User guide

This section provides information about using the client class. Detailed information on the API is available on the API page, and on the command-line interface at Command-line interface.

Creating a client instance

ligo.gracedb.rest.GraceDb is the client class and is used for all API interactions. To instantiate a client object, do:

from ligo.gracedb.rest import GraceDb

client = GraceDb()

By default, the client uses the API of the production GraceDB server, https://gracedb.ligo.org/api/. To specify another server, use the service_url keyword argument:

client = GraceDb(service_url='https://gracedb-playground.ligo.org/api/')

If you are working behind a proxy, use the proxy_host and proxy_port arguments to specify the parameter of the proxy server:

client = GraceDb(proxy_host='myproxy.com', proxy_port=8443)

More information about the client class and the options which can be provided to the constructor is covered in detail on the API page.

Credentials

Credentials are not required, but users who possess them will likely want to authenticate in order to gain full access to the GraceDB server.

X.509 certificates

LIGO/Virgo users can provide an X.509 certificate to the client for authenticating to the GraceDB server. This can be a proxy certificate which is generated by ligo-proxy-init, another certificate which has been registered with the LIGO auth system, or a robot certificate. There are multiple methods for making these credentials available to the client class, detailed in the documentation for ligo.gracedb.rest.GraceDb.

These certificates may expire after some period of time and need to be renewed. If you have long-running jobs where the lifetime of a client may exceed that of your certificate, use the reload_certificate argument (and optionally, the reload_buffer argument) when instantiating a client object. On each request, the client will check whether your certificate has expired; if it has, the client will attempt to reload the certificate before sending the request to the server.

NOTES: the client requires that your renewed certificate is in the same location as the old one. Users may want to set up a cron job to facilitate auto-renewal of their certificate.

Passwords

Password-based authentication to limited portions of the GraceDB API has historically been available to partner astronomers who have an MOU with LIGO/Virgo. The documentation for ligo.gracedb.rest.GraceDb details how to provide these credentials to the client. This authentication mechanism may be phased out in the future.

Response contents

Most of the client methods return a httplib.HTTPResponse object. The server API provides a JSON response which is loaded into a Python dict by using the json() method:

response = client.event('G1234')
data = response.json()

The exact structure of the resulting dictionary varies depending on which resource type you are retrieving (event, superevent, log entry, etc.). A variety of examples are available in the server code documentation.

Note that most client methods will raise a ligo.gracedb.exceptions.HTTPError if the response code indicates an error (>= 400).

Basic usage for events

Create an event

Create an event on the server with the ligo.gracedb.rest.GraceDb.createEvent() method:

response = client.createEvent('CBC', 'gstlal', '/path/to/event/data/file.xml', search='LowMass')

Any LVC user can create “test” events by specifying the first argument (analysis group) as 'Test'. Special permissions are required to upload non-test events. You can get a list of available analysis groups with ligo.gracedb.rest.GraceDb.groups, available analysis pipelines with ligo.gracedb.rest.GraceDb.pipelines, or a list of searches with ligo.gracedb.rest.GraceDb.searches.

The type of data file depends on which pipeline is submitting the event. If you are not a pipeline expert, you may want to download a file from an existing event and use that for creating test events.

Update an event

Update an event’s parameters by uploading a new event data file with the ligo.gracedb.rest.GraceDb.replaceEvent() method:

response = client.replaceEvent('G123456', '/path/to/new/event/data/file.xml')

Only the user who originally submitted the event is allowed to update it.

Search for events

Use the ligo.gracedb.rest.GraceDb.events() method to search for events and get an iterator:

event_iterator = client.events('far < 1e-10')
graceids = [event['graceid'] for event in event_iterator]

See the server documentation for help with constructing search queries. Note that test and MDC events are not included in the search results by default.

Retrieve an individual event

The ligo.gracedb.rest.GraceDb.event() method is used to get information about an individual event:

response = client.event('G1234')

Basic usage for superevents

Create a superevent

Use the ligo.gracedb.rest.GraceDb.createSuperevent() method to create a superevent:

response = client.createSuperevent(1238350677, 1238350680, 1238350682, 'G1234')

The event G1234 must already exist on the server, and the category (production, test, or MDC) of the superevent must match that of the event. Special permissions are required to create non-test superevents.

Update a superevent

Use the ligo.gracedb.rest.GraceDb.updateSuperevent() method to update a superevent:

response = client.updateSuperevent('S190202p', t_0=1238350700, preferred_event='G2345')

Note that this method is used to update the t_start, t_0, t_end, and preferred_event parameters of the superevent only. To add events to or remove events from a superevent, use ligo.gracedb.rest.GraceDb.addEventToSuperevent() or ligo.gracedb.rest.GraceDb.removeEventFromSuperevent() methods.

Search for superevents

Use the ligo.gracedb.rest.GraceDb.superevents() method to search for superevents and get an iterator:

superevent_iterator = client.superevents('public is_gw: True')
superevent_ids = [superevent['superevent_id'] for superevent in superevent_iterator]

See the server documentation for help with constructing search queries. Note that test and MDC superevents are not included in the search results by default.

Retrieve an individual superevent

The ligo.gracedb.rest.GraceDb.superevent() method is used to get information about an individual superevent:

response = client.superevent('S180331d')

Annotations

Both events and superevents can be annotated with log entries, file uploads, labels, and more. There are several methods attached to the client class for creating these annotations and for getting information about existing annotations. Most of these methods work for both events and superevents and automatically determine which one you are interested in based on the format of the ID provided.

Log entries

To create a log entry, use the ligo.gracedb.rest.GraceDb.writeLog() method:

response = client.writeLog('G1234', 'comment on event')

You can also upload a file with a log entry:

response = client.writeLog('S190202b', 'comment on event', filename='/path/to/file/')

To get a log or list of logs attached to an event or superevent, use the ligo.gracedb.rest.GraceDb.logs() method:

response = client.logs('G1234', 12)

Here the second argument is the index number of the log, which represents its chronological order in the entire set of logs for the event or superevent. If this argument is not provided, the entire set of logs for the event or superevent will be retrieved.

Files

The procedure for uploading files is covered in the previous section on log entries. To retrieve a list of files attached to an event or superevent, use ligo.gracedb.rest.GraceDb.files():

response = client.files('G1234')

If a specific filename is provided, the server will provide the contents of the file with that name that is associated with the given event or superevent:

response = client.files('G1234', 'skymap.fits.gz')
file_contents = response.read()

Note that files are the server are versioned; i.e., uploading a file with the same name as another file attached to the same event or superevent will generate a new version. Different versions are specified by appending ,N to the filename, where N is the version number. Filenames without a version always point to the latest version of the file.

Labels

Labels can be applied to or removed from events or superevents. They are generally used to indicate some sort of state. Examples:

  • ADVREQ: advocate signoff is requested
  • PE_READY: parameter estimation results are available
  • DQV: the event or superevent is vetoed due to poor data quality

New labels cannot be created by users. To see which labels are available on the server, use ligo.gracedb.rest.GraceDb.allowed_labels. A list of labels with descriptions is provided here.

To add a label, use ligo.gracedb.rest.GraceDb.writeLabel():

response = client.writeLabel('G1234', 'ADVREQ')

To remove a label, use ligo.gracedb.rest.GraceDb.removeLabel():

response = client.removeLabel('S190214g', 'INJ')

Tags

Tags can be added to log entries to indicate the topic or process which the log entry is related to. For example, the data_quality tag can be used to indicate file uploads or comments which are related to data quality studies. Tags can also be created by users - if the tag you specify does not presently exist on the server, it will be created.

To add a tag to a log entry, use the ligo.gracedb.rest.GraceDb.addTag() method and specify the event or superevent, the log entry ID number, and the tag name:

response = client.addTag('G1234', 12, 'em_follow')

To remove a tag from a log entry, use ligo.gracedb.rest.GraceDb.removeTag():

response = client.removeTag('S190301a', 16, 'pe')

There are a few tags which are used for exposing information (lvem, public) to non-internal users. Special permissions are required to apply or remove these tags.

Other methods

Additional methods are provided for managing signoffs, uploading EM observation data, and more. These are not covered in detail here because they are rather specialized options. See API for information about the client methods used for these actions.