Error Serializing an R object in POST request

[adanba]

Hi,
I try to create an API using Plumber 0.4.7.9000, this API will be consumed by an other R process.

The objectif is to send an R object (RDS, DataFrame, List) with a POST request and get a Transformation of this Object in response.

I got this errors but i don't know what i'm doing wrong ?!

Server Side :

1. plumber.R

library(dplyr)

do_something <- function(df){
  message(class(df))
  df %>% head
}

#' @post /api
#' @serializer rds
function(req) {
  do_something(req$postBody)
}

2. run.R

r <- plumb("plumber.R")
r$run(debug = TRUE, port = 8080)

Outputs Server Side :

Running plumber API at http://127.0.0.1:8080
Running swagger UI at http://127.0.0.1:8080/__docs__/

# Call 1
<simpleError in rawToChar(value): embedded nul in string: 'X\n\0\0\0\002\0\003\005\0\0\002\003\0\0\0\003\023\0\0\0\005\0\0\0\016\0\0\0\006@\024ffffff@\023\x99\x99\x99\x99\x99\x9a@\022\xcc\xcc\xcc\xcc\xcc\xcd@\022ffffff@\024\0\0\0\0\0\0@\025\x99\x99\x99\x99\x99\x9a\0\0\0\016\0\0\0\006@\f\0\0\0\0\0\0@\b\0\0\0\0\0\0@\t\x99\x99\x99\x99\x99\x9a@\b\xcc\xcc\xcc\xcc\xcc\xcd@\f\xcc\xcc\xcc\xcc\xcc\xcd@\017333333\0\0\0\016\0\0\0\006?\xf6ffffff?\xf6ffffff?\xf4\xcc\xcc\xcc\xcc\xcc\xcd?\xf8\0\0\0\0\0\0?\xf6ffffff?\xfb333333\0\0\0\016\0\0\0\006?ə\x99\x99\x99\x99\x9a?ə\x99\x99\x99\x99\x9a?ə\x99\x99\x99\x99\x9a?ə\x99\x99\x99\x99\x9a?ə\x99\x99\x99\x99\x9a?\u0659\x99\x99\x99\x99\x9a\0\0\003\r\0\0\0\006\0\0\0\001\0\0\0\001\0\0\0\001\0\0\0\001\0\0\0\001\0\0\0\001\0\0\004\002\0\0\0\001\0\004\0\t\0\0\0\006levels\0\0\0\020\0\0\0\003\0\004\0\t\0\0\0\006setosa\0\004\0\t\0\0\0\nversicolor\0\004\0\t\0\0\0\tvirginica\0\0\004\002\0\0\0\001\0\004\0\t\0\0\0\005class\0\0\0\020\0\0\0\001\0\004\0\t\0\0\0\006factor\0\0\0\xfe\0\0\004\002\0\0\0\001\>

# Call 2
character

# Call 3
<simpleError in getRelevantArgs(allArgs, plumberExpression = private$func): Can't call a Plumber function with unnammed arguments. Missing names for argument(s) #3. Names of argument list was: "req,res,">

Client Side :

1. Call 1 :

out_call_1 <- httr::POST(
  "http://127.0.0.1:8080/api",
  encode = "raw",
  body = base::serialize( iris %>% head, NULL),
  httr::content_type("application/rds")
)
base::unserialize(httr::content(out_call_1))

Outputs Client Side :

$error
[1] "500 - Internal server error"

$message
[1] "Error in rawToChar(value): embedded nul in string: 'X\\n\\0\\0\\0\\002\\0\\003\\005\\0\\0\\002\\003\\0\\0\\0\\003\\023\\0\\0\\0\\005\\0\\0\\0\\016\\0\\0\\0\\006@\\024ffffff@\\023\\x99\\x99\\x99\\x99\\x99\\x9a@\\022\\xcc\\xcc\\xcc\\xcc\\xcc\\xcd@\\022ffffff@\\024\\0\\0\\0\\0\\0\\0@\\025\\x99\\x99\\x99\\x99\\x99\\x9a\\0\\0\\0\\016\\0\\0\\0\\006@\\f\\0\\0\\0\\0\\0\\0@\\b\\0\\0\\0\\0\\0\\0@\\t\\x99\\x99\\x99\\x99\\x99\\x9a@\\b\\xcc\\xcc\\xcc\\xcc\\xcc\\xcd@\\f\\xcc\\xcc\\xcc\\xcc\\xcc\\xcd@\\017333333\\0\\0\\0\\016\\0\\0\\0\\006?\\xf6ffffff?\\xf6ffffff?\\xf4\\xcc\\xcc\\xcc\\xcc\\xcc\\xcd?\\xf8\\0\\0\\0\\0\\0\\0?\\xf6ffffff?\\xfb333333\\0\\0\\0\\016\\0\\0\\0\\006?ə\\x99\\x99\\x99\\x99\\x9a?ə\\x99\\x99\\x99\\x99\\x9a?ə\\x99\\x99\\x99\\x99\\x9a?ə\\x99\\x99\\x99\\x99\\x9a?ə\\x99\\x99\\x99\\x99\\x9a?\\u0659\\x99\\x99\\x99\\x99\\x9a\\0\\0\\003\\r\\0\\0\\0\\006\\0\\0\\0\\001\\0\\0\\0\\001\\0\\0\\0\\001\\0\\0\\0\\001\\0\\0\\0\\001\\0\\0\\0\\001\\0\\0\\004\\002\\0\\0\\0\\001\\0\\004\\0\\t\\0\\0\\0\\006levels\\0\\0\\0\\020\\0\\0\\0\\003\\0\\004\\0\\t\\0\\0\\0\\006setosa\\0\\004\\0\\t\\0\\0\\0\\nversicolor\\0\\004\\0\\t\\0\\0\\0\\tvirginica\\0\\0\\004\\002\\0\\0\\0\\001\\0\\004\\0\\t\\0\\0\\0\\005class\\0\\0\\0\\020\\0\\0\\0\\001\\0\\004\\0\\t\\0\\0\\0\\006factor\\0\\0\\0\\xfe\\0\\0\\004\\002\\0\\0\\0\\001\\\n"

2. Call 2 :

out_call_2 <- httr::POST(
  "http://127.0.0.1:8080/api",
  encode = "raw",
  body = base::serialize( iris %>% head, NULL, T),
  httr::content_type("application/rds")
)
base::unserialize(httr::content(out_call_2))

Outputs Client Side :

[1] "A\n2\n197888\n131840\n787\n5\n14\n6\n5.1\n4.9\n4.7\n4.6\n5\n5.4\n14\n6\n3.5\n3\n3.2\n3.1\n3.6\n3.9\n14\n6\n1.4\n1.4\n1.3\n1.5\n1.4\n1.7\n14\n6\n0.2\n0.2\n0.2\n0.2\n0.2\n0.4\n781\n6\n1\n1\n1\n1\n1\n1\n1026\n1\n262153\n6\nlevels\n16\n3\n262153\n6\nsetosa\n262153\n10\nversicolor\n262153\n9\nvirginica\n1026\n1\n262153\n5\nclass\n16\n1\n262153\n6\nfactor\n254\n1026\n1\n262153\n5\nnames\n16\n5\n262153\n12\nSepal.Length\n262153\n11\nSepal.Width\n262153\n12\nPetal.Length\n262153\n11\nPetal.Width\n262153\n7\nSpecies\n1026\n1\n262153\n9\nrow.names\n13\n2\nNA\n6\n1026\n767\n16\n1\n262153\n10\ndata.frame\n254"

3. Call 3 :

out_call_3 <- httr::POST(
  "http://127.0.0.1:8080/api",
  encode = "raw",
  body = base::serialize( iris %>% head, NULL, T),
  httr::content_type("application/octet-stream")
)
base::unserialize(httr::content(out_call_3))

Outputs Client Side :

$error
[1] "500 - Internal server error"

$message
[1] "Error in getRelevantArgs(allArgs, plumberExpression = private$func): Can't call a Plumber function with unnammed arguments. Missing names for argument(s) #3. Names of argument list was: \"req,res,\"\n"

Environment Info :

> sessionInfo()
R version 3.5.0 (2018-04-23)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS  10.15.5

Matrix products: default
BLAS: /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
LAPACK: /Library/Frameworks/R.framework/Versions/3.5/Resources/lib/libRlapack.dylib

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] dplyr_0.8.3        plumber_0.4.7.9000 webutils_1.1      

loaded via a namespace (and not attached):
 [1] Rcpp_1.0.4           pillar_1.4.2         compiler_3.5.0      
 [4] later_1.0.0          prettyunits_1.0.2    base64enc_0.1-3     
 [7] remotes_2.0.2        tools_3.5.0          testthat_2.3.1      
[10] digest_0.6.21        pkgbuild_1.0.2       pkgload_1.0.2       
[13] tibble_2.1.3         lifecycle_0.2.0      jsonlite_1.6.1      
[16] memoise_1.1.0.9000   pkgconfig_2.0.2      rlang_0.4.5         
[19] cli_1.0.0            rstudioapi_0.11      curl_4.3            
[22] yaml_2.2.0           yesno_0.1.0          swagger_3.20.3.99991
[25] withr_2.1.2          desc_1.2.0           fs_1.2.6            
[28] devtools_2.0.1       tidyselect_0.2.5     rprojroot_1.3-2     
[31] glue_1.3.2           R6_2.4.1             processx_3.2.0      
[34] sessioninfo_1.1.1    purrr_0.3.3          callr_3.0.0         
[37] magrittr_1.5         backports_1.1.2      ps_1.2.1            
[40] promises_1.1.0       usethis_1.4.0        assertthat_0.2.1    
[43] httpuv_1.5.2         stringi_1.4.6        crayon_1.3.4      

Is there an other way to do this whitout converting my R objet to a JSON and without writing the response to disk (ie as done by @meztez here) ?

Thank you for your help!

[meztez]

Parser are not all available by default, only a select few. Parser rds has to be specified to be used. See ?parser_form

Parsers are optional. When unspecified, only the parser_json(), parser_octet(), parser_form() and parser_text() are available. You can use @parser parser tag to activate parsers per endpoint. Multiple parsers can be activated for the same endpoint using multiple @parser parser tags.

Here I use another req named object to get access to your parsed body arguments.

do_something <- function(df){
  message(class(df))
  df %>% head
}

#* @post /api
#* @parser rds
#* @serializer rds
function(req) {
  do_something(req$argsPostBody)
}

[adanba]

Thank you very much @meztez, using parser resolves my problem.

I post the complet solution, hope this help others.

Server Side :

plumber.R

library(plumber)
do_something <- function(df){
  message(class(df))
  df %>% head
}

#* My API
#* @parser rds
#* @serializer rds
#* @post /api
function(req) {
  do_something(req$argsPostBody)
}

Run.R

r <- plumb("./plumber.R")
r$run(debug = TRUE, port = 8080)

Client Side :

out_call <- httr::POST(
  "http://127.0.0.1:8080/api",
  encode = "raw",
  body = base::serialize(trees, NULL),
  httr::content_type("application/rds")
)
base::unserialize(httr::content(out_call))

Output :