Docker Error - “jq: error: Cannot iterate over nul

问题:

So I'm trying to deploy a dockerfile on Elastic Beanstalk, but I can't get past this error - "jq: error: Cannot iterate over null".

Successfully built [myContainerId]
Successfully built aws_beanstalk/staging-app
[2015-01-29T10:35:59.494Z] INFO  [16343] - [CMD-AppDeploy/AppDeployStage0/AppDeployPreHook/04run.sh] : Starting activity...
[2015-01-29T10:36:05.507Z] INFO  [16343] - [CMD-AppDeploy/AppDeployStage0/AppDeployPreHook/04run.sh] : Activity execution failed, because: command failed with error code 1: /opt/elasticbeanstalk/hooks/appdeploy/pre/04run.sh
jq: error: Cannot iterate over null
Docker container quit unexpectedly after launch: Docker container quit unexpectedly on Thu Jan 29 10:36:05 UTC 2015:. Check snapshot logs for details. (Executor::NonZeroExitStatus)
at /opt/elasticbeanstalk/lib/ruby/lib/ruby/gems/2.1.0/gems/executor-1.0/lib/executor/exec.rb:81:in `sh'
from /opt/elasticbeanstalk/lib/ruby/lib/ruby/gems/2.1.0/gems/executor-1.0/lib/executor.rb:15:in `sh'
from /opt/elasticbeanstalk/lib/ruby/lib/ruby/gems/2.1.0/gems/beanstalk-core-1.1/lib/elasticbeanstalk/executable.rb:63:in `execute!'
from /opt/elasticbeanstalk/lib/ruby/lib/ruby/gems/2.1.0/gems/beanstalk-core-1.1/lib/elasticbeanstalk/hook-directory-executor.rb:29:in `block (2 levels) in run!'
from /opt/elasticbeanstalk/lib/ruby/lib/ruby/gems/2.1.0/gems/beanstalk-core-1.1/lib/elasticbeanstalk/activity.rb:169:in `call'
from /opt/elasticbeanstalk/lib/ruby/lib/ruby/gems/2.1.0/gems/beanstalk-core-1.1/lib/elasticbeanstalk/activity.rb:169:in `exec'

There aren't any other errors in the logs. My Docker container is successfully built, so it seems unlikely the error is coming from there.

My Dockerrun.aws.json looks like :

   {
  "AWSEBDockerrunVersion": "1",
  "Image": {
    "Name": "blah",
    "Update": "false"
  },
  "Ports": [
    {
      "ContainerPort": "8080"
    }
  ]
}

I'm banging my head against a wall with this one, nothing I change seems to affect it and googling hasn't been of any help.

Any ideas?

回答1:

If others are looking for how to avoid the Cannot iterate over null error in their own jq commands, add a question mark after []. For example

echo '{
  "AWSEBDockerrunVersion": "1",
  "Image": {
    "Name": "blah",
    "Update": "false"
  },
  "Ports": [
    {
      "ContainerPort": "8080"
    }
  ]
}'|jq -c '.Volumes[]?|[.HostDirectory,.ContainerDirectory]'

where [] was replaced with []? does not display the error.

From the manual:

.[]?
    Like .[], but no errors will be output if . is not an array or object.

回答2:

The problem is that your Dockerrun.aws.json file is missing the Volumes property.

The 04pre.sh script uses the jq tool in order to query the JSON file.

Specifically, it runs the following command on your file, which yields to an error:

$ jq -c '.Volumes[] | [.HostDirectory, .ContainerDirectory]' < Dockerrun.aws.json
jq: error: Cannot iterate over null

Specifying an empty "Volumes" array should resolve the error.

回答3:

Note that an Elastic Beanstalk deployment to the Docker platform can fail with the "jq: error ... Cannot iterate over null..." error message in various phases of an Elastic Beanstalk deployment, for various different reasons. This can include your application (Docker container) quitting or erroring on startup.

Although this particular reported occurrence of the problem may have been specific to a missing "Volumes" property in Dockerrun.aws.json, your problem may not be. If you get this error, then the best way to go about diagnosing the problem is to download your full EB logs and check the diagnostics in the following log file /var/log/eb-activity.log.

If the problem was caused by your application failing to startup then you'll find the error in /var/log/eb-docker/containers/eb-current-app/unexpected-quit.log.

回答4:

In my case issue was caused by ADD in Dockerfile instead of COPY instruction. Changing it fixed the issue.