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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-API] [PATCH 2 of 2] [database]: make the database upgrade code more robust
# HG changeset patch
# User David Scott <dave.scott@xxxxxxxxxxxxx>
# Date 1257263472 0
# Node ID 9b07adfbf56554b155f75490f602c37277ec24e0
# Parent 0baec4029c0a9f2b15c40dc912ce3f4b82a09740
[database]: make the database upgrade code more robust
We always 'upgrade' the database on xapi start, irrespective of schema versions.
-- it's nolonger a catastrophic error to forget to bump the schema version
when adding a field or a table: these updates are now automatic
-- it's nolonger a catastrophic error to bump the schema version and not have
the exact schema version in the upgrade check
We now have a list of upgrade rules where each rule applies to schema versions
<= some threshold. Any applicable rules are always applied.
-- the rules can now reference product versions so we can keep track of them
-- we can have rules for multiple product versions in one list and apply the
correct sequence for both multi-step and single-step upgrades
-- rule application failures are logged but do not cause xapi to exit
After 'upgrade' we don't restart xapi
-- the database cache has the right contents for startup to proceed
-- we unconditionally force-flush every database backend so the upgrade should
be irreversible
-- after a real host upgrade the backup database will be on the backup
partition anyway: no need to do a little dance to keep a '.prev-version' file
On failure, continue to start xapi
-- If the binary's schema is *older* than the database's, we log an error and
continue; this is probably safe (similar to being a slave in a rolling upgrade)
-- We never throw a schema mismatch exception: this was always a horrible
failure mode, both for developers and users, requiring manual database XML
hacking.
Signed-off-by: David Scott <dave.scott@xxxxxxxxxxxxx>
diff -r 0baec4029c0a -r 9b07adfbf565 ocaml/database/db_cache.ml
--- a/ocaml/database/db_cache.ml Tue Nov 03 15:51:10 2009 +0000
+++ b/ocaml/database/db_cache.ml Tue Nov 03 15:51:12 2009 +0000
@@ -494,26 +494,29 @@
Db_connections.init_gen_count connections;
(* If we have a temporary_restore_path (backup uploaded in previous run
of xapi process) then restore from that *)
- if Sys.file_exists Xapi_globs.db_temporary_restore_path then
- begin
- (* we know that the backup is XML format so, to get the
manifest, we jump right in and use the xml backend directly here.. *)
- let manifest = Backend_xml.populate_and_read_manifest
Parse_db_conf.backup_file_dbconn in
- Db_backend.post_restore_hook manifest;
- (* delete file that contained backup *)
- Db_backend.try_and_delete_db_file
Xapi_globs.db_temporary_restore_path;
- end
+ let db =
+ if Sys.file_exists Xapi_globs.db_temporary_restore_path then begin
+ (* we know that the backup is XML format so, to get the manifest, we
jump right in and use the xml backend directly here.. *)
+ let manifest = Backend_xml.populate_and_read_manifest
Parse_db_conf.backup_file_dbconn in
+ Db_backend.post_restore_hook manifest;
+ (* delete file that contained backup *)
+ Db_backend.try_and_delete_db_file
Xapi_globs.db_temporary_restore_path;
+ Parse_db_conf.backup_file_dbconn
+ end
else (* if there's no backup to restore from then.. *)
- begin
- (* Check schema vsn is current; if not try and upgrade; if
can't do that then fail startup.. *)
- let most_recent_db = Db_connections.pick_most_recent_db
connections in
- (* populate gets all field names from the existing (old) db
file, not the (current) schema... which is nice: *)
- Backend_xml.populate most_recent_db;
+ begin
+ (* Check schema vsn is current; if not try and upgrade; if can't do
that then fail startup.. *)
+ let most_recent_db = Db_connections.pick_most_recent_db connections in
+ (* populate gets all field names from the existing (old) db file, not
the (current) schema... which is nice: *)
+ Backend_xml.populate most_recent_db;
+ most_recent_db
+ end in
+ (* Always perform the generic database upgrade stuff *)
+ Db_upgrade.generic_database_upgrade ();
- debug "Path that I'm looking at to consider whether to
upgrade = %s" most_recent_db.Parse_db_conf.path;
- if Sys.file_exists most_recent_db.Parse_db_conf.path then
- Db_upgrade.maybe_upgrade most_recent_db;
+ (* Then look to see whether we have specific upgrade rules to consider *)
+ if Sys.file_exists db.Parse_db_conf.path then Db_upgrade.maybe_upgrade
db;
- end;
post_populate_hook ()
let spawn_db_flush_threads() =
diff -r 0baec4029c0a -r 9b07adfbf565 ocaml/database/db_upgrade.ml
--- a/ocaml/database/db_upgrade.ml Tue Nov 03 15:51:10 2009 +0000
+++ b/ocaml/database/db_upgrade.ml Tue Nov 03 15:51:12 2009 +0000
@@ -33,6 +33,30 @@
*)
module Names = Db_names
+
+(** {Release-specific custom database upgrade rules} *)
+
+(** The type of an upgrade rule. The rules should ideally be idempotent and
composable.
+ All new fields will have been created with default values and new tables
will exist. *)
+type upgrade_rule = {
+ description: string;
+ version: int * int; (** rule will be applied if the schema version is <=
this number *)
+ fn: unit -> unit;
+}
+
+(** Apply all the rules needed for the previous_version *)
+let apply_upgrade_rules rules previous_version =
+ debug "Looking for database upgrade rules:";
+ let required_rules = List.filter (fun r -> previous_version <= r.version)
rules in
+ List.iter
+ (fun r ->
+ debug "Applying database upgrade rule: %s" r.description;
+ try
+ r.fn ()
+ with exn ->
+ error "Database upgrade rule '%s' failed: %s" r.description
(Printexc.to_string exn)
+ ) required_rules
+
let (+++) = Int64.add
@@ -185,9 +209,7 @@
debug "Using generic BIOS strings";
update_vms Xapi_globs.generic_bios_strings
-(* !!! This fn is release specific: REMEMBER TO UPDATE IT AS WE MOVE TO NEW
RELEASES *)
-let non_generic_db_upgrade_rules () =
-
+let update_snapshots () =
(* GEORGE -> MIDNIGHT RIDE *)
let vm_table = lookup_table_in_cache Db_backend.cache Names.vm in
let vm_rows = get_rowlist vm_table in
@@ -207,93 +229,64 @@
set_field_in_row s2 Names.parent
(lookup_field_in_row s1 Names.ref);
aux (s2 :: t) in
aux ordered_snapshot_rows in
- List.iter update_snapshots vm_rows;
+ List.iter update_snapshots vm_rows
- upgrade_vm_records (); (* for DMC *)
- upgrade_bios_strings () (* GEORGE OEM -> BODIE/MNR *)
+(** A list of all the custom database upgrade rules known to the system. *)
+let upgrade_rules =
+ let george = Datamodel.george_release_schema_major_vsn,
Datamodel.george_release_schema_minor_vsn in
+ [ { description = "Updating snapshot parent references";
+ version = george;
+ fn = update_snapshots };
+ { description = "Upgrading VM memory fields for DMC";
+ version = george;
+ fn = upgrade_vm_records };
+ { description = "Upgrading VM BIOS strings";
+ version = george;
+ fn = upgrade_bios_strings } ]
-let upgrade_from_last_release dbconn =
- (* NB the database cache has been populated already *)
- debug "Database schema version is that of last release: attempting upgrade";
+(** {Generic database upgrade handling} *)
- (* !!! UPDATE THIS WHEN MOVING TO NEW RELEASE !!! *)
- let old_release = Datamodel_types.rel_george in
- let this_release = Datamodel_types.rel_midnight_ride in
-
- let objs_in_last_release =
- List.filter (fun x -> List.mem old_release
x.Datamodel_types.obj_release.Datamodel_types.internal) Db_backend.api_objs in
- let table_names_in_last_release =
- List.map (fun x->Escaping.escape_obj x.Datamodel_types.name)
objs_in_last_release in
-
- let objs_in_this_release =
- List.filter (fun x -> List.mem this_release
x.Datamodel_types.obj_release.Datamodel_types.internal) Db_backend.api_objs in
- let table_names_in_this_release =
- List.map (fun x->Escaping.escape_obj x.Datamodel_types.name)
objs_in_this_release in
-
- let table_names_new_in_this_release =
- List.filter (fun tblname -> not (List.mem tblname
table_names_in_last_release)) table_names_in_this_release in
-
- (* we also have to ensure that the in-memory cache contains the new tables
added in this release that will not have been
- created by the proceeding populate (cos this is restricted to table names
in last release). Unless the new tables are
- explicitly added to the in-memory cache they will not be written out into
the new db file across upgrade. In the XML
- backend there's no schema file from which tables are created, so this
needs to be made explicit..
- *)
- let create_blank_table_in_cache tblname =
- let newtbl = create_empty_table () in
- set_table_in_cache Db_backend.cache tblname newtbl in
- List.iter create_blank_table_in_cache table_names_new_in_this_release;
-
+(** Automatically insert blank tables and new columns with default values *)
+let generic_database_upgrade () =
+ let existing_table_names = fold_over_tables (fun name _ acc -> name :: acc)
Db_backend.cache [] in
+ let api_table_names = List.map (fun x -> Escaping.escape_obj
x.Datamodel_types.name) Db_backend.api_objs in
+ let created_table_names = Listext.List.set_difference api_table_names
existing_table_names in
+ let deleted_table_names = Listext.List.set_difference existing_table_names
api_table_names in
+ List.iter (fun tblname ->
+ debug "Adding new database table: '%s'" tblname;
+ let newtbl = create_empty_table () in
+ set_table_in_cache Db_backend.cache tblname newtbl)
created_table_names;
+ List.iter (fun tblname ->
+ debug "Ignoring legacy database table: '%s'" tblname
+ ) deleted_table_names;
+
(* for each table, go through and fill in missing default values *)
- let add_default_fields_to_tbl tblname =
- let tbl = lookup_table_in_cache Db_backend.cache tblname in
- let rows = get_rowlist tbl in
- let add_fields_to_row objref r =
- let kvs = fold_over_fields (fun k v env -> (k,v)::env) r [] in
- let new_kvs = Db_backend.add_default_kvs kvs tblname in
- (* now blank r and fill it with new kvs: *)
- let newrow = create_empty_row () in
- List.iter (fun (k,v) -> set_field_in_row newrow k v) new_kvs;
- set_row_in_table tbl objref newrow
- in
- iter_over_rows add_fields_to_row tbl in
-
- (* Go and fill in default values *)
- List.iter add_default_fields_to_tbl table_names_in_last_release;
-
- non_generic_db_upgrade_rules();
-
- (* Now do the upgrade: *)
- (* 1. move existing db out of the way *)
- Unix.rename dbconn.Parse_db_conf.path (dbconn.Parse_db_conf.path ^
".prev_version." ^ (string_of_float (Unix.gettimeofday())));
- let dbconn_to_flush_to = Db_connections.preferred_write_db() in
- (* 2. create a new empty db file (with current schema) *)
- Db_connections.create_empty_db dbconn_to_flush_to;
- (* 3. mark all tables we want to write data into as dirty, and all rows as
new *)
List.iter
- (fun tname ->
- Db_dirty.set_all_dirty_table_status tname;
- let rows = get_rowlist (lookup_table_in_cache Db_backend.cache
tname) in
- let objrefs = List.map (fun row -> lookup_field_in_row row
Db_backend.reference_fname) rows in
- List.iter (fun objref->Db_dirty.set_all_row_dirty_status objref
Db_dirty.New) objrefs
- )
- table_names_in_last_release;
- debug "Database upgrade complete, restarting to use new db";
- (* 4. flush and exit with restart return code, so watchdog kicks xapi off
again (this time with upgraded db) *)
- ignore (Db_connections.flush_dirty_and_maybe_exit dbconn_to_flush_to (Some
Xapi_globs.restart_return_code))
-
-exception Schema_mismatch
+ (fun tblname ->
+ let tbl = lookup_table_in_cache Db_backend.cache tblname in
+ let rows = get_rowlist tbl in
+ let add_fields_to_row objref r =
+ let kvs = fold_over_fields (fun k v env -> (k,v)::env) r [] in
+ let new_kvs = Db_backend.add_default_kvs kvs tblname in
+ (* now blank r and fill it with new kvs: *)
+ let newrow = create_empty_row () in
+ List.iter (fun (k,v) -> set_field_in_row newrow k v) new_kvs;
+ set_row_in_table tbl objref newrow
+ in
+ iter_over_rows add_fields_to_row tbl)
+ api_table_names
(* Maybe upgrade most recent db *)
let maybe_upgrade most_recent_db =
- debug "Considering upgrade...";
- let major_vsn, minor_vsn = Backend_xml.read_schema_vsn most_recent_db in
- debug "Db has schema major_vsn=%d, minor_vsn=%d (current is %d %d) (last is
%d %d)" major_vsn minor_vsn Datamodel.schema_major_vsn
Datamodel.schema_minor_vsn Datamodel.last_release_schema_major_vsn
Datamodel.last_release_schema_minor_vsn;
- begin
- if major_vsn=Datamodel.schema_major_vsn &&
minor_vsn=Datamodel.schema_minor_vsn then
- () (* current vsn: do nothing *)
- else if major_vsn=Datamodel.last_release_schema_major_vsn &&
minor_vsn=Datamodel.last_release_schema_minor_vsn then begin
- upgrade_from_last_release most_recent_db
- (* Note: redo log is not active at present because HA is always disabled
before an upgrade. *)
- (* If this ever becomes not the case, consider invalidating the redo-log
here (using Redo_log.empty()). *)
- end else raise Schema_mismatch
- end
+ let (previous_major_vsn, previous_minor_vsn) as previous_vsn =
Backend_xml.read_schema_vsn most_recent_db in
+ let (latest_major_vsn, latest_minor_vsn) as latest_vsn =
Datamodel.schema_major_vsn, Datamodel.schema_minor_vsn in
+ let previous_string = Printf.sprintf "(%d, %d)" previous_major_vsn
previous_minor_vsn in
+ let latest_string = Printf.sprintf "(%d, %d)" latest_major_vsn
latest_minor_vsn in
+ debug "Database schema version is %s; binary schema version is %s"
previous_string latest_string;
+ if previous_vsn > latest_vsn
+ then warn "Database schema version %s is more recent than binary %s:
downgrade is unsupported." previous_string previous_string
+ else
+ if previous_vsn < latest_vsn
+ then apply_upgrade_rules upgrade_rules previous_vsn
+ else
+ debug "Database schemas match, no upgrade required"
diff -r 0baec4029c0a -r 9b07adfbf565 ocaml/idl/datamodel.ml
--- a/ocaml/idl/datamodel.ml Tue Nov 03 15:51:10 2009 +0000
+++ b/ocaml/idl/datamodel.ml Tue Nov 03 15:51:12 2009 +0000
@@ -30,9 +30,12 @@
let orlando_release_schema_major_vsn = 5
let orlando_release_schema_minor_vsn = 55
+let george_release_schema_major_vsn = 5
+let george_release_schema_minor_vsn = 57
+
(* the schema vsn of the last release: used to determine whether we can
upgrade or not.. *)
-let last_release_schema_major_vsn = 5
-let last_release_schema_minor_vsn = 57
+let last_release_schema_major_vsn = george_release_schema_major_vsn
+let last_release_schema_minor_vsn = george_release_schema_minor_vsn
(** Bindings for currently specified releases *)
3 files changed, 103 insertions(+), 104 deletions(-)
ocaml/database/db_cache.ml | 37 +++++----
ocaml/database/db_upgrade.ml | 163 ++++++++++++++++++++----------------------
ocaml/idl/datamodel.ml | 7 +
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