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)	Alpha	Constructs a new instance of the EpochTracker class

Properties

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

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