Add infrastructure for backends to report whether file creation occurred.

This only concerns the LMDB backend, as no other backend is able to
create local storage.

To be used shortly in a pdnsutil near you.

diff --git a/ext/lmdb-safe/lmdb-safe.cc b/ext/lmdb-safe/lmdb-safe.cc
index f0db35fd811e14cba126887ccf20819620c364d0..dc081d25f6392ff3929d67934e1620943844abd1 100644 (file)
--- a/ext/lmdb-safe/lmdb-safe.cc
+++ b/ext/lmdb-safe/lmdb-safe.cc
@@ -80,17 +80,39 @@ namespace LMDBLS {
 
 #endif /* #ifndef DNSDIST */
 
+std::atomic<unsigned int> MDBDbi::d_creationCount{0};
+
 MDBDbi::MDBDbi(MDB_env* /* env */, MDB_txn* txn, const string_view dbname, int flags) : d_dbi(-1)
 {
   // A transaction that uses this function must finish (either commit or abort) before any other transaction in the process may use this function.
 
-  int rc = mdb_dbi_open(txn, dbname.empty() ? 0 : &dbname[0], flags, &d_dbi);
-  if(rc)
-    throw std::runtime_error("Unable to open named database: " + MDBError(rc));
+  int ret = MDBDbi::mdb_dbi_open(txn, dbname.empty() ? nullptr : dbname.data(), flags, &d_dbi);
+  if (ret != 0) {
+    throw std::runtime_error("Unable to open named database: " + MDBError(ret));
+  }
 
   // Database names are keys in the unnamed database, and may be read but not written.
 }
 
+// This is a wrapper around the real mdb_dbi_open(), in order to track creation
+// of new files.
+int MDBDbi::mdb_dbi_open(MDB_txn* txn, const char* name, unsigned int flags, MDB_dbi* dbi)
+{
+  if ((flags & MDB_CREATE) != 0) {
+    flags &= ~MDB_CREATE;
+    int retval = ::mdb_dbi_open(txn, name, flags, dbi);
+    if (retval == MDB_NOTFOUND) {
+      flags |= MDB_CREATE;
+      retval = ::mdb_dbi_open(txn, name, flags, dbi);
+      if (retval == 0) {
+        d_creationCount++;
+      }
+    }
+    return retval;
+  }
+  return ::mdb_dbi_open(txn, name, flags, dbi);
+}
+
 MDBEnv::MDBEnv(const char* fname, int flags, int mode, uint64_t mapsizeMB)
 {
   mdb_env_create(&d_env);

diff --git a/ext/lmdb-safe/lmdb-safe.hh b/ext/lmdb-safe/lmdb-safe.hh
index 07e96cffc11b261e4e4b2bb086117860ca910369..54850d954acd47b1a502ecec8245155430094753 100644 (file)
--- a/ext/lmdb-safe/lmdb-safe.hh
+++ b/ext/lmdb-safe/lmdb-safe.hh
@@ -13,6 +13,7 @@
 #include <mutex>
 #include <vector>
 #include <algorithm>
+#include <atomic>
 #include <arpa/inet.h>
 
 #ifndef DNSDIST
@@ -56,6 +57,9 @@ public:
   }
 
   MDB_dbi d_dbi;
+
+  static int mdb_dbi_open(MDB_txn *, const char *, unsigned int, MDB_dbi *);
+  static std::atomic<unsigned int> d_creationCount;
 };
 
 class MDBRWTransactionImpl;

diff --git a/modules/lmdbbackend/lmdbbackend.cc b/modules/lmdbbackend/lmdbbackend.cc
index 988639b147b6d0ed1bc5d9b85b063adbe7146aac..d75ec276879d769bf48bc4dc63f8f2ce40b2ea74 100644 (file)
--- a/modules/lmdbbackend/lmdbbackend.cc
+++ b/modules/lmdbbackend/lmdbbackend.cc
@@ -104,7 +104,7 @@ std::pair<uint32_t, uint32_t> LMDBBackend::getSchemaVersionAndShards(std::string
   MDB_dbi dbi;
 
   {
-    int retCode = mdb_dbi_open(txn, "pdns", 0, &dbi);
+    int retCode = MDBDbi::mdb_dbi_open(txn, "pdns", 0, &dbi);
     if (retCode != 0) {
       if (retCode == MDB_NOTFOUND) {
         // this means nothing has been inited yet
@@ -432,7 +432,7 @@ bool LMDBBackend::upgradeToSchemav5(std::string& filename)
 
     MDB_dbi shdbi = 0;
 
-    const auto dbiOpenRc = mdb_dbi_open(shtxn, "records", 0, &shdbi);
+    const auto dbiOpenRc = MDBDbi::mdb_dbi_open(shtxn, "records", 0, &shdbi);
     if (dbiOpenRc != 0) {
       if (dbiOpenRc == MDB_NOTFOUND) {
         mdb_txn_abort(shtxn);
@@ -446,7 +446,7 @@ bool LMDBBackend::upgradeToSchemav5(std::string& filename)
 
     MDB_dbi shdbi2 = 0;
 
-    if (mdb_dbi_open(shtxn, "records_v5", MDB_CREATE, &shdbi2) != 0) {
+    if (MDBDbi::mdb_dbi_open(shtxn, "records_v5", MDB_CREATE, &shdbi2) != 0) {
       mdb_dbi_close(shenv, shdbi);
       mdb_txn_abort(shtxn);
       mdb_env_close(shenv);
@@ -480,14 +480,14 @@ bool LMDBBackend::upgradeToSchemav5(std::string& filename)
     std::string tdbname = dbname + "_v5";
 
     // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
-    if (mdb_dbi_open(txn, dbname.c_str(), 0, &fromtypeddbi[index]) != 0) {
+    if (MDBDbi::mdb_dbi_open(txn, dbname.c_str(), 0, &fromtypeddbi[index]) != 0) {
       mdb_txn_abort(txn);
       mdb_env_close(env);
-      throw std::runtime_error("mdb_dbi_open typeddbi failed");
+      throw std::runtime_error("MDBDbi::mdb_dbi_open typeddbi failed");
     }
 
     // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
-    if (mdb_dbi_open(txn, tdbname.c_str(), MDB_CREATE, &totypeddbi[index]) != 0) {
+    if (MDBDbi::mdb_dbi_open(txn, tdbname.c_str(), MDB_CREATE, &totypeddbi[index]) != 0) {
       // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
       mdb_dbi_close(env, fromtypeddbi[index]);
       mdb_txn_abort(txn);
@@ -527,14 +527,14 @@ bool LMDBBackend::upgradeToSchemav5(std::string& filename)
     std::string tdbname = dbname + "_v5_0";
 
     // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
-    if (mdb_dbi_open(txn, fdbname.c_str(), 0, &fromindexdbi[index]) != 0) {
+    if (MDBDbi::mdb_dbi_open(txn, fdbname.c_str(), 0, &fromindexdbi[index]) != 0) {
       mdb_txn_abort(txn);
       mdb_env_close(env);
       throw std::runtime_error("mdb_dbi_open indexdbi failed");
     }
 
     // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
-    if (mdb_dbi_open(txn, tdbname.c_str(), MDB_CREATE, &toindexdbi[index]) != 0) {
+    if (MDBDbi::mdb_dbi_open(txn, tdbname.c_str(), MDB_CREATE, &toindexdbi[index]) != 0) {
       // NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-constant-array-index)
       mdb_dbi_close(env, fromindexdbi[index]);
       mdb_txn_abort(txn);
@@ -566,7 +566,7 @@ bool LMDBBackend::upgradeToSchemav5(std::string& filename)
   MDB_dbi dbi = 0;
 
   // finally, migrate the pdns db
-  if (mdb_dbi_open(txn, "pdns", 0, &dbi) != 0) {
+  if (MDBDbi::mdb_dbi_open(txn, "pdns", 0, &dbi) != 0) {
     mdb_txn_abort(txn);
     mdb_env_close(env);
     throw std::runtime_error("mdb_dbi_open pdns failed");
@@ -2831,6 +2831,16 @@ string LMDBBackend::directBackendCmd(const string& query)
   return "unknown lmdbbackend command\n";
 }
 
+bool LMDBBackend::hasCreatedLocalFiles() const
+{
+  // Since the lmdb file creation counter is global, if multiple LMDB backends
+  // are used, they may end up all reporting having created files even if
+  // not all of them did.
+  // But since this information is for the sake of pdnsutil, this is not
+  // really a problem.
+  return MDBDbi::d_creationCount != 0;
+}
+
 class LMDBFactory : public BackendFactory
 {
 public:

diff --git a/modules/lmdbbackend/lmdbbackend.hh b/modules/lmdbbackend/lmdbbackend.hh
index 70a712bf7864175b6ad1f60b147497916249521f..0b40b5284be5e2ebecb33ada7444e609549f2e6e 100644 (file)
--- a/modules/lmdbbackend/lmdbbackend.hh
+++ b/modules/lmdbbackend/lmdbbackend.hh
@@ -150,6 +150,8 @@ public:
   // other
   string directBackendCmd(const string& query) override;
 
+  bool hasCreatedLocalFiles() const override;
+
   // functions to use without constructing a backend object
   static std::pair<uint32_t, uint32_t> getSchemaVersionAndShards(std::string& filename);
   static bool upgradeToSchemav5(std::string& filename);

diff --git a/pdns/dnsbackend.hh b/pdns/dnsbackend.hh
index 7b7e4c211784f078cef053a85636bacc07afd592..221881ad859d271b5e96429207f90a8730c0eeb5 100644 (file)
--- a/pdns/dnsbackend.hh
+++ b/pdns/dnsbackend.hh
@@ -465,6 +465,12 @@ public:
     return false;
   }
 
+  //! Returns whether backend operations have caused files to be created.
+  virtual bool hasCreatedLocalFiles() const
+  {
+    return false;
+  }
+
   const string& getPrefix() { return d_prefix; };
 
 protected:

diff --git a/pdns/ueberbackend.cc b/pdns/ueberbackend.cc
index a0e986115a56fd18b059178df487eed8da03f18b..3d8b41e592cc594e6c9c5ab377dd9f51a240d747 100644 (file)
--- a/pdns/ueberbackend.cc
+++ b/pdns/ueberbackend.cc
@@ -886,6 +886,11 @@ bool UeberBackend::searchComments(const string& pattern, size_t maxResults, vect
   return ret;
 }
 
+bool UeberBackend::hasCreatedLocalFiles()
+{
+  return std::any_of(backends.begin(), backends.end(), [](std::unique_ptr<DNSBackend>& backend) { return backend->hasCreatedLocalFiles(); });
+}
+
 AtomicCounter UeberBackend::handle::instances(0);
 
 UeberBackend::handle::handle()

diff --git a/pdns/ueberbackend.hh b/pdns/ueberbackend.hh
index 0565abfaea0b2e147d92c9e91b63539497493607..47058680287f5297426a83640e886aaa699956e8 100644 (file)
--- a/pdns/ueberbackend.hh
+++ b/pdns/ueberbackend.hh
@@ -141,6 +141,8 @@ public:
 
   bool inTransaction();
 
+  bool hasCreatedLocalFiles();
+
 private:
   handle d_handle;
   vector<DNSZoneRecord> d_answers;