I've scoured App Engine documentations for an explanation on what is an entry point, and I frankly have hit a wall. Was hoping someone on SO can provide an explanation of what and the purpose of an entry point is.
An entrypoint is a Docker command that is executed when the container starts, allowing you to configure a container that will run as an executable.
For App Engine the entrypoint is specified in the app.yaml file, the command present in the entrypoint field will be included in the entrypoint of your app's Dockerfile, meaning that it is the one that will tell how the application has to be started when you are deploying it. The entrypoint should start a web server that will listen on the port 8080, which is the port used by App Engine to send requests to the deployed container. App Engine provides the PORT environment variable for ease of use.
For example:
entrypoint: gunicorn -b :$PORT main:app
With this entrypoint you are telling how you want the app to be started, in this case using gunicorn, and where do you want it to keep listening.
By default, this gunicorn command is the entrypoint used by App Engine when you do not explicitly set one in the app.yaml file.
You always need an entrypoint because all App Engine apps are deployed using Docker containers. Even if you only deploy a file with your code, App Engine will build a Docker container with the parameters set in the app.yaml, because when you deploy an app using App Engine, internally the process used is a build, where the image is given by App Engine.
Also when you deploy an app with App Engine you will be able to find the related build if you go to the Cloud Build section in your GCP console, where you’ll find all the steps and information for the build of the Docker container where your App Engine is being deployed.
In conclusion, App Engine uses the entrypoint from Docker because internally what App Engine is doing while the deploying is using Cloud Build service to build a container image for your app with the information given in the entrypoint.
The entrypoint tells the container what to do when it is run. I see it most frequently with Docker, but other container formats will have something equivalent.
For App Engine, the key thing the entrypoint setting does is start the HTTP server which listens for requests. Here is the Python documentation describing the entrypoint, but there are also links for other runtimes at the top of the page.
Related
I am trying to deploy an Helidon MP project to Google Cloud App Engine using java11 runtime but having trouble to define the app.yaml properly.
Tried to deploy the jar file directly using the below app.yaml using the command $ gcloud app deploy cord.jar. The app gets deployed but empty page on view.
runtime: java11
entrypoint: 'java -jar cord.jar'
Tried to modify the codewbase adding appengine\app.yaml to <project>\src\main\appengine\app.yaml and with contents as below and using command $ gcloud app deploy pom.xml:
runtime: java11
instance_class: F1
In all cases, the app got deployed but page loads empty.
They have examples on github but unfortunately not yet with Helidon.
I've put together an example for Helidon.
A couple things to note:
Make sure your application obeys the PORT environment variable, and configures its server to use that port.
Make sure your app.yaml is in the same directory as your jar and defines a custom entry point. For example:
runtime: java11
entrypoint: java -Xmx64m -jar helidon-quickstart-se.jar
Helidon uses "thin" jars and App Engine seems to handle this AOK as mentioned here: https://cloud.google.com/appengine/docs/standard/java11/runtime#application_startup
As an answer to my question.. issue for the page not loading was because of port 9090 that we were using (defined in src/main/resources/META-INF/microprofile-config.properties file). After i changed it to default 8080, my app worked.
microprofile-config.properties:
# Application properties. This is the default greeting
app.greeting=Hello
# Microprofile server properties
server.port=8080
server.host=0.0.0.0
References:
Helidon MP example for Google App Engine
There is a github thread regarding this and so far the current workaround is to add an app.yaml file similar to the one for the frameworks like Spring Boot or Vert.x
I have followed the tutorial where the github sample of the other responses is and it worked for me.
First I have cloned the repository and I used the quickstart mp:
git clone https://github.com/barchetta/helidon-google-app-engine-example/
cd helidon-google-app-engine-example/helidon-quickstart-mp
Then I have built and run the application and check if the port responds.
mvn package
export PORT=8888
java -jar target/helidon-quickstart-mp.jar
After all these previous steps I was able to see in localhost the result of the application.
For deploying I created the app.yaml file named "helidon-mp-app.yaml" and wrote this configuration inside:
runtime: java11
entrypoint: java -Xmx64m -jar helidon-quickstart-mp.jar
And copied it to the target/ directory:
cp helidon-mp-app.yaml target/
As the last configuration file, the file ".gcloudingonre" which also needs to be moved to target/
# Exclude everything. Then include just the app jar and runtime
# dependencies in libs/
*
*/
*/**
!helidon-quickstart-mp.jar
!libs/
!libs/**
Then as all the configuration files are ready, I executed
gcloud app deploy target/helidon-mp-app.yaml
gcloud app browse
And appending "/greet" in the URL we can see the result:
{"message":"Hello World!"}
Deploying an application to Google App Engine using the 'Custom Runtimes Flexible Environment' option requires a Dockerfile to build the docker image Google-side. I want to specify an image from my private Docker registry in the Dockerfile FROM clause. However, I cannot find any documentation or see any obvious options explaining where I would specify credentials for a private registry, or invoke a docker login. Without this, gcloud app deploy fails, of course, attempting to pull the image Google-side.
For example:
$ gcloud app deploy
...
Beginning deployment of service
...
Sending build context to Docker daemon 3.072kB
Step 1/1 : FROM registry.gitlab.com/my/private/registry/image:latest
Get https://registry.gitlab.com/v2/my/private/registry/image/manifests/latest: denied: access forbidden
The Dockerfile in this case would simply be:
FROM registry.gitlab.com/my/private/registry/image:latest
Does anyone out there know if this is possible with Google App Engine, and if so, how to configure it?
There is this Stackoverflow post that already covers the topic and provides an answer.
In fact, if you upload your image to Google Container Registry, it will be private and you will be able to control who has access to GCR by using IAM permissions. After that you can use it in your App Engine deployments:
gcloud app deploy --image-url $GCR_IMAGE_PATH
Where is the google app engine home root? I can't seem to find it, I want to edit the source code in there but I just can't. I want to use the default editor but I just can't seem to find the root project or wherever it is that's located at. Do you know where it is?
What you want to do is only possible if you are using App Engine Flex.
For App Engine Flex the deployment gets your files, build a Docker container with them, and then deploys this container inside a VM. As you can see on the documentation, you can connect directly to your container by running:
gcloud app instances ssh [INSTANCE-NAME] --service [SERVICE] --version [VERSION]
docker exec -it gaeapp /bin/bash
Once you run these commands you will be on the root folder of your container and changes you make on files will be reflected on the current running version of your app.
If you are using App Engine Standard, you cannot access the instances since it is a fully managed environment. Therefore you won't be able to find the root of the running app version.
NOTE: For App Engine Standard, since it uses a staging bucket to gather the code before compiling, you are able to get the files themselves but on a pre deployment state, meaning that if you change them it will not reflect on the current running version of your app. You can find your staging bucket through the App Engine Admin API. This bucket is usually staging.<PROJECT_ID>.appspot.com, although you can change this configuration.
I am currently using the app engine maven plugin, which seems to trigger a Google cloud build to build a docker image and then push to app engine.
Is it possible for me to just push an exiting docker image from docker hub or google container registry?
You can deploy to App Engine using a specific Docker image hosted on Google Container Registry by using the --image-url flag like this:
gcloud app deploy --image-url=[HOSTNAME]/[PROJECT-ID]/[IMAGE]
See doc here for more info on the hostname options.
It is also possible to do this through the Dockerfile in your app directory.
I noticed this while searching for ways to customize Google's own NGINX container in the App Engine instance (this is what is used to serve your app).
The first line of the Nginx Dockerfile is FROM nginx. This is referencing the 'nginx' image in the default image repository. As such this could be any image in the default registry as referenced by name. The default registry seems to be the Docker-hub registry (did not investigate if Google is mirroring or similar).
In this way, your app directory only need contain 2 files: app.yaml and Dockerfile.
I am deploying a binary on Google cloud flexible app engine for two different services. So I have {app-service1.yaml, Dockerfile-service1} and {app-service2.yaml, Dockerfile-service2}. And use "gcloud app deploy" command to deploy them.
Is it possible to send a param from app-service[1|2].yaml to a single Dockerfile, so that I can maintain only one Dockerfile?
I tried two things but they didn't work with "gcloud deploy" command:
"entrypoint:" in app.yaml -- It does not override what is set in CMD in Dockerfile.
"env_variables:" in app.yaml -- Dockerfile's ENV or ARG do not see any variables defined in env_variables:.
There's currently no way (I can think of) to pass parameters into the docker build process while using gcloud app deploy. If the dockerfiles you're using are similar, you may want to consider creating a base docker file, building a base image, and then sending it to gcr.io. Then you can extend the base image with your other Dockerfile(s).
Hope this helps!