RecordStream¶
RecordStream interface for SeisComP.
Description¶
SeisComP applications access waveform data through the RecordStream interface. The following tables lists available implementations:
Name |
Service Prefix |
Description |
---|---|---|
|
Connects to SeedLink server |
|
|
Connects to an ArcLink server |
|
|
Connects to FDSN Web service |
|
|
Reads records from file |
|
|
Reads records from SeisComP archive (SDS) |
|
|
Connects to a gempa CAPS server |
|
|
Reads records from memory |
|
|
Combines archive and real-time stream |
|
|
Distributes requests to multiple proxy streams |
|
|
Decimates (resamples) a proxy stream |
|
|
Resamples (up or down) a proxy stream to a given sampling rate |
Application¶
The RecordStream parameters considered by an application can be provided like a URI in 2 alternative ways:
Specification of the URI on the command line. Use the option
-I URI
Configuration of the URI using the global parameters. Adjust either:
the URI in
recordstream
orthe URI separated into
recordstream.service
andrecordstream.source
.
Implementations¶
SeedLink¶
This RecordStream fetches data from a SeedLink server. The source is read as an URL and supports URL encoded parameters. The default host is set to localhost, the default port to 18000. Optional parameters are:
timeout - connection timeout in seconds, default: 300
retries - number of connection retry attempts, default: 0
no-batch - disables BATCH mode to request data, does not take a value
Examples¶
URI: service://source?options
slink://
slink://geofon.gfz-potsdam.de?timeout=60&retries=5
slink://localhost:18000
ArcLink¶
This RecordStream fetches data from a ArcLink server. The source is read as an URL and supports URL encoded parameters. The default host is set to localhost, the default port to 18001. Optional parameters are:
user - user name required on some servers
pwd - password required on some servers
dump - optional output file for all records being received
Examples¶
URI: service://source?options
arclink://
arclink://geofon.gfz-potsdam.de?user=foo&pwd=secret
arclink://localhost:18042
arclink://localhost?dump=test.mseed
FDSNWS¶
This RecordStream fetches data from a FDSN Web service. The source is read as an URL.
File¶
This RecordStream reads data from a file. The source is read as an file path. If the source is set to ‘-‘ the data is read from stdin. By default the record type is set to mseed. If a file name extension is available the record type is set as follows:
Extension |
Record Type |
---|---|
*.xml |
xml |
*.bin |
binary |
*.mseed |
mseed |
SDSArchive¶
This RecordStream reads data from one or more SeisComP (SDS) archives using the File RecordStream. The source is interpreted as a directory path list separated using commas.
Example¶
URI: service://source
sdsarchive:///home/sysop/seiscomp/var/lib/archive
sdsarchive:///SDSA,/SDSB,/SDSC
Different SDS are not merged, but are read sequentially depending on data existence. If a requested file is missing in the current SDS, it is searched for in the archive next in the list. On success it will deliver all the rest of files for the current channel from this SDS archive. On failure the next SDS archive is searched.
This process is repeated for each requested channel individually. It always starts to search data from the first given SDS to the last one, for each data channel.
CAPS¶
This RecordStream reads data from a gempa CAPS server. The source is an URL. The default host is set to localhost, the default port to 18002 for unencrypted connections and 18022 for SSL connections. Optional parameters are:
- arch - No parameter. Retrieve only archived data. In this mode the connection
finished when all available data has been sent. It won’t wait for additional real-time data.
ooo - Allow out-of-order data
timeout - The socket timeout in seconds
user - The user name of an authenticated request
pwd - The password of an authenticated request
request-file - Use the given file to feed the request
The service can either be caps or capss. The latter establishes an SSL connection.
Example¶
URI: service://user:password@source?options
caps://localhost:18002
capss://localhost:18022
caps://localhost:18002?arch
caps://user:mysecret@localhost:18002
Memory¶
This RecordStream reads data from memory and is only useful for developing applications. For instance a record sequence stored in an internal buffer could be passed to an instance of this RecordStream for reading.
Combined¶
This RecordStream combines one archive and one real-time RecordStream, e.g. ArcLink and SeedLink. First the archive stream is read up to the size of the real-time buffer. Then the acquisition is switched to the real-time stream. The syntax for the source is similar to an URL:
URI: service://source??options
combined://real-time-stream;archive-stream??parameters
By default the real-time stream is set to SeedLink and the archive-stream is set to ArcLink. Any other streams may be configured. The parameters of the combined stream are separated by 2 question marks (??) in order to distinguish them from the parameters used in the proxy streams:
slinkMax|rtMax|1stMax - Buffer size in seconds of the first stream (typically the real-time stream), default: 3600
Time spans can be configured with an additional and optional suffix:
Suffix
Multiplicator
s
1
m
60
h
3600
d
86400
w
86400*7
splitTime - The absolute time of the separation of both sources. The argument is an ISO time string, e.g. 2018-05-10T12:00:00Z or a year, e.g. 2018, which is the same as 2018-01-01T00:00:00.000Z. splitTime can be used if the waveform archives are spread over several directories or harddisks. See also the examples.
The combined record stream may be nested allowing the configuration of a (theoretically) infinite number of archive streams. The URI syntax for a nested configuration uses parenthesis:
combined://real-time-stream;combined/(archive-stream1;archive-stream2??parameters)??parameters
Examples¶
URI: service://source?options
URI |
Description |
---|---|
|
Seedlink on localhost:18000 combined with Arclink on localhost 18001 |
|
Same as above |
|
Same as above |
|
Seedlink on localhost:18042 combined with Arclink on localhost 18001, real-time (SeedLink) buffer size set to 30min |
|
Seedlink combined with SDS archive |
|
Seedlink combined with a combined record stream using two Arclink sources |
|
Seedlink combined with a combined recordStream providing access to 3 different SDS archives separated by time. The first SDS archive contains the most recent archived data. The other two contain the data from 2016 and 2017. |
|
Seedlink combined with a combined recordStream providing access to 3 different SDS archives separated by time. The first SDS archive contains the most recent archived data. The other two are separated in mid of 2016. |
Balanced¶
This RecordStream distributes requests quasi-equally (but deterministically) to multiple proxy streams. It can be used for load balancing and to improve failure tolerance. The algorithm to choose a proxy stream (counting from 0) is based on station code and can be expressed in Python as follows:
stationCode = "WLF"
nproxies = 2
x = 0
for c in stationCode:
x += ord(c)
print("choosing proxy stream", x % nproxies)
Decimation¶
This RecordStream decimates (resamples) a proxy stream, e.g. SeedLink. The syntax for the source is similar to an URL:
dec://proxy-stream?parameters/address
Optional parameters are:
rate - target sampling rate in Hz, default: 1
fp - default: 0.7
fs - default: 0.9
cs - coefficient scale, default: 10
Examples¶
URI: service://source?options
dec://slink/localhost:18000
dec://file?rate=2/-
dec://combined/;
Resample¶
This RecordStream resamples (up or down) a proxy stream, e.g. SeedLink, to a given sampling rate. The syntax for the source is similar to an URL:
resample://proxy-stream?parameters/address
Optional parameters are:
rate - target sampling rate in Hz, default: 1
fp - default: 0.7
fs - default: 0.9
cs - coefficient scale, default: 10
lw - lanczos kernel width, default: 3
debug - enables debug output, default: false
Examples¶
URI: service://source?options
resample://slink/localhost:18000
resample://file?rate=2/-
resample://combined/;