API reference

Router public API

vshard.router.bootstrap()

Perform the initial cluster bootstrap and distribute all buckets across the replica sets.

Parameters:	timeout – a number of seconds before ending a bootstrap attempt as unsuccessful. Recreate the cluster in case of bootstrap timeout. if_not_bootstrapped – by default is set to false that means raise an error, when the cluster is already bootstrapped. True means consider an already bootstrapped cluster a success.

Example:

vshard.router.bootstrap({timeout = 4, if_not_bootstrapped = true})

Note

To detect whether a cluster is bootstrapped, vshard looks for at least one bucket in the whole cluster. If the cluster was bootstrapped only partially (for example, due to an error during the first bootstrap), then it will be considered a bootstrapped cluster on a next bootstrap call with if_not_bootstrapped. So this is still a bad practice. Avoid calling bootstrap() multiple times.

vshard.router.cfg(cfg)

Configure the database and start sharding for the specified router instance. See the sample configuration.

Parameters:	cfg – a configuration table

vshard.router.new(name, cfg)

Create a new router instance. vshard supports multiple routers in a single Tarantool instance. Each router can be connected to any vshard cluster, and multiple routers can be connected to the same cluster.

A router created via vshard.router.new() works in the same way as a static router, but the method name is preceded by a colon (vshard.router:method_name(...)), while for a static router the method name is preceded by a period (vshard.router.method_name(...)).

A static router can be obtained via the vshard.router.static() method and then used like a router created via the vshard.router.new() method.

Note

box.cfg is shared among all the routers of a single instance.

Parameters:	name – a router instance name. This name is used as a prefix in logs of the router and must be unique within the instance cfg – a configuration table. See the sample configuration.
Return:	a router instance, if created successfully; otherwise, nil and an error object

vshard.router.call(bucket_id, mode, function_name, {argument_list}, {options})

Call the function identified by function-name on the shard storing the bucket identified by bucket_id. See the Processing requests section for details on function operation.

Parameters:

bucket_id – a bucket identifier mode – either a string = ‘read’|’write’, or a map with mode=’read’|’write’ and/or prefer_replica=true|false and/or balance=true|false. function_name – a function to execute argument_list – an array of the function’s arguments options – timeout – a request timeout, in seconds. If the router cannot identify a shard with the specified bucket_id, the operation will be repeated until the timeout is reached. other net.box options, such as is_async, buffer, on_push are also supported.

The mode parameter has two possible forms: a string or a map. Examples of the string form are: 'read', 'write'. Examples of the map form are: {mode='read'}, {mode='write'}, {mode='read', prefer_replica=true}, {mode='read', balance=true}, {mode='read', prefer_replica=true, balance=true}.

If 'write' is specified then the target is the master.

If prefer_replica=true is specified then the preferred target is one of the replicas, but the target is the master if there is no conveniently available replica.

It may be good to specify prefer_replica=true for functions which are expensive in terms of resource use, to avoid slowing down the master.

If balance=true then there is load balancing – reads are distributed over all the nodes in the replica set in round-robin fashion, with a preference for replicas if prefer_replica=true is also set.

Return:

The original return value of the executed function, or nil and error object. The error object has a type attribute equal to ShardingError or one of the regular Tarantool errors (ClientError, OutOfMemory, SocketError, etc.). ShardingError is returned on errors specific for sharding: the master is missing, wrong bucket id, etc. It has an attribute code containing one of the values from the vshard.error.code.* LUA table, an optional attribute containing a message with the human-readable error description, and other attributes specific for the error code.

Examples:

To call customer_add function from vshard/example, say:

vshard.router.call(100,
                   'write',
                   'customer_add',
                   {{customer_id = 2, bucket_id = 100, name = 'name2', accounts = {}}},
                   {timeout = 5})
-- or, the same thing but with a map for the second argument
vshard.router.call(100,
                   {mode='write'},
                   'customer_add',
                   {{customer_id = 2, bucket_id = 100, name = 'name2', accounts = {}}},
                   {timeout = 5})

vshard.router.callro(bucket_id, function_name, {argument_list}, {options})

Call the function identified by function-name on the shard storing the bucket identified by bucket_id, in read-only mode (similar to calling vshard.router.call with mode=’read’). See the Processing requests section for details on function operation.

Parameters:	bucket_id – a bucket identifier function_name – a function to execute argument_list – an array of the function’s arguments options – timeout – a request timeout, in seconds. In case the router cannot identify a shard with the bucket id, the operation will be repeated until the timeout is reached. other net.box options, such as is_async, buffer, on_push are also supported.
Return:

The original return value of the executed function, or nil and error object. The error object has a type attribute equal to ShardingError or one of the regular Tarantool errors (ClientError, OutOfMemory, SocketError, etc.).

ShardingError is returned on errors specific for sharding: the replica set is not available, the master is missing, wrong bucket id, etc. It has an attribute code containing one of the values from the vshard.error.code.* LUA table, an optional attribute containing a message with the human-readable error description, and other attributes specific for this error code.

vshard.router.callrw(bucket_id, function_name, {argument_list}, {options})

Call the function identified by function-name on the shard storing the bucket identified by bucket_id, in read-write mode (similar to calling vshard.router.call with mode=’write’). See the Processing requests section for details on function operation.

Parameters:	bucket_id – a bucket identifier function_name – a function to execute argument_list – an array of the function’s arguments options – timeout – a request timeout, in seconds. In case the router cannot identify a shard with the bucket id, the operation will be repeated until the timeout is reached. other net.box options, such as is_async, buffer, on_push are also supported.
Return:

The original return value of the executed function, or nil and error object. The error object has a type attribute equal to ShardingError or one of the regular Tarantool errors (ClientError, OutOfMemory, SocketError, etc.).

ShardingError is returned on errors specific for sharding: the replica set is not available, the master is missing, wrong bucket id, etc. It has an attribute code containing one of the values from the vshard.error.code.* LUA table, an optional attribute containing a message with the human-readable error description, and other attributes specific for this error code.

vshard.router.callre(bucket_id, function_name, {argument_list}, {options})

Call the function identified by function-name on the shard storing the bucket identified by bucket_id, in read-only mode (similar to calling vshard.router.call with mode='read'), with preference for a replica rather than a master (similar to calling vshard.router.call with prefer_replica = true). See the Processing requests section for details on function operation.

Parameters:	bucket_id – a bucket identifier function_name – a function to execute argument_list – an array of the function’s arguments options – timeout – a request timeout, in seconds. In case the router cannot identify a shard with the bucket id, the operation will be repeated until the timeout is reached. other net.box options, such as is_async, buffer, on_push are also supported.
Return:

The original return value of the executed function, or nil and error object. The error object has a type attribute equal to ShardingError or one of the regular Tarantool errors (ClientError, OutOfMemory, SocketError, etc.).

ShardingError is returned on errors specific for sharding: the replica set is not available, the master is missing, wrong bucket id, etc. It has an attribute code containing one of the values from the vshard.error.code.* LUA table, an optional attribute containing a message with the human-readable error description, and other attributes specific for this error code.

vshard.router.callbro(bucket_id, function_name, {argument_list}, {options})

This has the same effect as vshard.router.call() with mode parameter = {mode='read', balance=true}.

vshard.router.callbre(bucket_id, function_name, {argument_list}, {options})

This has the same effect as vshard.router.call() with mode parameter = {mode='read', balance=true, prefer_replica=true}.

vshard.router.route(bucket_id)

Return the replica set object for the bucket with the specified bucket id value.

Parameters:	bucket_id – a bucket identifier
Return:	a replica set object

Example:

replicaset = vshard.router.route(123)

vshard.router.routeall()

Return all available replica set objects.

Return:	a map of the following type: {UUID = replicaset}
Rtype:	a map of replica set objects

Example:

function selectall()
    local resultset = {}
    shards, err = vshard.router.routeall()
    if err ~= nil then
        error(err)
    end
    for uid, replica in pairs(shards) do
        local set = replica:callro('box.space.*space-name*:select', {{}, {limit=10}}, {timeout=5})
        for _, item in ipairs(set) do
            table.insert(resultset, item)
        end
    end
    table.sort(resultset, function(a, b) return a[1] < b[1] end)
    return resultset
end

vshard.router.bucket_id(key)

Deprecated. Logs a warning when used because it is not consistent for cdata numbers.

In particular, it returns 3 different values for normal Lua numbers like 123, for unsigned long long cdata (like 123ULL, or ffi.cast('unsigned long long',123)), and for signed long long cdata (like 123LL, or ffi.cast('long long', 123)). And it is important.

vshard.router.bucket_id(123)
vshard.router.bucket_id(123LL)
vshard.router.bucket_id(123ULL)

For float and double cdata (ffi.cast('float', number), ffi.cast('double', number)) these functions return different values even for the same numbers of the same floating point type. This is because tostring() on a floating point cdata number returns not the number, but a pointer at it. Different on each call.

vshard.router.bucket_id_strcrc32() behaves exactly the same, but does not log a warning. In case you need that behavior.

vshard.router.bucket_id_strcrc32(key)

Calculate the bucket id using a simple built-in hash function.

Parameters:	key – a hash key. This can be any Lua object (number, table, string).
Return:	a bucket identifier
Rtype:	number

Example:

tarantool> vshard.router.bucket_count()
---
- 3000
...

tarantool> vshard.router.bucket_id_strcrc32("18374927634039")
---
- 2032
...

tarantool> vshard.router.bucket_id_strcrc32(18374927634039)
---
- 2032
...

tarantool> vshard.router.bucket_id_strcrc32("test")
---
- 1216
...

tarantool> vshard.router.bucket_id_strcrc32("other")
---
- 2284
...

Note

Remember that it is not safe. See details in bucket_id()

vshard.router.bucket_id_mpcrc32(key)

This function is safer than bucket_id_strcrc32. It takes a CRC32 from a MessagePack encoded value. That is, bucket id of integers does not depend on their Lua type. In case of a string key, it does not encode it into MessagePack, but takes a hash right from the string.

Parameters:	key – a hash key. This can be any Lua object (number, table, string).
Return:	a bucket identifier
Rtype:	number

However it still may return different values for not equal floating point types. That is, ffi.cast('float', number) may be reflected into a bucket id not equal to ffi.cast('double', number). This can’t be fixed, because a float value, even being casted to double, may have a garbage tail in its fraction.

Floating point keys should not be used to calculate a bucket id, usually.

Be very careful in case you store floating point types in a space. When data is returned from a space, it is cast to Lua number. And if that value had an empty fraction part, it will be treated as an integer by bucket_id_mpcrc32(). So you need to do explicit casts in such cases. Here is an example of the problem:

tarantool> s = box.schema.create_space('test', {format = {{'id', 'double'}}}); _ = s:create_index('pk')
---
...

tarantool> inserted = ffi.cast('double', 1)
---
...

-- Value is stored as double
tarantool> s:replace({inserted})
---
- [1]
...

-- But when returned to Lua, stored as Lua number, not cdata.
tarantool> returned = s:get({inserted}).id
---
...

tarantool> type(returned), returned
---
- number
- 1
...

tarantool> vshard.router.bucket_id_mpcrc32(inserted)
---
- 1411
...
tarantool> vshard.router.bucket_id_mpcrc32(returned)
---
- 1614
...

vshard.router.bucket_count()

Return the total number of buckets specified in vshard.router.cfg().

Return:	the total number of buckets
Rtype:	number

tarantool> vshard.router.bucket_count()
---
- 10000
...

vshard.router.sync(timeout)

Wait until the dataset is synchronized on replicas.

Parameters:	timeout – a timeout, in seconds
Return:	true if the dataset was synchronized successfully; or nil and err explaining why the dataset cannot be synchronized.

vshard.router.discovery_wakeup()

Force wakeup of the bucket discovery fiber.

vshard.router.discovery_set(mode)

Turn on/off the background discovery fiber used by the router to find buckets.

Parameters:	mode – working mode of a discovery fiber. There are three modes: on, off and once

When the mode is on (default), the discovery fiber works during all the lifetime of the router. Even after all buckets are discovered, it will still come to storages and download their buckets with some big period (DISCOVERY_IDLE_INTERVAL). This is useful if the bucket topology changes often and the number of buckets is not big. The router will keep its route table up to date even when no requests are processed.

When the mode is off, discovery is disabled completely.

When the mode is once, discovery starts and finds the locations of all buckets, and then the discovery fiber is terminated. This is good for a large bucket count and for clusters, where rebalancing is rare.

The method is good to enable/disable discovery after the router is already started, but discovery is enabled by default. You may want to never enable it even for a short time – then specify the discovery_mode option in the configuration. It takes the same values as vshard.router.discovery_set(mode).

You may decide to turn off discovery or make it once if you have many routers, or tons of buckets (hundreds of thousands and more), and you see that the discovery process consumes notable CPU % on routers and storages. In that case it may be wise to turn off the discovery when there is no rebalancing in the cluster. And turn it on for new routers, as well as for all routers when rebalancing is started.

vshard.router.info()

Return information about each instance.

Return:

Replica set parameters:

• replica set uuid
• master instance parameters
• replica instance parameters

Instance parameters:

• uri — URI of the instance
• uuid — UUID of the instance
• status – status of the instance (available, unreachable, missing)
• network_timeout – a timeout for the request. The value is updated automatically on each 10th successful request and each 2nd failed request.

Bucket parameters:

• available_ro – the number of buckets known to the router and available for read requests
• available_rw – the number of buckets known to the router and available for read and write requests
• unavailable – the number of buckets known to the router but unavailable for any requests
• unreachable – the number of buckets whose replica sets are not known to the router

Example:

tarantool> vshard.router.info()
---
- replicasets:
    ac522f65-aa94-4134-9f64-51ee384f1a54:
      replica: &0
        network_timeout: 0.5
        status: available
        uri: storage@127.0.0.1:3303
        uuid: 1e02ae8a-afc0-4e91-ba34-843a356b8ed7
      uuid: ac522f65-aa94-4134-9f64-51ee384f1a54
      master: *0
    cbf06940-0790-498b-948d-042b62cf3d29:
      replica: &1
        network_timeout: 0.5
        status: available
        uri: storage@127.0.0.1:3301
        uuid: 8a274925-a26d-47fc-9e1b-af88ce939412
      uuid: cbf06940-0790-498b-948d-042b62cf3d29
      master: *1
  bucket:
    unreachable: 0
    available_ro: 0
    unknown: 0
    available_rw: 3000
  status: 0
  alerts: []
...

vshard.router.buckets_info()

Return information about each bucket. Since a bucket map can be huge, only the required range of buckets can be specified.

Parameters:	offset – the offset in a bucket map of the first bucket to show limit – the maximum number of buckets to show
Return:	a map of the following type: {bucket_id = 'unknown'/replicaset_uuid}

tarantool> vshard.router.buckets_info()
---
- - uuid: aaaaaaaa-0000-4000-a000-000000000000
    status: available_rw
  - uuid: aaaaaaaa-0000-4000-a000-000000000000
    status: available_rw
  - uuid: aaaaaaaa-0000-4000-a000-000000000000
    status: available_rw
  - uuid: bbbbbbbb-0000-4000-a000-000000000000
    status: available_rw
  - uuid: bbbbbbbb-0000-4000-a000-000000000000
    status: available_rw
  - uuid: bbbbbbbb-0000-4000-a000-000000000000
    status: available_rw
  - uuid: bbbbbbbb-0000-4000-a000-000000000000
    status: available_rw
...

object replicaset_object

replicaset_object:call(function_name, {argument_list}, {options})

Call a function on a nearest available master (distances are defined using replica.zone and cfg.weights matrix) with specified arguments.

Note

The replicaset_object:call method is similar to replicaset_object:callrw.

Parameters:	function_name – function to execute argument_list – array of the function’s arguments options – timeout – a request timeout, in seconds. In case the router cannot identify a shard with the bucket id, the operation will be repeated until the timeout is reached. other net.box options, such as is_async, buffer, on_push are also supported.
Return:	result of function_name on success nill, err otherwise

replicaset_object:callrw(function_name, {argument_list}, {options})

Call a function on a nearest available master (distances are defined using replica.zone and cfg.weights matrix) with a specified arguments.

Note

The replicaset_object:callrw method is similar to replicaset_object:call.

Parameters:	function_name – function to execute argument_list – array of the function’s arguments options – timeout – a request timeout, in seconds. In case the router cannot identify a shard with the bucket id, the operation will be repeated until the timeout is reached. other net.box options, such as is_async, buffer, on_push are also supported.
Return:	result of function_name on success nill, err otherwise

tarantool> local bucket = 1; return vshard.router.callrw(
         >     bucket,
         >     'box.space.actors:insert',
         >     {{
         >         1, bucket, 'Renata Litvinova',
         >         {theatre="Moscow Art Theatre"}
         >     }},
         >     {timeout=5}
         > )

replicaset_object:callro(function_name, {argument_list}, {options})

Call a function on the nearest available replica (distances are defined using replica.zone and cfg.weights matrix) with specified arguments. It is recommended to use replicaset_object:callro() for calling only read-only functions, as the called functions can be executed not only on a master, but also on replicas.

Parameters:	function_name – function to execute argument_list – array of the function’s arguments options – timeout – a request timeout, in seconds. In case the router cannot identify a shard with the bucket id, the operation will be repeated until the timeout is reached. other net.box options, such as is_async, buffer, on_push are also supported.
Return:	result of function_name on success nill, err otherwise

replicaset:callre(function_name, {argument_list}, {options})

Call a function on the nearest available replica (distances are defined using replica.zone and cfg.weights matrix) with specified arguments, with preference for a replica rather than a master (similar to calling vshard.router.call with prefer_replica = true). It is recommended to use replicaset_object:callre() for calling only read-only functions, as the called function can be executed not only on a master, but also on replicas.

Parameters:	function_name – function to execute argument_list – array of the function’s arguments options – timeout – a request timeout, in seconds. In case the router cannot identify a shard with the bucket id, the operation will be repeated until the timeout is reached. other net.box options, such as is_async, buffer, on_push are also supported.
Return:	result of function_name on success nill, err otherwise

Router internal API

vshard.router.bucket_discovery(bucket_id)

Search for the bucket in the whole cluster. If the bucket is not found, it is likely that it does not exist. The bucket might also be moved during rebalancing and currently is in the RECEIVING state.

Parameters:	bucket_id – a bucket identifier

Storage public API

vshard.storage.cfg(cfg, name)

Configure the database and start sharding for the specified storage instance.

Parameters:	cfg – a storage configuration instance_uuid – UUID of the instance

vshard.storage.info()

Return information about the storage instance in the following format:

tarantool> vshard.storage.info()
---
- buckets:
    2995:
      status: active
      id: 2995
    2997:
      status: active
      id: 2997
    2999:
      status: active
      id: 2999
  replicasets:
    2dd0a343-624e-4d3a-861d-f45efc571cd3:
      uuid: 2dd0a343-624e-4d3a-861d-f45efc571cd3
      master:
        state: active
        uri: storage:storage@127.0.0.1:3301
        uuid: 2ec29309-17b6-43df-ab07-b528e1243a79
    c7ad642f-2cd8-4a8c-bb4e-4999ac70bba1:
      uuid: c7ad642f-2cd8-4a8c-bb4e-4999ac70bba1
      master:
        state: active
        uri: storage:storage@127.0.0.1:3303
        uuid: 810d85ef-4ce4-4066-9896-3c352fec9e64
...

vshard.storage.call(bucket_id, mode, function_name, {argument_list})

Call the specified function on the current storage instance.

Parameters:	bucket_id – a bucket identifier mode – a type of the function: ‘read’ or ‘write’ function_name – function to execute argument_list – array of the function’s arguments
Return:

The original return value of the executed function, or nil and error object.

vshard.storage.sync(timeout)

Wait until the dataset is synchronized on replicas.

Parameters:	timeout – a timeout, in seconds
Return:	true if the dataset was synchronized successfully; or nil and err explaining why the dataset cannot be synchronized.

vshard.storage.bucket_pin(bucket_id)

Pin a bucket to a replica set. A pinned bucket cannot be moved even if it breaks the cluster balance.

Parameters:	bucket_id – a bucket identifier
Return:	true if the bucket is pinned successfully; or nil and err explaining why the bucket cannot be pinned

vshard.storage.bucket_unpin(bucket_id)

Return a pinned bucket back into the active state.

Parameters:	bucket_id – a bucket identifier
Return:	true if the bucket is unpinned successfully; or nil and err explaining why the bucket cannot be unpinned

vshard.storage.bucket_ref(bucket_id, mode)

Create an RO or RW ref.

Parameters:	bucket_id – a bucket identifier mode – ‘read’ or ‘write’
Return:	true if the bucket ref is created successfully; or nil and err explaining why the ref cannot be created

vshard.storage.bucket_refro()

An alias for vshard.storage.bucket_ref in the RO mode.

vshard.storage.bucket_refrw()

An alias for vshard.storage.bucket_ref in the RW mode.

vshard.storage.bucket_unref(bucket_id, mode)

Remove a RO/RW ref.

Parameters:	bucket_id – a bucket identifier mode – ‘read’ or ‘write’
Return:	true if the bucket ref is removed successfully; or nil and err explaining why the ref cannot be removed

vshard.storage.bucket_unrefro()

An alias for vshard.storage.bucket_unref in the RO mode.

vshard.storage.bucket_unrefrw()

An alias for vshard.storage.bucket_unref in the RW mode.

vshard.storage.find_garbage_bucket(bucket_index, control)

Find a bucket which has data in a space but is not stored in a _bucket space; or is in a GARBAGE state.

Parameters:	bucket_index – index of a space with the part of a bucket id control – a garbage collector controller. If there is an increased buckets generation, then the search should be interrupted.
Return:	an identifier of the bucket in the garbage state, if found; otherwise, nil

vshard.storage.buckets_info()

Return information about each bucket located in storage. For example:

tarantool> vshard.storage.buckets_info(1)
---
- 1:
    status: active
    ref_rw: 1
    ref_ro: 1
    ro_lock: true
    rw_lock: true
    id: 1

vshard.storage.buckets_count()

Return the number of buckets located in storage.

vshard.storage.recovery_wakeup()

Immediately wake up a recovery fiber, if it exists.

vshard.storage.rebalancing_is_in_progress()

Return a flag indicating whether rebalancing is in progress. The result is true if the node is currently applying routes received from a rebalancer node in the special fiber.

vshard.storage.is_locked()

Return a flag indicating whether storage is invisible to the rebalancer.

vshard.storage.rebalancer_disable()

Disable rebalancing. A disabled rebalancer sleeps until it is enabled again with vshard.storage.rebalancer_enable().

vshard.storage.rebalancer_enable()

Enable rebalancing.

vshard.storage.sharded_spaces()

Show the spaces that are visible to rebalancer and garbage collector fibers.

tarantool> vshard.storage.sharded_spaces()
---
- 513:
    engine: memtx
    before_replace: 'function: 0x010e50e738'
    field_count: 0
    id: 513
    on_replace: 'function: 0x010e50e700'
    temporary: false
    index:
      0: &0
        unique: true
        parts:
        - type: number
          fieldno: 1
          is_nullable: false
        id: 0
        type: TREE
        name: primary
        space_id: 513
      1: &1
        unique: false
        parts:
        - type: number
          fieldno: 2
          is_nullable: false
        id: 1
        type: TREE
        name: bucket_id
        space_id: 513
      primary: *0
      bucket_id: *1
    is_local: false
    enabled: true
    name: actors
    ck_constraint: []
...

Storage internal API

vshard.storage.bucket_recv(bucket_id, from, data)

Receive a bucket identified by bucket id from a remote replica set.

Parameters:	bucket_id – a bucket identifier from – UUID of source replica set data – data logically stored in a bucket identified by bucket_id, in the same format as the return value from bucket_collect() <storage_api-bucket_collect>

vshard.storage.bucket_stat(bucket_id)

Return information about the bucket id:

tarantool> vshard.storage.bucket_stat(1)
---
- 0
- status: active
  id: 1
...

Parameters:	bucket_id – a bucket identifier

vshard.storage.bucket_delete_garbage(bucket_id)

Force garbage collection for the bucket identified by bucket_id in case the bucket was transferred to a different replica set.

Parameters:	bucket_id – a bucket identifier

vshard.storage.bucket_collect(bucket_id)

Collect all the data that is logically stored in the bucket identified by bucket_id:

tarantool> vshard.storage.bucket_collect(1)
---
- 0
- - - 514
    - - [10, 1, 1, 100, 'Account 10']
      - [11, 1, 1, 100, 'Account 11']
      - [12, 1, 1, 100, 'Account 12']
      - [50, 5, 1, 100, 'Account 50']
      - [51, 5, 1, 100, 'Account 51']
      - [52, 5, 1, 100, 'Account 52']
  - - 513
    - - [1, 1, 'Customer 1']
      - [5, 1, 'Customer 5']
...

Parameters:	bucket_id – a bucket identifier

vshard.storage.bucket_force_create(first_bucket_id, count)

Force creation of the buckets (single or multiple) on the current replica set. Use only for manual emergency recovery or for initial bootstrap.

Parameters:	first_bucket_id – an identifier of the first bucket in a range count – the number of buckets to insert (default = 1)

vshard.storage.bucket_force_drop(bucket_id)

Drop a bucket manually for tests or emergency cases.

Parameters:	bucket_id – a bucket identifier

vshard.storage.bucket_send(bucket_id, to)

Send a specified bucket from the current replica set to a remote replica set.

Parameters:	bucket_id – bucket identifier to – UUID of a remote replica set

vshard.storage.rebalancer_request_state()

Check all buckets of the host storage that have the SENT or ACTIVE state, return the number of active buckets.

Return:	the number of buckets in the active state, if found; otherwise, nil

vshard.storage.buckets_discovery()

Collect an array of active bucket identifiers for discovery.