EpochTracker Class

In ODSP, the concept of "epoch" refers to binary updates to files. For example, this might include using version restore, or if the user downloads a Fluid file and then uploads it again. These result in the epoch value being incremented.

The implications of these binary updates is that the Fluid state is disrupted: the sequence number might go backwards, the data might be inconsistent with the latest state of collaboration, etc. As a result, it's not safe to continue collaboration across an epoch change. We need to detect these epoch changes and error out from the collaboration.

This class is a wrapper around fetch calls. It adds epoch to the request made so that the server can match it with its epoch value in order to match the version. It also validates the epoch value received in response of fetch calls. If the epoch does not match, then it also clears all the cached entries for the given container.

This API is provided for existing users, but is not recommended for new users.

To use, import via @fluidframework/odsp-driver/legacy.

For more information about our API support guarantees, see here.

Signature

export declare class EpochTracker implements IPersistedFileCache

Implements: IPersistedFileCache

Constructors

Constructor	Alerts	Description
(constructor)(cache, fileEntry, logger, clientIsSummarizer)	Beta	Constructs a new instance of the EpochTracker class

Properties

Property	Alerts	Modifiers	Type	Description
cache	Beta	readonly	IPersistedCache
clientIsSummarizer	Beta	optional, readonly	boolean | undefined
fileEntry	Beta	readonly	IFileEntry
fluidEpoch	Beta	readonly	string | undefined
logger	Beta	readonly	ITelemetryLoggerExt
rateLimiter	Beta	readonly	RateLimiter

Methods

Method	Alerts	Return Type	Description
fetch(url, fetchOptions, fetchType, addInBody, fetchReason)	Beta	Promise<IOdspResponse<Response>>	Api to fetch the response for given request and parse it as json.
fetchAndParseAsJSON(url, fetchOptions, fetchType, addInBody, fetchReason)	Beta	Promise<IOdspResponse<T>>	Api to fetch the response for given request and parse it as json.
fetchArray(url, fetchOptions, fetchType, addInBody, fetchReason)	Beta	Promise<IOdspResponse<ArrayBuffer>>	Api to fetch the response as it is for given request.
get(entry)	Beta	Promise<any>
put(entry, value)	Beta	Promise<void>
removeEntries()	Beta	Promise<void>
setEpoch(epoch, fromCache, fetchType)	Beta	void
validateEpoch(epoch, fetchType)	Beta	Promise<void>
validateEpochFromResponse(epochFromResponse, fetchType, fromCache)	Beta	void

Constructor Details

(constructor)

Constructs a new instance of the EpochTracker class

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

constructor(cache: IPersistedCache, fileEntry: IFileEntry, logger: ITelemetryLoggerExt, clientIsSummarizer?: boolean | undefined);

Parameters

Parameter	Modifiers	Type	Description
cache		IPersistedCache
fileEntry		IFileEntry
logger		ITelemetryLoggerExt
clientIsSummarizer	optional	boolean | undefined

Property Details

cache

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

protected readonly cache: IPersistedCache;

Type: IPersistedCache

clientIsSummarizer

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

protected readonly clientIsSummarizer?: boolean | undefined;

Type: boolean | undefined

fileEntry

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

protected readonly fileEntry: IFileEntry;

Type: IFileEntry

fluidEpoch

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

get fluidEpoch(): string | undefined;

Type: string | undefined

logger

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

protected readonly logger: ITelemetryLoggerExt;

Type: ITelemetryLoggerExt

rateLimiter

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

readonly rateLimiter: RateLimiter;

Type: RateLimiter

Method Details

fetch

Api to fetch the response for given request and parse it as json.

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

fetch(url: string, fetchOptions: RequestInit, fetchType: FetchType, addInBody?: boolean, fetchReason?: string): Promise<IOdspResponse<Response>>;

Parameters

Parameter	Modifiers	Type	Description
url		string	url of the request
fetchOptions		RequestInit	fetch options for request containing body, headers etc.
fetchType		FetchType	method for which fetch is called.
addInBody	optional	boolean	Pass True if caller wants to add epoch in post body.
fetchReason	optional	string	fetch reason to add to the request.

Returns

Return type: Promise<IOdspResponse<Response>>

fetchAndParseAsJSON

Api to fetch the response for given request and parse it as json.

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

fetchAndParseAsJSON<T>(url: string, fetchOptions: RequestInit, fetchType: FetchType, addInBody?: boolean, fetchReason?: string): Promise<IOdspResponse<T>>;

Type Parameters

Parameter	Description
T

Parameters

Parameter	Modifiers	Type	Description
url		string	url of the request
fetchOptions		RequestInit	fetch options for request containing body, headers etc.
fetchType		FetchType	method for which fetch is called.
addInBody	optional	boolean	Pass True if caller wants to add epoch in post body.
fetchReason	optional	string	fetch reason to add to the request.

Returns

Return type: Promise<IOdspResponse<T>>

fetchArray

Api to fetch the response as it is for given request.

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

fetchArray(url: string, fetchOptions: {
        [index: string]: RequestInit;
    }, fetchType: FetchType, addInBody?: boolean, fetchReason?: string): Promise<IOdspResponse<ArrayBuffer>>;

Parameters

Parameter	Modifiers	Type	Description
url		string	url of the request
fetchOptions		{ [index: string]: RequestInit; }	fetch options for request containing body, headers etc.
fetchType		FetchType	method for which fetch is called.
addInBody	optional	boolean	Pass True if caller wants to add epoch in post body.
fetchReason	optional	string	fetch reason to add to the request.

Returns

Return type: Promise<IOdspResponse<ArrayBuffer>>

get

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

get(entry: IEntry): Promise<any>;

Parameters

Parameter	Type	Description
entry	IEntry

Returns

Return type: Promise<any>

put

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

put(entry: IEntry, value: any): Promise<void>;

Parameters

Parameter	Type	Description
entry	IEntry
value	any

Returns

Return type: Promise<void>

removeEntries

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

removeEntries(): Promise<void>;

Returns

Return type: Promise<void>

setEpoch

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

setEpoch(epoch: string, fromCache: boolean, fetchType: FetchTypeInternal): void;

Parameters

Parameter	Type	Description
epoch	string
fromCache	boolean
fetchType	FetchTypeInternal

validateEpoch

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

validateEpoch(epoch: string | undefined, fetchType: FetchType): Promise<void>;

Parameters

Parameter	Type	Description
epoch	string | undefined
fetchType	FetchType

Returns

Return type: Promise<void>

validateEpochFromResponse

This API is provided for existing users, but is not recommended for new users.

For more information about our API support guarantees, see here.

Signature

protected validateEpochFromResponse(epochFromResponse: string | undefined, fetchType: FetchTypeInternal, fromCache?: boolean): void;

Parameters

Parameter	Modifiers	Type	Description
epochFromResponse		string | undefined
fetchType		FetchTypeInternal
fromCache	optional	boolean