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107 lines
3.9 KiB
Go
107 lines
3.9 KiB
Go
// Copyright 2017 Google Inc. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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/*
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Package rpcreplay supports the capture and replay of gRPC calls. Its main goal is
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to improve testing. Once one captures the calls of a test that runs against a real
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service, one has an "automatic mock" that can be replayed against the same test,
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yielding a unit test that is fast and flake-free.
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Recording
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To record a sequence of gRPC calls to a file, create a Recorder and pass its
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DialOptions to grpc.Dial:
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rec, err := rpcreplay.NewRecorder("service.replay", nil)
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if err != nil { ... }
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defer func() {
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if err := rec.Close(); err != nil { ... }
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}()
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conn, err := grpc.Dial(serverAddress, rec.DialOptions()...)
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It's essential to close the Recorder when the interaction is finished.
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There is also a NewRecorderWriter function for capturing to an arbitrary
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io.Writer.
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Replaying
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Replaying a captured file looks almost identical: create a Replayer and use
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its DialOptions. (Since we're reading the file and not writing it, we don't
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have to be as careful about the error returned from Close).
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rep, err := rpcreplay.NewReplayer("service.replay")
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if err != nil { ... }
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defer rep.Close()
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conn, err := grpc.Dial(serverAddress, rep.DialOptions()...)
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Initial State
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A test might use random or time-sensitive values, for instance to create unique
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resources for isolation from other tests. The test therefore has initial values --
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the current time, a random seed -- that differ from run to run. You must record this
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initial state and re-establish it on replay.
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To record the initial state, serialize it into a []byte and pass it as the second
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argument to NewRecorder:
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timeNow := time.Now()
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b, err := timeNow.MarshalBinary()
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if err != nil { ... }
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rec, err := rpcreplay.NewRecorder("service.replay", b)
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On replay, get the bytes from Replayer.Initial:
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rep, err := rpcreplay.NewReplayer("service.replay")
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if err != nil { ... }
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defer rep.Close()
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err = timeNow.UnmarshalBinary(rep.Initial())
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if err != nil { ... }
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Nondeterminism
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A nondeterministic program may invoke RPCs in a different order each time
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it is run. The order in which RPCs are called during recording may differ
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from the order during replay.
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The replayer matches incoming to recorded requests by method name and request
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contents, so nondeterminism is only a concern for identical requests that result
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in different responses. A nondeterministic program whose behavior differs
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depending on the order of such RPCs probably has a race condition: since both the
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recorded sequence of RPCs and the sequence during replay are valid orderings, the
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program should behave the same under both.
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Other Replayer Differences
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Besides the differences in replay mentioned above, other differences may cause issues
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for some programs. We list them here.
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The Replayer delivers a response to an RPC immediately, without waiting for other
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incoming RPCs. This can violate causality. For example, in a Pub/Sub program where
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one goroutine publishes and another subscribes, during replay the Subscribe call may
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finish before the Publish call begins.
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For streaming RPCs, the Replayer delivers the result of Send and Recv calls in
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the order they were recorded. No attempt is made to match message contents.
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At present, this package does not record or replay stream headers and trailers, or
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the result of the CloseSend method.
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*/
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package rpcreplay // import "cloud.google.com/go/internal/rpcreplay"
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