Question

I am using Memcache in my ASP.NET application. I have 3 memcache servers that it connects to. If all of them are down, there is a significant delay in loading the pages. When all servers are down, I would want to not use memcache.

When I was stepping through the code, I noticed that when the servers are down, memcache code does not throw an exception (I thought I could “Catch” it in my application and take the necessary steps).

How would I handle this situation?

Answer 1

Since Enyim is Open Source, you could edit ServerPool.cs, like so:

    /// <summary>
    /// Marks a node as dead (unusable)
    ///  - moves hte node to the  "dead list"
    ///  - recreates the locator based on the new list of still functioning servers
    /// </summary>
    /// <param name="node"></param>
    private void MarkAsDead(MemcachedNode node)
    {
        this.serverAccessLock.UpgradeToWriterLock(Timeout.Infinite);

        try
        {
            // server gained AoeREZ while AFK?
            if (!node.IsAlive)
            {
                this.workingServers.Remove(node);
                this.deadServers.Add(node);

                // check if all servers are dead
                if (this.workingServers.Count == 0)
                    throw new NoMoreServersException();

                this.RebuildIndexes();
            }
        }
        finally
        {
            this.serverAccessLock.ReleaseLock();
        }
    }

I haven’t tested above code. BTW, my changes are these three lines:

    // check if all servers are dead
    if (this.workingServers.Count == 0)
        throw new NoMoreServersException();

You should also create NoMoreServersException (or use a generic exception (not advisable though)).