fdsn-ws

FDSN-WS

fdsn-station

Deploying

fdsn-station service requires a full fdsn-station xml as the data source. (NOTE: The full fdsn-station xml can be generated by command line tool tools/stationxml in https://github.com/GeoNet/delta.)

Simply upload the fdsn-station xml file to a S3 bucket, then set environment variable:

AWS_REGION=
STATION_XML_BUCKET= (bucket name only)
STATION_XML_META_KEY= (eg. file name)

(NOTE: An environment with credential to access S3 is required.)

Downloading and unmarshaling the fdsn-station xml could take long : Unmarshaling a 174MB xml takes about 10 seconds in my MacBookPro(2017), and downloading it takes much longer. So the initial time will be longer than usual - could be more than 10 seconds. The service periodically (defaults to 300 seconds, set by STATION_RELOAD_INTERVAL) checks if the data source xml in the S3 bucket has been updated.

Testing

There's a small fdsn-station-test.xml file in "etc/" for testing. Simply set STATION_XML_META_KEY to fdsn-station-test.xml then run the test.

Query samples

There's a file etc/station-sample.txt which consists of sample query parameter extracted from previous fdsnws's log. You can verify the station service with full station xml by using:

awk -F '[ ]' '{ print "http://localhost:8080/fdsnws/station/1/query?network="$1"&station="$2"&location="$3"&channel="$4}' parms.log | xargs curl -Ssf > /dev/null

Then check the log to see if their status code and return bytes.

Generating fdsn_station_type.go

fdsn_station_type.go is generated from etc/fdsn-station-1.0.xsd by tool xsdgen from https://github.com/droyo/go-xml. In the directory fdsn-ws, issue the command:

xsdgen -r 'RootType -> FDSNStationXML' -pkg main -o fdsn_station_type.go etc/fdsn-station-1.0.xsd 

However there're something you'll have to do manually.

1. The generated fields' tags in struct contains xmlns. This caused unnecessary url for EACH tag when we marshaling the xml. To resolve this, we'll have to manually remove all "http://www.fdsn.org/xml/station/1" in the tags of generated go file.
2. There's no "omitempty" attribute in the tag, so you'll have to add "omitempty" to all tags. For example, change

Unit       string  `xml:"unit,attr"`

to

Unit       string  `xml:"unit,attr,omitempty"`

However, some fields can't add omitempty attribute. All fields named "Value" with float64 type and without field name:

Value      float64 `xml:",chardata"`

must leave unchanged. 3. Change all fields with omitempty tag to pointer type, except:

• slice type
• string type
• Int type for accumulate - TotalNumberChannels, SelectedNumberChannels, TotalNumberStations, and SelectedNumberStations.

The changes above have 2 effects:

• For fields with struct type, the pointer makes the omitempty tag takes effect so no empty xml tags such as <InputUnits/> being generated.
• For fields with numeric type (float, int), the pointer type distinguishes "fields with zero value (uninitialized, should be omitted)" versus "fields with value of 0".