New in OpenCPU 1.4.4: session namespaces
August 25, 2014
The OpenCPU system exposes an HTTP API for embedded scientific computing with R. This provides reliable and scalable foundations for integrating R based analysis and visualization modules into pipelines, web applications or big data infrastructures.
New: session namespaces
A new feature in this version is support for session namespaces. Clients can now refer to objects within a temporary session using
sessionid::name. This makes it easier to reuse objects that were created from a script. For example let’s execute the ch01.R script which is included with the MASS package:
>> curl https://cloud.opencpu.org/ocpu/library/MASS/scripts/ch01.R -X POST /ocpu/tmp/x05af9fe89a/R/dd /ocpu/tmp/x05af9fe89a/R/m /ocpu/tmp/x05af9fe89a/R/std.dev /ocpu/tmp/x05af9fe89a/R/t.stat /ocpu/tmp/x05af9fe89a/R/t.test.p /ocpu/tmp/x05af9fe89a/R/v /ocpu/tmp/x05af9fe89a/R/z /ocpu/tmp/x05af9fe89a/stdout /ocpu/tmp/x05af9fe89a/source /ocpu/tmp/x05af9fe89a/console /ocpu/tmp/x05af9fe89a/info /ocpu/tmp/x05af9fe89a/files/ch01.pdf
x05af9fe89a is the temporary session ID, which will be different for every execution. From the output we can see that this script stored 7 objects in the session namespace. To retrieve the
z object in
json format, use:
But what if we want to reuse
z the object in a subsequent function call? We can now do this using the sesssion namespace. For example, to calculate
stats::sd(x = z), we need to refer to
x05af9fe89a::z as shown below:
curl https://cloud.opencpu.org/ocpu/library/stats/R/sd/json -d x=x05af9fe89a::z [ 1.9368 ]
This way, we can chain script executions and function calls by passing output objects as arguments to subsequent requests.
For remote function calls, you can still use the session id alone to refer to the return object of the function call. For example to calculate
stats::rnorm(n = 5) we do:
>> curl https://cloud.opencpu.org/ocpu/library/stats/R/rnorm -d n=5 /ocpu/tmp/x009f9e7630/R/.val /ocpu/tmp/x009f9e7630/stdout /ocpu/tmp/x009f9e7630/source /ocpu/tmp/x009f9e7630/console /ocpu/tmp/x009f9e7630/info
To calculate the standard deviation of our newly created object, the client can either use
x009f9e7630::.val or simply
curl https://cloud.opencpu.org/ocpu/library/stats/R/sd -d x=x009f9e7630 curl https://cloud.opencpu.org/ocpu/library/stats/R/sd -d x=x009f9e7630::.val
The above two requests are equivalent.