func StartOTRProcessWithEnv(mongoURL string, redisURL string, port int, extraEnv []string) *OTRProcess {
	proc := OTRProcess{
		port: port,
		env: append([]string{
			"OTR_MONGO_URL=" + mongoURL,
			"OTR_REDIS_URL=" + redisURL,
			"OTR_LOG_DEBUG=true",
			"OTR_METADATA_PREFIX=" + randString(16),
			fmt.Sprintf("OTR_HTTP_SERVER_ADDR=0.0.0.0:%d", port),
		}, extraEnv...),
	}
	proc.Start()
	return &proc
}
StartOTRProcessWithEnv is like StartOTRProcess, but lets you customize
the environment variables for oplogtoredis. OTR_MONGO_URL, OTR_REDIS_URL,
OTR_LOG_DEBUG, and OTR_HTTP_SERVER_ADDR are always set for you, so you only
need this function if you want to set options other than those.
package harness
import (
	"fmt"
	"log"
	"math/rand"
	"net/http"
	"os/exec"
	promdata "github.com/prometheus/client_model/go"
	"github.com/prometheus/common/expfmt"
)
type OTRProcess struct {
	env  []string
	cmd  *exec.Cmd
	port int
}
func StartOTRProcess(mongoURL string, redisURL string, port int) *OTRProcess {
	return StartOTRProcessWithEnv(mongoURL, redisURL, port, []string{})
}