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管理 Azure Cosmos DB 中的冲突解决策略

项目
06/01/2023

适用范围： NoSQL

对于多区域写入，当多个客户端写入同一项时，可能会发生冲突。发生冲突时，可以通过使用不同的冲突解决策略来解决冲突。本文介绍如何管理冲突解决策略。

提示

冲突解决策略只能在容器创建时指定，并且不得在容器创建后修改。

创建“以最后写入者为准”冲突解决策略

这些示例介绍如何使用“以最后写入者为准”冲突解决策略设置一个容器。 “以最后写入者为准”的默认路径是时间戳字段或 _ts 属性。对于 API for NoSQL，也可以将其设置为数值类型的用户定义路径。如果发生冲突，最高值优先。如果路径未设置或无效，则它默认为 _ts。使用此策略解决的冲突不会显示在冲突源中。此策略可供所有 API 使用。

DocumentCollection lwwCollection = await createClient.CreateDocumentCollectionIfNotExistsAsync(
  UriFactory.CreateDatabaseUri(this.databaseName), new DocumentCollection
  {
      Id = this.lwwCollectionName,
      ConflictResolutionPolicy = new ConflictResolutionPolicy
      {
          Mode = ConflictResolutionMode.LastWriterWins,
          ConflictResolutionPath = "/myCustomId",
      },
  });

Container container = await createClient.GetDatabase(this.databaseName)
    .CreateContainerIfNotExistsAsync(new ContainerProperties(this.lwwCollectionName, "/partitionKey")
    {
        ConflictResolutionPolicy = new ConflictResolutionPolicy()
        {
            Mode = ConflictResolutionMode.LastWriterWins,
            ResolutionPath = "/myCustomId",
        }
    });

Java V4 SDK

异步
Sync

Java SDK V4 (Maven com.azure::azure-cosmos) 异步 API


ConflictResolutionPolicy policy = ConflictResolutionPolicy.createLastWriterWinsPolicy("/myCustomId");

CosmosContainerProperties containerProperties = new CosmosContainerProperties(container_id, partition_key);
containerProperties.setConflictResolutionPolicy(policy);
/* ...other container config... */
database.createContainerIfNotExists(containerProperties).block();

Java SDK V4 (Maven com.azure::azure-cosmos) 同步 API


ConflictResolutionPolicy policy = ConflictResolutionPolicy.createLastWriterWinsPolicy("/myCustomId");

CosmosContainerProperties containerProperties = new CosmosContainerProperties(container_id, partition_key);
containerProperties.setConflictResolutionPolicy(policy);
/* ...other container config... */
database.createContainerIfNotExists(containerProperties);

Java V2 SDK

Async Java V2 SDK
Sync Java V2 SDK

Async Java V2 SDK (Maven com.microsoft.azure::azure-cosmosdb)

DocumentCollection collection = new DocumentCollection();
collection.setId(id);
ConflictResolutionPolicy policy = ConflictResolutionPolicy.createLastWriterWinsPolicy("/myCustomId");
collection.setConflictResolutionPolicy(policy);
DocumentCollection createdCollection = client.createCollection(databaseUri, collection, null).toBlocking().value();

(Maven com.microsoft.azure::azure-documentdb)

DocumentCollection lwwCollection = new DocumentCollection();
lwwCollection.setId(this.lwwCollectionName);
ConflictResolutionPolicy lwwPolicy = ConflictResolutionPolicy.createLastWriterWinsPolicy("/myCustomId");
lwwCollection.setConflictResolutionPolicy(lwwPolicy);
DocumentCollection createdCollection = this.tryCreateDocumentCollection(createClient, database, lwwCollection);

Node.js/JavaScript/TypeScript SDK

const database = client.database(this.databaseName);
const { container: lwwContainer } = await database.containers.createIfNotExists(
  {
    id: this.lwwContainerName,
    conflictResolutionPolicy: {
      mode: "LastWriterWins",
      conflictResolutionPath: "/myCustomId"
    }
  }
);

Python SDK

database = client.get_database_client(database=database_id)
lww_conflict_resolution_policy = {'mode': 'LastWriterWins', 'conflictResolutionPath': '/regionId'}
lww_container = database.create_container(id=lww_container_id, partition_key=PartitionKey(path="/id"), 
    conflict_resolution_policy=lww_conflict_resolution_policy)

使用存储过程创建自定义冲突解决策略

这些示例介绍如何使用自定义冲突解决策略设置一个容器。此策略使用存储过程中的逻辑来解决冲突。如果指定了存储过程来解决冲突，则除非指定的存储过程中出现错误，否则冲突不会显示在冲突源中。

使用容器创建策略后，需要创建存储的过程。下面的 .NET SDK 示例显示了此工作流的示例。仅 API for NoSQL 支持此策略。

自定义冲突解决存储过程示例

必须使用下面显示的函数签名实现自定义冲突解决存储过程。函数名称不需要与使用容器注册存储过程时使用的名称匹配，但它确实可以简化命名。下面介绍了此存储过程必须实现的参数。

incomingItem：在生成冲突的提交中插入或更新的项。对于删除操作为 null。
existingItem：当前已提交的项。此值在更新中为非 null，对于插入或删除是 null。
isTombstone：指示 incomingItem 是否与以前删除的项冲突的布尔值。如果为 true，existingItem 也为 null。
conflictingItems：容器中所有项目的已提交版本的数组，与 ID 上的 incomingItem 或唯一索引属性冲突。

重要

与任何存储过程一样，自定义冲突解决过程可以访问具有相同分区键的任何数据，并可以执行任何插入、更新或删除操作来解决冲突。

此存储过程示例通过从 /myCustomId 路径中选择最小值来解决冲突。

function resolver(incomingItem, existingItem, isTombstone, conflictingItems) {
  var collection = getContext().getCollection();

  if (!incomingItem) {
      if (existingItem) {

          collection.deleteDocument(existingItem._self, {}, function (err, responseOptions) {
              if (err) throw err;
          });
      }
  } else if (isTombstone) {
      // delete always wins.
  } else {
      if (existingItem) {
          if (incomingItem.myCustomId > existingItem.myCustomId) {
              return; // existing item wins
          }
      }

      var i;
      for (i = 0; i < conflictingItems.length; i++) {
          if (incomingItem.myCustomId > conflictingItems[i].myCustomId) {
              return; // existing conflict item wins
          }
      }

      // incoming item wins - clear conflicts and replace existing with incoming.
      tryDelete(conflictingItems, incomingItem, existingItem);
  }

  function tryDelete(documents, incoming, existing) {
      if (documents.length > 0) {
          collection.deleteDocument(documents[0]._self, {}, function (err, responseOptions) {
              if (err) throw err;

              documents.shift();
              tryDelete(documents, incoming, existing);
          });
      } else if (existing) {
          collection.replaceDocument(existing._self, incoming,
              function (err, documentCreated) {
                  if (err) throw err;
              });
      } else {
          collection.createDocument(collection.getSelfLink(), incoming,
              function (err, documentCreated) {
                  if (err) throw err;
              });
      }
  }
}

.NET SDK

.NET SDK V2
.NET SDK V3

DocumentCollection udpCollection = await createClient.CreateDocumentCollectionIfNotExistsAsync(
  UriFactory.CreateDatabaseUri(this.databaseName), new DocumentCollection
  {
      Id = this.udpCollectionName,
      ConflictResolutionPolicy = new ConflictResolutionPolicy
      {
          Mode = ConflictResolutionMode.Custom,
          ConflictResolutionProcedure = string.Format("dbs/{0}/colls/{1}/sprocs/{2}", this.databaseName, this.udpCollectionName, "resolver"),
      },
  });

//Create the stored procedure
await clients[0].CreateStoredProcedureAsync(
UriFactory.CreateStoredProcedureUri(this.databaseName, this.udpCollectionName, "resolver"), new StoredProcedure
{
    Id = "resolver",
    Body = File.ReadAllText(@"resolver.js")
});

Container container = await createClient.GetDatabase(this.databaseName)
    .CreateContainerIfNotExistsAsync(new ContainerProperties(this.udpCollectionName, "/partitionKey")
    {
        ConflictResolutionPolicy = new ConflictResolutionPolicy()
        {
            Mode = ConflictResolutionMode.Custom,
            ResolutionProcedure = string.Format("dbs/{0}/colls/{1}/sprocs/{2}", this.databaseName, this.udpCollectionName, "resolver")
        }
    });

await container.Scripts.CreateStoredProcedureAsync(
    new StoredProcedureProperties("resolver", File.ReadAllText(@"resolver.js"))
);

Java V4 SDK

异步
Sync

Java SDK V4 (Maven com.azure::azure-cosmos) 异步 API


ConflictResolutionPolicy policy = ConflictResolutionPolicy.createCustomPolicy("resolver");

CosmosContainerProperties containerProperties = new CosmosContainerProperties(container_id, partition_key);
containerProperties.setConflictResolutionPolicy(policy);
/* ...other container config... */
database.createContainerIfNotExists(containerProperties).block();

Java SDK V4 (Maven com.azure::azure-cosmos) 同步 API


ConflictResolutionPolicy policy = ConflictResolutionPolicy.createCustomPolicy("resolver");

CosmosContainerProperties containerProperties = new CosmosContainerProperties(container_id, partition_key);
containerProperties.setConflictResolutionPolicy(policy);
/* ...other container config... */
database.createContainerIfNotExists(containerProperties);

Java V2 SDK

Async Java V2 SDK
Sync Java V2 SDK

Async Java V2 SDK (Maven com.microsoft.azure::azure-cosmosdb)

DocumentCollection collection = new DocumentCollection();
collection.setId(id);
ConflictResolutionPolicy policy = ConflictResolutionPolicy.createCustomPolicy("resolver");
collection.setConflictResolutionPolicy(policy);
DocumentCollection createdCollection = client.createCollection(databaseUri, collection, null).toBlocking().value();

(Maven com.microsoft.azure::azure-documentdb)

DocumentCollection udpCollection = new DocumentCollection();
udpCollection.setId(this.udpCollectionName);
ConflictResolutionPolicy udpPolicy = ConflictResolutionPolicy.createCustomPolicy(
        String.format("dbs/%s/colls/%s/sprocs/%s", this.databaseName, this.udpCollectionName, "resolver"));
udpCollection.setConflictResolutionPolicy(udpPolicy);
DocumentCollection createdCollection = this.tryCreateDocumentCollection(createClient, database, udpCollection);

创建容器后，必须创建 resolver 存储过程。

Node.js/JavaScript/TypeScript SDK

const database = client.database(this.databaseName);
const { container: udpContainer } = await database.containers.createIfNotExists(
  {
    id: this.udpContainerName,
    conflictResolutionPolicy: {
      mode: "Custom",
      conflictResolutionProcedure: `dbs/${this.databaseName}/colls/${
        this.udpContainerName
      }/sprocs/resolver`
    }
  }
);

创建容器后，必须创建 resolver 存储过程。

Python SDK

database = client.get_database_client(database=database_id)
udp_custom_resolution_policy = {'mode': 'Custom' }
udp_container = database.create_container(id=udp_container_id, partition_key=PartitionKey(path="/id"),
    conflict_resolution_policy=udp_custom_resolution_policy)

创建容器后，必须创建 resolver 存储过程。

创建自定义冲突解决策略

这些示例介绍如何使用自定义冲突解决策略设置一个容器。使用此实现，每个冲突都将显示在冲突源中。由你单独处理冲突源中的冲突。

.NET SDK

.NET SDK V2
.NET SDK V3

DocumentCollection manualCollection = await createClient.CreateDocumentCollectionIfNotExistsAsync(
  UriFactory.CreateDatabaseUri(this.databaseName), new DocumentCollection
  {
      Id = this.manualCollectionName,
      ConflictResolutionPolicy = new ConflictResolutionPolicy
      {
          Mode = ConflictResolutionMode.Custom,
      },
  });

Container container = await createClient.GetDatabase(this.databaseName)
    .CreateContainerIfNotExistsAsync(new ContainerProperties(this.manualCollectionName, "/partitionKey")
    {
        ConflictResolutionPolicy = new ConflictResolutionPolicy()
        {
            Mode = ConflictResolutionMode.Custom
        }
    });

Java V4 SDK

异步
Sync

Java SDK V4 (Maven com.azure::azure-cosmos) 异步 API


ConflictResolutionPolicy policy = ConflictResolutionPolicy.createCustomPolicy();

CosmosContainerProperties containerProperties = new CosmosContainerProperties(container_id, partition_key);
containerProperties.setConflictResolutionPolicy(policy);
/* ...other container config... */
database.createContainerIfNotExists(containerProperties).block();

Java SDK V4 (Maven com.azure::azure-cosmos) 同步 API


ConflictResolutionPolicy policy = ConflictResolutionPolicy.createCustomPolicy();

CosmosContainerProperties containerProperties = new CosmosContainerProperties(container_id, partition_key);
containerProperties.setConflictResolutionPolicy(policy);
/* ...other container config... */
database.createContainerIfNotExists(containerProperties);

Java V2 SDK

Async Java V2 SDK
Sync Java V2 SDK

Async Java V2 SDK (Maven com.microsoft.azure::azure-cosmosdb)

DocumentCollection collection = new DocumentCollection();
collection.setId(id);
ConflictResolutionPolicy policy = ConflictResolutionPolicy.createCustomPolicy();
collection.setConflictResolutionPolicy(policy);
DocumentCollection createdCollection = client.createCollection(databaseUri, collection, null).toBlocking().value();

(Maven com.microsoft.azure::azure-documentdb)

DocumentCollection manualCollection = new DocumentCollection();
manualCollection.setId(this.manualCollectionName);
ConflictResolutionPolicy customPolicy = ConflictResolutionPolicy.createCustomPolicy(null);
manualCollection.setConflictResolutionPolicy(customPolicy);
DocumentCollection createdCollection = client.createCollection(database.getSelfLink(), collection, null).getResource();

Node.js/JavaScript/TypeScript SDK

const database = client.database(this.databaseName);
const {
  container: manualContainer
} = await database.containers.createIfNotExists({
  id: this.manualContainerName,
  conflictResolutionPolicy: {
    mode: "Custom"
  }
});

Python SDK

database = client.get_database_client(database=database_id)
manual_resolution_policy = {'mode': 'Custom'}
manual_container = database.create_container(id=manual_container_id, partition_key=PartitionKey(path="/id"), 
    conflict_resolution_policy=manual_resolution_policy)

从冲突源读取

这些示例介绍如何从容器的冲突源读取。冲突可能仅出于以下几个原因显示在冲突源中：

冲突未自动解决
冲突导致指定存储过程出错
冲突解决策略设置为“自定义”，并且不指定用于处理冲突的存储过程

.NET SDK

.NET SDK V2
.NET SDK V3

FeedResponse<Conflict> conflicts = await delClient.ReadConflictFeedAsync(this.collectionUri);

FeedIterator<ConflictProperties> conflictFeed = container.Conflicts.GetConflictQueryIterator();
while (conflictFeed.HasMoreResults)
{
    FeedResponse<ConflictProperties> conflicts = await conflictFeed.ReadNextAsync();
    foreach (ConflictProperties conflict in conflicts)
    {
        // Read the conflicted content
        MyClass intendedChanges = container.Conflicts.ReadConflictContent<MyClass>(conflict);
        MyClass currentState = await container.Conflicts.ReadCurrentAsync<MyClass>(conflict, new PartitionKey(intendedChanges.MyPartitionKey));

        // Do manual merge among documents
        await container.ReplaceItemAsync<MyClass>(intendedChanges, intendedChanges.Id, new PartitionKey(intendedChanges.MyPartitionKey));

        // Delete the conflict
        await container.Conflicts.DeleteAsync(conflict, new PartitionKey(intendedChanges.MyPartitionKey));
    }
}

Java SDK

Java V4 SDK (Maven com.azure::azure-cosmos)

int requestPageSize = 3;
CosmosQueryRequestOptions options = new CosmosQueryRequestOptions();

CosmosPagedFlux<CosmosConflictProperties> conflictReadFeedFlux = container.readAllConflicts(options);

conflictReadFeedFlux.byPage(requestPageSize).toIterable().forEach(page -> {

    int expectedNumberOfConflicts = 0;
    int numberOfResults = 0;
    Iterator<CosmosConflictProperties> pageIt = page.getElements().iterator();

    while (pageIt.hasNext()) {
        CosmosConflictProperties conflictProperties = pageIt.next();

        // Read the conflict and committed item
        CosmosAsyncConflict conflict = container.getConflict(conflictProperties.getId());
        CosmosConflictResponse response = conflict.read(new CosmosConflictRequestOptions()).block();

        // response.
    }
});

Async Java V2 SDK (Maven com.microsoft.azure::azure-cosmosdb)

FeedResponse<Conflict> response = client.readConflicts(this.manualCollectionUri, null)
                    .first().toBlocking().single();
for (Conflict conflict : response.getResults()) {
    /* Do something with conflict */
}

(Maven com.microsoft.azure::azure-documentdb)

Iterator<Conflict> conflictsIterator = client.readConflicts(this.collectionLink, null).getQueryIterator();
while (conflictsIterator.hasNext()) {
    Conflict conflict = conflictsIterator.next();
    /* Do something with conflict */
}

Node.js/JavaScript/TypeScript SDK

const container = client
  .database(this.databaseName)
  .container(this.lwwContainerName);

const { result: conflicts } = await container.conflicts.readAll().toArray();

Python

conflicts_iterator = iter(container.list_conflicts())
conflict = next(conflicts_iterator, None)
while conflict:
    # Do something with conflict
    conflict = next(conflicts_iterator, None)

后续步骤

了解以下 Azure Cosmos DB 概念：

管理 Azure Cosmos DB 中的冲突解决策略

创建“以最后写入者为准”冲突解决策略

.NET SDK

Java V4 SDK

Java V2 SDK

Node.js/JavaScript/TypeScript SDK

Python SDK

使用存储过程创建自定义冲突解决策略

自定义冲突解决存储过程示例

.NET SDK

Java V4 SDK

Java V2 SDK

Node.js/JavaScript/TypeScript SDK

Python SDK

创建自定义冲突解决策略

.NET SDK

Java V4 SDK

Java V2 SDK

Node.js/JavaScript/TypeScript SDK

Python SDK

从冲突源读取

.NET SDK

Java SDK

Node.js/JavaScript/TypeScript SDK

Python

后续步骤

其他资源