It never returns NULL anymore, because it uses xmalloc for memory
allocations.

An mhash is used for allocating system objects. Failing to grow it is
likely to render the Tarantool instance unusuable so better fail early.

Checks of mh(new) and mh(put) return value will be removed in follow-up
patches.

We want to use the xmalloc helper throughout the code, not only in
the core lib. Move its definition to trivia/util.h and use fprintf+exit
instead of say/panic in order not to create circular dependencies.

Exporting symbols of a third party library is not a best practice,
as we know from [1]. Let's wrap the msgpack symbols that need to
be exported with the "tnt_" prefix.

While working on the patch, it was decided to export the msgpack
symbols that are used in "msgpuckffi.lua".
In test shared libraries where the symbols "mp_***_{decimal,uuid}"
are used, they are replaced to exported "tnt_mp_***_{decimal,uuid}",
because in the case of linking with "libcore.a" the "libcore.a"
needs to be rebuild with the "-fPIC" flag, that seems as overkill
for tests.

1. https://github.com/tarantool/memcached/issues/59

Closes #5932

If we insert a tuple in space with an index that is being built in background,
new tuple will or will not be inserted into new index depending on the result of
lexicographical comparison with tuple which was inserted into new index last.
The problem is hash index is unordered, so background build will not work properly
if primary key is HASH index.

To avoid this, disable building index in background if primary index is hash.

Closes #5977

The test uses error injection.

Follow-up 0428bbce ("vinyl: fix use of
dropped space in deferred DELETE handler").

For deferred DELETE statements to be recovered after restart, we write
them to a special 'blackhole' system space, _vinyl_deferred_delete,
which doesn't store any data, but is logged in the WAL, as a normal
space. In the on_replace trigger installed for this space, we insert
deferred DELETE statements into the memory (L0) level of the LSM tree
corresponding to the space for which the statement was generated. We
also wait for L0 quota in the trigger. The problem is a space can be
dropped while we are waiting for quota, in which case the trigger
function will crash once it resumes execution.

To fix this, let's wait for quota before we write the information about
the deferred DELETE statement to the _vinyl_deferred_delete space and
check if the LSM tree was dropped after yield. This way, everything will
work as expected even if a new space is created with the same id,
because we don't yield after checking quota.

Closes #6448

Will come in handy for testing #6448.

@TarantoolBot document
Title: Document box.stat.vinyl().regulator.blocked_writers

The new stat counter shows the number of fibers that are blocked waiting
for Vinyl level0 memory quota.

Use a special luaL_serializer with encode_error_as_ext disabled.
Default options are propagated to it via an update trigger.

It's not needed now, because error marshaling is enabled automatically
if the connector supports it (IPROTO_FEATURE_ERROR_EXTENSION is set in
IPROTO_ID features).

Closes #6428

@TarantoolBot document
Title: Drop error_marshaling_enabled session setting

box.session.setting.error_marshaling_enabled was used to enable encoding
errors returned by CALL/EVAL in the extended format (as the MP_ERROR
MsgPack extension). Now, the feature is enabled automatically if the
connector supports it (sets IPROTO_FEATURE_ERROR_EXTENSION in IPROTO_ID
features).

The new IPROTO protocol feature IPROTO_FEATURE_ERROR_EXTENSION enables
encoding errors returned by CALL/EVAL commands as the MP_ERROR MsgPack
extension. Note, the MP_ERROR extension can still be disabled globally
by setting msgpack.cfg.encode_error_as_ext to false. If an IPROTO client
doesn't set the feature bit, errors will be encoded as generic cdata
objects (converted to strings by default).

Needed for #6428

@TarantoolBot document
Title: Document IPROTO_FEATURE_ERROR_EXTENSION

A new feature bit for the IPROTO_ID command was added:

```
IPROTO_FEATURE_ERROR_EXTENSION = 2
```

The protocol version was incremented - now it equals 2.

If a network client sets this bit, errors returned by CALL/EVAL will be
encoded as the MP_ERROR MsgPack extension (unless disabled globally by
msgpack.cfg.encode_error_as_ext). If the bit is unset, errors will be
encoded according to the serialization rules used for generic cdata
objects (converted to strings by default).

The built-in net.box connector sets this feature bit.

The server sets this feature bit if it supports the MP_ERROR MsgPack
extension so a net.box client can explicitly request the feature upon
connecting to a server:

```lua
net.box.connect(uri, {required_protocol_features = {'error_extension'}})
```

This patch adds a new msgpack.cfg: encode_error_as_ext. Setting it makes
msgpack and msgpackffi modules encode errors as the MP_ERROR msgpack
extension. If the flag is unset, msgpack.encode behavior depends on
encode_load_metatables, encode_use_tostring, and encode_invalid_as_nil
options, see luaL_convertfield(), while msgpackffi.encode() will always
encode errors as strings. The latter needs to be fixed, but it's out of
the scope of this work and tracked separately, see #4499.

The new option is enabled by default.

Interaction with box.session.settings.error_marshaling_enabled: errors
are encoded as the MP_ERROR msgpack extension when returned via IPROTO
iff both error_marshaling_enabled and encode_error_as_ext are set.

Closes #6433

@TarantoolBot document
Title: Document msgpack.cfg.encode_error_as_ext

The new option determines how error objects (see box.error.new) are
encoded in the msgpack format:
 - If it's set, errors are encoded as the MP_ERROR msgpack extension.
   This is the default behavior.
 - If it's unset, the encoded format depends on other msgpack
   configuration options (encode_load_metatables, encode_use_tostring,
   encode_invalid_as_nil). With the otherwise default configuration,
   they are encoded as strings (see error.message).

Functions affected by the default configuration (msgpack.cfg):
 - msgpack and msgpackffi modules
 - Storing errors in tuples and spaces (box.tuple.new)
 - Returning errors from IPROTO CALL/EVAL

There's no reason not to enable extended errors for CALL_16.
Enable the feature and add a test.

Needed for #6433

There's no way to encode an error yet so the test just hard-codes
msgpack data. It will be fixed in the future, once we allow to encode
errors with msgpack/msgpackffi.

Needed for #6433

It's not used anymore.

Whether errors are encoded as a msgpack extension or not is determined
by the serializer_opts::error_marshaling_enabled flag. Although an
instance of serizlier_opts is passed to luamp_encode(), it doesn't
propagate it to luamp_encode_extension_box(). The latter encodes an
error as a msgpack extension if the error_marshaling_enabled flag is set
in serializer_opts of the current session. This leads to a bug when
luamp_encode() is called with error_marshaling_enabled unset while the
current session has the flag set:

 1. luaL_tofield() sets field->type to MP_EXT and field->ext_type to
    MP_UNKNOWN_EXTENSION, because the error_marshaling_enabled flag is
    unset:

    https://github.com/tarantool/tarantool/blob/b0431cf8f47e9d081f6a402bc18edb1d6ad49847/src/lua/serializer.c#L548

 2. Basing on the ext_type, luamp_encode_r() skips the MP_ERROR
    swtich-case branch for the default branch and calls the
    luamp_encode_extension callback:

    https://github.com/tarantool/tarantool/blob/b0431cf8f47e9d081f6a402bc18edb1d6ad49847/src/lua/msgpack.c#L203

 3. The callback implementation (luamp_encode_extension_box()) encodes
    the error, because the error_marshaling_enabled flag is set in the
    current session settings, and returns MP_EXT:

    https://github.com/tarantool/tarantool/blob/b0431cf8f47e9d081f6a402bc18edb1d6ad49847/src/box/lua/init.c#L420

 4. luamp_encode_r() assumes that the callback didn't encode the
    extension, because it returned MP_EXT, and encodes it again as
    a string:

    https://github.com/tarantool/tarantool/blob/b0431cf8f47e9d081f6a402bc18edb1d6ad49847/src/lua/msgpack.c#L209

This results in a broken msgpack content.

To fix this bug, let's do the following:
 - luaL_tofield() now sets ext_type to MP_ERROR unconditionally,
   irrespective of serializer_opts::error_marshaling_enabled.
 - luamp_encode_r() invokes the luamp_encode_extension callback for
   a MP_ERROR field only if error_marshaling_enabled is set. If the flag
   is unset, it proceeds with converting the field to string.
 - luamp_encode_extension_box() doesn't check serializer_opts anymore.
   It doesn't need to, because it's called iff error_marshaling_enabled
   is set.
 - YAML and JSON encoders are patched to handle the MP_ERROR field type
   by appending error::errmsg to the output (they use luaL_tofield()
   internally to determine the field type so they have to handle
   MP_ERROR).

This basically disables error encoding as msgpack extension
everywhere except returning an error from a Lua CALL/EVAL, in
particular:
 - when creating a tuple with box.tuple.new(),
 - when inserting an error into a space,
 - when encoding an error with the msgpack module.

This is okay, because the functionality has always been broken anyway.
We will introduce a separate msgpack encoder option to enable encoding
errors as MP_ERROR msgpack extension.

Looking at the code links above, one is likely to wonder why error
encoding was implemented via the encode extension callback in the first
place. The lua/msgpack module knows about the MP_ERROR extension and
even partially handles it so it'd be only natural to call the error
encoder function directly, as we do with decimals and uuids.
Unfortunately, we can't do it, because the error encoder is (surprise!)
a part of the box library. I filed a ticket to move it to the core lib,
see #6432.

Closes #6431

Now net.box sends IPROTO_ID request on (re)connect to query features
supported by the server and report its own features. The version and
features reported by the server are checked against the new connection
options:

 - required_protocol_version - min version (unsigned)
 - required_protocol_features - required features (array of strings)

If the server version is older than specified or the server lacks
certain features, the connection will fail.

Features supported by the server are stored in the peer_protocol_version
and peer_protocol_features fields of a connection.

Closes #6253

@TarantoolBot document
Title: Document required_protocol_version/features net.box options

Two new options can now be passed to net.box.connect():

 - required_protocol_version: min IPROTO protocol version that must be
   supported by the server. Type: unsigned integer.
 - required_protocol_features: array of IPROTO protocol features that
   must be supported by the server. Type: array of strings.

If the server version is less than the specified or the server lacks
certain features, the connection will fail with the corresponding error.

Querying server features is implemented via the IPROTO_ID command.
Currently, there are two features defined: streams and transactions.

Irrespective of the options used, the actual version and features are
reported via peer_protocol_version and peer_protocol_features fields of
the connection. Example:

```
tarantool> require('net.box').connect(3301, {
         > required_protocol_version = 1,
         > required_protocol_features = {'transactions'},
         > })
---
- peer_protocol_version: 1
  peer_uuid: 7a8cfdbd-6bbc-4d10-99e5-cbbd06a2382f
  opts:
    required_protocol_version: 1
    required_protocol_features:
    - transactions
  peer_protocol_features:
    transactions: true
    streams: true
  schema_version: 80
  protocol: Binary
  state: active
  peer_version_id: 133632
  port: '3301'
...
```

The new request can be used by a client to let the server know about
supported IPROTO protocol features. The request body contains two
fields: IPROTO protocol version and supported IPROTO protocol features.
In reply to a IPROTO_ID request, the server sends its own protocol
version and supported features.

Currently, the actual protocol version is 1 and there are two features
defined which are always set - streams and transactions.

Part of #6253

@TarantoolBot document
Title: Document IPROTO_ID request

The new request code is 73. It takes a map in the body with the
following keys:
 - IPROTO_VERSION (0x54) - protocol version (unsigned).
 - IPROTO_FEATURES (0x55) - array of protocol feature ids (unsigned).

A client (connector) can send this request to let the server know about
the protocol version and features it supports. The server may enable or
disable certain functionality basing on the features supported by the
client. In reply to the request, the server sends an IPROTO_OK response,
in the body of which it reports its own protocol version and features
(the format of the response body is the same as the request body).
The request doesn't need authentication to pass.

Currently, the actual protocol version is 1 and there are two features
defined:
 - IPROTO_FEATURE_STREAMS - streams support (IPROTO_STREAM_ID header
   key), id = 0.
 - IPROTO_FEATURE_TRANSACTIONS - transactions support (IPROTO_BEGIN,
   IPROTO_COMMIT, IPROTO_ROLLBACK commands), id = 1.

So that it can be used in a struct definition.

Also, upper-case the name to conform to our coding conventions.

The test is flaky, supposedly because of a bug in Lua JIT.
Disabling Lua JIT makes the test pass.

Workaround for #5081

The problem is if we add a tuple to index and then fiber yield occurs (build-in-background),
replace of this tuple will change it in building index, but it will not be changed back
in case of rollback.

Closes #5958

Currently, if we delete tuple while primary index is altering in background,
a reference to removed tuple will be kept by primary index.

Closes #6290

Part of #5958

This patch fixes the comparison between DECIMAL as a left value and
DOUBLE greater than or equal to 1e38 or less than or equal to -1e38 as a
right value. Any DOUBLE value greater than or equal to 1e38 is now
greater than any DECIMAL value, and a DOUBLE value less than or equal to
-1e38 is less than any DECIMAL value. This is because our decimal cannot
contain more than 38 digits.

Closes #6376

Fixed dropping incoming messages when connection is closed or SHUT_RDWR
received and net_msg_max or readahead limit is reached. Now we don't close
connection if an error occurred while writing response, but only set a
special flag to stop further writing. Connection will be closed when we
read 0 from socket and process all requests.

Closes #6292

Currently there are several statistic metrics for iproto, which can
be obtained by using `box.stat.net`: `CONNECTIONS`, `REQUESTS`, `SENT`
and `RECEIVED`. Add new metric `STREAMS` which contain statistics for
iproto streams.

Part of #6293

@TarantoolBot document
Title: getting statistics for iproto streams was implemented
Add new  metric `STREAMS` to `box.stat.net`, which contain statistics
for iproto streams. `STREAMS` contains same counters as `CONNECTIONS`
metric in `box.stat.net`: current, rps and total. For example:
STREAMS:
  current: 0
  rps: 17980
  totat: 112623

Currently getting iproto statistics per thread is possible only
in debug mode, using `ERRINJ_IPROTO_SINGLE_THREAD_STAT` (it can be
used only in tests). This way have several disadvantages: first of
all `errinj` is not a place to get statistics, secondly user may be
interested in getting iproto statistics per thread. In this patch
`box.stat.net.thread` was implemented, it can be used for getting
same statistics as from `box.stat.net` but per thread.

Part of #6293

@TarantoolBot document
Title: getting network statistic per thread was implemented
User has possibility to run several iproto threads, but at the moment
he can get only general statistics, which combines statistics for all
threads. Now `box.stat.net.thread` has been implemented to get the same
statistics as when using `box.stat.net`, but for a thread. User can call
`box.stat.net.thread()` as a function to get general network statistics
per threads. For example for two iproto threads:
---
- - SENT:
      total: 0
      rps: 0
    CONNECTIONS:
      current: 0
      rps: 0
      total: 0
    REQUESTS:
      current: 0
      rps: 0
      total: 0
    RECEIVED:
      total: 0
      rps: 0
  - SENT:
      total: 0
      rps: 0
    CONNECTIONS:
      current: 0
      rps: 0
      total: 0
    REQUESTS:
      current: 0
      rps: 0
      total: 0
    RECEIVED:
      total: 0
      rps: 0
...

Also user can indexed it as a table by thread number. For example
`box.stat.net.thread[1]` returns network statistics for first iproto
thread:
---
- SENT:
    total: 0
    rps: 0
  CONNECTIONS:
    current: 0
    rps: 0
    total: 0
  REQUESTS:
    current: 0
    rps: 0
    total: 0
  RECEIVED:
    total: 0
    rps: 0
...

Make lbox_tuple_format_new (exported as box.internal.new_tuple_format to
Lua) reuse tuple formats. It's safe, because formats exported to Lua are
immutable. This fixes a net.box error when one creates/closes a lot of
net.box connections: a net.box connection creates a few formats for a
local version of the schema so if the garbage collector isn't invoked to
clean up after it, Tarantool can run out of format ids.

Closes #6217

This patch adds xmalloc, xcalloc, xrealloc, xstrdup, and xstrndup helper
functions. Each of them calls the corresponding memory allocation
function and panics if it fails. See the issue description for the full
justification.

Closes #3534

This patch fixes the problem with copying an empty string in mem_copy().
Previously, because the string length was 0, an error was thrown, but
the diag was not set, which could lead to an error due to an empty diag
or to a double free.

Closes #6157
Closes #6399

It contains test case verifying that during parallel index build the
first index to finish wins the race and aborts another TX(s). For the
synchronization sake channels were used. However, in fact containing the
same number of tuples in indexes we can't predict which index finishes
first, so sometimes channel:get() executed inside fiber building index
may hang. Hence, let's simply fill one of spaces with a bit more tuples
and remove channel:get() from functions building indexes.

Closes #6354

In case we are updating "cluster" field in on_replace_dd_schema trigger
we do not check verifying that value corresponding to "cluster" key is
uuid. Meanwhile in contrast to other tuple_field_*() decoding functions
tuple_field_uuid() EXPECTS that passed value is type of mp_string. So
let's add extra string check to tuple_field_uuid().

Closes #6332

On replace data-dictionary triggers do not expect that exceptions can be
raised from their body. Unfortunately, on_replace_dd_schema still
contains one invocation of diag_raise() which may lead to unpredictable
results. So let's replace it with diag_set().

Part of #5332

In previous commit closing connection without dropping requests
was implemented. Now we can enable part of iproto transaction test
which depends on it. Also test was reworked to make it more clear
and all tests for 'vinyl' was removed because they are not related
to streams.

At the moment, when a net.box connection is closing we are cancel worker
fiber. In this case, data that was not sent is lost. In this patch connection
closing without dropping requests was implemented: before canceling fiber we
wait on conditional variable until all data will be sent.

Closes #6338

After this patch, DECIMAL values can be bound like any other supported
by SQL values.

Closes #4717

After this patch, getting an unknown msgpack extension in SQL will throw
the correct error.

Closes #6375

__tostring always returns the type name, which is 'net.box.request'.

__serialize returns user-defined fields attached to the future or an
empty table if there's none.

Closes #6314

The new version (2.10.0) is considered to be lower than 2.2.1, because
the test uses string comparison, which results in a test failure.

Remove the useless check.

First, several facts:

* The maximal unix socket file length is 108 symbols on Linux (in fact,
  107 for tarantool console socket, see #4634).
* We run testing during building of RPM packages.
* When tests are run, they use the build directory for temporary testing
  files and tarantool console unix socket files.
* Test-run uses an instance script name to form a unix socket name for
  tarantool console.
* We plan to change package version format and add .dev suffix for
  transient (non tagged) commits.
* The package version participates in the build directory name, when
  we're building an RPM package.

If we'll enable the new version format just now, we'll unable to listen
on the unix socket like the following (the length is 111):

```
/build/usr/src/debug/tarantool-2.9.0.353.dev/test/var/023_box/gh-3633-simple-tuple-size-increasing.socket-admin
```

So I changed the instance file name to make it shorter.

Of course, there are ways to solve the problem at all, this commit is
just workaround.

Part of #6184
Follows up #3633

This patch enables static and dynamic type check for functions SUBSTR(),
GROUP_CONCAT(), REPLACE(), TRIM(). All these functions afther this patch
will be able to return VARINARY value when VARBINARY arguments are given
instead of STRING arguments.

Closes #6105