Add support for ccache

This is set up so that each individual project repository has its own
ccache, all under one defined directory.

The top-level ccache directory is added as the setting
'compiler-cache-dir', and defaults to $cachedir/ccache.

When a build is performed, this will bind-mount a project's ccache into
the /tmp/ccache of the staging-area and set up the environment variables
so that ccache will be used (if appropriate executables are installed
to /usr/lib/ccache in the staging-area).

In addition, this removes code for ccache-remotedir, as it is unrelated
to this implementation of ccache.

Reviewed-by: Jannis Pohlmann <jannis.pohlmann@codethink.co.uk>
Reviewed-by: Lars Wirzenius <lars.wirzenius@codethink.co.uk>

3 files changed, 30 insertions, 17 deletions

diff --git a/morphlib/app.py b/morphlib/app.py
index d154f8b9..a13d26a1 100755
--- a/morphlib/app.py
+++ b/morphlib/app.py
@@ -43,8 +43,6 @@ defaults = {
     'max-jobs': morphlib.util.make_concurrency(),
     'prefix': '/usr',
     'toolchain-target': '%s-baserock-linux-gnu' % os.uname()[4],
-    'ccache-remotedir': '',
-    'ccache-remotenlevels': 2,
     'build-ref-prefix': 'baserock/builds'
 }
 
@@ -61,6 +59,11 @@ class Morph(cliapp.Application):
                              'cache git repositories and build results in DIR',
                              metavar='DIR',
                              default=defaults['cachedir'])
+        self.settings.string(['compiler-cache-dir'],
+                             'cache compiled objects in CCDIR/REPO_NAME',
+                             metavar='CCDIR',
+                             default=os.path.join(self.settings['cachedir'],
+                                                  'ccache'))
         self.settings.string(['build-ref-prefix'],
                              'Prefix to use for temporary build refs',
                              metavar='PREFIX',
@@ -109,18 +112,6 @@ class Morph(cliapp.Application):
                               'DANGEROUS and will install stuff on your '
                               'system',
                               group=group_build)
-        self.settings.string(['ccache-remotedir'],
-                             'allow ccache to download objects from REMOTEDIR '
-                             'if they are not cached locally',
-                             metavar='REMOTEDIR',
-                             default=defaults['ccache-remotedir'],
-                             group=group_build)
-        self.settings.integer(['ccache-remotenlevels'],
-                              'assume ccache directory objects are split into '
-                              'NLEVELS levels of subdirectories',
-                              metavar='NLEVELS',
-                              default=defaults['ccache-remotenlevels'],
-                              group=group_build)
         self.settings.boolean(['keep-path'],
                               'do not touch the PATH environment variable',
                               group=group_build)
diff --git a/morphlib/buildenvironment.py b/morphlib/buildenvironment.py
index c9c12cc4..d9e3210f 100644
--- a/morphlib/buildenvironment.py
+++ b/morphlib/buildenvironment.py
@@ -88,14 +88,12 @@ class BuildEnvironment():
 # FIXME: we should set CCACHE_BASEDIR so any objects that refer to their
 #        current directory get corrected. This improve the cache hit rate
 #            env['CCACHE_BASEDIR'] = self.tempdir.dirname
+            env['CCACHE_DIR'] = '/tmp/ccache'
             env['CCACHE_EXTRAFILES'] = ':'.join(
                 f for f in ('/baserock/binutils.meta',
                             '/baserock/eglibc.meta',
                             '/baserock/gcc.meta') if os.path.exists(f)
             )
-            if settings['ccache-remotedir'] != '':
-                env['CCACHE_REMOTEDIR'] = settings['ccache-remotedir']
-            env['CCACHE_REMOTENLEVELS'] = str(settings['ccache-remotenlevels'])
             if not settings['no-distcc']:
                 env['CCACHE_PREFIX'] = 'distcc'
 
diff --git a/morphlib/builder2.py b/morphlib/builder2.py
index c7d25e1a..0c1acfde 100644
--- a/morphlib/builder2.py
+++ b/morphlib/builder2.py
@@ -289,6 +289,28 @@ class ChunkBuilder(BuilderBase):
         ('dev/shm', 'tmpfs', 'none'),
     )
 
+    def mount_ccachedir(self): #pragma: no cover
+        ccache_dir = self.app.settings['compiler-cache-dir']
+        if not os.path.isdir(ccache_dir):
+            os.makedirs(ccache_dir)
+        # Get a path for the repo's ccache
+        ccache_repobase = os.path.basename(self.artifact.source.repo.path)
+        ccache_repodir = os.path.join(ccache_dir,
+                                      ccache_repobase)
+        # Make sure that directory exists
+        if not os.path.isdir(ccache_repodir):
+            os.mkdir(ccache_repodir)
+        # Get the destination path
+        ccache_destdir= os.path.join(self.staging_area.tempdir,
+                                     'tmp', 'ccache')
+        # Make sure that the destination exists
+        if not os.path.isdir(ccache_destdir):
+            os.mkdir(ccache_destdir)
+        # Mount it into the staging-area
+        self.app.runcmd(['mount', '--bind', ccache_repodir,
+                         ccache_destdir])
+        return ccache_destdir
+
     def do_mounts(self):  # pragma: no cover
         mounted = []
         if not self.setup_mounts:
@@ -300,6 +322,8 @@ class ChunkBuilder(BuilderBase):
                 os.makedirs(path)
             self.app.runcmd(['mount', '-t', mount_type, source, path])
             mounted.append(path)
+        if not self.app.settings['no-ccache']:
+            mounted.append(self.mount_ccachedir())
         return mounted
 
     def do_unmounts(self, mounted):  # pragma: no cover