| // Copyright 2015 The Vanadium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package nosql |
| |
| import ( |
| "time" |
| "v.io/v23/security/access" |
| ) |
| |
| // BatchOptions configures a batch. |
| // TODO(sadovsky): Add more options, e.g. to configure isolation, timeouts, |
| // whether to track the read set and/or write set, etc. |
| // TODO(sadovsky): Maybe add a DefaultBatchOptions() function that initializes |
| // BatchOptions with our desired defaults. Clients would be encouraged to |
| // initialize their BatchOptions object using that function and then modify it |
| // to their liking. |
| type BatchOptions struct { |
| // Arbitrary string, typically used to describe the intent behind a batch. |
| // Hints are surfaced to clients during conflict resolution. |
| // TODO(sadovsky): Use "any" here? |
| Hint string |
| |
| // ReadOnly specifies whether the batch should allow writes. |
| // If ReadOnly is set to true, Abort() should be used to release any resources |
| // associated with this batch (though it is not strictly required), and |
| // Commit() will always fail. |
| ReadOnly bool |
| } |
| |
| // PrefixPermissions represents a pair of (prefix, perms). |
| type PrefixPermissions struct { |
| Prefix string |
| Perms access.Permissions |
| } |
| |
| // KeyValue is a key-value pair. |
| type KeyValue struct { |
| Key string |
| Value []byte |
| } |
| |
| // TableRow encapsulates the table name and row key or row prefix. |
| type TableRow struct { |
| TableName string |
| Row string |
| } |
| |
| // SyncgroupSpec contains the specification for a syncgroup. |
| type SyncgroupSpec struct { |
| // Human-readable description of this syncgroup. |
| Description string |
| |
| // Permissions governing access to this syncgroup. |
| Perms access.Permissions |
| |
| // Data (tableName-rowPrefix pairs) covered by this syncgroup. |
| Prefixes []TableRow |
| |
| // Mount tables at which to advertise this syncgroup, for rendezvous purposes. |
| // (Note that in addition to these mount tables, Syncbase also uses |
| // network-neighborhood-based discovery for rendezvous.) |
| // We expect most clients to specify a single mount table, but we accept an |
| // array of mount tables to permit the mount table to be changed over time |
| // without disruption. |
| // TODO(hpucha): Figure out a convention for advertising syncgroups in the |
| // mount table. |
| MountTables []string |
| |
| // Specifies the privacy of this syncgroup. More specifically, specifies |
| // whether blobs in this syncgroup can be served to clients presenting |
| // blobrefs obtained from other syncgroups. |
| IsPrivate bool |
| } |
| |
| // SyncgroupMemberInfo contains per-member metadata. |
| type SyncgroupMemberInfo struct { |
| SyncPriority byte |
| IsServer bool // This member should be given blob ownership preferentially. |
| } |
| |
| // ResolverType defines the possible conflict resolution policies. |
| // A Conflict is defined as presence of two independent sets of updates |
| // originating from the same version of an object. Syncbase |
| // uses version vectors to determine sequence of changes to a given row. Hence |
| // if device A updates a row with key "foo" from version V3 to V4, then syncs |
| // with device B which further updates the same row from version V4 to V5 and |
| // then V5 is synced back to device A, device A will see V5 as a forward |
| // progression of "foo" and not a conflict with V3 of "foo". But in the |
| // meantime if device A had already updated "foo" again from version V4 to |
| // version V6 then there is a conflict between V5 and V6 with V4 being the |
| // common ancestor. |
| type ResolverType enum { |
| // LastWins is a policy which resolves a conflict between two writes by |
| // choosing the version which has the greatest timestamp. |
| // For example, if device A created V6 at time T1 and device B created V5 at |
| // time T2 where timestamp T2 > T1, then V5 will be accepted as the |
| // resolution of the conflict. |
| // Syncbase maintains an internal clock for creating write timestamps. This |
| // clock is kept up to date via regular synchronization with NTP and with |
| // other syncbases. As long as the syncbase has access to an NTP server |
| // directly or indirectly via another syncbase, the internal clock will |
| // track NTP time and correct any skews suffered by the local system clock. |
| LastWins |
| |
| // AppResolves is a policy which allows an App to handle resolution of a |
| // conflict on its own. In order to receive the conflicts, the app needs to |
| // register a conflict resolution stream using |
| // Database.StartConflictResolver(). |
| AppResolves |
| |
| // Defer is a policy that allows an instance of an App to outsource its |
| // conflict resolution to some other instance, typically a more capable |
| // instance (in terms of resources, knowledge or permissions) such as a |
| // cloud or admin instance. |
| Defer |
| } |
| |
| // ConflictInfo contains information to fully specify a conflict |
| // for a key, providing the (local, remote, ancestor) tuple. |
| // A key under conflict can be a part of a batch in local, remote or both |
| // updates. Since the batches can have more than one key, all ConflictInfos |
| // for the keys within the batches are grouped together into a single conflict |
| // batch and sent as a stream with the Continued field representing conflict |
| // batch boundaries. |
| type ConflictInfo struct { |
| // Data is a unit chunk of ConflictInfo which can be sent over the conflict |
| // stream. |
| Data ConflictData |
| |
| // Continued represents whether the batch of ConflictInfos has ended. |
| Continued bool |
| } |
| |
| // ConflictData represents a unit of conflict data sent over the stream. It |
| // can either contain information about a Batch or about an operation done |
| // on a row. |
| type ConflictData union { |
| Batch BatchInfo |
| Row RowInfo |
| } |
| |
| type BatchInfo struct { |
| // Id is an identifier for a batch contained in a conflict. It is |
| // unique only in the context of a given conflict. Its purpose is solely to |
| // group one or more RowInfo objects together to represent a batch that |
| // was committed by the client. |
| Id uint64 |
| |
| // Hint is the hint provided by the client when this batch was committed. |
| Hint string |
| |
| // Source states where the batch comes from. |
| Source BatchSource |
| } |
| |
| // BatchSource represents where the batch was committed. |
| type BatchSource enum { |
| // Local represents that the batch was committed on local syncbase. |
| Local |
| |
| // Remote represents that the batch was committed on remote syncbase. |
| Remote |
| } |
| |
| // RowInfo contains a single operation performed on a row (in case of read or |
| // write) or a range or rows (in case of scan) along with a mapping to each |
| // of the batches that this operation belongs to. |
| // For example, if Row1 was updated on local syncbase conflicting with a write |
| // on remote syncbase as part of two separate batches, then it will be |
| // represented by a single RowInfo with Write Operation containing the |
| // respective local and remote values along with the batch id for both batches |
| // stored in the BatchIds field. |
| type RowInfo struct { |
| // Op is a specific operation represented by RowInfo |
| Op Operation |
| // BatchIds contains ids of all batches that this RowInfo is a part of. |
| BatchIds []uint64 |
| } |
| |
| // Operation represents a specific operation on a row or a set of rows that is |
| // a part of the conflict. |
| type Operation union { |
| // Read represents a read operation performed on a specific row. For a given |
| // row key there can only be at max one Read operation within a conflict. |
| Read RowOp |
| |
| // Write represents a write operation performed on a specific row. For a |
| // given row key there can only be at max one Write operation within a |
| // conflict. |
| Write RowOp |
| |
| // Scan represents a scan operation performed over a specific range of keys. |
| // For a given key range there can be at max one ScanOp within the Conflict. |
| Scan ScanOp |
| } |
| |
| // RowOp represents a read or write operation on a row corresponding to the |
| // given key. |
| type RowOp struct { |
| // The key under conflict. |
| Key string |
| |
| // LocalValue contains the value read or written by local syncbase or nil. |
| LocalValue ?Value |
| |
| // RemoteValue contains the value read or written by remote syncbase or nil. |
| RemoteValue ?Value |
| |
| // AncestorValue contains the value for the key which is the lowest common |
| // ancestor of the two values represented by LocalValue and RemoteValue or |
| // nil if no ancestor exists or if the operation was read. |
| AncestorValue ?Value |
| } |
| |
| // ScanOp provides details of a scan operation. |
| type ScanOp struct { |
| // Start contains the starting key for a range scan. |
| Start string |
| |
| // Limit contains the end key for a range scan. |
| Limit string |
| } |
| |
| // Value contains the encoded bytes for a row's value stored in syncbase. |
| type Value struct { |
| // State provides information about whether the field Bytes is empty or |
| // not and if it is empty then why. |
| State ValueState |
| |
| // VOM encoded bytes for a row's value or nil if the row was deleted. |
| Bytes []byte |
| |
| // Write timestamp for this value |
| WriteTs time.Time |
| } |
| |
| // ValueState represents the state for Value object providing information about |
| // whether the Value object's Byte field is empty or not. |
| type ValueState enum { |
| // Exists means that the value can be obtained from Bytes field. |
| Exists |
| |
| // NoExists means that the value is known not to exist and Bytes field is |
| // empty. |
| NoExists |
| |
| // Deleted means that this value was deleted and the Bytes field is empty. |
| Deleted |
| |
| // Unknown means that the Bytes field is empty but there may or may not be |
| // an associated value. This can happen if a local row, which does |
| // not have a conflict, was pulled into a conflict due to a batch. In such |
| // a case we don't have the corresponding value for remote and the |
| // RemoteValue will have "Unknown" state and empty Bytes field. |
| Unknown |
| } |
| |
| // ValueSelection represents the value that was selected as the final resolution |
| // for a conflict. |
| type ValueSelection enum { |
| // Local should be used if local value is picked as the final result. |
| Local |
| |
| // Remote should be used if remote value is picked as the final result. |
| Remote |
| |
| // Other should be used if a new value different from local and remote is |
| // used as the final result. |
| Other |
| } |
| |
| // ResolutionInfo contains the application’s reply to a conflict for a key, |
| // providing the resolution value. The resolution may be over a group of keys |
| // in which case the application must send a stream of ResolutionInfos with |
| // the Continued field for the last ResolutionInfo representing the end of the |
| // batch with a value false. ResolutionInfos sent as part of a batch will be |
| // committed as a batch. If the commit fails, the Conflict will be re-sent. |
| type ResolutionInfo struct { |
| // Key is the key under conflict. |
| Key string |
| |
| // Selection represents the value that was selected as resolution. |
| Selection ValueSelection |
| |
| // Result is the resolved value for the key. This field should be used only |
| // if value of Selection field is 'Other'. If the result of a resolution is |
| // delete for this key then add Value with nil Bytes. |
| Result ?Value |
| |
| // Continued represents whether the batch of ResolutionInfos has ended. |
| Continued bool |
| } |
| |
| // SchemaMetadata maintains metadata related to the schema of a given database. |
| // There is one SchemaMetadata per database. |
| type SchemaMetadata struct { |
| // Non negative Schema version number. Should be increased with every schema change |
| // (e.g. adding fields to structs) that cannot be handled by previous |
| // versions of the app. |
| Version int32 |
| Policy CrPolicy |
| } |
| |
| // For a given row with a conflict, all rules are matched against the row. |
| // If no rules match the row, we default to "LastWins". If multiple |
| // rules match the row, ties are broken as follows: |
| // 1. If one match has a longer prefix than the other, take that one. |
| // 2. Else, if only one match specifies a type, take that one. |
| // 3. Else, the two matches are identical; take the last one in the Rules array. |
| type CrPolicy struct { |
| Rules []CrRule |
| } |
| |
| // CrRule provides a filter and the type of resolution to perform for a row |
| // under conflict that passes the filter. |
| type CrRule struct { |
| // TableName is the name of the table that this rule applies to. |
| TableName string |
| |
| // KeyPrefix represents the set of keys within the given table for which |
| // this policy applies. TableName must not be empty if this field is set. |
| KeyPrefix string |
| |
| // Type includes the full package path for the value type for which this |
| // policy applies. |
| Type string |
| |
| // Policy for resolving conflict. |
| Resolver ResolverType |
| } |
| |
| // BlobRef is a reference to a blob. |
| type BlobRef string |
| |
| const ( |
| NullBlobRef = BlobRef("") |
| ) |
| |
| // BlobFetchState represents the state transitions of a blob fetch. |
| type BlobFetchState enum { |
| Pending // Fetch request is queued. |
| Locating // Blob discovery is in progress to find a source for the blob. |
| Fetching // Blob transfer is in progress. |
| Done // Blob is locally cached. |
| } |
| |
| // BlobFetchStatus describes the progress of an asynchronous blob fetch. |
| type BlobFetchStatus struct { |
| State BlobFetchState // State of the blob fetch request. |
| Received int64 // Total number of bytes received. |
| Total int64 // Blob size. |
| } |
| |
| // StoreChange is the new value for a watched entity. |
| // TODO(rogulenko): Consider adding the Shell state. |
| type StoreChange struct { |
| // Value is the new value for the row if the Change state equals to Exists, |
| // otherwise the Value is nil. |
| Value []byte |
| |
| // FromSync indicates whether the change came from sync. If FromSync is |
| // false, then the change originated from the local device. |
| FromSync bool |
| } |