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Initial import of the go-grpc-http1 client/server proxy code.
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‎.gitignore

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/.idea/
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/deps

‎LICENSE

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Apache License
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Version 2.0, January 2004
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http://www.apache.org/licenses/
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‎Makefile

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# Copyright (c) 2020 StackRox Inc.
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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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export GO111MODULE := on
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export GOBIN := $(CURDIR)/.gobin
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export PATH := $(GOBIN):$(PATH)
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TESTFLAGS := -p 4 -race
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### STYLE
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.PHONY: style
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style: imports lint vet
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.PHONY: imports
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imports: dev deps
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@echo "+ $@"
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@git ls-files -- '*.go' | xargs goimports -l -w
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.PHONY: lint
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lint: dev deps
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@echo "+ $@"
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@echo $(sort $(dir $(shell git ls-files -- '*.go'))) | xargs -n 1 golint
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.PHONY: vet
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vet: dev deps
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@echo "+ $@"
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@go vet ./...
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.PHONY: dev
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dev:
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@echo "+ $@"
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@go install golang.org/x/tools/cmd/goimports
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@go install golang.org/x/lint/golint
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@go install github.com/mauricelam/genny
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deps: go.mod go.sum
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@echo "+ $@"
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@go mod tidy
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@$(MAKE) download-deps
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@touch deps
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.PHONY: download-deps
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download-deps:
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@echo "+ $@"
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@go mod download
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### SOURCE GENERATION
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.PHONY: generate-go-srcs
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generate-go-srcs: dev
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@echo "+ $@"
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@go generate ./...
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### UNIT TESTS
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.PHONY: unit-tests
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unit-tests: deps
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@echo "+ $@"
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@go test $(TESTFLAGS) ./...

‎README.md

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grpc-http1: A gRPC via HTTP/1 Enabling Library for Go
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====================================================
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This library enables using a subset of the functionality of a gRPC server even if it is exposed behind
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a reverse proxy that does not support HTTP/2, or only supports it for clients (such as Amazon's ALB).
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This is accomplished via adaptive downgrading to the gRPC-web response format. This library allows
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instrumenting both clients and servers to that extent.
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For a high-level overview, see [this Medium post](https://medium.com/stackrox-engineering/how-to-expose-grpc-services-behind-almost-any-load-balancer-e9ebf8e6d12a).
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Connection Compatibility Overview
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---------------------------------
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The following table shows what can be expected when a client/server instrumented with the capability
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offered by this library compared to an unmodified gRPC client/server, both when accessing it directly and
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when accessing it via a reverse proxy not supporting HTTP/2.
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<table>
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<tr><th></th><th colspan="2">Plain Old gRPC Server</th><th colspan="2">HTTP/1 Downgrading gRPC Server</th></tr>
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<tr><th></th><th>direct</th><th>behind reverse proxy</th><th>direct</th><th>behind reverse proxy</th></tr>
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<tr><td>Plain Old gRPC Client</td><td>:white_check_mark:</td><td>:x:</td><td>:white_check_mark:</td><td>:x:</td></tr>
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<tr><td>HTTP/1 downgrading gRPC client</td><td>:white_check_mark:</td><td>:x:</td><td>:white_check_mark:</td><td>(:white_check_mark:)</td></tr>
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</table>
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The (:white_check_mark:) in the bottom right cell indicates that a subset of gRPC calls will be possible, but not
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all. These include all calls that do not rely on client-side streaming (i.e., all unary and server-streaming calls).
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Support for client-side streaming calls is active work in progress.
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As you can see, it is possible to instrument the client or the server only without any (functional) regressions - there
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may be a small but fairly negligible performance penalty. This means rolling this feature out to your clients and
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servers does not need to happen in a strictly synchronous fashion. However, you will only be able to work with a server
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behind an HTTP/2-incompatible reverse proxy if both the client and the server have been instrumented via
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this library.
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Usage
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-------------
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This library has the canonical import path `golang.stackrox.io/grpc-http1`. It fully supports Go modules
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and requires Go version 1.13+ to be built and used. To add it as a dependency in your current project,
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run `go get golang.stackrox.io/grpc-http1`.
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### Server-side
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For using this library on the server-side, you'll need to bypass the regular `(*grpc.Server).Serve` method
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and instead use the `ServeHTTP` method of the `*grpc.Server` object -- it is experimental, but we found it
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to be fairly stable and reliable.
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The only exported function in the `golang.grpc.io/grpc-http1/server` package is `CreateDowngradingHandler`,
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which returns a `http.Handler` that can be served by a Go HTTP server. It is crucial that this server is
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configured to support HTTP/2; otherwise, your clients using the vanilla gRPC client will no longer be able
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to talk to it. You can find an example of how to do so in the `_integration-tests/` directory.
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### Client-Side
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For connecting to a gRPC server via a client-side proxy, use the `ConnectViaProxy` function exported from the
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`golang.grpc.io/grpc-http1/client` package. This function has the following signature:
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```go
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func ConnectViaProxy(ctx context.Context, endpoint string, tlsClientConf *tls.Config, opts ...ConnectOption) (*grpc.ClientConn, error)
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```
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The first two arguments are the same as for `grpc.DialContext`. The third argument specifies the TLS client
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config to be used for connecting to the target address. Note that this is different from the usual gRPC API,
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which specifies client TLS config via the `grpc.WithTransportCredentials`. For a plaintext (unencrypted)
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connection to the server, pass a `nil` TLS config; however, this does *not* free you from passing the
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`grpc.WithInsecure()` gRPC dial option.
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The last (variadic) parameter specifies options that modify the dialing behavior. You can pass any gRPC dial
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options via `client.DialOpts(...)`. Another important option is `client.ForceHTTP2()`, which needs to be used for
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a plaintext connection to a server that is *not* HTTP/1.1 capable (e.g., the vanilla gRPC server). Again, check out the
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code in the `_integration-tests` directory.

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