From: Jonathan McDowell <noodles@earth.li>
Date: Tue, 29 Mar 2011 01:35:25 +0000 (-0700)
Subject: Configure db4 locks according to maxkeys and actually check maxkeys
X-Git-Url: https://git.sommitrealweird.co.uk/onak.git/commitdiff_plain/b66594a4e361b7363ccec13680d158f90a71e04b?ds=sidebyside;hp=d718a44cfeca2dca68d582b6242d832c4f8864ef

Configure db4 locks according to maxkeys and actually check maxkeys

  The number of db4 objects iin use is related to the maximum number of
  keys we return at once. Configure the locking subsystem accordingly
  and limit the number of returned keys to maxkeys.

  Significantly improves the reliability of the db4 backend on a large
  busy server.
---

diff --git a/keydb_db4.c b/keydb_db4.c
index 8990758..6fbf9da 100644
--- a/keydb_db4.c
+++ b/keydb_db4.c
@@ -277,6 +277,7 @@ static void db4_initdb(bool readonly)
 	int        i = 0;
 	u_int32_t  flags = 0;
 	struct stat statbuf;
+	int        maxlocks;
 
 	snprintf(buf, sizeof(buf) - 1, "%s/%s", config.db_dir,
 			DB4_UPGRADE_FILE);
@@ -329,6 +330,17 @@ static void db4_initdb(bool readonly)
 		}
 	}
 
+	/*
+	 * Up the number of locks we're allowed at once. We base this on
+	 * the maximum number of keys we're going to return.
+	 */
+	maxlocks = config.maxkeys * 16;
+	if (maxlocks < 1000) {
+		maxlocks = 1000;
+	}
+	dbenv->set_lk_max_locks(dbenv, maxlocks);
+	dbenv->set_lk_max_objects(dbenv, maxlocks);
+
 	/*
 	 * Enable deadlock detection so that we don't block indefinitely on
 	 * anything. What we really want is simple 2 state locks, but I'm not
@@ -690,6 +702,10 @@ static int db4_fetch_key_text(const char *search,
 	}
 	llfree(wordlist, NULL);
 	wordlist = NULL;
+
+	if (keylist.count > config.maxkeys) {
+		keylist.count = config.maxkeys;
+	}
 	
 	db4_starttrans();
 	for (i = 0; i < keylist.count; i++) {