Set up Perforce for an Unreal Engine build machine

Sooner or later, most Unreal teams on Perforce want a machine that syncs the depot and packages the game without anyone touching it. Most of the problems people run into come down to a few server and workspace settings. Here they are, in the order you'll need them.

Set up the typemap first

Perforce decides how to store each file based on its type, and the defaults aren't great for Unreal. You want two things:

• Assets can only be checked out by one person at a time. Unreal assets can't be merged, so two people editing the same Blueprint means one of them loses their work. In Perforce this is the +l (exclusive lock) flag.
• Executables and DLLs stay writable. Otherwise the engine and build tools can't overwrite them. That's the +w flag.

Run p4 typemap as a super user and add:

TypeMap:
	binary+l //....uasset
	binary+l //....umap
	binary+l //....ubulk
	binary+w //....exe
	binary+w //....dll
	binary+w //....pdb
	binary+w //....dylib
	text //....ini
	text //....uproject
	text //....uplugin
	text //....cs
	text //....cpp
	text //....h

Do this before anyone submits assets. Files that were already submitted keep their old type, and you'd have to fix them one by one with p4 retype.

Keep generated folders out

Unreal creates folders it can always rebuild. Make sure nobody submits them by adding a .p4ignore file to the project root:

Binaries/
DerivedDataCache/
Intermediate/
Saved/
.vs/
*.sln

Perforce only uses this file when P4IGNORE is set, so run this on every computer:

p4 set P4IGNORE=.p4ignore

Use a stream depot

With streams, each line of work gets its own path, like //MyGame/main or //MyGame/release-1.0. Your build machine then just needs to know which stream to build, and Perforce sets up the workspace mapping for you.

Give the build machine its own account

Don't build with someone's personal account. If they leave or change their password, your builds stop. As a super user:

p4 user -f buildbot
p4 passwd buildbot

read user buildbot * //MyGame/...

p4 group buildbots

Set up the workspace

A build machine should never have local edits. These workspace options make sure a sync always wins:

Options: allwrite clobber nocompress unlocked nomodtime rmdir

clobber lets a sync overwrite files that were left writable, and rmdir removes folders that end up empty. nocompress is faster on a fast network. If your build machine is far from the server, remove it.

Then every build follows the same three steps:

p4 sync -q //MyGame/main/...
p4 clean //MyGame/main/...

p4 clean undoes anything a previous build changed, so every build starts from exactly what's been submitted. It leaves the folders in .p4ignore alone, so the next build can reuse the work in Intermediate and DerivedDataCache.

Make syncs faster

Big depots sync much faster over several connections at once. Allow it on the server (as a super user):

p4 configure set net.parallel.max=8

and sync in parallel on the build machine:

p4 sync --parallel=threads=8 //MyGame/main/...

Network and security

If the build machine isn't on the same network as your server, it needs to reach the Perforce port, usually 1666:

Two rules:

• Use SSL. Start the server on an ssl: address so passwords and files are encrypted on the way. Each client confirms the server's fingerprint once with p4 trust.
• Only open the port to the addresses that need it. Allow the build machine's IP in your firewall, not the whole internet.

Or skip the build machine

If you'd rather not run the build machine at all, Unreal Cloud builds Unreal projects straight from Perforce on cloud machines. It uses the same setup as above: an SSL server, a read-only account, and one fixed IP address to allow in your firewall. See Perforce integration.