crush/CrushWrapper: add get_common_ancestor_distance()

Calculate closest common ancestor (type) in the hierarchy.

Signed-off-by: Sage Weil <sage@inktank.com>

src/crush/CrushWrapper.cc

@@ -193,6 +193,33 @@ int CrushWrapper::remove_item_under(CephContext *cct, int item, int ancestor, bo
   return ret;
 }
 
+int CrushWrapper::get_common_ancestor_distance(CephContext *cct, int id,
+			       const std::multimap<string,string>& loc)
+{
+  ldout(cct, 5) << __func__ << " " << id << " " << loc << dendl;
+  if (!item_exists(id))
+    return -ENOENT;
+  map<string,string> id_loc = get_full_location(id);
+  ldout(cct, 20) << " id is at " << id_loc << dendl;
+
+  for (map<int,string>::const_iterator p = type_map.begin();
+       p != type_map.end();
+       ++p) {
+    map<string,string>::iterator ip = id_loc.find(p->second);
+    if (ip == id_loc.end())
+      continue;
+    for (std::multimap<string,string>::const_iterator q = loc.find(p->second);
+	 q != loc.end();
+	 ++q) {
+      if (q->first != p->second)
+	break;
+      if (q->second == ip->second)
+	return p->first;
+    }
+  }
+  return -ERANGE;
+}
+
 int CrushWrapper::parse_loc_map(const std::vector<string>& args,
 				std::map<string,string> *ploc)
 {

src/crush/CrushWrapper.h

@@ -472,6 +472,19 @@ private:
 public:
   int remove_item_under(CephContext *cct, int id, int ancestor, bool unlink_only);
 
+  /**
+   * calculate the locality/distance from a given id to a crush location map
+   *
+   * Specifically, we look for the lowest-valued type for which the
+   * location of id matches that described in loc.
+   *
+   * @param cct cct
+   * @param id the existing id in the map
+   * @param loc a set of key=value pairs describing a location in the hierarchy
+   */
+  int get_common_ancestor_distance(CephContext *cct, int id,
+				   const std::multimap<string,string>& loc);
+
   /**
    * parse a set of key/value pairs out of a string vector
    *

src/test/Makefile.am

@@ -274,6 +274,11 @@ unittest_str_map_CXXFLAGS = $(UNITTEST_CXXFLAGS)
 unittest_str_map_LDADD = $(UNITTEST_LDADD) $(CEPH_GLOBAL)
 check_PROGRAMS += unittest_str_map
 
+unittest_crushwrapper_SOURCES = test/test_crushwrapper.cc
+unittest_crushwrapper_CXXFLAGS = $(UNITTEST_CXXFLAGS)
+unittest_crushwrapper_LDADD = $(UNITTEST_LDADD) $(CEPH_GLOBAL) $(LIBCRUSH)
+check_PROGRAMS += unittest_crushwrapper
+
 unittest_sharedptr_registry_SOURCES = test/common/test_sharedptr_registry.cc
 unittest_sharedptr_registry_CXXFLAGS = $(UNITTEST_CXXFLAGS)
 unittest_sharedptr_registry_LDADD = $(UNITTEST_LDADD) $(CEPH_GLOBAL)

src/test/test_crushwrapper.cc

@@ -0,0 +1,107 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2013 Inktank <info@inktank.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library Public License for more details.
+ *
+ */
+
+#include "crush/CrushWrapper.h"
+#include "gtest/gtest.h"
+#include "global/global_init.h"
+#include "global/global_context.h"
+#include "common/ceph_argparse.h"
+#include "common/Formatter.h"
+
+TEST(CrushWrapper, distance) {
+  CrushWrapper c;
+  c.create();
+  c.set_type_name(1, "host");
+  c.set_type_name(2, "rack");
+  c.set_type_name(3, "root");
+  int bno;
+  int r = c.add_bucket(0, CRUSH_BUCKET_STRAW,
+		       CRUSH_HASH_DEFAULT, 3, 0, NULL,
+		       NULL, &bno);
+  ASSERT_EQ(0, r);
+  ASSERT_EQ(-1, bno);
+  c.set_item_name(bno, "default");
+
+  c.set_max_devices(10);
+
+  //JSONFormatter jf(true);
+
+  map<string,string> loc;
+  loc["host"] = "a1";
+  loc["rack"] = "a";
+  loc["root"] = "default";
+  c.insert_item(g_ceph_context, 0, 1, "osd.0", loc);
+
+  loc.clear();
+  loc["host"] = "a2";
+  loc["rack"] = "a";
+  loc["root"] = "default";
+  c.insert_item(g_ceph_context, 1, 1, "osd.1", loc);
+
+  loc.clear();
+  loc["host"] = "b1";
+  loc["rack"] = "b";
+  loc["root"] = "default";
+  c.insert_item(g_ceph_context, 2, 1, "osd.2", loc);
+
+  loc.clear();
+  loc["host"] = "b2";
+  loc["rack"] = "b";
+  loc["root"] = "default";
+  c.insert_item(g_ceph_context, 3, 1, "osd.3", loc);
+
+  vector<pair<string,string> > ol;
+  c.get_full_location_ordered(3, ol);
+  ASSERT_EQ(3u, ol.size());
+  ASSERT_EQ(make_pair(string("host"),string("b2")), ol[0]);
+  ASSERT_EQ(make_pair(string("rack"),string("b")), ol[1]);
+  ASSERT_EQ(make_pair(string("root"),string("default")), ol[2]);
+
+  //c.dump(&jf);
+  //jf.flush(cout);
+
+  multimap<string,string> p;
+  p.insert(make_pair("host","b2"));
+  p.insert(make_pair("rack","b"));
+  p.insert(make_pair("root","default"));
+  ASSERT_EQ(3, c.get_common_ancestor_distance(g_ceph_context, 0, p));
+  ASSERT_EQ(3, c.get_common_ancestor_distance(g_ceph_context, 1, p));
+  ASSERT_EQ(2, c.get_common_ancestor_distance(g_ceph_context, 2, p));
+  ASSERT_EQ(1, c.get_common_ancestor_distance(g_ceph_context, 3, p));
+  ASSERT_EQ(-ENOENT, c.get_common_ancestor_distance(g_ceph_context, 123, p));
+
+  // make sure a "multipath" location will reflect a minimal
+  // distance for both paths
+  p.insert(make_pair("host","b1"));
+  ASSERT_EQ(1, c.get_common_ancestor_distance(g_ceph_context, 2, p));
+  ASSERT_EQ(1, c.get_common_ancestor_distance(g_ceph_context, 3, p));
+}
+
+
+int main(int argc, char **argv) {
+  vector<const char*> args;
+  argv_to_vec(argc, (const char **)argv, args);
+  env_to_vec(args);
+
+  global_init(NULL, args, CEPH_ENTITY_TYPE_CLIENT, CODE_ENVIRONMENT_UTILITY, 0);
+  common_init_finish(g_ceph_context);
+
+  ::testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}