Class: Switchman::Shard
- Inherits:
-
ActiveRecord::Base
- Object
- ActiveRecord::Base
- Switchman::Shard
- Defined in:
- app/models/switchman/shard.rb
Constant Summary collapse
- IDS_PER_SHARD =
ten trillion possible ids per shard. yup.
10_000_000_000_000
- NIL_NIL_ID =
takes an id-ish, and returns a local id and the shard it’s local to. [nil, nil] if it can’t be interpreted. [id, nil] if it’s already a local ID. [nil, nil] if it’s a well formed id, but the shard it refers to does not exist
[nil, nil].freeze
Class Method Summary collapse
- ._load(str) ⇒ Object
- .activate(shards) ⇒ Object
- .activate!(shards) ⇒ Object
- .categories ⇒ Object
- .clear_cache ⇒ Object
- .current(category = :primary) ⇒ Object
- .default(reload_deprecated = false, reload: false, with_fallback: false) ⇒ Object
-
.determine_max_procs(max_procs_input, parallel_input = 2) ⇒ Object
given the provided option, determines whether we need to (and whether it’s possible) to determine a reasonable default.
-
.global_id_for(any_id, source_shard = nil) ⇒ Object
takes an id-ish, and returns an integral global id.
-
.integral_id_for(any_id) ⇒ Object
converts an AR object, integral id, string id, or string short-global-id to a integral id.
- .local_id_for(any_id) ⇒ Object
- .lookup(id) ⇒ Object
- .partition_by_shard(array, partition_proc = nil) ⇒ Object
-
.relative_id_for(any_id, source_shard, target_shard) ⇒ Object
takes an id-ish, and returns an integral id relative to target_shard.
- .shard_for(any_id, source_shard = nil) ⇒ Object
-
.short_id_for(any_id) ⇒ Object
takes an id-ish, and returns a shortened global string id if global, and itself if local.
-
.signed_id_operation(input_id) ⇒ Object
it’s tedious to hold onto this same kind of sign state and transform the result in multiple places, so here we can operate on the absolute value in a provided block and trust the sign will stay as provided.
-
.with_each_shard(*args) ⇒ Object
Parameters.
Instance Method Summary collapse
-
#_dump(depth) ⇒ Object
custom serialization, since shard is self-referential.
- #activate(*categories) ⇒ Object
-
#activate!(*categories) ⇒ Object
for use from console ONLY.
- #database_server ⇒ Object
- #database_server=(database_server) ⇒ Object
- #description ⇒ Object
- #destroy ⇒ Object
- #drop_database ⇒ Object
-
#global_id_for(local_id) ⇒ Object
takes an id local to this shard, and returns a global id.
-
#hash ⇒ Object
skip global_id.hash.
- #name ⇒ Object
- #name=(name) ⇒ Object
- #primary? ⇒ Boolean
-
#shard ⇒ Object
Shards are always on the default shard.
Class Method Details
._load(str) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 657 def self._load(str) lookup(str.to_i) end |
.activate(shards) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 96 def activate(shards) old_shards = activate!(shards) yield ensure active_shards.merge!(old_shards) if old_shards end |
.activate!(shards) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 103 def activate!(shards) old_shards = nil currently_active_shards = active_shards shards.each do |category, shard| next if category == :unsharded unless currently_active_shards[category] == shard old_shards ||= {} old_shards[category] = currently_active_shards[category] currently_active_shards[category] = shard end end old_shards end |
.categories ⇒ Object
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# File 'app/models/switchman/shard.rb', line 38 def categories CATEGORIES.keys end |
.clear_cache ⇒ Object
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# File 'app/models/switchman/shard.rb', line 132 def clear_cache cached_shards.clear end |
.current(category = :primary) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 92 def current(category = :primary) active_shards[category] || Shard.default end |
.default(reload_deprecated = false, reload: false, with_fallback: false) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 42 def default(reload_deprecated = false, reload: false, with_fallback: false) if reload_deprecated reload = reload_deprecated ::ActiveSupport::Deprecation.warn("positional reload parameter to Switchman::Shard.default is deprecated; use `reload: true`") end if !@default || reload # Have to create a dummy object so that several key methods still work # (it's easier to do this in one place here, and just assume that sharding # is up and running everywhere else). This includes for looking up the # default shard itself. This also needs to be a local so that this method # can be re-entrant default = DefaultShard.instance # if we already have a default shard in place, and the caller wants # to use it as a fallback, use that instead of the dummy instance if with_fallback && @default default = @default end # the first time we need a dummy dummy for re-entrancy to avoid looping on ourselves @default ||= default # Now find the actual record, if it exists; rescue the fake default if the table doesn't exist @default = begin find_cached("default_shard") { Shard.where(default: true).take } || default rescue default end # rebuild current shard activations - it might have "another" default shard serialized there active_shards.replace(active_shards.dup.map do |category, shard| shard = Shard.lookup((!shard || shard.default?) ? 'default' : shard.id) [category, shard] end.to_h) activate!(primary: @default) if active_shards.empty? # make sure this is not erroneously cached if @default.database_server.instance_variable_defined?(:@primary_shard) @default.database_server.remove_instance_variable(:@primary_shard) end # and finally, check for cached references to the default shard on the existing connection if ::ActiveRecord::Base.connected? && ::ActiveRecord::Base.connection.shard.default? ::ActiveRecord::Base.connection.shard = @default end end @default end |
.determine_max_procs(max_procs_input, parallel_input = 2) ⇒ Object
given the provided option, determines whether we need to (and whether it’s possible) to determine a reasonable default.
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# File 'app/models/switchman/shard.rb', line 549 def determine_max_procs(max_procs_input, parallel_input=2) max_procs = nil if max_procs_input max_procs = max_procs_input.to_i max_procs = nil if max_procs == 0 else return 1 if parallel_input.nil? || parallel_input < 1 cpus = Environment.cpu_count if cpus && cpus > 0 max_procs = cpus * parallel_input end end return max_procs end |
.global_id_for(any_id, source_shard = nil) ⇒ Object
takes an id-ish, and returns an integral global id. returns nil if it can’t be interpreted
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# File 'app/models/switchman/shard.rb', line 528 def global_id_for(any_id, source_shard = nil) id = integral_id_for(any_id) return any_id unless id signed_id_operation(id) do |abs_id| if abs_id >= IDS_PER_SHARD abs_id else source_shard ||= Shard.current source_shard.global_id_for(abs_id) end end end |
.integral_id_for(any_id) ⇒ Object
converts an AR object, integral id, string id, or string short-global-id to a integral id. nil if it can’t be interpreted
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# File 'app/models/switchman/shard.rb', line 459 def integral_id_for(any_id) if any_id.is_a?(::Arel::Nodes::Casted) any_id = any_id.val elsif any_id.is_a?(::Arel::Nodes::BindParam) && ::Rails.version >= "5.2" any_id = any_id.value.value_before_type_cast end case any_id when ::ActiveRecord::Base any_id.id when /^(\d+)~(-?\d+)$/ local_id = $2.to_i signed_id_operation(local_id) do |id| return nil if id > IDS_PER_SHARD $1.to_i * IDS_PER_SHARD + id end when Integer, /^-?\d+$/ any_id.to_i else nil end end |
.local_id_for(any_id) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 487 def local_id_for(any_id) id = integral_id_for(any_id) return NIL_NIL_ID unless id return_shard = nil local_id = signed_id_operation(id) do |abs_id| if abs_id < IDS_PER_SHARD abs_id elsif return_shard = lookup(abs_id / IDS_PER_SHARD) abs_id % IDS_PER_SHARD else return NIL_NIL_ID end end [local_id, return_shard] end |
.lookup(id) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 117 def lookup(id) id_i = id.to_i return current if id_i == current.id || id == 'self' return default if id_i == default.id || id.nil? || id == 'default' id = id_i raise ArgumentError if id == 0 unless cached_shards.has_key?(id) cached_shards[id] = Shard.default.activate do find_cached(['shard', id]) { find_by(id: id) } end end cached_shards[id] end |
.partition_by_shard(array, partition_proc = nil) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 411 def partition_by_shard(array, partition_proc = nil) shard_arrays = {} array.each do |object| partition_object = partition_proc ? partition_proc.call(object) : object case partition_object when Shard shard = partition_object when ::ActiveRecord::Base if partition_object.respond_to?(:associated_shards) partition_object.associated_shards.each do |a_shard| shard_arrays[a_shard] ||= [] shard_arrays[a_shard] << object end next else shard = partition_object.shard end when Integer, /^\d+$/, /^(\d+)~(\d+)$/ local_id, shard = Shard.local_id_for(partition_object) local_id ||= partition_object object = local_id if !partition_proc end shard ||= Shard.current shard_arrays[shard] ||= [] shard_arrays[shard] << object end # TODO: use with_each_shard (or vice versa) to get # connection management and parallelism benefits shard_arrays.inject([]) do |results, (shard, objects)| results.concat shard.activate { Array.wrap(yield objects) } end end |
.relative_id_for(any_id, source_shard, target_shard) ⇒ Object
takes an id-ish, and returns an integral id relative to target_shard. returns nil if it can’t be interpreted, or the integral version of the id if it refers to a shard that does not exist
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# File 'app/models/switchman/shard.rb', line 507 def relative_id_for(any_id, source_shard, target_shard) integral_id = integral_id_for(any_id) local_id, shard = local_id_for(integral_id) return integral_id unless local_id shard ||= source_shard return local_id if shard == target_shard shard.global_id_for(local_id) end |
.shard_for(any_id, source_shard = nil) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 541 def shard_for(any_id, source_shard = nil) return any_id.shard if any_id.is_a?(::ActiveRecord::Base) _, shard = local_id_for(any_id) shard || source_shard || Shard.current end |
.short_id_for(any_id) ⇒ Object
takes an id-ish, and returns a shortened global string id if global, and itself if local. returns any_id itself if it can’t be interpreted
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# File 'app/models/switchman/shard.rb', line 519 def short_id_for(any_id) local_id, shard = local_id_for(any_id) return any_id unless local_id return local_id unless shard "#{shard.id}~#{local_id}" end |
.signed_id_operation(input_id) ⇒ Object
it’s tedious to hold onto this same kind of sign state and transform the result in multiple places, so here we can operate on the absolute value in a provided block and trust the sign will stay as provided. This assumes no consumer will return a nil value from the block.
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# File 'app/models/switchman/shard.rb', line 451 def signed_id_operation(input_id) sign = input_id < 0 ? -1 : 1 output = yield input_id.abs output * sign end |
.with_each_shard(*args) ⇒ Object
Parameters
-
shards
- an array or relation of Shards to iterate over -
categories
- an array of categories to activate -
options
-:parallel - true/false to execute in parallel, or a integer of how many sub-processes per database server. Note that parallel invocation currently uses forking, so should be used sparingly because errors are not raised, and you cannot get results back :max_procs - only run this many parallel processes at a time :exception - :ignore, :raise, :defer (wait until the end and raise the first error), or a proc
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# File 'app/models/switchman/shard.rb', line 148 def with_each_shard(*args) raise ArgumentError, "wrong number of arguments (#{args.length} for 0...3)" if args.length > 3 unless default.is_a?(Shard) return Array.wrap(yield) end = args. if args.length == 1 if Array === args.first && args.first.first.is_a?(Symbol) categories = args.first else scope = args.first end else scope, categories = args end parallel = case [:parallel] when true 1 when false, nil 0 else [:parallel] end .delete(:parallel) scope ||= Shard.all if ::ActiveRecord::Relation === scope && scope.order_values.empty? scope = scope.order(::Arel.sql("database_server_id IS NOT NULL, database_server_id, id")) end if parallel > 0 max_procs = determine_max_procs(.delete(:max_procs), parallel) if ::ActiveRecord::Relation === scope # still need a post-uniq, cause the default database server could be NULL or Rails.env in the db database_servers = scope.reorder('database_server_id').select(:database_server_id).distinct. map(&:database_server).compact.uniq # nothing to do return if database_servers.count == 0 parallel = [(max_procs.to_f / database_servers.count).ceil, parallel].min if max_procs scopes = Hash[database_servers.map do |server| server_scope = server.shards.merge(scope) if parallel == 1 subscopes = [server_scope] else subscopes = [] total = server_scope.count ranges = [] server_scope.find_ids_in_ranges(:batch_size => (total.to_f / parallel).ceil) do |min, max| ranges << [min, max] end # create a half-open range on the last one ranges.last[1] = nil ranges.each do |min, max| subscope = server_scope.where("id>=?", min) subscope = subscope.where("id<=?", max) if max subscopes << subscope end end [server, subscopes] end] else scopes = scope.group_by(&:database_server) if parallel > 1 parallel = [(max_procs.to_f / scopes.count).ceil, parallel].min if max_procs scopes = Hash[scopes.map do |(server, shards)| [server, shards.in_groups(parallel, false).compact] end] else scopes = Hash[scopes.map { |(server, shards)| [server, [shards]] }] end end exception_pipes = [] pids = [] out_fds = [] err_fds = [] pid_to_name_map = {} fd_to_name_map = {} errors = [] wait_for_output = lambda do |out_fds, err_fds, fd_to_name_map| ready, _ = IO.select(out_fds + err_fds) ready.each do |fd| if fd.eof? fd.close out_fds.delete(fd) err_fds.delete(fd) next end line = fd.readline puts "#{fd_to_name_map[fd]}: #{line}" end end # only one process; don't bother forking if scopes.length == 1 && parallel == 1 return with_each_shard(scopes.first.last.first, categories, ) { yield } end # clear connections prior to forking (no more queries will be executed in the parent, # and we want them gone so that we don't accidentally use them post-fork doing something # silly like dealloc'ing prepared statements) ::ActiveRecord::Base.clear_all_connections! scopes.each do |server, subscopes| subscopes.each_with_index do |subscope, idx| if subscopes.length > 1 name = "#{server.id} #{idx + 1}" else name = server.id end exception_pipe = IO.pipe exception_pipes << exception_pipe pid, io_in, io_out, io_err = Open4.pfork4(lambda do begin Switchman.config[:on_fork_proc]&.call # set a pretty name for the process title, up to 128 characters # (we don't actually know the limit, depending on how the process # was started) # first, simplify the binary name by stripping directories, # then truncate arguments as necessary bin = File.basename($0) # Process.argv0 doesn't work on Ruby 2.5 (https://bugs.ruby-lang.org/issues/15887) max_length = 128 - bin.length - name.length - 3 args = ARGV.join(" ") if max_length >= 0 args = args[0..max_length] end new_title = [bin, args, name].join(" ") Process.setproctitle(new_title) with_each_shard(subscope, categories, ) { yield } exception_pipe.last.close rescue Exception => e begin dumped = Marshal.dump(e) dumped = nil if dumped.length > 64 * 1024 rescue dumped = nil end if dumped.nil? # couldn't dump the exception; create a copy with just # the message and the backtrace e2 = e.class.new(e.) backtrace = e.backtrace # truncate excessively long backtraces if backtrace.length > 50 backtrace = backtrace[0...25] + ['...'] + backtrace[-25..-1] end e2.set_backtrace(backtrace) e2.instance_variable_set(:@active_shards, e.instance_variable_get(:@active_shards)) dumped = Marshal.dump(e2) end exception_pipe.last.set_encoding(dumped.encoding) exception_pipe.last.write(dumped) exception_pipe.last.flush exception_pipe.last.close exit! 1 end end) exception_pipe.last.close pids << pid io_in.close # don't care about writing to stdin out_fds << io_out err_fds << io_err pid_to_name_map[pid] = name fd_to_name_map[io_out] = name fd_to_name_map[io_err] = name while max_procs && pids.count >= max_procs while max_procs && out_fds.count >= max_procs # wait for output if we've hit the max_procs limit wait_for_output.call(out_fds, err_fds, fd_to_name_map) end # we've gotten all the output from one fd so wait for its child process to exit found_pid, status = Process.wait2 pids.delete(found_pid) errors << pid_to_name_map[found_pid] if status.exitstatus != 0 end end end while out_fds.any? || err_fds.any? wait_for_output.call(out_fds, err_fds, fd_to_name_map) end pids.each do |pid| _, status = Process.waitpid2(pid) errors << pid_to_name_map[pid] if status.exitstatus != 0 end # check for an exception; we only re-raise the first one exception_pipes.each do |exception_pipe| begin serialized_exception = exception_pipe.first.read next if serialized_exception.empty? exception = Marshal.load(serialized_exception) raise exception ensure exception_pipe.first.close end end unless errors.empty? raise ParallelShardExecError.new("The following subprocesses did not exit cleanly: #{errors.sort.join(", ")}") end return end categories ||= [] previous_shard = nil close_connections_if_needed = lambda do |shard| # prune the prior connection unless it happened to be the same if previous_shard && shard != previous_shard && !previous_shard.database_server.shareable? previous_shard.activate do ::GuardRail.activated_environments.each do |env| ::GuardRail.activate(env) do if ::ActiveRecord::Base.connected? && ::ActiveRecord::Base.connection.open_transactions == 0 ::ActiveRecord::Base.connection_pool.current_pool.disconnect! end end end end end end result = [] exception = nil scope.each do |shard| # shard references a database server that isn't configured in this environment next unless shard.database_server close_connections_if_needed.call(shard) shard.activate(*categories) do begin result.concat Array.wrap(yield) rescue case [:exception] when :ignore when :defer exception ||= $! when Proc [:exception].call when :raise raise else raise end end end previous_shard = shard end close_connections_if_needed.call(Shard.current) raise exception if exception result end |
Instance Method Details
#_dump(depth) ⇒ Object
custom serialization, since shard is self-referential
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# File 'app/models/switchman/shard.rb', line 653 def _dump(depth) self.id.to_s end |
#activate(*categories) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 638 def activate(*categories) shards = hashify_categories(categories) Shard.activate(shards) do yield end end |
#activate!(*categories) ⇒ Object
for use from console ONLY
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# File 'app/models/switchman/shard.rb', line 646 def activate!(*categories) shards = hashify_categories(categories) Shard.activate!(shards) nil end |
#database_server ⇒ Object
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# File 'app/models/switchman/shard.rb', line 616 def database_server @database_server ||= DatabaseServer.find(self.database_server_id) end |
#database_server=(database_server) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 620 def database_server=(database_server) self.database_server_id = database_server.id @database_server = database_server end |
#description ⇒ Object
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# File 'app/models/switchman/shard.rb', line 629 def description [database_server.id, name].compact.join(':') end |
#destroy ⇒ Object
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# File 'app/models/switchman/shard.rb', line 720 def destroy raise("Cannot destroy the default shard") if self.default? super end |
#drop_database ⇒ Object
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# File 'app/models/switchman/shard.rb', line 661 def drop_database raise("Cannot drop the database of the default shard") if self.default? return unless read_attribute(:name) begin adapter = self.database_server.config[:adapter] sharding_config = Switchman.config || {} drop_statement = sharding_config[adapter]&.[](:drop_statement) drop_statement ||= sharding_config[:drop_statement] if drop_statement drop_statement = Array(drop_statement).dup. map { |statement| statement.gsub('%{name}', self.name) } end case adapter when 'mysql', 'mysql2' self.activate do ::GuardRail.activate(:deploy) do drop_statement ||= "DROP DATABASE #{self.name}" Array(drop_statement).each do |stmt| ::ActiveRecord::Base.connection.execute(stmt) end end end when 'postgresql' self.activate do ::GuardRail.activate(:deploy) do # Shut up, Postgres! conn = ::ActiveRecord::Base.connection old_proc = conn.raw_connection.set_notice_processor {} begin drop_statement ||= "DROP SCHEMA #{self.name} CASCADE" Array(drop_statement).each do |stmt| ::ActiveRecord::Base.connection.execute(stmt) end ensure conn.raw_connection.set_notice_processor(&old_proc) if old_proc end end end end rescue logger.info "Drop failed: #{$!}" end end |
#global_id_for(local_id) ⇒ Object
takes an id local to this shard, and returns a global id
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# File 'app/models/switchman/shard.rb', line 708 def global_id_for(local_id) return nil unless local_id self.class.signed_id_operation(local_id) do |abs_id| abs_id + self.id * IDS_PER_SHARD end end |
#hash ⇒ Object
skip global_id.hash
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# File 'app/models/switchman/shard.rb', line 716 def hash id.hash end |
#name ⇒ Object
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# File 'app/models/switchman/shard.rb', line 602 def name unless instance_variable_defined?(:@name) # protect against re-entrancy @name = nil @name = read_attribute(:name) || default_name end @name end |
#name=(name) ⇒ Object
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# File 'app/models/switchman/shard.rb', line 611 def name=(name) write_attribute(:name, @name = name) remove_instance_variable(:@name) if name == nil end |
#primary? ⇒ Boolean
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# File 'app/models/switchman/shard.rb', line 625 def primary? self == database_server.primary_shard end |