| 摘要 |
Techniques are provided for executing an operation in which a client invokes a replicated object. According to one technique, a primary replica of a replicated object receives a first request from a client, wherein the first request includes a request identifier. Rather than immediately attempting to process the request, the primary replica determines whether a record exists that corresponds to the request identifier. If a record exists that corresponds to the request identifier, then the primary replica responds to the first request with a reply associated with the record. If no record exis ts that corresponds to the request identifier, then the primary replica perform s the steps of: starting a transaction; as part of the transaction, processing the request; as part of the transaction, storing a record associated with th e request identifier and a reply to the request; committing the transaction; a nd delivering the reply to the client. The client may itself be a replicated object. If the client is nondeterministic, then the transaction initiated by the primary replica may be a nested transaction relative to a transaction executed by the client, or be executed as part of the same transaction as th e client. If the transaction executed by the primary replica is executed as pa rt of the same transaction as the client, then a savepoint may be established before the primary replica processes the request, so that a failure will not necessarily require all processing performed by the client to be rolled back .
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