1MongoDB::Upgrading::v1(U3s)er Contributed Perl DocumentatMioonngoDB::Upgrading::v1(3)
2
3
4

NAME

6       MongoDB::Upgrading::v1 - Deprecations and behavior changes from v0 to
7       v1
8

VERSION

10       version v2.2.2
11

DESCRIPTION

13       The v1 driver represents a substantial step forward in functionality
14       and consistency.  There are many areas where the old API has been
15       deprecated or changed in a backward breaking way.
16
17       This document is intended to help developers update their code to take
18       into account API changes from the v0 driver to the v1 driver.
19

RATIONALE

21       Changes to the driver were deemed necessary to achieve certain goals:
22
23       •   consistency (intra-driver) – many parts of the v0 API were
24           inconsistent, behaving differently from method to method; the v1
25           API minimizes developer surprises by improving consistency in
26           return types and exception mechanisms.
27
28       •   consistency (inter-driver) — "next-generation" MongoDB drivers
29           across all languages are converging on common APIs and common
30           behaviors; this simplifies developer education and support, as
31           cross-language examples will be similar.
32
33       •   encapsulation – too many low-level, internal operations were
34           exposed as part of the API, which complicates maintenance work; the
35           v1 API aims to minimize the "public surface" available to
36           developers, allowing faster future development keeping up with
37           MongoDB server enhancements with less risk of breakage.
38
39       •   abstraction – many v0 methods returned raw server documents for
40           end-user code to inspect, which is brittle in the face of changes
41           in server responses over time; the v1 API uses result classes to
42           abstract the details behind standardized accessors.
43
44       •   server compatibility – some new features and behavior changes in
45           the MongoDB server no longer fit the old driver design; the v1
46           driver transparently supports both old and new servers.
47
48       •   portability – the v0 driver had a large dependency tree and
49           substantial non-portable C code; the v1 driver removes some
50           dependencies and uses widely-used, well-tested CPAN modules in
51           place of custom C code where possible; it lays the groundwork for a
52           future "pure-Perl optional" driver.
53
54       •   round-trippable data – the v0 BSON implementation could easily
55           change data types when round-tripping documents; the v1 driver is
56           designed to round-trip data correctly whenever possible (within the
57           limits of Perl's dynamic typing).
58

INSTALLATION AND DEPENDENCY CHANGES

60   Moo instead of Moose
61       The v1 driver uses Moo instead of Moose.  This change results in a
62       slightly faster driver and a significantly reduced deep dependency
63       tree.
64
65   SSL and SASL
66       The v0 driver required a compiler and OpenSSL and libgsasl for SSL and
67       SASL support, respectively.  The v1 driver instead relies on CPAN
68       modules "IO::Socket::SSL" and "Authen::SASL" for SSL and SASL support,
69       respectively.
70
71       SSL configuration is now possible via the ssl attribute.
72
73       Authentication configuration is described in "AUTHENTICATION" in
74       MongoDB::MongoClient.
75

BEHAVIOR CHANGES

77   MongoClient configuration
78       New configuration options
79
80       Several configuration options have been added, with particular emphasis
81       on adding more granular control of timings and timeout behaviors.
82
83       •   "auth_mechanism"
84
85       •   "auth_mechanism_properties"
86
87       •   "bson_codec"
88
89       •   "connect_timeout_ms"
90
91       •   "heartbeat_frequency_ms"
92
93       •   "local_threshold_ms"
94
95       •   "max_time_ms"
96
97       •   "replica_set_name"
98
99       •   "read_pref_mode"
100
101       •   "read_pref_tag_sets"
102
103       •   "server_selection_timeout_ms"
104
105       •   "socket_check_interval_ms"
106
107       •   "socket_timeout_ms"
108
109       Replica set configuration
110
111       Connecting to a replica set now requires a replica set name, given
112       either with the "replica_set_name" option for MongoDB::MongoClient or
113       with the "replicaSet" option in a connection string.  For example:
114
115           $client = MongoDB::MongoClient->new(
116               host => "mongodb://rs1.example.com,rs2.example.com/",
117               replica_set_name => 'the_set',
118           );
119
120           $client = MongoDB::MongoClient->new(
121               host => "mongodb://rs1.example.com,rs2.example.com/?replicaSet=the_set"
122           );
123
124       Configuration options changed to read-only
125
126       Configuration options are changing to be immutable to prevent
127       surprising action-at-a-distance.  (E.g. changing an attribute value in
128       some part of the code changes it for other parts of the code that
129       didn't expect it.)  Going forward, options may be set at
130       MongoDB::MongoClient construction time only.
131
132       The following options have changed to be read-only:
133
134       •   "db_name"
135
136       •   "j"
137
138       •   "password"
139
140       •   "ssl"
141
142       •   "username"
143
144       •   "w"
145
146       •   "wtimeout"
147
148       Write concern may be overridden at the MongoDB::Database and
149       MongoDB::Collection level during construction of those objects.  For
150       more details, see the later section on write concern changes.
151
152       Mapping between connection string and configuration options
153
154       Many configuration options may be set via a connection string URI in
155       the "host" option.  In the v0 driver, the precedence between the
156       connection string and constructor options was completely inconsistent.
157       In the v1 driver, options set via a connection string URI will take
158       precedence over options passed to the constructor.  This is consistent
159       with with other MongoDB drivers (as well as how DBI treats Data Source
160       Names).
161
162       The list of servers and ports as well as the optional "username",
163       "password" and "db_name" options come directly from URI structure.
164       Other options are parsed as key-value parameters at the end of the
165       connection string.  The following table shows how connection string
166       keys map to configuration options in the MongoDB::MongoClient:
167
168           Connection String Key           MongoClient option
169           ---------------------------     -----------------------------
170           authMechanism                   auth_mechanism
171           authMechanismProperties         auth_mechanism_properties
172           connectTimeoutMS                connect_timeout_ms
173           heartbeatFrequencyMS            heartbeat_frequency_ms
174           journal                         j
175           localThresholdMS                local_threshold_ms
176           maxTimeMS                       max_time_ms
177           readPreference                  read_pref_mode
178           readPreferenceTags              read_pref_tag_sets
179           replicaSet                      replica_set_name
180           serverSelectionTimeoutMS        server_selection_timeout_ms
181           socketCheckIntervalMS           socket_check_interval_ms
182           socketTimeoutMS                 socket_timeout_ms
183           ssl                             ssl
184           w                               w
185           wTimeoutMS                      wtimeout
186
187       The "readPreferenceTags" and "authMechanismProperties" keys take colon-
188       delimited, comma-separated pairs:
189
190           readPreferenceTags=dc:nyeast,rack:1
191           authMechanismProperties=SERVICE_NAME:mongodb
192
193       The "readPreferenceTags" option may be repeated to build up a list of
194       tag set documents:
195
196           readPreferenceTags=dc:nyc,rack:1&readPreferenceTags=dc:nyc
197
198       Deprecated configuration options
199
200       Several options have been superseded, replaced or renamed for clarity
201       and are thus deprecated and undocumented.  They are kept for a limited
202       degree of backwards compatibility.  They will be generally be used as
203       fallbacks for other options.  If any were read-write, they have also
204       been changed to read-only.
205
206       •   "dt_type" — see "BSON encoding changes" for details.
207
208       •   "query_timeout" — replaced by "socket_timeout_ms"; if set, this
209           will be used as a fallback default for "socket_timeout_ms".
210
211       •   "sasl" — superseded by "auth_mechanism"; if set, this will be used
212           along with "sasl_mechanism" as a fallback default for
213           "auth_mechanism".
214
215       •   "sasl_mechanism" — superseded by "auth_mechanism"; if set, this
216           will be used as a fallback default for "auth_mechanism".
217
218       •   "timeout" — replaced by "connect_timeout_ms"; if set, this will be
219           used as a fallback default for "connect_timeout_ms".
220
221       These will be removed in a future major release.
222
223       Configuration options removed
224
225       Some configuration options have been removed entirely, as they no
226       longer serve any purpose given changes to server discovery, server
227       selection and connection handling:
228
229       •   "auto_connect"
230
231       •   "auto_reconnect"
232
233       •   "find_master"
234
235       •   "max_bson_size"
236
237       As described further below in the "BSON encoding changes" section,
238       these BSON encoding configuration options have been removed as well:
239
240       •   "inflate_dbrefs"
241
242       •   "inflate_regexps"
243
244       Removed configuration options will be ignored if passed to the
245       MongoDB::MongoClient constructor.
246
247   Lazy connections and reconnections on demand
248       The improved approach to server monitoring and selection allows all
249       connections to be lazy.  When the client is constructed, no connections
250       are made until the first network operation is needed.  At that time,
251       the client will scan all servers in the seed list and begin regular
252       monitoring.  Connections that drop will be re-established when needed.
253
254       IMPORTANT: Code that used to rely on a fatal exception from
255       "MongoDB::MongoClient->new" when no mongod is available will break.
256       Instead, users are advised to just conduct their operations and be
257       prepared to handle errors.
258
259       For testing, users may wish to run a simple command to check that a
260       mongod is ready:
261
262           use Test::More;
263
264           # OLD WAY: BROKEN
265           plan skip_all => 'no mongod' unless eval {
266               MongoDB::MongoClient->new
267           };
268
269           # NEW WAY 1: with MongoDB::MongoClient
270           plan skip_all => 'no mongod' unless eval {
271               MongoDB::MongoClient->new->db('admin')->run_command(
272                   [ ismaster => 1 ]
273               )
274           };
275
276           # NEW WAY 2: with MongoDB and connect
277           plan skip_all => 'no mongod' unless eval {
278               MongoDB->connect->db('admin')->run_command([ ismaster => 1 ])
279           };
280
281       See SERVER SELECTION and SERVER MONITORING AND FAILOVER in
282       MongoDB::MongoClient for details.
283
284   Exceptions are the preferred error handling approach
285       In the v0 driver, errors could be indicated in various ways:
286
287       •   boolean return value
288
289       •   string return value is an error; hash ref is success
290
291       •   document that might contain an 'err', 'errmsg' or '$err' field
292
293       •   thrown string exception
294
295       Regardless of the documented error handling, every method that involved
296       a network operation would throw an exception on various network errors.
297
298       In the v1 driver, exceptions objects are the standard way of indicating
299       errors.  The exception hierarchy is described in MongoDB::Error.
300
301   Cursors and query responses
302       In v0, MongoDB::Cursor objects were used for ordinary queries as well
303       as the query-like commands aggregation and parallel scan.  However,
304       only cursor iteration commands worked for aggregation and parallel scan
305       "cursors"; the rest of the MongoDB::Cursor API didn't apply and was
306       fatal.
307
308       In v1, all result iteration is done via the new MongoDB::QueryResult
309       class.  MongoDB::Cursor is now just a thin wrapper that holds query
310       parameters, instantiates a MongoDB::QueryResult on demand, and passes
311       iteration methods through to the query result object.
312
313       This significantly simplifies the code base and should have little end-
314       user visibility unless users are specifically checking the return type
315       of queries and query-like methods.
316
317       The "explain" cursor method no longer resets the cursor.
318
319       The "slave_okay" cursor method now sets the "read_preference" to
320       'secondaryPreferred' or clears it to 'primary'.
321
322       The "snapshot" cursor method now requires a boolean argument, allowing
323       it to be turned on or off before executing the query.  Calling it
324       without an argument (as it was in v0) is a fatal exception.
325
326       Parallel scan "cursors" are now QueryResult objects, with the same
327       iteration methods as in v0.
328
329       The $MongoDB::Cursor::slave_okay global variable has been removed as
330       part of the revision to read preference handling.  See the read
331       preferences section below for more details.
332
333       The $MongoDB::Cursor::timeout global variable has also been removed.
334       Timeouts are set during MongoDB::MongoClient configuration and are
335       immutable.  See the section on configuration changes for more.
336
337   Aggregation API
338       On MongoDB 2.6 or later, "aggregate" always uses a cursor to execute
339       the query.  The "batchSize" option has been added (but has no effect
340       prior to 2.6).  The "cursor" option is deprecated.
341
342       The return types for the "aggregate" method are now always QueryResult
343       objects, regardless of whether the aggregation uses a cursor internally
344       or is an 'explain'.
345
346       NOTE: To help users with a 2.6 mongos and mixed version shards with
347       versions before 2.6, passing the deprecated 'cursor' option with a
348       false value will disable the use of a cursor.  This workaround is
349       provided for convenience and will be removed when 2.4 is no longer
350       supported.
351
352   Read preference objects and the read_preference method
353       A new MongoDB::ReadPreference class is used to encapsulate read
354       preference attributes.  In the v1 driver, it is constructed from the
355       "read_pref_mode" and "read_pref_tag_sets" attributes on
356       MongoDB::MongoClient:
357
358           MongoDB::MongoClient->new(
359               read_pref_mode => 'primaryPreferred',
360               read_pref_tag_sets => [ { dc => 'useast' }, {} ],
361           );
362
363       The old "read_preference" method to change the read preference has been
364       removed and trying to set a read preference after the client has been
365       created is a fatal error.  The old mode constants PRIMARY, SECONDARY,
366       etc. have been removed.
367
368       The "read_preference" method now returns the MongoDB::ReadPreference
369       object generated from "read_pref_mode" and "read_pref_tag_sets".
370
371       It is inherited by MongoDB::Database, MongoDB::Collection, and
372       MongoDB::GridFS objects unless provided as an option to the relevant
373       factory methods:
374
375           my $coll = $db->get_collection(
376               "foo", { read_preference => 'secondary' }
377           );
378
379       Such "read_preference" arguments may be a MongoDB::ReadPreference
380       object, a hash reference of arguments to construct one, or a string
381       that represents the read preference mode.
382
383       MongoDB::Database and MongoDB::Collection also have "clone" methods
384       that allow easy alteration of a read preference for a limited scope.
385
386           my $coll2 = $coll->clone( read_preference => 'secondaryPreferred' );
387
388       For MongoDB::Cursor, the "read_preference" method sets a hidden read
389       preference attribute that is used for the query in place of the
390       MongoDB::MongoClient default "read_preference" attribute.  This means
391       that calling "read_preference" on a cursor object no longer changes the
392       read preference globally on the client – the read preference change is
393       scoped to the cursor object only.
394
395   Write concern objects and removing the safe argument
396       A new MongoDB::WriteConcern class is used to encapsulate write concern
397       attributes.  In the v1 driver, it is constructed from the "w",
398       "wtimeout" and "j" attributes on MongoDB::MongoClient:
399
400           MongoDB::MongoClient->new( w => 'majority', wtimeout => 1000 );
401
402       The "write_concern" method now returns the MongoDB::WriteConcern object
403       generated from "w", "wtimeout" and "j".
404
405       It is inherited by MongoDB::Database, MongoDB::Collection, and
406       MongoDB::GridFS objects unless provided as an option to the relevant
407       factory methods:
408
409           $db = $client->get_database(
410               "test", { write_concern => { w => 'majority' } }
411           );
412
413       Such "write_concern" arguments may be a MongoDB::WriteConcern object, a
414       hash reference of arguments to construct one, or a string that
415       represents the "w" mode.
416
417       MongoDB::Database and MongoDB::Collection also have "clone" methods
418       that allow easy alteration of a write concern for a limited scope.
419
420           my $coll2 = $coll->clone( write_concern => { w => 1 } );
421
422       The "safe" argument is no longer used in the new CRUD API.
423
424   Authentication based only on configuration options
425       Authentication now happens automatically on connection during the
426       "handshake" with any given server based on the auth_mechanism
427       attribute.
428
429       The old "authenticate" method in MongoDB::MongoClient has been removed.
430
431   Bulk API
432       Bulk method names changed to match CRUD API
433
434       Method names match the new CRUD API, e.g. "insert_one" instead of
435       "insert" and so one.  The legacy names are deprecated.
436
437       Bulk insertion
438
439       Insertion via the bulk API will NOT insert an "_id" into the original
440       document if one does not exist.  Previous documentation was not
441       specific whether this was the case or if the "_id" was added to the
442       document sent to the server.
443
444       Bulk write results
445
446       The bulk write results class has been renamed to
447       MongoDB::BulkWriteResult.  It keeps "MongoDB::WriteResult" as an empty
448       superclass for some backwards compatibility so that
449       "$result->isa("MongoDB::WriteResult")" will continue to work as
450       expected.
451
452       The attributes have been renamed to be consistent with the new CRUD
453       API.  The legacy names are deprecated, but are available as aliases.
454
455   GridFS
456       The MongoDB::GridFS class now has explicit read preference and write
457       concern attributes inherited from MongoDB::MongoClient or
458       MongoDB::Database, just like MongoDB::Collection.  This means that
459       GridFS operations now default to an acknowledged write concern, just
460       like collection operations have been doing since v0.502.0 in 2012.
461
462       The use of "safe" is deprecated.
463
464       Support for ancient, undocumented positional parameters circa 2010 has
465       been removed.
466
467   Low-level functions removed
468       Low-level driver functions have been removed from the public API.
469
470   MongoDB::Connection removed
471       The "MongoDB::Connection" module was deprecated in v0.502.0 and has
472       been removed.
473
474   BSON encoding changes
475       In the v1 driver, BSON encoding and decoding have been encapsulated
476       into a MongoDB::BSON codec object.  This can be provided at any level,
477       from MongoDB::MongoClient to MongoDB::Collection.  If not provided, a
478       default will be created that behaves similarly to the v0
479       encoding/decoding functions, except for the following changes.
480
481       $MongoDB::BSON::use_binary removed
482
483       Historically, this defaulted to false, which corrupts binary data when
484       round tripping.  Retrieving a binary data element and re-inserting it
485       would have resulted in a field with UTF-8 encoded string of binary
486       data.
487
488       Going forward, binary data will be returned as a MongoDB::BSON::Binary
489       object.  A future driver may add the ability to control decoding to
490       allow alternative representations.
491
492       $MongoDB::BSON::use_boolean removed
493
494       This global variable never worked. BSON booleans were always
495       deserialized as boolean objects.  A future driver may add the ability
496       to control boolean representation.
497
498       $MongoDB::BSON::utf8_flag_on removed
499
500       In order to ensure round-tripping of string data, this variable is
501       removed.  BSON strings will always be decoded to Perl character
502       strings.  Anything else risks double-encoding a round-trip.
503
504       $MongoDB::BSON::looks_like_number and $MongoDB::BSON::char deprecated
505       and re-scoped
506
507       In order to allow a future driver to provide more flexible user-
508       customized encoding and decoding, these global variables are
509       deprecated.  If set, they will be examined during
510       "MongoDB::MongoClient->new()" to set the configuration of a default
511       MongoDB::BSON codec (if one is not provided).  Changing them later will
512       NOT change the behavior of the codec object.
513
514       "MongoDB::MongoClient" option "inflate_regexps" removed
515
516       Previously, BSON regular expressions decoded to "qr{}" references by
517       default and the "MongoDB::MongoClient" "inflate_regexps" option was
518       available to decode instead to MongoDB::BSON::Regexps.
519
520       Going forward in the v1.0.0 driver, for safety and consistency with
521       other drivers, BSON regular expressions always decode to
522       MongoDB::BSON::Regexp objects.
523
524       "MongoDB::MongoClient" option "inflate_dbrefs" removed
525
526       The "inflate_dbrefs" configuration option has been removed and replaced
527       with a "dbref_callback" option in MongoDB::BSON.
528
529       By default, the "MongoDB::MongoClient" will create a MongoDB::BSON
530       codec that will construct MongoDB::DBRef objects.  This ensures that
531       DBRefs properly round-trip.
532
533       "MongoDB::MongoClient" option "dt_type" deprecated and changed to read-
534       only
535
536       The "dt_type" option is now only takes effect if "MongoDB::MongoClient"
537       constructs a MongoDB::BSON codec object.  It has been changed to a
538       read-only attribute so that any code that relied on changing "dt_type"
539       after constructing a "MongoDB::MongoClient" object will fail instead of
540       being silently ignored.
541
542       Int32 vs Int64 encoding changes
543
544       On 64-bit Perls, integers that fit in 32-bits will be encoded as BSON
545       Int32 (whereas previously these were always encoded as BSON Int64).
546
547       Math::BigInt objects will always be encoded as BSON Int64, which allows
548       users to force 64-bit encoding if desired.
549
550       Added support for Time::Moment
551
552       Time::Moment is a much faster replacement for the venerable DateTime
553       module.  The BSON codec will serialize Time::Moment objects correctly
554       and can use that module as an argument for the "dt_type" codec
555       attribute.
556
557       Added support for encoding common JSON boolean classes
558
559       Most JSON libraries on CPAN implement their own boolean classes.  The
560       following libraries boolean types will now encode correctly as BSON
561       booleans:
562
563       •   JSON::XS
564
565       •   Cpanel::JSON::XS
566
567       •   JSON::PP
568
569       •   JSON::Tiny
570
571       •   Mojo::JSON
572
573   DBRef objects
574       The "fetch" method and related attributes "client", "verify_db", and
575       "verify_coll" have been removed from MongoDB::DBRef.
576
577       Providing a "fetch" method was inconsistent with other MongoDB drivers,
578       which either never provided it, or have dropped it in the next-
579       generation drivers.  It requires a "client" attribute, which tightly
580       couples BSON decoding to the client model, causing circular reference
581       issues and triggering Perl memory bugs under threads.  Therefore, the
582       v1.0.0 driver no longer support fetching directly from MongoDB::DBRef;
583       users will need to implement their own methods for dereferencing.
584
585       Additionally, the "db" attribute is now optional, consistent with the
586       specification for DBRefs.
587
588       Also, all attributes ("ref", "id" and "db") are now read-only,
589       consistent with the move toward immutable objects throughout the
590       driver.
591
592       To support round-tripping DBRefs with additional fields other than
593       $ref, $id and $db, the DBRef class now has an attribute called "extra".
594       As not all drivers support this feature, using it for new DBRefs is not
595       recommended.
596

DEPRECATED METHODS

598       Deprecated options and methods may be removed in a future release.
599       Their documentation has been removed to discourage ongoing use.  Unless
600       otherwise stated, they will continue to behave as they previously did,
601       allowing a degree of backwards compatibility until code is updated to
602       the new MongoDB driver API.
603
604   MongoDB::Database
605       •   eval – MongoDB 3.0 deprecated the '$eval' command, so this helper
606           method is deprecated as well.
607
608       •   last_error — Errors are now indicated via exceptions at the time
609           database commands are executed.
610
611   MongoDB::Collection
612       •   insert, batch_insert, remove, update, save, query and
613           find_and_modify — A new common driver CRUD API replaces these
614           legacy methods.
615
616       •   get_collection — This method implied that collections could be
617           contained inside collection.  This doesn't actually happen so it's
618           confusing to have a Collection be a factory for collections.  Users
619           who want nested namespaces should be explicit and create them off
620           Database objects instead.
621
622       •   ensure_index, drop_indexes, drop_index, get_index — A new
623           MongoDB::IndexView class is accessible through the "indexes"
624           method, offering greater consistency in behavior across drivers.
625
626       •   validate — The return values have changed over different server
627           versions, so this method is risky to use; it has more use as a one-
628           off tool, which can be accomplished via "run_command".
629
630   MongoDB::CommandResult
631       •   result — has been renamed to 'output' for clarity
632
633   MongoDB::Cursor
634       •   slave_ok — this modifier method is superseded by the
635           'read_preference' modifier method
636
637       •   count — this is superseded by the "MongoDB::Collection#count" in
638           MongoDB::Collection count method.  Previously, this ignored
639           skip/limit unless a true argument was passed, which was a bizarre,
640           non-intuitive and inconsistent API.
641
642   MongoDB::BulkWrite and MongoDB::BulkWriteView
643       •   insert — renamed to 'insert_one' for consistency with CRUD API
644
645       •   update — renamed to 'update_many' for consistency with CRUD API
646
647       •   remove — renamed to 'delete_many' for consistency with CRUD API
648
649       •   remove_one — renamed to 'delete_one' for consistency with CRUD API
650

AUTHORS

652       •   David Golden <david@mongodb.com>
653
654       •   Rassi <rassi@mongodb.com>
655
656       •   Mike Friedman <friedo@friedo.com>
657
658       •   Kristina Chodorow <k.chodorow@gmail.com>
659
660       •   Florian Ragwitz <rafl@debian.org>
661
663       This software is Copyright (c) 2020 by MongoDB, Inc.
664
665       This is free software, licensed under:
666
667         The Apache License, Version 2.0, January 2004
668
669
670
671perl v5.32.1                      2021-01-27         MongoDB::Upgrading::v1(3)
Impressum