Mads::MongoFetch Class Reference

Replay reader over one or more MongoDB collections. More...

#include <mongo_fetch.hpp>

Public Member Functions
	MongoFetch (const std::string &uri)
	Construct a fetcher bound to the specified MongoDB URI.
	~MongoFetch ()
	Destroy the fetcher instance.
	MongoFetch (const MongoFetch &)=delete
MongoFetch &	operator= (const MongoFetch &)=delete
	MongoFetch (MongoFetch &&) noexcept
MongoFetch &	operator= (MongoFetch &&) noexcept
void	connect ()
	Open the connection to the MongoDB server.
void	disconnect ()
	Close the connection to the MongoDB server and clear replay state.
void	select_database (const std::string &db_name)
	Select the database on which to operate.
void	select_collections (const std::vector< std::string > &collections)
	Define the list of collections to fetch data from.
void	select_time_range (const std::string &start, const std::string &end)
	Select the time range of interest.
void	select_time_range (const std::string &start)
	Select the time range of interest, using the current time as the end of the period.
std::size_t	fetch_data ()
	Create a replay view over the selected MongoDB data.
std::size_t	fetch_data (std::string &view_name)
	Create a replay view over the selected MongoDB data.
std::size_t	fetch_data (const std::string &view_name)
	Create a persistent replay view with the specified name.
std::size_t	fetch_data_from (const std::string &view_name)
	Reuse an existing persistent replay view.
void	set_repeat (bool repeat)
	Set whether replay restarts from the beginning after the last record.
std::chrono::milliseconds	load_next (nlohmann::json &out, std::string &collection_name)
	Load the next record from the replay view.
void	set_unwrap_original (bool unwrap)
	Set whether to unwrap the original document.

Detailed Description

Replay reader over one or more MongoDB collections.

Note

The MongoDB driver types this class is built on are hidden behind a pointer to implementation, so this header pulls in no bsoncxx/mongocxx headers and sizeof(MongoFetch) does not depend on the driver ABI.

Definition at line 31 of file mongo_fetch.hpp.

Constructor & Destructor Documentation

MongoFetch() [1/3]

Mads::MongoFetch::MongoFetch ( const std::string &  uri )

explicit

Construct a fetcher bound to the specified MongoDB URI.

Parameters

uri	MongoDB connection URI used when connect() is called.

~MongoFetch()

Mads::MongoFetch::~MongoFetch

(

)

Destroy the fetcher instance.

If still connected, this calls disconnect() to release the connection and clean up any owned temporary replay view.

MongoFetch() [2/3]

Mads::MongoFetch::MongoFetch ( const MongoFetch &  )

delete

MongoFetch() [3/3]

Mads::MongoFetch::MongoFetch ( MongoFetch &&  )

noexcept

Member Function Documentation

connect()

void Mads::MongoFetch::connect

(

)

Open the connection to the MongoDB server.

disconnect()

void Mads::MongoFetch::disconnect

(

)

Close the connection to the MongoDB server and clear replay state.

If the active replay view was auto-generated by fetch_data(), it is dropped from the database before the connection is closed.

fetch_data() [1/3]

std::size_t Mads::MongoFetch::fetch_data

(

)

Create a replay view over the selected MongoDB data.

The resulting view has a temporary random name and is deleted automatically on disconnect or object destruction. Each record in the view is represented as a JSON object with these fields:

• timestamp: the record timestamp as a BSON UTC date
• collection_name: the name of the source collection
• data: the original BSON document

Records are sorted by timestamp and filtered using the time range selected with select_time_range().

Returns

Number of documents exposed by the created replay view.

fetch_data() [2/3]

std::size_t Mads::MongoFetch::fetch_data

(

const std::string &

view_name

)

Create a persistent replay view with the specified name.

The view is created on the server and is not deleted automatically on object destruction or disconnect.

Parameters

view_name

Name of the server-side replay view to create or replace.

Returns

Number of documents exposed by the created replay view.

fetch_data() [3/3]

std::size_t Mads::MongoFetch::fetch_data

(

std::string &

view_name

)

Create a replay view over the selected MongoDB data.

The resulting view has a temporary random name, unless view_name already contains one. If a name is provided, the view remains in the database after disconnect or object destruction. Each record in the view is represented as a JSON object with these fields:

• timestamp: the record timestamp as a BSON UTC date
• collection_name: the name of the source collection
• data: the original BSON document

Records are sorted by timestamp and filtered using the time range selected with select_time_range().

Parameters

view_name

Optional caller-provided name for the generated view. If empty, a name is generated and written back.

Returns

Number of documents exposed by the created replay view.

fetch_data_from()

std::size_t Mads::MongoFetch::fetch_data_from

(

const std::string &

view_name

)

Reuse an existing persistent replay view.

The named server-side object must exist, must be a MongoDB view, and must expose replay rows compatible with load_next().

Parameters

view_name

Name of the existing replay view to attach to.

Returns

Number of documents exposed by the reused view.

load_next()

std::chrono::milliseconds Mads::MongoFetch::load_next	(	nlohmann::json &	out,
		std::string &	collection_name
	)

Load the next record from the replay view.

Only the data field of the current record is loaded into out, while collection_name receives the originating collection name.

Parameters

out	JSON object populated with the next record payload.
collection_name	Output string receiving the source collection name.

Returns

Delay before loading the following record, or a negative duration when no more data are available.

operator=() [1/2]

MongoFetch & Mads::MongoFetch::operator= ( const MongoFetch &  )

delete

operator=() [2/2]

MongoFetch & Mads::MongoFetch::operator= ( MongoFetch &&  )

noexcept

select_collections()

void Mads::MongoFetch::select_collections

(

const std::vector< std::string > &

collections

)

Define the list of collections to fetch data from.

Parameters

collections

Collection names to merge into the replay view.

select_database()

void Mads::MongoFetch::select_database

(

const std::string &

db_name

)

Select the database on which to operate.

Parameters

db_name

Database name to use for subsequent operations.

select_time_range() [1/2]

void Mads::MongoFetch::select_time_range

(

const std::string &

start

)

Select the time range of interest, using the current time as the end of the period.

Parameters

start

Inclusive lower bound, expressed as epoch milliseconds or ISO-8601 UTC string.

select_time_range() [2/2]

void Mads::MongoFetch::select_time_range	(	const std::string &	start,
		const std::string &	end
	)

Select the time range of interest.

Parameters

start	Inclusive lower bound, expressed as epoch milliseconds or ISO-8601 UTC string.
end	Inclusive upper bound, expressed as epoch milliseconds or ISO-8601 UTC string.

set_repeat()

void Mads::MongoFetch::set_repeat

(

bool

repeat

)

Set whether replay restarts from the beginning after the last record.

Parameters

repeat

If true, load_next() loops over the replay view; otherwise it stops at the end.

set_unwrap_original()

void Mads::MongoFetch::set_unwrap_original

(

bool

unwrap

)

Set whether to unwrap the original document.

Parameters

unwrap

If true, the original document is unwrapped; otherwise, it is kept as a nested object.

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The documentation for this class was generated from the following file:

• src/mongo_fetch.hpp