1# httpr, a Record/Replay Proxy
2
3httpr is an HTTP proxy that records and replays traffic. It is designed
4specifically for Google APIs that use HTTP exclusively. These include the Google
5Cloud Storage and BigQuery clients, as well as the clients in the
6`github.com/google/google-api-*-client` repos.
7
8If you are writing Go code, you should use the `cloud.google.com/go/httpreplay` package, which
9is a simpler way to use the proxy.
10
11## Using a Record/Replay Proxy
12
13A record/replay proxy lets you run an "integration" test that accesses a
14backend like a Google service and record the interaction. Subsequent runs of the
15test can replay the server's responses without actually contacting the server,
16turning the integration test into a fast and inexpensive unit test.
17
18## Usage
19
20First, obtain the `httpr` binary. If you have the Go toolchain, you can run `go
21get -u cloud.google.com/go/httpreplay/cmd/httpr`. Otherwise, precompiled
22binaries for various architectures and operating systems are available from [the
23releases page](https://github.com/googleapis/google-cloud-go/releases).
24
25### Recording
26
271. Start `httpr` in record mode by passing it the `-record` flag with a filename:
28 ```
29 httpr -record myclient.replay
30 ```
31 By default, `httpr` will run on port 8080, and open a control port on 8181.
32 You can change these with the `-port` and `-control-port` flags.
33 You will want to run `httpr` in the background or in another window.
341. In order for `httpr` to record HTTPS traffic, your client must trust it. It
35 does so by installing a CA certificate created by `httpr` during the
36 recording session. To obtain the certificate in PEM form, GET the URL
37 `http://localhost:8181/authority.cer`. (If you changed the control port, use
38 it in place of 8181.) Consult your language to determine
39 how to install the certificate. Note that the certificate is different for each run
40 of `httpr`.
411. Arrange for your test program to use `httpr` as a proxy. This may be as
42 simple as setting the `HTTPS_PROXY` environment variable.
431. Run your test program, using whatever authentication for your Google API
44 clients that you wish.
451. Send `httpr` a SIGINT signal (`kill -2`). `httpr` will write
46 the replay file, then exit.
47
48### Replaying
49
501. Start `httpr` in replay mode, in the background or another window:
51 ```
52 httpr -replay myclient.replay
53 ```
541. Install the CA certificate as described above.
551. Have your test program treat `httpr` as a proxy, as described above.
561. Run your test program. Your Google API clients should use no authentication.
57
58## Tips
59
60You must remove all randomness from your interaction while recording,
61so that the replay is fully deterministic.
62
63Note that BigQuery clients choose random values for job IDs and insert ID if you
64do not supply them. Either supply your own, or seed the client's random number
65generator if possible.
66
67## Examples
68
69Examples of running `httpr` can be found in `examples` under this file's directory.
70
71
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