE_RUNTIME_DATA_DIR=/var
VMWARE_PYTHON_PATH=/usr/lib/vmware/site-packages
VMWARE_TMP_DIR=/var/tmp/vmware
VMWARE_PERFCHARTS_COMPONENT=perfcharts
VMWARE_PYTHON_MODULES_HOME=/usr/lib/vmware/site-packages/cis
VMWARE_JAVA_WRAPPER=/bin/heapsize_wrapper.sh
VMWARE_COMMON_JARS=/usr/lib/vmware/common-jars
VMWARE_TCROOT=/opt/vmware/vfabric-tc-server-standard
VMWARE_PYTHON_BIN=/opt/vmware/bin/python
VMWARE_CLOUDVM_RAM_SIZE=/usr/sbin/cloudvm-ram-size
VMWARE_VAPI_CFG_DIR=/etc/vmware/vmware-vapi
VMWARE_CFG_DIR=/etc/vmware
VMWARE_JAVA_HOME=/usr/java/jre-vmware

*/5 * * * * /root/checkPSCHealth.sh

Step 7 - Finally, you will probably want to test the script to ensure it is doing what you expect. The easiest way to do this is by disconnecting the vNIC on psc-01 and depending on how you have configured the script, in a short amount of time it should automatically start the failover. All operations are automatically logged to the system logs which you can find under /var/log/messages.log and I have also tagged the log entries with a prefix of vGhetto-PSC-HEALTH-CHECK, so you can easily filter out those message in Syslog as seen in the screenshot below.

If a failover occurs, the script will also log additional output to /root/psc-failover.log which can be used to troubleshoot in the case a failover was attempted but failed. To ensure that the script does not try to failover again, it creates an empty file under /root/ran-psc-failover which the script checks at the beginning before proceeding. Once you have verified the script is doing what you expect, you will probably want to manually fail back the VCSA to the original PSC node and then remove the /root/ran-psc-failover file else the script will not run when it is schedule to.

As mentioned earlier, though this is specifically for the the VCSA, you can build a similar solution on a Windows system using Windows Task Scheduler and the scripting language of your choice. I, of course highly recommend customers to take a look at the VCSA for its simplicity in management and deployment, but perhaps thats just my bias 🙂

A couple of weeks back, I had received a question around backing up and restoring the Embedded vPostgres Database found within the new vCenter Server Appliance (VCSA) 6.0. At the time, the only thing I had seen was KB 2110294 and vSphere 6.0 Documentation here which recommends that a full VM backup be taken for either the vCenter Server for Windows as well as the VCSA to be able to properly protect your vCenter Server.

It was just recently that I came across VMware KB 2091961 which provides some details on just backing up the individual vPostgres DB. Having said that, just having a database backup is not sufficient to perform a proper restore in the case of completely losing your vCenter Server. There are other sources of data within the vCenter Server as well as the Platform Services Controller that are required and restoring a database would only work if you still had access to the original system. This is why a full VM backup is still the recommended approach.

For those who want to be able to just restore the database, the process listed in the KB is currently a manual step which uses a Python script that is provided in the KB. I thought it would be useful to demonstrate how you could schedule continuous backups during off peak hours using a simple cronjob and more interesting to me, is the how and where of the overall process? One option would be to mount a backup NFS share directly onto the VCSA and place all backups on that volume. Another option could have the backups directly uploaded to a Storage Cloud Provider like an Amazon S3 for example. I decided to take a look into the latter option.

In searching online, I found that Amazon offers a nice CLI called AWS CLI which provides S3 functionality like the 'cp' command and I was able to install it on the VCSA without any issues. You can find the instructions for installing the AWS CLI here and I would also recommend that you create a dedicate user assigned to the S3 bucket for storing the backups and then following the steps here to configure access to the AWS CLI. When asked about the Amazon Region as part of the configuration, I found this page to be helpful in listing the region names.

Disclaimer: Installing 3rd Party tools and products on the (VCSA) is not officially supported, you may be asked by GSS to remove them during troubleshooting.

If everything is installed correct, you should be able to run the following command to ensure you can reach the S3 bucket:

aws s3 ls s3:\\[NAME-OF-YOUR-S3-BUCKET]

To tie everything together, I created a simple shell script called backup_vcsa_vpostgres_db.sh which contains a couple of variables that you will need to edit:

VPOSTGRES_BACKUP_SCRIPT - The path to the Python vPostgres backup script
AWS_CLI - The full path to the AWS CLI binary
AWS_S3_BUCKET - The name of the S3 bucket using syntax s3:\\NAME-OF-YOUR-S3-BUCKET

Before creating the cronjob, I would recommend that you manually run the script to ensure everything works as expected and you are able to upload to your S3 bucket. Here is an example execution of the script which is backing up to my S3 bucket which I called "vcsa-backup".

You can quickly verify that the backup has been uploaded to the S3 bucket by running the "ls" command as shown earlier or you can login to the Amazon S3 console and you should be able to see the backup files as shown in the screenshot below.

To schedule the script to automatically run during a certain period, you can create a cronjob by running the following command:

crontab -e

For more information about setting up a cronjob, you can take a look here or Google your favorite resource. If you plan on storing backups with a Cloud Storage Provider and do not have direct internet access like most customers do, you can configure an HTTP(S) proxy by editing /etc/sysconfig/proxy If you prefer not to install AWS CLI, you can also use this simple bash script which uses an HTTP POST to upload to Amazon S3.

How to automatically repoint & failover VCSA to another replicated Platform Services Controller (PSC)?

Schedule automated backups of VCSA 6.0 vPostgres embedded database to Amazon S3