Add are you alive example

examples/are-you-alive/.gitignore

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+vendor
+are-you-alive

examples/are-you-alive/Makefile

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+# We are using the public "planetscale-vitess" registry for this
+NAME   := "us.gcr.io/planetscale-vitess/are-you-alive"
+TAG    := $$(git log -1 --pretty=%H)
+IMG    := ${NAME}:${TAG}
+LATEST := ${NAME}:latest
+
+.PHONY: build push
+
+build:
+	@docker build -f build/release/Dockerfile -t ${IMG} .
+	@docker tag ${IMG} ${LATEST}
+
+push:
+	@docker push ${IMG}
+	@docker push ${LATEST}

examples/are-you-alive/README.md

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+# Are You Alive?
+
+What does it mean to be alive?
+
+Well we don't know what it means for you, but we know what it means for our
+Cloud Database!
+
+This project contains a simulated client application that can be used to measure
+the health of a Vitess cluster over time.
+
+## Design
+
+For now, there is a specific database schema and vschema that you must apply to
+the database that you are using for this test.
+
+This client application:
+
+1. Hammers the database with random data (not a load test though).
+1. Measures all the important things:
+   - Client connection errors
+   - Write latency
+   - Read latency from masters
+   - Read latency from replicas
+   - Write errors
+   - Read errors on masters
+   - Write errors on replicas
+   - Errors in other operations on masters and replicas (e.g. COUNT)
+   - Latency on other operations on masters and replicas (e.g. COUNT)
+   - Data loss (by writing predictable data and testing for that)
+1. Reports all these metrics to Prometheus.
+
+That's it!  Keep it as simple and generic as possible, and someday our customers
+can use this to test their clusters too!
+
+## Usage
+
+First, [initialize your database with the correct schemas](schemas/README.md).
+
+Run `are-you-alive --help` for usage.  You can us the command line flags to
+control the dataset size, whether to target reads at masters and replicas, your
+mysql connection string, and the rate at which to send requests.
+
+Example:
+
+```
+./are-you-alive --mysql_connection_string <mysql_connection_string>
+```
+
+Where `<mysql_connection_string>` points to the database you are trying to test,
+and everything else will be set to defaults.
+
+## Building
+
+```
+go build vitess.io/vitess/examples/are-you-alive/cmd/are-you-alive
+```
+
+## Testing
+
+First, [install docker compose](https://docs.docker.com/compose/install/) and
+make sure it's working.  Then run:
+
+```
+docker-compose build
+docker-compose up
+```
+
+This will create a local mysqld and a local prometheus to scrape the app.  It
+will also start the app with the `--initialize` flag which tells it to
+automatically create the test database.  You might have to run this twice to
+give mysql a chance to do its first initialization.
+
+After you run docker compose, navigate to `http://localhost:9090` to see
+Prometheus and `http://localhost:8080/metrics` to see the raw metrics being
+exported.
+
+## Push to Registry
+
+```
+make build
+make push
+```

examples/are-you-alive/build/dev/Dockerfile

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+# Use a [multi stage
+# build](https://docs.docker.com/develop/develop-images/multistage-build/) to
+# build [reflex](https://github.com/cespare/reflex), a tool that will allow us
+# to automatically rerun the project when any files change.
+FROM golang:1.12.5 AS build
+# Build reflex as a static binary (CGO_ENABLED=0) so we can run it in our final
+# container.
+RUN CGO_ENABLED=0 go get -v github.com/cespare/reflex
+
+FROM golang:1.12.5-alpine AS runtime
+COPY --from=build /go/bin/reflex /go/bin/reflex
+COPY reflex.conf /
+ENTRYPOINT ["/go/bin/reflex", "-c", "/reflex.conf"]

examples/are-you-alive/build/dev/reflex.conf

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+# Rerun "go run" every time a ".go" file changes.
+-r '(\.go$)' -s -- go run vitess.io/vitess/examples/are-you-alive/cmd/are-you-alive --initialize

examples/are-you-alive/build/release/Dockerfile

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+FROM golang:1.12.5 AS build
+COPY . /go/src/vitess.io/vitess/examples/are-you-alive
+RUN CGO_ENABLED=0 go install vitess.io/vitess/examples/are-you-alive/cmd/are-you-alive
+
+FROM debian:stretch-slim AS runtime
+COPY --from=build /go/bin/are-you-alive /go/bin/are-you-alive
+ENTRYPOINT ["/go/bin/are-you-alive"]