FAQs

Meni Vaitsi edited this page Jan 18, 2017 · 78 revisions

Contents

Can I run multiple apps on one deployment?

Yes. Make sure you use different app IDs for each application.

What version of the GAE API do you support?

GAE version 1.8.0 for Python and 1.8.4 for Java. Make sure your Java apps are compiled using this version. Failure to do so will result in unexpected behavior.

AppScale does not yet support applications created for the flexible environment (previously called Managed VMs). If you are starting a new application that you would like to work on AppScale, please make sure that you are using the documentation for the standard environment.

What APIs do you support? What APIs are not supported?

Supported APIs Not currently supported
Datastore Versions
Memcache Modules
Taskqueue Capabilities
Images Logs (although we provide tools to easily download the logs)
Cron Backends
Channel Endpoints
Multi-tenancy
Mail (out bound only)
OAuth (client side)
URLFetch
Users
Sockets
JDO/JDA for Java
MapReduce (Python)
Cloud SQL
Remote
Search (experimental)
XMPP

Is it possible to update AppScale?

Yes. Backup your data first! Currently, the upgrade process will require some downtime. Then you can run appscale upgrade from AppScale Tools 2.9 onwards.

In dev environments with custom changes or to minimize downtime you might need to run the upgrade steps manually. You'd better know what you're doing. New code can be pulled in by doing "git pull origin master" for both appscale and appscale-tools repos. If a change has happened to the build script, it may involve updating the new technology (example: A new version of Nginx or Cassandra) by running the appscale_build.sh script in appscale/debian and appscale-tools/debian.

How do I set the number of replicas of my data?

In your AppScale file you can set

replication : 1

Make sure you have at least these many number of datastore nodes.

How do I set my Flower TaskQueue password?

The default username and password are: appscale/appscale

It is highly recommended to change it. To change it though edit in your AppScalefile:

flower_password: "newpassword"

How do I set the number of TaskQueue workers?

You can set the number of workers processing your tasks on each TaskQueue node by modifying this line of code in /root/appscale/AppTaskQueue/tq_config.py. You will then have to restart the TaskQueue service and redeploy your app to ensure your changes are applied.

What is my monit status page password and how do I change it?

The default username and password are: admin/monit. Edit the following lines in the /etc/monit/monitrc file on the head node to set your username and password:

set httpd port 2812 and
    allow admin:monit         # require user 'admin' with password 'monit'

Reload monit to apply your changes by running:

service monit reload

Does AppScale autoscale?

Yes. It will scale up and down the processes on your node (only if there is CPU available). If the node does not have enough resources to spin up another process, it will vote to spin up another virtual machine. If there is a consensus on scaling up, then a new machine will be added (only in IaaS environments such as GCE and AWS). Once the load has decreased, the processes will slowly be terminated and once a node is no longer running an application, that node will be terminated.

To set this in your AppScalefile:

min: 1
max: 2

Here we will start with one node, and scale up to two nodes.

You can also manually scale up. See Adding Machines to an AppScale Deployment.

What Linux distribution does AppScale run on?

This shouldn't matter since AppScale tries to abstract away lower level details by running in virtual machines. AppScale runs on Ubuntu 14.04 LTS (Trusty Tahr), Ubuntu 12.04 LTS (Precise Pangolin) and Debian Wheezy. It is simple to port to other Debian distributions.

Can I setup a web domain pointing to my AppScale deployment?

Yes. Set up your CNAME record pointing to the IP address of the machine. Amazon's Route 53 is a great service for doing this.

Can I setup a static IP for Amazon elastic IPs and GCE static IPs?

Yes. Set them up in the cloud console of your IaaS provider and then you can set them in your AppScalefile.

static_ip: '1.2.3.4'

I have a company firewall and can only come in through a certain DNS or IP. How do I set it?

Set login_host in your AppScalefile.

Is AppScale production ready?

Yes. AppScale has been developed since 2008 when GAE first came out. We've had over 30 releases and have users in production throughout the world.

What is the largest AppScale deployment run so far?

100 nodes. You don't need this many nodes unless you're running a high traffic site.

Does AppScale support transactions?

Yes. Both within entity groups and cross entity group. AppScale uses ZK for locking. We have garbage collection for failed transactions.

What are the timeouts on requests? Can I increase/shorten them?

All URL paths are set to 600 seconds (10 minutes). You can increase them or decrease them via the code (AppController/lib/nginx.rb).

What libraries can I run in AppScale?

PHP: https://cloud.google.com/appengine/docs/php/

Python: https://cloud.google.com/appengine/docs/python/tools/libraries27

Java: https://cloud.google.com/appengine/docs/java/jrewhitelist

Go: https://cloud.google.com/appengine/docs/go/

Can I run libraries that are restricted in App Engine?

Yes. You have full access to the VMs running AppScale. You can either white list the library or add your own custom GAE APIs.

You'll see a list of white listed items. You would just add in the one you want to add. Here is an example of how pyexpat was whitelisted:

appscale/AppServer/google/appengine/tools/dev_appserver_import_hook.py:801:      'pyexpat',

appscale/AppServer/google/appengine/tools/devappserver2/python/sandbox.py:787:    'pyexpat',

Optionally, you'll see the code checking a list of white listed items. You can disable this check altogether.

dev_appserver_import_hook.py:1419 and sandbox.py:821

if (file_type not in self._ENABLED_FILE_TYPES and                     

              submodule not in self._white_list_c_modules):     

How can my application connect to a remote database?

White list the client library as seen above and then connect it directly to the database that you have already stood up and configured. Note: This is direct access to the database, not using the App Engine Datastore API.

What languages do you support?

We support applications written in Python, Java, PHP, and Go.

Does AppScale generate metadata about my data?

Yes. We generate statistics about namespaces and kinds once a day. Or you can start it in the AppConsole in the AppScale Dashboard.

What is AppScale written in?

Mostly Python. The AppController is written in Ruby. There is also some Java, PHP, and Go.

How do I deploy updates to the AppScale core code without building a new VM?

In your AppScalefile put in a "scp: ~/location_to_your_appscale_dir". Now this will be rsynced to all nodes in your AppScale deployment. If you change the build script (changing underlying technologies), you can still have the nodes run custom commands on boot using "user_commands" in your AppScalefile.

Example:

scp : "~/appscale"
user_commands:
- 'apt-get install -y htop'
- 'apt-get install -y vim'

How do I change the port that my app responds on from the default 8080?

This can be changed by running the appscale command similarly to how you started your cluster: appscale relocate <appname> 80 443 The above command sets the application to listen to HTTP on port 80 and HTTPs to port 443 (again the standardized ports for HTTP and secure HTTP via SSL respectively).

Relocate does not work.

Verify that the relocation port is available (no process has already binded it) on the head node.

lsof -i:80

How do I set up my own SSL cert?

Overwrite the cert and private key used by AppScale in /etc/nginx/ and /etc/appscale/certs on your head node. Then do "service nginx reload".

root@appscale-image0:~# cp ~/my_own_cert.crt /etc/nginx/mycert.pem
root@appscale-image0:~# cp ~/my_own_pk.pem /etc/nginx/mykey.pem
root@appscale-image0:~# cp ~/my_own_cert.crt /etc/appscale/certs/mycert.pem
root@appscale-image0:~# cp ~/my_own_pk.pem /etc/appscale/certs/mykey.pem
root@appscale-image0:~# service nginx reload
Reloading nginx configuration: nginx.

Which database does AppScale support?

AppScale is designed to support multiple databases, and it indeed supported multiple when it started. But regression testing on multiple databases caused release delay, so at this time AppScale comes with Cassandra as default.

How can I deploy my app with MySQL (CloudSQL) on AppScale?

You need to install MySQL server and client on your AppScale instance. You can do so by running:

sudo apt-get install mysql-server mysql-client

Then you need to add data into your MySQL server, create a user (username, password) that your app will use to connect to the database and grant them privileges on the database(s) that your app will be accessing.

Do not forget to specify the database URL in the configuration file of your application.

For a Java app that works straight with MySQL, you need to include the following in your appengine-web.xml file:

<system-properties>
  <property name="MYSQL" value="jdbc:mysql://<hostname>:<port>/<database_name>"/>
</system-properties>

For a Python app, you can use MySQLdb. You'll need to explicitly install the MySQLdb Python package with: sudo apt-get install python-mysqldb

If you are using the Fast Start launch and have an issue installing the python mysql library. Do the following to install the library:

   sudo apt-get update && sudo apt-get upgrade
   sudo apt-get install mysql-server-5.6
   sudo apt-get install python-mysqldb

You can find a sample guestbook app using MySQL here.

What is a recommended production deployment?

Ideally, you want to have a minimum of three machines with at least 4GB or RAM each. Cassandra's requirements alone are listed at 4 gigs. Since hardware is dedicated to serving your application, you should disable autoscaling (within a machine, not scaling out vertically with more machines) using the "appengine" flag. Your layout on the AppScalefile should look like such:

ips_layout :
  master : 192.168.1.2
  zookeeper : 192.168.1.2
  appengine : 192.168.1.3
  database : 192.168.1.4

appengine: 8

Here we placed an "appengine" node and "database" node on their own machines, while zookeeper is sitting on the head node. If you want additional fault tolerance, you can add more database nodes, zookeeper nodes, and appengine nodes. Here is a layout with more fault tolerance:

ips_layout :
  master : 192.168.1.2
  appengine : 
    - 192.168.1.3
    - 192.168.1.4
  database : 
    - 192.168.1.5
    - 192.168.1.6
    - 192.168.1.7
  zookeeper : 
    - 192.168.1.2
    - 192.168.1.3
    - 192.168.1.5

appengine: 8
replication: 3

In this deployment we have 2 database nodes, with replication set to 2. Cassandra is set to be strongly consistent, so both replicas should always be identical. We have two "appengine" nodes, therefore there are a total of 16 application servers hosting your application. If you were to deploy more applications, they too will have another 16 application servers (be careful with memory hungry applications). We have 3 "zookeeper" nodes so that we can achieve a quorum between them. We still have a single point of failure at the master node, but all other services have redundancies.

Learn more at https://github.com/AppScale/appscale/wiki/Distributed-Deployment

I want to run the AppScale tools from a different machine. How do I do so?

All the meta data (ssh keys and such) are stored in ~/.appscale. Move this folder along with your AppScalefile to whichever machine you want to run the tools and you'll have access to your current AppScale deployment.

Is there a way to not have the tools prompt me for my username and password every time?

Yes. In your AppScalefile you can use the testing account by putting

test: True

What is the testing default cloud admin username and password?

Username: a@a.com Password: aaaaaa

Can I change the default testing username and password?

Yes. In your AppScalefile:

admin_user: my_new_user@whatever.com
admin_pass: my_new_password

TaskQueue tasks seem to not being run. What do I do?

In some cases, Celery might get backed up on tasks because of testing or resource issues and there can be delays in executing a task. You can delete all enqueued tasks and start from scratch by running:

celery amqp queue.purge <app_ID>___<queue_name>

from the command line.

What does a cron job look like?

The timezone field is ignored by AppScale when parsing the cron.yaml file. The synchronize parameter used in Appspot cron.yaml files is not required in AppScale and will render your cron file invalid if you use it. An example cron.yaml follows:

cron:
- description: Runs every fifteen minutes during off peak times
  url:  /segmentUpdater
  schedule: every 15 minutes from 19:15 to 04:45
- description: Runs every five minutes during peak times
  url:  /segmentUpdater
  schedule: every 5 minutes from 05:00 to 19:00

ZooKeeper is taking up a lot of disk space. What do I do?

You can easily check out how much space zookeeper logs take up by running:

du -sh /opt/appscale/zookeeper

You may want to add the following in as a cron job to clean up disk space:

bash /root/appscale/scripts/zookeeper_cleanup.sh

Check /opt/appscale/zookeeper size. It should have reduced a good deal in size.

How do I enable the datastore viewer?

You can use the the /root/appscale/scripts/enable-datastore-viewer.sh script.

Do not use this script in production because it will expose your app's data to a publicly accessible location. If you need something like this in production, you can manually add the needed changes along with additional restrictions (such as only allowing a single IP address) in /etc/nginx/sites-enabled/your-app-id_datastore_viewer.conf.

Since the script is for testing purposes, it assumes that you are on a single-node deployment. If this is not the case, you'll need to forward the app admin port from one of the AppServers on another node to the head node. The script will give you the SSH tunneling command to run in the background for as long as you need the datastore viewer enabled. It should resemble the following:

ssh -L 3000X:localhost:3000Y your-app-engine-node -N

Can I get commercial support?

Yes. Contact us at support@appscale.com or visit our website.

Something is broken. How do I fix it?

Check out the Troubleshooting page.

AppScale sucks. Make it better!

Firstly, that's not a question. =) Secondly, We love new contributors! Help us improve the code or docs and AppScale will love you forever.

Send us a pull request! Contribute!.

This FAQ doesn't answer my question.

Please email the mailing list at https://groups.google.com/forum/#!forum/appscale_community and we'll do our best to answer your questions.