As your SharePoint environment grows and more solutions are built on the platform it becomes critical to the business. Often it gets to the level that the business is very reluctant to allow SharePoint to be unavailable. This makes it difficult to plan application deployments which generally cause downtime.
Recently, I have been working on an environment which was in use globally and therefore the window for taking down the SharePoint farm is very small.
With that in mind I thought I’d share the process that I now use to deploy SharePoint WSP solutions without any downtime to the SharePoint farm. There are going to be times where you cannot avoid downtime, certain SharePoint object model calls cause all the server to recycle their application pools.
In order for deployments to be executed with no downtime there are a few requirements. There are infrastructure requirements as well as following a process.
Farm Configuration Requirements
In order to deploy SharePoint solutions there must be at least two SharePoint Servers configured as Web Front Ends. These web front ends are running the Web Application Service instance.
The next step is to ensure that these servers are being load balanced, either using software load balancing such as Windows Network Load Balancing (NLB) or using hardware load balancers such as the F5 Network’s BIG IP.
The F5 Network’s BIG IP configuration guide can be found here.
Without either the load balancers or the two web front ends then you are not going to be able to prevent downtime.
Regarding the load balancers, they must be configured so that when a server is down then no traffic is directed to that server.
At one client this required a bit more thought. The client used the F5 Network BIG IP load balancers unfortunately the load was not balanced as Round Robin balancing was being used.
Also the method to detect whether a server was down did not work. The way that the load balancers tested that a server was available was by using a low level call into IIS looking for an HTTP status of 200. This meant that as long as IIS up then the server was up and it would receive requests, even if SharePoint was failing for some reason.
This was fixed by using a cURL script which allows Windows Authentication to be used to call into SharePoint. The script would then look for a particular text string in the page. As long as this was found then the server is up and available.
The last tweak to the load balancers were configured to use Observed dynamic balancing. The following article by Don MacVitte gives a great overview of the different types of load balancing.
Observed load balancing, balances the load by using a number of metrics, this snippet from the article explains in more detail:-
Observed: The Observed method uses a combination of the logic used in the Least Connections and Fastest algorithms to load balance connections to servers being load-balanced. With this method, servers are ranked based on a combination of the number of current connections and the response time. Servers that have a better balance of fewest connections and fastest response time receive a greater proportion of the connections. This Application Delivery Controller method is rarely available in a simple load balancer., including the response time from each server.
With these infrastructure requirements in place it is possible to deploy solutions without downtime.
For SharePoint 2010 deployments, PowerShell is the tool of choice when deploying SharePoint Solutions.
Once you have the farm configured correctly then you will need to deploy the solutions through the SharePoint 2010 Management Shell.
So generally I login onto the server through Remote Desktop, copy over the solution file(s) into a folder such as c:\install\[solutionname]\[solutionversion].
Once the files are copied over:
Next is the important part, the solution has been added to the Configuration database and the next step is to deploy the solution to the servers. To ensure that there is no downtime, we will ensure that the deployment only occurs on one machine at a time.
Depending on the type of solution being deployed there are a few additional attributes that you may have to specify to the Install-SPSolution command.
However the most important attribute we need to remember is the –Local attribute this will only ensure that the solution deployment will only occur on the local server.
Other attributes include:-
- WebApplication – this will deploy the solution to a specific Sharepoint Web Application
- GacDeployment – this option allows a solution which contains .NET assemblies to be installed in to the GAC to be installed.
- CasPolicies – this option allows a solution which contains code access security policies for the assemblies / web parts to be deployed.
Once the Install-SPSolution command has been run then the solution deployment success needs to be checked. This can also be achieved using PowerShell.
$checkSolution = Get-SPSolution $solutionname; $checkSolution.LastOperationalDetails;
When this has been executed an output such as the following will be displayed for the local server.
The process now has to wait until the SPSolution.LastOperationDetails call returns back that the deployment is successful.
Once the deployment has completed, I now restart IIS and the SharePoint Timer Job Service using the following PowerShell.
Restart-Service sptimerv4; iisreset;
The installation of the SharePoint solutions will have caused IIS to restart and therefore the server will not have responded to the load balancer. Provided that the load balancer has been configured correctly the server should no longer be processing requests to clients and therefore there is no loss of service.
Depending on configuration of the load balancers, the time it takes for a server to start responding to requests will based on a setting called ramp up time.
The slow ramp up time is the time the load balancer will wait after the server has come back online before it starts sending all requests to the server. This gives the server time to get back on its feet and processing those requests.
Once the server is back online, the SharePoint solution process can be repeated for each of the other SharePoint Servers.
Although this approach will for most cases work there are a few gotchas that you need to watch out for. In some of these occasions all SharePoint WFEs will have their application pools restarted.
Currently these are:-
- SPWebConfigModification – its a good practice to apply changes to the web.config files for an IIS Web Application using the SharePoint SPWebConfigModification object. This will ensure that any settings required in the web.config for your solution will be applied. This reduces the likelihood of an issue with the solution due to down to missing configuration. Also if new servers are added to the farm then their web.config files wil be setup correctly. This will save you lots of time if you ever have to do a disaster recovery exercise!
- SharePoint Field Controls – if your solution includes a new custom SharePoint field. Then this will not be available until all SharePoint servers have been updated. This can be more of a problem when for example you are using something like Telerik’s RadEditor control and are performing an upgrade. When these type of deployments are being made then its best to inform the users that the application will not be available. At least the rest of the SharePoint farm is up and running!
Note: As more issues are found then this section will be updated.
The final deployment script is as follows:-
cd c:\install\[solutionname]\[versionnumber]; $curdir=gl; $solutionname=”SolutionName.wsp”; Add-SPSolution –LiteralPath $curdir\$solutionname; Install-SPSolution –Local –Identity $solutionname –GACDeployment –CASPolicies; $checksolution = Get-SPSolution $solutionname; $checksolution.LastOperationalDetails;
I hope that you find this useful and would love to hear about your experience and approach to deployment of SharePoint solutions.