DDRR's blog

Windows Service Support for svnserve ==================================== svnserve can now be run as a native Windows service. This means that the service can be started at system boot, or at any other time, without the need for any wrapper code to start the service. The service can be managed like any other Windows service, using command-line tools ("net start", "net stop", or sc.exe) or GUI tools (the Services administrative tool). Installation ———— For now, no means is provided to install the service. Most Windows OSes derived from Windows NT (such as Windows XP, Windows 2000, Windows 2003 Server) provide a command-line tool for installing services, called SC.EXE for "Service Control". To create a service for svnserve, use SC.EXE: sc create binpath= "c:\svn\bin\svnserve.exe –service " displayname= "Subversion Repository" depend= Tcpip where is any service name you want, e.g. "svnserve", and are the arguments to svnserve, such as –root, –listen-port, etc. (All of this should be specified on a single line, of course.) In order for svnserve to run as a Windows service, you MUST specify the –service argument, and you must NOT specify any other run mode argument, such as –daemon, –tunnel, –inetd, or any of their short forms. There is no short form for –service. If the path to svnserve.exe contains spaces or other characters that must be escaped, then you must enclose the path to svnserve.exe with double-quotes, which themselves must be quoted using a backslash. Fortunately the syntax is similar to that on Unix platforms: sc create binpath= "\"c:\program files\subversion\bin\svnserve.exe\" …" SC has many options; use "sc /?". The most relevant are: sc create create a new service sc qc query config for a service sc query query status sc delete delete any service — BE CAREFUL! sc config … update service config; same args as sc create sc start start a service (does NOT wait for completion!) sc stop stop a service (does NOT wait for it to stop!) Note that the command-line syntax for SC is rather odd. Key/value pairs are specified as "key= value" (without the double-quotes). The "key=" part must not have any spaces, and
the "value" part MUST be separated from the "key=" by a space. If you want to be able to see the command shell, add these arguments to the "sc create" command-line: type= own type= interact This sets the "interactive" bit on the service, which allows it to interact with the local console session. You can create as many services as you need; there is no restriction on the number of services, or their names. I use a prefix, like "svn.foo", "svn.bar", etc. Each service runs in a separate process. As usual, it is your responsbility as an administrator to make sure that no two service instances use the same repository root path, or the same combination of –listen-port and –listen-host. Uninstalling ———— To uninstall a service, stop the service, then delete it, using "sc delete ". Be very careful with this command, since you can delete any system service, including essential Windows services, accidentally. Also, make sure that you stop the service before you delete it. If you delete the service before stopping it, the Service Control Manager will mark the service "deleted", but will intentionally not stop the service. The service will be deleted when the system reboots, or when the service finally exits. After all, you only asked to delete the service, not to stop it. That's all there is to it. Automatically Starting Service on System Boot ——————————————— By default, SC creates the service with the start mode set to "demand" (manual). If you want the service to start automatically when the system boots, add "start= auto" to the command line. You can change the start mode for an existing service using "sc config start= auto", or also by using the Windows GUI interface for managing services. (Start, All Programs, Administrative Tools, Services, or just run "services.msc" from Start/Run or from a command-line.) Note: In order for svnserve to start correctly on system boot, you must properly declare its startup dependencies. The Service Control Manager will start services as early as it can, and if you do not properly declare its startup dependencies, it can potentially start before the TCP/IP stack has been started. This is why you must provide specify 'depend= Tcpip' to SC.EXE when creating the service. Starting and Stopping the Service ——————————— You start and stop the service like any other Windows service. You can use the command-line "net start ", use the GUI Services interface. Debugging ——— Debugging a Windows service can be difficult, because the service runs in a very different context than a user who is logged in. By default, services run in a "null" desktop environment. They cannot interact with the user (desktop) in any way, and vice versa. Also, by default, services run as a special user, called LocalSystem. LocalSystem is not a "user" in the normal sense; it is an NT security ID (SID) that is sort of like root, but different. LocalSystem typically does NOT have access to any network shares, even if you use "net use" to connect to a remote file server. Again, this is because services run in a different login session. Depending on which OS you are running, you may have difficulty attaching a debugger to a running service process. Also, if you are having trouble *starting* a service, then you can't attach to the process early enough to debug it. So what's a developer to do? Well, there are several ways you can debug services. First, you'll want to enable "interactive" access for the service. This allows the service to interact with the local desktop — you'll be able to see the command shell that the service runs in, see console output, etc. To do this, you can either use the standard Windows Services tool (services.msc), or you can do it using sc.exe. * With the GUI tool, open the properties page for a service, and go to the "Log On" page. Select "Local System account", and make sure the "Allow service to interact with desktop" box is checked. * With SC.EXE, configure the service using the command: sc config type= own type= interact Yes, you must specify type= twice, and with exactly the spacing shown. In both cases, you'll need to restart the service. When you do, if the service started successfully, you'll see the console window of the service. By default, it doesn't print anything out. Next, you'll want to attach a debugger, or configure the service to start under a debugger. Attaching a debugger should be straightforward — just find the process ID. But if you need to debug something in the service startup path, you'll need to have a debugger attached from the very beginning. There are two ways to do this. In the first method, you alter the command-line of the service (called the "binary path"). To do this, use SC.EXE to set the binary path to whatever debugger you are going to use. I use the most recent version of WinDbg, which is excellent, and is available at: http://www.microsoft.com/whdc/devtools/debugging/installx86.mspx For example, this command would configure the service to start under a debugger: sc config binpath= "d:\dbg\windbg.exe -g -G d:\svn\bin\svnserve.exe –root d:\path\root –listen-port 9000" depend= Tcpip The entire command must be on a single line, of course, and the binary path must be in double-quotes. Also, the spacing MUST be: binpath= "…" Substitute whatever debugger you want, with whatever command-line you want, in place of windbg.exe. Then start the service (sc start ), and the Service Control Manager should execute the command-line you provided as the binary path. Then your debugger should start, and should launch the svnserve process. Known Issues ———— * No management tool (installer, etc.). For the first version, this is intentional; we just want to get the service functionality tested and committed before dealing with installation. * Right now, I don't know of a way to cleanly stop the svnserve process. Instead, the implementation closes the listen socket, which causes the main loop to exit. This isn't as bad as it sounds, and is a LOT better than other options (such as terminating a thread). To Do —– * The support for running svnserve as a Windows service is complete, but there is still more work to be done for installing and managing services. from:http://svn.collab.net/repos/svn/trunk/notes/windows-service.txt