A friend of mine messed up his php website and accidentally deployed the bad code to the website. Is there a way to recover to the last working deployment instance?
If new code was deployed with a new version number, you may be able to set the previous version as default, if it was not deleted.
If new code was deployed with the same version number, it replaced the previous code - there is no way to restore it.
Typically, version control for your source code takes care of this - you cannot rely on a production environment for restoring previous versions.
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I have a python27 appengine application. My application generates a 500 error early in the code initialization, and I can inspect the stack trace in the StackDriver debugger in the GCP console.
I've since patched the code, and I've re-deployed under the same service name and version name (i.e. gcloud app deploy --version=SAME). Unfortunately, the old error still comes up, and line numbers in the stack traces reflect the files in the buggy deployment. If I use the code viewer to debug the error, I am however brought to the updated patched code in the online viewer -- and there is a mismatch. It behave as if the app instance is holding on to a previous snapshot of the code.
I'm fuzzy on the freshness and eventual consistency guarantees of GAE. Do I have to wait to get everything to serve the latest deployed version? Can I force it to use the newer code right away?
Things I've tried:
I initially assumed the problem had to do with versioning, i.e. maybe requests being load-balanced between instances with the same version, but each with slightly different code. I'm a bit fuzzy on the actual rules that govern which GAE instance gets chosen for a new request (esp whether GAE tries to reuse previous instances based on a source IP). I'm also fuzzy on whether or not active instances get destroyed right away when different code is redeployed under the same version name.
To take that possibility out of the equation, I tried pushing to a new version name, and then deleting all previous versions (using gcloud app versions list to get the list). But it doesn't help -- I still get stack traces from the old code, despite the source being up to date in the GCP console debugger. Waiting a couple hours doesn't do anything either.
I've tried two things:
disabling and re-enabling the application in GAE->Settings
I'd also noticed that there were some .pyc files uploaded in the snapshot, so I removed those and re-deployed.
I discovered that (1) is a very effective way to stop all running appengine instances. When you deploy a new version of a project, a traffic split is created (i.e. 0% for the old version and 100% for the new), but in my experience old instances might still be running if they've been used recently (despite them being configured to receive 0% of traffic). Toggling kills them all immediately. I unfortunately found that my stale code was still being used after re-enabling.
(2) did the trick. It wasn't obvious that .pyc were being uploaded. I discovered it by looking at GCP->StackDriver->Debug and I saw .pyc files in the tree snapshot.
I had recently updated my .gitignore to ignore locally installed pip runtime dependencies for the project (output of pip install -t lib requirements.txt). I don't want those in git, but they do need to ship as part of my appengine project. I had removed the #!.gitignore special include line from .gcloudignore. However, I forgot to re-add *.pyc into my .gcloudignore.
Another way to see the complete set of files included in an app deployment is to increase the verbosity to info on the gcloud app deploy command -- you see a giant json manifest with checksums. I don't typically leave that on because it's hard to visually inspect, but I would have spotted the .pyc in there.
I have a website on AppEngine that is 99% static. It is running on Python 2.7 runtime. Now the time has come to evolve this webapp, and since I have almost none Python code in it, I'd prefer to write it in Go instead.
Can I change runtime from Python 2.7 to Go, while keeping the project intact? Specifically, I want to keep the same app-ID, the same custom domain attached to it, the same SSL certificate, and so on.
What do I have to do in order to do that? I surely have to change runtime in the app.yaml. Is there anything else?
Bonus question: will such change happen without a downtime?
I'd be grateful for any links to documentation on exactly that (swapping runtime on a live app). I can't find any.
Specify a runtime as well as a new value for version. When deployed you'll have an older version that is Python and a newer version that is Go. There won't be any downtime (same as when deploying a newer version of Python).
Rather than trusting links/docs (that may be out of date or not 100% exactly what you're trying to do), why not create a new GAE-Std project for testing purposes and try it yourself. Having a GAE-Std test project is good for testing new function (especially by other testers who won't have access to the dev environ on your laptop).
The GAE services offer complete code isolation. So it should be possible to simply deploy a new version of the service, which can be written in a different language or even use a different GAE (standard/flex) environment. Personally I didn't go through a language change, but I did go through a split of a single-service app into a multi-service one, I see no reason for which the same principles wouldn't apply.
Maybe develop the new version as a separate app first, to be able to test it properly without risking an accidental impact on the old version and only after that bring the code as a new version in the old app. That'd be using the GAE project isolation. You can, in fact, test the entire version migration as a separate app if you so desire without even touching the existing app. I am using this technique - a separate app ID - to implement a staging environment for my app, completely isolated from my production app, see How to copy / clone entire Google App Engine Project
Make sure to not switch traffic to the new version at deployment time. This keeps the app working with the old version. Test first that the new version works as expected using Targeted routing. Then maybe use Splitting traffic across multiple versions to perform A/B testing with just a small percentage of the traffic going to the new version. Finally, when happy with the results, switch all traffic to the new version.
You need to pay special attention to the app-level configs (dispatch, cron, queue, datastore indexes), shared by all services/versions. They need to be functionally equivalent in the 2 versions. The service isolation doesn't apply to them, only project isolation can ensure no impact to the old version.
There should be no need to make any change to the app ID, custom domain mapping or SSL config. The above mentioned tests should confirm that.
A few potentially interesting posts related to re-working services/modules:
Converting App Engine frontend versions to modules
Google App Engine upgrading part by part
Migrating to app engine modules, test versions first?
Advantages of implementing CI/CD environments at GAE project/app level vs service/module level?
Consider a case where an appengine project was done in PHP, but is now being completely replaced by a Go rewrite (not a new module/version, but complete rewrite and no need to maintain the old PHP version).
Is it ok to deploy the new project over the existing one, or is it better to delete the existing project and creating a new one (it's not really a public project yet, and in any case it is served via custom domain- assume downtime isn't a concern)?
My specific concern is that there might be some cached junk from the PHP version, and in general I'd like to understand a bit better of what deploying actually does- is it like rsync and deletes from remote if the file isn't local? Along with the codebase I'm also concerned about old static folders etc.
It's perfectly fine switching to another language for a new version of an app (i.e., without using a new app id). Older versions, in the prior language(s), are available until either you delete them manually, or deploy enough new versions in the new language that the older versions age out.
As long as you change the version, there's no issue with cached junk.
This is a subject of common discussion, but through all my research I have not actually found a sound answer to this.
I develop my websites offline, and then launch them live through my hosting account.
I utilize codeigniter, and on that basis there are some fundamental differences between my offline and online copies, namely base urls and database configurations. As such I cannot simply develop and test my websites offline and then upload them as it requires small configuration changes which are easy to overlook and good lead to a none working live website.
The other factor is that when I am developing offline, I might add a database table or a column whilst creating some functionality. When I upload my local developments to my host, they often do not work as I have forgotten to upload the new database structure. Obviously this cannot happen - there cannot be any opportunity for a damaged or broken live website.
Further to this, I'd like to be able to have logs of my development - version control of sorts such that if i develop a feature, and then something else stops working I can easily look backwards to at least see the code changes which could have caused the change.
My fourth requirement is as follows: if i go away on holiday for a week without my development laptop, and then get a bug report, I have no way of fixing it. If i fix it on the live copy, not only is it dangerous, but i'll inevitably not update it on my local copy - as such when i update my live copy next time, that change will be lost. Is there a way that on any computer i can access my development setup, edit and test, launch to the live site, whilst also committing it such that my laptop local copy is up to date.
So yes.. in general im looking for a solution to make my development processes more efficient/suitable. Any ideas?
Thanks
Don't deploy by simply copying. Deploy by using a script (I use Apache Ant) that will automate the copy of specific files for each environment, the replacement of some values, etc.
This just needs rigor. Make a todo list while developing, and check that every modification on the server is done. You might also test the deploy procedure on a pre-production server which has an similar configuration as the production server, make sure everything is OK, and then apply the same, tested procedure on the production server
Just use a version control system. SVN or Git are two free candidates.
Make your version control server available from anywhere. If it's an open-source project, free hosting solutions exist. Of course, if you don't have a development computer wvailable, you'll have to checkout the whole project, and probably install some tools to be able to develop, test and deploy. Just try to make it as easy as possible, or always have your laptop available. If you plan to work, have your toolbox with you. If you don't plan to work, then don't work. When you have finished some development, commit to the server. When you go back to your laptop, update your working copy from the server.
Small additions and clarifications to JB
Use any VCS, which can work (in a good way) with branches - your local and prod systems are good candidates for separate branches, where you share common code but have branch-specific config. It'll require some changes in your everyday workflow (code in "test", merge finished with "prod", deploy /by tools, not hand/ only after merge...), but it's fair price
Changing of workflow, again. As JB noted - don't deploy by hand, don't deploy wrong branch, don't deploy "prod" before finished merge. But now build-tools are rather smart, you can check such pre-condition inside builder
Just use VCS, maybe DVCS will be somehow better. I say strong "No-no" for Git as first VCS, but you have wide choice even without it - SVN (poor branch|merge comparing to DVCS), Bazaar (not a tool of my dream, but, who knows), Mercurial, Fossil SCM, Monotone
Don't work on live, never do anyting outside your SCM. One source of changes is a rule of happy developer. Or don't work at all at free-time, or have codebase always reacheable for you (free code-hosting /GoogleCode, SourceForge, BitBucket, Github, Assembla, LaunchPad/ or own server), get it as needed, change, save, deploy
I accidently deleted my application code from my own machine, however it's running on Google App Engine (GAE), is there a way I could download it from there?
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app engine actually recently added the ability for the developer who uploaded a given app version to download its source code:
http://code.google.com/appengine/docs/python/tools/uploadinganapp.html#Downloading_Source_Code
You cannot do this unless you have prepared your app ahead of time properly. There is a chance the trick described by Nick in the duplicate question here might work for you. Otherwise, I would suggest using source control like git or svn.