Custom Runtime taking long time to respond

[Prateek Malhotra]

I have a custom runtime for app engine flexible using Go (one of my dependencies has a gccgo requirement). Building and running the docker image locally it runs fine, I have it communicating with Datastore and logging/tracing without much issue. However, when I deploy this, the responses seem to hang. Logs show the request was processed quickly (sub 300ms), but the request itself takes 1+ seconds to complete!

Here is an example where the response is a simple 302 redirect, not a whole lot of data to download there:

From my browser:

And the associated log entry:

httpRequest: {
  latency:  "0.126517789s"  
  remoteIp:  "173.70.21.194"  
  requestMethod:  "GET"  
  requestSize:  "956"  
  requestUrl:  "<REMOVED>"  
  responseSize:  "106"  
  status:  302  
  userAgent:  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36"  
 }

What could be causing it to behave like this? Is it because I'm using a custom runtime? Here is my Dockerfile for reference:

FROM golang:stretch as build


COPY . /go/src/app

WORKDIR /go/src/app


RUN go get -d -v ./...



RUN go build -o app .


FROM gcr.io/distroless/base:latest
COPY --from=build /go/src/app/app /
CMD ["/app"]


EXPOSE 8080/tcp

And my app.yaml:

runtime: custom
env: flex
service: auth


manual_scaling:
  instances: 1
resources:
  cpu: 1
  memory_gb: 0.5
  disk_size_gb: 10

Any help/guidance would be much appreciated, thanks in advanced!