Replication dump commands

Inventory

The inventory method can be used to query an ArangoDB database’s current set of collections plus their indexes. Clients can use this method to get an overview of which collections are present in the database. They can use this information to either start a full or a partial synchronization of data, e.g. to initiate a backup or the incremental data synchronization.

Get a replication inventory

GET /_api/replication/inventory

Returns the array of collections and their indexes, and the array of Views available. These arrays can be used by replication clients to initiate an initial synchronization with the server. The response will contain all collections, their indexes and views in the requested database if global is not set, and all collections, indexes and views in all databases if global is set. In case global is not set, it is possible to restrict the response to a single collection by setting the collection parameter. In this case the response will contain only information about the requested collection in the collections array, and no information about views (i.e. the views response attribute will be an empty array).

The response will contain a JSON object with the collections, views, state and tick attributes.

collections is an array of collections with the following sub-attributes:

• parameters: the collection properties

• indexes: an array of the indexes of a the collection. Primary indexes and edge indexes are not included in this array.

The state attribute contains the current state of the replication logger. It contains the following sub-attributes:

• running: whether or not the replication logger is currently active. Note: since ArangoDB 2.2, the value will always be true

• lastLogTick: the value of the last tick the replication logger has written

• time: the current time on the server

views is an array of available views.

Replication clients should note the lastLogTick value returned. They can then fetch collections’ data using the dump method up to the value of lastLogTick, and query the continuous replication log for log events after this tick value.

To create a full copy of the collections on the server, a replication client can execute these steps:

• call the /inventory API method. This returns the lastLogTick value and the array of collections and indexes from the server.

• for each collection returned by /inventory, create the collection locally and call /dump to stream the collection data to the client, up to the value of lastLogTick. After that, the client can create the indexes on the collections as they were reported by /inventory.

If the clients wants to continuously stream replication log events from the logger server, the following additional steps need to be carried out:

• the client should call /_api/wal/tail initially to fetch the first batch of replication events that were logged after the client’s call to /inventory.

  The call to /_api/wal/tail should use a from parameter with the value of the lastLogTick as reported by /inventory. The call to /_api/wal/tail will return the x-arango-replication-lastincluded header which will contain the last tick value included in the response.

• the client can then continuously call /_api/wal/tail to incrementally fetch new replication events that occurred after the last transfer.

  Calls should use a from parameter with the value of the x-arango-replication-lastincluded header of the previous response. If there are no more replication events, the response will be empty and clients can go to sleep for a while and try again later.

Note: on a Coordinator, this request must have a DBserver query parameter which must be an ID of a DB-Server. The very same request is forwarded synchronously to that DB-Server. It is an error if this attribute is not bound in the Coordinator case.

Note: Using the global parameter the top-level object contains a key databases under which each key represents a database name, and the value conforms to the above description.

Query Parameters

• includeSystem (boolean, optional): Include system collections in the result. The default value is true.

• global (boolean, optional): Include all databases in the response. Only works on _system The default value is false.

• batchId (number, required): A valid batchId is required for this API call

• collection (string, optional): If this parameter is set, the response will be restricted to a single collection (the one specified), and no views will be returned. This can be used as an optimization to reduce the size of the response.

Responses

HTTP 200: is returned if the request was executed successfully.

HTTP 405: is returned when an invalid HTTP method is used.

HTTP 500: is returned if an error occurred while assembling the response.

Batch

The batch method will create a snapshot of the current state that then can be dumped. A batchId is required when using the dump API with RocksDB.

Create a new dump batch

POST /_api/replication/batch

Creates a new dump batch and returns the batch’s id.

The response is a JSON object with the following attributes:

• id: the id of the batch
• lastTick: snapshot tick value using when creating the batch
• state: additional leader state information (only present if the state URL parameter was set to true in the request)

Note: on a Coordinator, this request must have a DBserver query parameter which must be an ID of a DB-Server. The very same request is forwarded synchronously to that DB-Server. It is an error if this attribute is not bound in the Coordinator case.

Query Parameters

• state (boolean, optional): setting state to true will make the response also contain a state attribute with information about the leader state. This is used only internally during the replication process and should not be used by client applications.

Request Body

• ttl (integer, required): The time-to-live for the new batch (in seconds).

Responses

HTTP 200: is returned if the batch was created successfully.

HTTP 400: is returned if the TTL value is invalid or if the DBserver attribute is not specified or illegal on a Coordinator.

HTTP 405: is returned when an invalid HTTP method is used.

Delete an existing dump batch

DELETE /_api/replication/batch/{id}

Deletes the existing dump batch, allowing compaction and cleanup to resume.

Note: on a Coordinator, this request must have a DBserver query parameter which must be an ID of a DB-Server. The very same request is forwarded synchronously to that DB-Server. It is an error if this attribute is not bound in the Coordinator case.

Path Parameters

• id (string, required): The id of the batch.

Responses

HTTP 204: is returned if the batch was deleted successfully.

HTTP 400: is returned if the batch was not found.

HTTP 405: is returned when an invalid HTTP method is used.

Extend the TTL of a dump batch

PUT /_api/replication/batch/{id}

Extends the time-to-live (TTL) of an existing dump batch, using the batch’s ID and the provided TTL value.

If the batch’s TTL can be extended successfully, the response is empty.

Note: on a Coordinator, this request must have a DBserver query parameter which must be an ID of a DB-Server. The very same request is forwarded synchronously to that DB-Server. It is an error if this attribute is not bound in the Coordinator case.

Path Parameters

• id (string, required): The id of the batch.

Request Body

• ttl (integer, required): the time-to-live for the new batch (in seconds)

Responses

HTTP 204: is returned if the batch’s ttl was extended successfully.

HTTP 400: is returned if the ttl value is invalid or the batch was not found.

HTTP 405: is returned when an invalid HTTP method is used.

Dump

The dump method can be used to fetch data from a specific collection. As the results of the dump command can be huge, dump may not return all data from a collection at once. Instead, the dump command may be called repeatedly by replication clients until there is no more data to fetch. The dump command will not only return the current documents in the collection, but also document updates and deletions.

Note that the dump method will only return documents, updates, and deletions from a collection’s journals and datafiles. Operations that are stored in the write-ahead log only will not be returned. In order to ensure that these operations are included in a dump, the write-ahead log must be flushed first.

To get to an identical state of data, replication clients should apply the individual parts of the dump results in the same order as they are provided.

Get a replication dump

GET /_api/replication/dump

Returns the data from a collection for the requested range.

The chunkSize query parameter can be used to control the size of the result. It must be specified in bytes. The chunkSize value will only be honored approximately. Otherwise a too low chunkSize value could cause the server to not be able to put just one entry into the result and return it. Therefore, the chunkSize value will only be consulted after an entry has been written into the result. If the result size is then greater than chunkSize, the server will respond with as many entries as there are in the response already. If the result size is still less than chunkSize, the server will try to return more data if there’s more data left to return.

If chunkSize is not specified, some server-side default value will be used.

The Content-Type of the result is application/x-arango-dump. This is an easy-to-process format, with all entries going onto separate lines in the response body.

Each line itself is a JSON object, with at least the following attributes:

• tick: the operation’s tick attribute

• key: the key of the document/edge or the key used in the deletion operation

• rev: the revision id of the document/edge or the deletion operation

• data: the actual document/edge data for types 2300 and 2301. The full document/edge data will be returned even for updates.

• type: the type of entry. Possible values for type are:

  • 2300: document insertion/update

  • 2301: edge insertion/update

  • 2302: document/edge deletion

Note: there will be no distinction between inserts and updates when calling this method.

Query Parameters

• collection (string, required): The name or id of the collection to dump.

• chunkSize (number, optional): Approximate maximum size of the returned result.

• batchId (number, required): The id of the snapshot to use

Responses

HTTP 200: is returned if the request was executed successfully and data was returned. The header x-arango-replication-lastincluded is set to the tick of the last document returned.

HTTP 204: is returned if the request was executed successfully, but there was no content available. The header x-arango-replication-lastincluded is 0 in this case.

HTTP 404: is returned when the collection could not be found.

HTTP 405: is returned when an invalid HTTP method is used.

HTTP 500: is returned if an error occurred while assembling the response.

Get the replication revision tree

GET /_api/replication/revisions/tree

Returns the Merkle tree associated with the specified collection.

The result will be JSON/VelocyPack in the following format:

{
  version: <Number>,
  branchingFactor: <Number>
  maxDepth: <Number>,
  rangeMin: <String, revision>,
  rangeMax: <String, revision>,
  nodes: [
    { count: <Number>, hash: <String, revision> },
    { count: <Number>, hash: <String, revision> },
    ...
    { count: <Number>, hash: <String, revision> }
  ]
}

At the moment, there is only one version, 1, so this can safely be ignored for now.

Each <String, revision> value type is a 64-bit value encoded as a string of 11 characters, using the same encoding as our document _rev values. The reason for this is that 64-bit values cannot necessarily be represented in full in JavaScript, as it handles all numbers as floating point, and can only represent up to 2^53-1 faithfully.

The node count should correspond to a full tree with the given maxDepth and branchingFactor. The nodes are laid out in level-order tree traversal, so the root is at index 0, its children at indices [1, branchingFactor], and so on.

Query Parameters

• collection (string, required): The name or id of the collection to query.

• batchId (number, required): The id of the snapshot to use

Responses

HTTP 200: is returned if the request was executed successfully and data was returned.

HTTP 401: is returned if necessary parameters are missing

HTTP 404: is returned when the collection or snapshot could not be found.

HTTP 405: is returned when an invalid HTTP method is used.

HTTP 500: is returned if an error occurred while assembling the response.

HTTP 501: is returned if called on a collection which doesn’t support sync-by-revision

Rebuild the replication revision tree

POST /_api/replication/revisions/tree

Rebuilds the Merkle tree for a collection.

If successful, there will be no return body.

Query Parameters

• collection (string, required): The name or id of the collection to query.

Responses

HTTP 204: is returned if the request was executed successfully.

HTTP 401: is returned if necessary parameters are missing

HTTP 404: is returned when the collection or could not be found.

HTTP 405: is returned when an invalid HTTP method is used.

HTTP 500: is returned if an error occurred while assembling the response.

HTTP 501: is returned if called on a collection which doesn’t support sync-by-revision

List document revision IDs within requested ranges

PUT /_api/replication/revisions/ranges

Returns the revision IDs of documents within the requested ranges.

The body of the request should be JSON/VelocyPack and should consist of an array of pairs of string-encoded revision IDs:

[
  [<String, revision>, <String, revision>],
  [<String, revision>, <String, revision>],
  ...
  [<String, revision>, <String, revision>]
]

In particular, the pairs should be non-overlapping, and sorted in ascending order of their decoded values.

The result will be JSON/VelocyPack in the following format:

{
  ranges: [
    [<String, revision>, <String, revision>, ... <String, revision>],
    [<String, revision>, <String, revision>, ... <String, revision>],
    ...,
    [<String, revision>, <String, revision>, ... <String, revision>]
  ]
  resume: <String, revision>
}

The resume field is optional. If specified, then the response is to be considered partial, only valid through the revision specified. A subsequent request should be made with the same request body, but specifying the resume URL parameter with the value specified. The subsequent response will pick up from the appropriate request pair, and omit any complete ranges or revisions which are less than the requested resume revision. As an example (ignoring the string-encoding for a moment), if ranges [1, 3], [5, 9], [12, 15] are requested, then a first response may return [], [5, 6] with a resume point of 7 and a subsequent response might be [8], [12, 13].

If a requested range contains no revisions, then an empty array is returned. Empty ranges will not be omitted.

Each <String, revision> value type is a 64-bit value encoded as a string of 11 characters, using the same encoding as our document _rev values. The reason for this is that 64-bit values cannot necessarily be represented in full in JavaScript, as it handles all numbers as floating point, and can only represent up to 2^53-1 faithfully.

Query Parameters

• collection (string, required): The name or id of the collection to query.

• batchId (number, required): The id of the snapshot to use

• resume (string, optional): The revision at which to resume, if a previous request was truncated

Responses

HTTP 200: is returned if the request was executed successfully and data was returned.

HTTP 401: is returned if necessary parameters are missing or incorrect

HTTP 404: is returned when the collection or snapshot could not be found.

HTTP 405: is returned when an invalid HTTP method is used.

HTTP 500: is returned if an error occurred while assembling the response.

HTTP 501: is returned if called on a collection which doesn’t support sync-by-revision

Get documents by revision

PUT /_api/replication/revisions/documents

Returns documents by revision for replication.

The body of the request should be JSON/VelocyPack and should consist of an array of string-encoded revision IDs:

[
  <String, revision>,
  <String, revision>,
  ...
  <String, revision>
]

In particular, the revisions should be sorted in ascending order of their decoded values.

The result will be a JSON/VelocyPack array of document objects. If there is no document corresponding to a particular requested revision, an empty object will be returned in its place.

The response may be truncated if it would be very long. In this case, the response array length will be less than the request array length, and subsequent requests can be made for the omitted documents.

Each <String, revision> value type is a 64-bit value encoded as a string of 11 characters, using the same encoding as our document _rev values. The reason for this is that 64-bit values cannot necessarily be represented in full in JavaScript, as it handles all numbers as floating point, and can only represent up to 2^53-1 faithfully.

Query Parameters

• collection (string, required): The name or id of the collection to query.

• batchId (number, required): The id of the snapshot to use

Responses

HTTP 200: is returned if the request was executed successfully and data was returned.

HTTP 401: is returned if necessary parameters are missing or incorrect

HTTP 404: is returned when the collection or snapshot could not be found.

HTTP 405: is returned when an invalid HTTP method is used.

HTTP 500: is returned if an error occurred while assembling the response.

HTTP 501: is returned if called on a collection which doesn’t support sync-by-revision

Start replication from a remote endpoint

PUT /_api/replication/sync

Starts a full data synchronization from a remote endpoint into the local ArangoDB database.

The sync method can be used by replication clients to connect an ArangoDB database to a remote endpoint, fetch the remote list of collections and indexes, and collection data. It will thus create a local backup of the state of data at the remote ArangoDB database. sync works on a per-database level.

sync will first fetch the list of collections and indexes from the remote endpoint. It does so by calling the inventory API of the remote database. It will then purge data in the local ArangoDB database, and after start will transfer collection data from the remote database to the local ArangoDB database. It will extract data from the remote database by calling the remote database’s dump API until all data are fetched.

In case of success, the body of the response is a JSON object with the following attributes:

• collections: an array of collections that were transferred from the endpoint

• lastLogTick: the last log tick on the endpoint at the time the transfer was started. Use this value as the from value when starting the continuous synchronization later.

WARNING: calling this method will synchronize data from the collections found on the remote endpoint to the local ArangoDB database. All data in the local collections will be purged and replaced with data from the endpoint.

Use with caution!

Note: this method is not supported on a Coordinator in a cluster.

Request Body

• endpoint (string, required): the leader endpoint to connect to (e.g. “tcp://192.168.173.13:8529”).

• database (string, optional): the database name on the leader (if not specified, defaults to the name of the local current database).

• username (string, optional): an optional ArangoDB username to use when connecting to the endpoint.

• password (string, required): the password to use when connecting to the endpoint.

• includeSystem (boolean, optional): whether or not system collection operations will be applied

• incremental (boolean, optional): if set to true, then an incremental synchronization method will be used for synchronizing data in collections. This method is useful when collections already exist locally, and only the remaining differences need to be transferred from the remote endpoint. In this case, the incremental synchronization can be faster than a full synchronization. The default value is false, meaning that the complete data from the remote collection will be transferred.

• restrictType (string, optional): an optional string value for collection filtering. When specified, the allowed values are include or exclude.

• restrictCollections (array of strings, optional): an optional array of collections for use with restrictType. If restrictType is include, only the specified collections will be synchronized. If restrictType is exclude, all but the specified collections will be synchronized.

• initialSyncMaxWaitTime (integer, optional): the maximum wait time (in seconds) that the initial synchronization will wait for a response from the leader when fetching initial collection data. This wait time can be used to control after what time the initial synchronization will give up waiting for a response and fail. This value will be ignored if set to 0.

Responses

HTTP 200: is returned if the request was executed successfully.

HTTP 400: is returned if the configuration is incomplete or malformed.

HTTP 405: is returned when an invalid HTTP method is used.

HTTP 500: is returned if an error occurred during synchronization.

HTTP 501: is returned when this operation is called on a Coordinator in a cluster.

Get the cluster collections and indexes

GET /_api/replication/clusterInventory

Returns the array of collections and indexes available on the cluster.

The response will be an array of JSON objects, one for each collection. Each collection contains exactly two keys, parameters and indexes. This information comes from Plan/Collections/{DB-Name}/* in the Agency, just that the indexes attribute there is relocated to adjust it to the data format of arangodump.

Query Parameters

• includeSystem (boolean, optional): Include system collections in the result. The default value is true.

Responses

HTTP 200: is returned if the request was executed successfully.

HTTP 405: is returned when an invalid HTTP method is used.

HTTP 500: is returned if an error occurred while assembling the response.