GAE Golang - How to properly schedule a Task Queue to a Backend? - google-app-engine

There is little information on how to schedule a Task Queue to a Backend in Google App Engine in Go. In TQ's Reference we can read:
// Additional HTTP headers to pass at the task's execution time.
// To schedule the task to be run with an alternate app version
// or backend, set the "Host" header.
Header http.Header
But there is no explanation on what to really set the "Host" to. In Backends' Overview we can similarly read:
Private backends can be accessed by application administrators, instances of the application, and by App Engine APIs and services (such as Task Queue tasks and Cron jobs) without any special configuration.
But again, no explanation is given.
I tried setting the "Host" value to the name of the backend, but the tasks are executed by the normal application.
t := taskqueue.NewPOSTTask("/", map[string][]string{"key": {key}})
t.Header.Add("Host", "backend")
if _, err := taskqueue.Add(c, t, ""); err != nil {
return
}
What is the correct way to schedule a Backend call in GAE Go?

It's easiest to target a backend by using a named queue. e.g.:
_, err = taskqueue.Add(c, &taskqueue.Task{
Path: "/myProcessorPath",
Payload: myPayload,
}, "myQueueName")
Your queue definition specifies the backend. e.g. for myQueueName, you might have a queue.yaml entry that looks like this:
- name: myQueueName
target: myBackendName
rate: 400/s
max_concurrent_requests: 64
bucket_size: 25
retry_parameters:
task_age_limit: 7d

Use the appengine.BackendHostname function to get the hostname for a backend. That should be usable as the Host header for a task.

Related

Exceeded soft memory limit of 512 MB with 532 MB after servicing 3 requests total. Consider setting a larger instance class in app.yaml

We are on Google App engine standard environment, F2 instance (generation 1 - python 2.7). We have a reporting module that follows this flow.
Worker Task is initiated in a queue.
task = taskqueue.add(
url='/backendreport',
target='worker',
queue_name = 'generate-reports',
params={
"task_data" : task_data
})
In the worker class, we query Google datastore and write the data to a Google Sheet. We paginate through the records to find additional report elements. When we find additional page, we call the same task again to spawn another write, so it can fetch the next set of report elements and write them to Google sheet.
in the backendreport.py we have the following code.
class BackendReport():
# Query google datastore to find the records(paginated)
result = self.service.spreadsheets().values().update(
spreadsheetId=spreadsheet_Id,
range=range_name,
valueInputOption=value_input_option,
body=resource_body).execute()
# If pagination finds additional records
task = taskqueue.add(
url='/backendreport',
target='worker',
queue_name = 'generate-reports',
params={
"task_data" : task_data
})
We run the same BackendReport (with pagination) as a front end job (not as a task). The pagination works without any error - meaning we fetch each page of records and display to the front end. But when we execute the tasks iteratively it fails with the soft memory limit issue. We were under the impression that every time a task is called (for each pagination) it should act independently and there shouldn't be any memory constraints. What are we doing wrong here?
Why doesn't GCP spin a different instance when the soft memory limit is reached - automatically (our instance class is F2).
The error message says soft memory limit of 512 MB reached after servicing 3 requests total - does this mean that the backendreport module spun up 3 requests - does it mean there were 3 tasks calls (/backendreport)?
Why doesn't GCP spin a different instance when the soft memory limit is reached
One of the primary mechanisms for when app engine decides to spin up a new instance is max_concurrent_requests. You can checkout all of the automatic_scaling params you can configure here:
https://cloud.google.com/appengine/docs/standard/python/config/appref#scaling_elements
does this mean that the backendreport module spun up 3 requests - does it mean there were 3 tasks calls (/backendreport)?
I think so. To be sure, you can open up Logs viewer, find the log where this was printed and filter your logs by that instance-id to see all the requests it handled that lead to that point.
you're creating multiple tasks in Cloud Tasks, but there's no limitation for the dispatching queue there, and as the queue tries to dispatch multiple tasks at the same time, it reaches the memory limit. So the limitations you want to set in place is really max_concurrent_requests, however not for the instances in app.yaml, it should be set for the queue dispatching in queue.yaml, so only one task at a time is dispatched:
- name: generate-reports
rate: 1/s
max_concurrent_requests: 1

Creating a cluster before sending a job to dataproc programmatically

I'm trying to schedule a PySpark Job. I followed the GCP documentation and ended up deploying a little python script to App Engine which does the following :
authenticate using a service account
submit a job to a cluster
The problem is, I need the cluster to be up and running otherwise the job won't be sent (duh !) but I don't want the cluster to always be up and running, especially since my job needs to run once a month.
I wanted to add the creation of a cluster in my python script but the call is asynchronous (it makes an HTTP request) and thus my job is submitted after the cluster creation call but before the cluster is really up and running.
How could I do ?
I'd like something cleaner than just waiting for a few minutes in my script !
Thanks
EDIT : Here's what my code looks like so far :
To launch the job
class EnqueueTaskHandler(webapp2.RequestHandler):
def get(self):
task = taskqueue.add(
url='/run',
target='worker')
self.response.write(
'Task {} enqueued, ETA {}.'.format(task.name, task.eta))
app = webapp2.WSGIApplication([('/launch', EnqueueTaskHandler)], debug=True)
The job
class CronEventHandler(webapp2.RequestHandler):
def create_cluster(self, dataproc, project, zone, region, cluster_name):
zone_uri = 'https://www.googleapis.com/compute/v1/projects/{}/zones/{}'.format(project, zone)
cluster_data = {...}
dataproc.projects().regions().clusters().create(
projectId=project,
region=region,
body=cluster_data).execute()
def wait_for_cluster(self, dataproc, project, region, clustername):
print('Waiting for cluster to run...')
while True:
result = dataproc.projects().regions().clusters().get(
projectId=project,
region=region,
clusterName=clustername).execute()
# Handle exceptions
if result['status']['state'] != 'RUNNING':
time.sleep(60)
else:
return result
def wait_for_job(self, dataproc, project, region, job_id):
print('Waiting for job to finish...')
while True:
result = dataproc.projects().regions().jobs().get(
projectId=project,
region=region,
jobId=job_id).execute()
# Handle exceptions
print(result['status']['state'])
if result['status']['state'] == 'ERROR' or result['status']['state'] == 'DONE':
return result
else:
time.sleep(60)
def submit_job(self, dataproc, project, region, clusterName):
job = {...}
result = dataproc.projects().regions().jobs().submit(projectId=project,region=region,body=job).execute()
return result['reference']['jobId']
def post(self):
dataproc = googleapiclient.discovery.build('dataproc', 'v1')
project = '...'
region = "..."
zone = "..."
clusterName = '...'
self.create_cluster(dataproc, project, zone, region, clusterName)
self.wait_for_cluster(dataproc, project, region, clusterName)
job_id = self.submit_job(dataproc,project,region,clusterName)
self.wait_for_job(dataproc,project,region,job_id)
dataproc.projects().regions().clusters().delete(projectId=project, region=region, clusterName=clusterName).execute()
self.response.write("JOB SENT")
app = webapp2.WSGIApplication([('/run', CronEventHandler)], debug=True)
Everything works until the deletion of the cluster. At this point I get a "DeadlineExceededError: The overall deadline for responding to the HTTP request was exceeded." Any idea ?
In addition to general polling either through list or get requests on the Cluster or the Operation returned with the CreateCluster request, for single-use clusters like this you can also consider using the Dataproc Workflows API and possibly its InstantiateInline interface if you don't want to use full-fledged workflow templates; in this API you use a single request to specify cluster settings along with jobs to submit, and the jobs will automatically run as soon as the cluster is ready to take it, after which the cluster will be deleted automatically.
You can use the Google Cloud Dataproc API to create, delete and list clusters.
The list operation can be (repeatedly) performed after create and delete operations to confirm that they completed successfully, since it provides the ClusterStatus of the clusters in the results with the relevant State information:
UNKNOWN The cluster state is unknown.
CREATING The cluster is being created and set up. It is not ready for use.
RUNNING The cluster is currently running and healthy. It is ready for use.
ERROR The cluster encountered an error. It is not ready for use.
DELETING The cluster is being deleted. It cannot be used.
UPDATING The cluster is being updated. It continues to accept and process jobs.
To prevent plain waiting between the (repeated) list invocations (in general not a good thing to do on GAE) you can enqueue delayed tasks in a push task queue (with the relevant context information) allowing you to perform such list operations at a later time. For example, in python, see taskqueue.add():
countdown -- Time in seconds into the future that this task should run or be leased. Defaults to zero. Do not specify this argument if
you specified an eta.
eta -- A datetime.datetime that specifies the absolute earliest time at which the task should run. You cannot specify this argument if
the countdown argument is specified. This argument can be time
zone-aware or time zone-naive, or set to a time in the past. If the
argument is set to None, the default value is now. For pull tasks, no
worker can lease the task before the time indicated by the eta
argument.
If at the task execution time the result indicates the operation of interest is still in progress simply enqueue another such delayed task - effectively polling but without an actual wait/sleep.

How do I create push queue tasks for multiple queues

I have defined two Google App Engine push queues called "default" and "fast". How do I create a task in the "fast" queue?
Here is the queue.yaml:
queue:
- name: default
rate: 20/s
bucket_size: 10
- name: fast
rate: 50/s
bucket_size: 10
I have tried multiple things such as modifying the url parameter, but everything lands in the default queue.
Does anybody have code that shows how to send tasks to multiple queues within the same module?
taskque takes an argument called queue_name.
from google.appengine.api import taskqueue
task = taskqueue.add(
url='/your_task_handler_url',
params={'param1': 'paramval'}, queue_name='fast')

GAE taskqueue access application storage

My GAE application is written in Python with webapp2. My application targets at analyzing user's online social network. Users could login and authorize my application, hence the access token will be stored for further crawling the data. Then i use the taskqueue to launch a backend task, as the crawling process is time consuming. However, when i access the datastore to fetch the access token, i can get it. I wonders whether there is a way to access the data of the frontend, rather than the temporary storage for the taskqueue.
the handler to the process http request from the user
class Callback(webapp2.RequestHandler):
def get(self):
global client
global r
code = self.request.get('code')
try:
client = APIClient(app_key=APP_KEY, app_secret=APP_SECRET,redirect_uri=CALLBACK_URL)
r = client.request_access_token(code)
access_token = r.access_token
record = model.getAccessTokenByUid(r.uid)
if record is None or r.access_token != record.accessToken:
# logging.debug("access token stored")
**model.insertAccessToken(long(r.uid), access_token, r.expires_in, "uncrawled", datetime.datetime.now())** #data stored here
session = self.request.environ['beaker.session']
session['uid'] = long(r.uid)
self.redirect(CLUSTER_PAGE % ("true"))
except Exception, e:
logging.error("callback:%s" % (str(e)));
self.redirect(CLUSTER_PAGE % ("false"))
the handle to process task submitted to taskqueue
class CrawlWorker(webapp2.RequestHandler):
def post(self): # should run at most 1/s
uid = self.request.get('uid')
logging.debug("start crawling uid:%s in the backend" % (str(uid)))
global client
global client1
global r
tokenTuple = model.getAccessTokenByUid(uid)
if tokenTuple is None: **#here i always get a None**
logging.error("CounterWorker:oops, authorization token is missed.")
return
The question is not clear (is it can or cant?) But if you want to access frontend data from the taskqueue, pass it as parameters to the task queue.

How to delete all datastore in Google App Engine?

Does anyone know how to delete all datastore in Google App Engine?
If you're talking about the live datastore, open the dashboard for your app (login on appengine) then datastore --> dataviewer, select all the rows for the table you want to delete and hit the delete button (you'll have to do this for all your tables).
You can do the same programmatically through the remote_api (but I never used it).
If you're talking about the development datastore, you'll just have to delete the following file: "./WEB-INF/appengine-generated/local_db.bin". The file will be generated for you again next time you run the development server and you'll have a clear db.
Make sure to clean your project afterwards.
This is one of the little gotchas that come in handy when you start playing with the Google Application Engine. You'll find yourself persisting objects into the datastore then changing the JDO object model for your persistable entities ending up with obsolete data that'll make your app crash all over the place.
The best approach is the remote API method as suggested by Nick, he's an App Engine engineer from Google, so trust him.
It's not that difficult to do, and the latest 1.2.5 SDK provides the remote_shell_api.py out of the shelf. So go to download the new SDK. Then follow the steps:
connect remote server in your commandline: remote_shell_api.py yourapp /remote_api
The shell will ask for your login info, and if authorized, will make a Python shell for you. You need setup url handler for /remote_api in your app.yaml
fetch the entities you'd like to delete, the code looks something like:
from models import Entry
query = Entry.all(keys_only=True)
entries =query.fetch(1000)
db.delete(entries)
\# This could bulk delete 1000 entities a time
Update 2013-10-28:
remote_shell_api.py has been replaced by remote_api_shell.py, and you should connect with remote_api_shell.py -s your_app_id.appspot.com, according to the documentation.
There is a new experimental feature Datastore Admin, after enabling it in app settings, you can bulk delete as well as backup your datastore through the web ui.
The fastest and efficient way to handle bulk delete on Datastore is by using the new mapper API announced on the latest Google I/O.
If your language of choice is Python, you just have to register your mapper in a mapreduce.yaml file and define a function like this:
from mapreduce import operation as op
def process(entity):
yield op.db.Delete(entity)
On Java you should have a look to this article that suggests a function like this:
#Override
public void map(Key key, Entity value, Context context) {
log.info("Adding key to deletion pool: " + key);
DatastoreMutationPool mutationPool = this.getAppEngineContext(context)
.getMutationPool();
mutationPool.delete(value.getKey());
}
EDIT:
Since SDK 1.3.8, there's a Datastore admin feature for this purpose
You can clear the development server datastore when you run the server:
/path/to/dev_appserver.py --clear_datastore=yes myapp
You can also abbreviate --clear_datastore with -c.
If you have a significant amount of data, you need to use a script to delete it. You can use remote_api to clear the datastore from the client side in a straightforward manner, though.
Here you go: Go to Datastore Admin, and then select the Entity type you want to delete and click Delete. Mapreduce will take care of deleting!
There are several ways you can use to remove entries from App Engine's Datastore:
First, think whether you really need to remove entries. This is expensive and it might be cheaper to not remove them.
You can delete all entries by hand using the Datastore Admin.
You can use the Remote API and remove entries interactively.
You can remove the entries programmatically using a couple lines of code.
You can remove them in bulk using Task Queues and Cursors.
Or you can use Mapreduce to get something more robust and fancier.
Each one of these methods is explained in the following blog post:
http://www.shiftedup.com/2015/03/28/how-to-bulk-delete-entries-in-app-engine-datastore
Hope it helps!
The zero-setup way to do this is to send an execute-arbitrary-code HTTP request to the admin service that your running app already, automatically, has:
import urllib
import urllib2
urllib2.urlopen('http://localhost:8080/_ah/admin/interactive/execute',
data = urllib.urlencode({'code' : 'from google.appengine.ext import db\n' +
'db.delete(db.Query())'}))
Source
I got this from http://code.google.com/appengine/articles/remote_api.html.
Create the Interactive Console
First, you need to define an interactive appenginge console. So, create a file called appengine_console.py and enter this:
#!/usr/bin/python
import code
import getpass
import sys
# These are for my OSX installation. Change it to match your google_appengine paths. sys.path.append("/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine")
sys.path.append("/Applications/GoogleAppEngineLauncher.app/Contents/Resources/GoogleAppEngine-default.bundle/Contents/Resources/google_appengine/lib/yaml/lib")
from google.appengine.ext.remote_api import remote_api_stub
from google.appengine.ext import db
def auth_func():
return raw_input('Username:'), getpass.getpass('Password:')
if len(sys.argv) < 2:
print "Usage: %s app_id [host]" % (sys.argv[0],)
app_id = sys.argv[1]
if len(sys.argv) > 2:
host = sys.argv[2]
else:
host = '%s.appspot.com' % app_id
remote_api_stub.ConfigureRemoteDatastore(app_id, '/remote_api', auth_func, host)
code.interact('App Engine interactive console for %s' % (app_id,), None, locals())
Create the Mapper base class
Once that's in place, create this Mapper class. I just created a new file called utils.py and threw this:
class Mapper(object):
# Subclasses should replace this with a model class (eg, model.Person).
KIND = None
# Subclasses can replace this with a list of (property, value) tuples to filter by.
FILTERS = []
def map(self, entity):
"""Updates a single entity.
Implementers should return a tuple containing two iterables (to_update, to_delete).
"""
return ([], [])
def get_query(self):
"""Returns a query over the specified kind, with any appropriate filters applied."""
q = self.KIND.all()
for prop, value in self.FILTERS:
q.filter("%s =" % prop, value)
q.order("__key__")
return q
def run(self, batch_size=100):
"""Executes the map procedure over all matching entities."""
q = self.get_query()
entities = q.fetch(batch_size)
while entities:
to_put = []
to_delete = []
for entity in entities:
map_updates, map_deletes = self.map(entity)
to_put.extend(map_updates)
to_delete.extend(map_deletes)
if to_put:
db.put(to_put)
if to_delete:
db.delete(to_delete)
q = self.get_query()
q.filter("__key__ >", entities[-1].key())
entities = q.fetch(batch_size)
Mapper is supposed to be just an abstract class that allows you to iterate over every entity of a given kind, be it to extract their data, or to modify them and store the updated entities back to the datastore.
Run with it!
Now, start your appengine interactive console:
$python appengine_console.py <app_id_here>
That should start the interactive console. In it create a subclass of Model:
from utils import Mapper
# import your model class here
class MyModelDeleter(Mapper):
KIND = <model_name_here>
def map(self, entity):
return ([], [entity])
And, finally, run it (from you interactive console):
mapper = MyModelDeleter()
mapper.run()
That's it!
You can do it using the web interface. Login into your account, navigate with links on the left hand side. In Data Store management you have options to modify and delete data. Use respective options.
I've created an add-in panel that can be used with your deployed App Engine apps. It lists the kinds that are present in the datastore in a dropdown, and you can click a button to schedule "tasks" that delete all entities of a specific kind or simply everything. You can download it here:
http://code.google.com/p/jobfeed/wiki/Nuke
For Python, 1.3.8 includes an experimental admin built-in for this. They say: "enable the following builtin in your app.yaml file:"
builtins:
- datastore_admin: on
"Datastore delete is currently available only with the Python runtime. Java applications, however, can still take advantage of this feature by creating a non-default Python application version that enables Datastore Admin in the app.yaml. Native support for Java will be included in an upcoming release."
Open "Datastore Admin" for your application and enable Admin. Then all of your entities will be listed with check boxes. You can simply select the unwanted entites and delete them.
This is what you're looking for...
db.delete(Entry.all(keys_only=True))
Running a keys-only query is much faster than a full fetch, and your quota will take a smaller hit because keys-only queries are considered small ops.
Here's a link to an answer from Nick Johnson describing it further.
Below is an end-to-end REST API solution to truncating a table...
I setup a REST API to handle database transactions where routes are directly mapped through to the proper model/action. This can be called by entering the right url (example.com/inventory/truncate) and logging in.
Here's the route:
Route('/inventory/truncate', DataHandler, defaults={'_model':'Inventory', '_action':'truncate'})
Here's the handler:
class DataHandler(webapp2.RequestHandler):
#basic_auth
def delete(self, **defaults):
model = defaults.get('_model')
action = defaults.get('_action')
module = __import__('api.models', fromlist=[model])
model_instance = getattr(module, model)()
result = getattr(model_instance, action)()
It starts by loading the model dynamically (ie Inventory found under api.models), then calls the correct method (Inventory.truncate()) as specified in the action parameter.
The #basic_auth is a decorator/wrapper that provides authentication for sensitive operations (ie POST/DELETE). There's also an oAuth decorator available if you're concerned about security.
Finally, the action is called:
def truncate(self):
db.delete(Inventory.all(keys_only=True))
It looks like magic but it's actually very straightforward. The best part is, delete() can be re-used to handle deleting one-or-many results by adding another action to the model.
You can Delete All Datastore by deleting all Kinds One by One.
with google appengine dash board. Please follow these Steps.
Login to https://console.cloud.google.com/datastore/settings
Click Open Datastore Admin. (Enable it if not enabled.)
Select all Entities and press delete.(This Step run a map reduce job for deleting all selected Kinds.)
for more information see This image http://storage.googleapis.com/bnifsc/Screenshot%20from%202015-01-31%2023%3A58%3A41.png
If you have a lot of data, using the web interface could be time consuming. The App Engine Launcher utility lets you delete everything in one go with the 'Clear datastore on launch' checkbox. This utility is now available for both Windows and Mac (Python framework).
For the development server, instead of running the server through the google app engine launcher, you can run it from the terminal like:
dev_appserver.py --port=[portnumber] --clear_datastore=yes [nameofapplication]
ex: my application "reader" runs on port 15080. After modify the code and restart the server, I just run "dev_appserver.py --port=15080 --clear_datastore=yes reader".
It's good for me.
Adding answer about recent developments.
Google recently added datastore admin feature. You can backup, delete or copy your entities to another app using this console.
https://developers.google.com/appengine/docs/adminconsole/datastoreadmin#Deleting_Entities_in_Bulk
I often don't want to delete all the data store so I pull a clean copy of /war/WEB-INF/local_db.bin out source control. It may just be me but it seems even with the Dev Mode stopped I have to physically remove the file before pulling it. This is on Windows using the subversion plugin for Eclipse.
PHP variation:
import com.google.appengine.api.datastore.Query;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
define('DATASTORE_SERVICE', DatastoreServiceFactory::getDatastoreService());
function get_all($kind) {
$query = new Query($kind);
$prepared = DATASTORE_SERVICE->prepare($query);
return $prepared->asIterable();
}
function delete_all($kind, $amount = 0) {
if ($entities = get_all($kind)) {
$r = $t = 0;
$delete = array();
foreach ($entities as $entity) {
if ($r < 500) {
$delete[] = $entity->getKey();
} else {
DATASTORE_SERVICE->delete($delete);
$delete = array();
$r = -1;
}
$r++; $t++;
if ($amount && $amount < $t) break;
}
if ($delete) {
DATASTORE_SERVICE->delete($delete);
}
}
}
Yes it will take time and 30 sec. is a limit. I'm thinking to put an ajax app sample to automate beyond 30 sec.
for amodel in db.Model.__subclasses__():
dela=[]
print amodel
try:
m = amodel()
mq = m.all()
print mq.count()
for mw in mq:
dela.append(mw)
db.delete(dela)
#~ print len(dela)
except:
pass
If you're using ndb, the method that worked for me for clearing the datastore:
ndb.delete_multi(ndb.Query(default_options=ndb.QueryOptions(keys_only=True)))
For any datastore that's on app engine, rather than local, you can use the new Datastore API. Here's a primer for how to get started.
I wrote a script that deletes all non-built in entities. The API is changing pretty rapidly, so for reference, I cloned it at commit 990ab5c7f2063e8147bcc56ee222836fd3d6e15b
from gcloud import datastore
from gcloud.datastore import SCOPE
from gcloud.datastore.connection import Connection
from gcloud.datastore import query
from oauth2client import client
def get_connection():
client_email = 'XXXXXXXX#developer.gserviceaccount.com'
private_key_string = open('/path/to/yourfile.p12', 'rb').read()
svc_account_credentials = client.SignedJwtAssertionCredentials(
service_account_name=client_email,
private_key=private_key_string,
scope=SCOPE)
return Connection(credentials=svc_account_credentials)
def connect_to_dataset(dataset_id):
connection = get_connection()
datastore.set_default_connection(connection)
datastore.set_default_dataset_id(dataset_id)
if __name__ == "__main__":
connect_to_dataset(DATASET_NAME)
gae_entity_query = query.Query()
gae_entity_query.keys_only()
for entity in gae_entity_query.fetch():
if entity.kind[0] != '_':
print entity.kind
entity.key.delete()
continuing the idea of svpino it is wisdom to reuse records marked as delete. (his idea was not to remove, but mark as "deleted" unused records). little bit of cache/memcache to handle working copy and write only difference of states (before and after desired task) to datastore will make it better. for big tasks it is possible to write itermediate difference chunks to datastore to avoid data loss if memcache disappeared. to make it loss-proof it is possible to check integrity/existence of memcached results and restart task (or required part) to repeat missing computations. when data difference is written to datastore, required computations are discarded in queue.
other idea similar to map reduced is to shard entity kind to several different entity kinds, so it will be collected together and visible as single entity kind to final user. entries are only marked as "deleted". when "deleted" entries amount per shard overcomes some limit, "alive" entries are distributed between other shards, and this shard is closed forever and then deleted manually from dev console (guess at less cost) upd: seems no drop table at console, only delete record-by-record at regular price.
it is possible to delete by query by chunks large set of records without gae failing (at least works locally) with possibility to continue in next attempt when time is over:
qdelete.getFetchPlan().setFetchSize(100);
while (true)
{
long result = qdelete.deletePersistentAll(candidates);
LOG.log(Level.INFO, String.format("deleted: %d", result));
if (result <= 0)
break;
}
also sometimes it useful to make additional field in primary table instead of putting candidates (related records) into separate table. and yes, field may be unindexed/serialized array with little computation cost.
For all people that need a quick solution for the dev server (as time of writing in Feb. 2016):
Stop the dev server.
Delete the target directory.
Rebuild the project.
This will wipe all data from the datastore.
I was so frustrated about existing solutions for deleting all data in the live datastore that I created a small GAE app that can delete quite some amount of data within its 30 seconds.
How to install etc: https://github.com/xamde/xydra
For java
DatastoreService db = DatastoreServiceFactory.getDatastoreService();
List<Key> keys = new ArrayList<Key>();
for(Entity e : db.prepare(new Query().setKeysOnly()).asIterable())
keys.add(e.getKey());
db.delete(keys);
Works well in Development Server
You have 2 simple ways,
#1: To save cost, delete the entire project
#2: using ts-datastore-orm:
https://www.npmjs.com/package/ts-datastore-orm
await Entity.truncate();
The truncate can delete around 1K rows per seconds
Here's how I did this naively from a vanilla Google Cloud Shell (no GAE) with python3:
from google.cloud import datastore
client = datastore.Client()
query.keys_only()
for counter, entity in enumerate(query.fetch()):
if entity.kind.startswith('_'): # skip reserved kinds
continue
print(f"{counter}: {entity.key}")
client.delete(entity.key)
This takes a very long time even with a relatively small amount of keys but it works.
More info about the Python client library: https://googleapis.dev/python/datastore/latest/client.html
As of 2022, there are two ways to delete a kind from a (largeish) datastore to the best of my knowledge. Google recommends using a Dataflow template. The template will basically pull each entity one by one subject to a GQL query, and then delete it. Interestingly, if you are deleting a large number of rows (> 10m), you will run into datastore troubles; as it will fail to provide enough capacity, and your operations to the datastore will start timing out. However, only the kind you are mass deleting from will be effected.
If you have less than 10m rows, you can just use this go script:
import (
"cloud.google.com/go/datastore"
"context"
"fmt"
"google.golang.org/api/option"
"log"
"strings"
"sync"
"time"
)
const (
batchSize = 10000 // number of keys to get in a single batch
deleteBatchSize = 500 // number of keys to delete in a single batch
projectID = "name-of-your-GCP-project"
serviceAccount = "path-to-sa-file"
table = "kind-to-delete"
)
func min(a, b int) int {
if a < b {
return a
}
return b
}
func deleteBatch(table string) int {
ctx := context.Background()
client, err := datastore.NewClient(ctx, projectID, option.WithCredentialsFile(serviceAccount))
if err != nil {
log.Fatalf("Failed to open client: %v", err)
}
defer client.Close()
query := datastore.NewQuery(table).KeysOnly().Limit(batchSize)
keys, err := client.GetAll(ctx, query, nil)
if err != nil {
fmt.Printf("%s Failed to get %d keys : %v\n", table, batchSize, err)
return -1
}
var wg sync.WaitGroup
for i := 0; i < len(keys); i += deleteBatchSize {
wg.Add(1)
go func(i int) {
batch := keys[i : i+min(len(keys)-i, deleteBatchSize)]
if err := client.DeleteMulti(ctx, batch); err != nil {
// not a big problem, we'll get them next time ;)
fmt.Printf("%s Failed to delete multi: %v", table, err)
}
wg.Done()
}(i)
}
wg.Wait()
return len(keys)
}
func main() {
var globalStartTime = time.Now()
fmt.Printf("Deleting \033[1m%s\033[0m\n", table)
for {
startTime := time.Now()
count := deleteBatch(table)
if count >= 0 {
rate := float64(count) / time.Since(startTime).Seconds()
fmt.Printf("Deleted %d keys from %s in %.2fs, rate %.2f keys/s\n", count, table, time.Since(startTime).Seconds(), rate)
if count == 0 {
fmt.Printf("%s is now clear.\n", table)
break
}
} else {
fmt.Printf("Retrying after short cooldown\n")
time.Sleep(10 * time.Second)
}
}
fmt.Printf("Total time taken %s.\n", time.Since(globalStartTime))
}

Resources