support concurrent builds

Add new table "building" for recording builds in progress. When a
concurrent build is issued, it will avoid building a source package that
is presently built. It will also avoid building for an architecture that
is presently built for. The latter condition helps reduce the number of
satisfiability issues.

2 files changed, 43 insertions, 21 deletions

diff --git a/build.py b/build.py
index 3312bd0..340802b 100755
--- a/build.py
+++ b/build.py
@@ -6,6 +6,7 @@ import collections
 import contextlib
 import datetime
 import lzma
+import os
 import os.path
 import sqlite3
 import subprocess
@@ -50,6 +51,7 @@ def main():
     args = argp.parse_args()
     db = sqlite3.connect("db", detect_types=sqlite3.PARSE_DECLTYPES)
     with contextlib.closing(db.cursor()) as cur:
+        cur.execute("BEGIN IMMEDIATE;")
         cur.execute("""
             SELECT d.source, d.version, d.architecture, r.id
                 FROM depstate AS d
@@ -59,6 +61,9 @@ def main():
                     JOIN depcheck
                         ON d.architecture = depcheck.architecture
                 WHERE d.satisfiable = 1 AND depcheck.giveback = 0
+                    AND NOT EXISTS (SELECT 1 FROM building
+                        WHERE d.source = building.source
+                            OR d.architecture = building.architecture)
                 ORDER BY r.priority DESC, r.requesttime ASC, random()
                 LIMIT 1;""")
         row = cur.fetchone()
@@ -70,27 +75,39 @@ def main():
                     WHERE satisfiable = 1 AND giveback = 0
                     ORDER BY random() LIMIT 1;""")
             row = cur.fetchone()
-    if not row:
-        print("no package satisfiable")
-        time.sleep(60)
-        return
-    source, version, architecture, requestid = row
-    print("building %s_%s for %s%s" %
-          (source, version, architecture,
-           "" if requestid is None else " (request %d)" % requestid))
-    timestamp, success, filename, giveback = \
-        do_build(source, version, architecture, args.server)
-    with contextlib.closing(db.cursor()) as cur:
-        cur.execute("INSERT INTO builds (source, version, architecture, success, starttime, filename) VALUES (?, ?, ?, ?, ?, ?);",
-                    (source, version, architecture, success, timestamp,
-                     filename))
-        if requestid is not None:
-            cur.execute("DELETE FROM buildrequests WHERE id = ?;",
-                        (requestid,))
-        if giveback:
-            cur.execute("UPDATE depcheck SET giveback = 1 WHERE architecture = ?;",
-                        (architecture,))
-    db.commit()
+        if not row:
+            cur.execute("ROLLBACK;")
+            print("no package satisfiable")
+            time.sleep(60)
+            return
+        source, version, architecture, requestid = row
+        cur.execute("""INSERT INTO building (source, architecture, pid)
+                           VALUES (?, ?, ?);""",
+                    (source, architecture, os.getpid()))
+        cur.execute("COMMIT;")
+    try:
+        print("building %s_%s for %s%s" %
+              (source, version, architecture,
+               "" if requestid is None else " (request %d)" % requestid))
+        timestamp, success, filename, giveback = \
+            do_build(source, version, architecture, args.server)
+        with contextlib.closing(db.cursor()) as cur:
+            cur.execute("""INSERT INTO builds
+                            (source, version, architecture, success, starttime,
+                             filename) VALUES (?, ?, ?, ?, ?, ?);""",
+                        (source, version, architecture, success, timestamp,
+                         filename))
+            if requestid is not None:
+                cur.execute("DELETE FROM buildrequests WHERE id = ?;",
+                            (requestid,))
+            if giveback:
+                cur.execute("""UPDATE depcheck SET giveback = 1
+                                WHERE architecture = ?;""",
+                            (architecture,))
+    finally:
+        with contextlib.closing(db.cursor()) as cur:
+            cur.execute("DELETE FROM building WHERE pid = ?;", (os.getpid(),))
+        db.commit()
 
 if __name__ == "__main__":
     main()
diff --git a/schema.sql b/schema.sql
index d57867b..56184be 100644
--- a/schema.sql
+++ b/schema.sql
@@ -46,3 +46,8 @@ CREATE TABLE bugs (
 	title TEXT,
 	patched BOOLEAN NOT NULL CHECK (patched in (0, 1)));
 CREATE INDEX bugs_affects_index ON bugs(affects);
+
+CREATE TABLE building (
+	source TEXT NOT NULL,
+	architecture TEXT NOT NULL,
+	pid INTEGER NOT NULL);