YottaDB Web Server




To install the YottaDB Web Server, first download the YDB-Web-Server repository by cloning it with git or downloading and extracting the zip file.

Then, create a build directory in the root directory of the repository:

mkdir build
cd build

Next, run cmake to generate the Makefiles

cmake ..

Finally, install the plugin:

[sudo] make install

To uninstall, run the following from the same directory:

[sudo] xargs rm < install_manifest.txt

Initial setup

After installation, set ydb_routines to contain $ydb_dist/plugin/o/_ydbmwebserver.so, e.g.:

export ydb_routines="$ydb_dist/plugin/o/_ydbmwebserver.so $ydb_routines"

Then, you can start the server by running:

$ydb_dist/yottadb -run start^%ydbwebreq

You can then stop the server with CTRL-C. Alternatively, you can run the following from another terminal:

$ydb_dist/yottadb -run stop^%ydbwebreq

You can then verify the operation of the web server by navigating to http://localhost:9080/api/ping, assuming you started the server without the --port option. Otherwise, use the specified port instead of 9080. For example:

    $ curl http://localhost:9080/api/ping

The returned JSON object contains the child process PID ("self") and the main server process PID ("server").

Overview of YDB Web Server operation

The YDB Web Server does two things:

  1. Serve pages on the file system from the directory specified by the --directory start-up parameter, or the current directory by default.

  2. Serve web services defined in the _ydbweburl.m M routine.

The server uses the classic forking model, where the main server process simply forks child processes whenever it receives a connection. Then, the child processes handle all communication with the client(s).

The server listens for a maximum of 5 concurrent connections. There can be as many forked child processes as the operating system allows.

The expected use case for the YDB Web Server is to provide web services from YottaDB and, optionally, to serve web pages used by these web services.

See the YDB Web Server README.md for how to start and stop the web server, as well as a list of options.

Development process

These are the steps that you need to more or less take to develop code that uses the YDB Web Server:

  1. Install YDB-Web-Server.

  2. Source $ydb_dist/ydb_env_set to set the requisite YottaDB environment variables, including $ydb_routines. You may also set $ydb_routines manually to include the web server library, which may be in either:

    • M mode: $ydb_dist/plugin/o/_ydbmwebserver.so, or

    • UTF-8 mode: $ydb_dist/plugin/o/utf8/_ydbmwebserver.so j

  3. Set $ydb_routines to include a routine directory for storing the routines written in the next two steps. $ydb_dist/ydb_env_set sets up a $ydb_dir/r directory by default.

  4. Start the Web Server by running the M command: do start^%ydbwebreq

  5. Add a URL mapping to your copy of _ydbweburl.m to map a URL to a tag^routine.

  6. Write code in tag^routine.

  7. Test the code by using curl.

  8. Rewrite and test the code until it works as desired. You do not need to restart the web server when you save a new copy of the routine. After 1 second, the old child process that used the old code dies, so you will get the new copy.

To deploy code to production, you need to do the following steps:

  1. Install YDB-Web-Server using the standard install process.

  2. Install _ydbweburl.m and the routine that you wrote above by placing it in the desired directory and including this file or directory in $ydb_routines.

  3. Set $ydb_routines to contain both _ydbmwebserver.so library files as well as your application code.

  4. Start the Web Server. A permanently running server process can be configured using Systemd, if desired.

Serving pages from the filesystem

YDB Web Server serves pages similarly to python3 -m http.server. By default, it serves from the current directory. However, if you start the server with a --directory /x/y/z argument, the pages will be served from directory /x/y/z.

If you supply the --gzip command line flag, HTTP responses will be compressed using gzip. If you use gzip, note that it uses /dev/shm for temporary files. If space is limited, e.g. in Docker images, you may face problems with gzipping, since --gzip causes extra processing to decrease the size of HTTP responses.

All file system calls send back an ETag. This way resources will be fetched only once.

Permanent API endpoints

The following API endpoints are always accessible via the YottaDB Web Server, regardless of the application:

  • /api/ping: Returns a JSON object containing the worker process PID ("self") and the server process PID ("server").

  • /api/version: Returns a JSON object containing the YottaDB Web Server version number.

  • /api/auth-mode: Returns a JSON object containing a Boolean value of true if the server was started with a user configuration via the --auth-stdin or --auth-file options.

  • /api/login: See the Authentication and Authorization section below.

  • /api/logout: See the Authentication and Authorization section below.

For example:

curl http://localhost:9081/api/ping  # Sample output: `{"self":"19341","server":"19338"}`
curl http://localhost:9081/api/version  # Sample output: `{"version":"4.2.0"}`
curl http://localhost:9081/api/auth-mode  # Sample output: `{"auth":false}`

Serving Web Services

The most common use case for the YDB Web Server is to provide web services.

Web services are specified in the _ydbweburl.m file. You can test the web server using this sample copy of _ydbweburl.m. However, this file is not packaged in the default installation, which assumes the user will provide a custom copy of the file with a custom URL mapping.

Here's an excerpt from the sample file:

 ;;GET /test/xml xml^%ydbwebapi
 ;;POST test/post posttest^%ydbwebapi
 ;;GET test/json getjson^%ydbwebapi

For example, an HTTP GET of /test/xml will execute the code in xml^%ydbwebapi.

xml ; GET /test/xml XML sample
 set httprsp("mime")="text/xml"
 set httprsp(1)="<?xml version=""1.0"" encoding=""UTF-8""?>"
 set httprsp(2)="<note>"
 set httprsp(3)="<to>Tovaniannnn</to>"
 set httprsp(4)="<from>Jani</from>"
 set httprsp(5)="<heading>Reminders</heading>"
 set httprsp(6)="<body>Don't forget me this weekend!</body>"
 set httprsp(7)="</note>"

How to create such code will be explained in the following sections.


Let's examine how the server figures out which routine to invoke in those simple examples using HTTP GET, starting with the aforementioned entry:

;;GET /test/xml xml^%ydbwebapi

Assuming that your server is listening at http://localhost:9080, navigate your browser to http://localhost:9080/test/xml.

The server will first check the HTTP request type, e.g. GET. Then, it will try to match the path, e.g. [/]test/xml, and derive the routine name, e.g. xml.

In this case, it will run the routine xml^%ydbwebapi. Instructions on how to write such a routine will be provided later.

Now, consider this more complex example:

;;GET test/r/{routine} r^%ydbwebapi

In this case, the server will accept GET HTTP requests in the variable format test/r/routine-name. In the M code, HTTPARGS("routine") (or lowercase httpargs("routine")) will contain the value of {routine}. For example, if you call this with curl localhost:9080/test/r/XUP, HTTPARGS("routine") will be XUP.

Here is yet another, slightly different example:

;;GET test/r/{routine?.1"%25".32AN} r^%ydbwebapi

This matches routine names as long as they fit the pattern of 0-1 % and 0-32 characters. If a routine doesn't match this pattern, then a 404 error is returned. For example, entering an invalid routine name of 1AAAA will cause a 404 error. HTTPARGS/httpargs will contain the value of {routine} as before.

With any URL, you can pass HTTP Query Parameters. For example, you can ask for curl localhost:9080/test/XUS?format=color. In this case, HTTPARGS will contain two values: HTTPARGS("routine")="XUS" and HTTPARGS("format")="color".


HTTP verbs POST and PUT are used to amend or add data. If you follow a rigid RESTful model, POST is used to amend data or add data when the location of the additional data is not known. In contrast, PUT which is used to add or overwrite data when the location of the data is known. Thus a POST can be used to add data to a database when record numbers are not required, while a PUT can be used to overwrite the data mapped to a given record number.

Despite the distinction between them, YDB Web Server handles both POST and PUT the same way. It's up to the developer adhere to aforementioned the semantics, if desired. For example:

;;POST test/post posttest^%ydbwebapi

Calling test/post with data will invoke posttest^%ydbwebapi. posttest^%ydbwebapi does a little processing then returns the data location in an HTTP Location header before returning the same data in the body.


  • HTTP HEAD is internally handled as a GET, except we don't send out the data.

  • HTTP DELETE is supported with the same semantics as a PUT.

  • HTTP OPTIONS is not supported as a verb in _ydbweburl.m, but it's handled internally in the web server to allow for CORS access.

Configuring the YottaDB Web Server environment via HTTP headers

Some aspects of the YottaDB Web Server environment can be configured using HTTP headers. Specifically:

  1. The global directory can be set using the X-YDB-Global-Directory header.

  2. The current working directory can be set using the X-YDB-Working-Directory header.

  3. Various environment variables can be set using the X-YDB-Env-Vars header.

See the test routine _ydbwebtest.m in the server source code for examples how to use this advanced functionality.

Creating and handling a new web server entry point

For all the following examples, we will use a very simple web service that just multiplies two numbers. The service will handle URLs like the following:


In this case, 5 is the multiplier and 8 is multiplicand. The server will multiply these numbers then return the result: 40, in this case.

You will need to add the following to the _ydbweburl.m file:

    ;;GET /multiply/{multiplier}/{multiplicand} m^mul

_ydbweburl.m must contain a URLMAP label, which contains a list of URL entry points defined as M comments. Each entry point must begin with two semicolons ;; followed immediately by the HTTP request type in all capital letters. There should be no spaces between the initial two semicolons and the request type.

After the request type comes the URL entry point definition, e.g. /multiply/{multiplier}/{multiplicand}.

After the entry point URL comes the M routine or label that should be called when a request is sent to the entry point URL, e.g. m^mul.

Note that the spelling of the parameter names, e.g. multiplier and multiplicand, must match the subscripts referenced by httpargs in the M routine targeted by the URL, e.g. m^mul.

A sample _ydbweburl.m file can be found in the src directory of the YDB-Web-Server repository.

Creating a handling routine

Here's the multiplier routine, mul.m:

mul ; Web Server Math Routine;2014-11-28  5:58 PM
m ; multiplication
    ; `httprsp` is where you return the result
    ; `httprsp("mime")` is where you specify the MIME type for the client
    ; If you don't specify a MIME, `application/json; charset=utf-8` is returned.
    ; Get our arguments
    new m1 set m1=$get(httpargs("multiplier"))
    new m2 set m2=$get(httpargs("multiplicand"))
    ; If for some reason our arguments are empty, don't go any further
    if (m1="")!(m2="")  do setError^%ydbwebutils(400,"Input parameters are not correct") QUIT
    set httprsp=m1*m2
    set httprsp("mime")="text/plain; charset=utf-8"

Test this routine by first running it from the command line:

YDB>set httpargs("multiplier")=5,httpargs("multiplicand")=40

YDB>kill httprsp

YDB>do m^mul

YDB>zwrite httprsp
httprsp("mime")="text/plain; charset=utf-8"

Running the code from the Web Server

To test the multiplier web service, use curl to submit a request to the multiplier URI:

$ curl http://localhost:9081/multiply/5/8

A closer look at routine input variables

The multiply routine is fairly straightforward. However, httpargs and httprsp can be explained in greater detail.


First, let's examine the httpargs variable. Recall the URL format for the multiplier routine:


This URL can be accessed by passing literal values for multiplier and multiplicand, e.g.:


In this case, the httpargs variable will contain the following nodes:


You can also pass additional URL query parameters - for example, numeric base - like this:


The httpargs will now have these nodes:


Here's a modified routine to handle the base parameter in addition to multiplier and multiplicand:

mul ; Web Server Math Routine;2014-11-28  6:31 PM
m   ; multiplication
    ; `httprsp` is where you return the result
    ; `httprsp("mime")` is where you specify the MIME type for the client
    ; If you don't specify a MIME, `application/json; charset=utf-8` is returned.
    ; Get our arguments
    new m1 set m1=$get(httpargs("multiplier"))
    new m2 set m2=$get(httpargs("multiplicand"))
    new base set base=$get(httpargs("base"))
    ; If for some reason our httpargs are empty, don't go any further
    if (m1="")!(m2="")  do setError^%ydbwebutils(400,"Input parameters are not correct") QUIT
    set httprsp=m1*m2
    if +base set httprsp=$$BASE(httprsp,10,base) ; convert to the requested base
    set httprsp("mime")="text/plain; charset=utf-8"
BASE(%X1,%X2,%X3) ;Convert %X1 from %X2 base to %X3 base
    I (%X2<2)!(%X2>16)!(%X3<2)!(%X3>16) Q -1
    Q $$CNV($$DEC(%X1,%X2),%X3)
DEC(N,B) ;Cnv N from B to 10
    Q:B=10 N N I,Y S Y=0
    F I=1:1:$L(N) S Y=Y*B+($F("0123456789ABCDEF",$E(N,I))-2)
    Q Y
CNV(N,B) ;Cnv N from 10 to B
    Q:B=10 N N I,Y S Y=""
    F I=1:1 S Y=$E("0123456789ABCDEF",N#B+1)_Y,N=N\B Q:N<1
    Q Y

Test this with curl:

$ curl http://localhost:9081/multiply/5/8?base=2

Expressed in base 10:

2**(6-1) + 2**(4-1) = 40.


The httprsp argument is simpler to use than httpargs, since it returns a scalar value. For example:

set httprsp=5
set httprsp("mime")="text/plain; charset=utf-8"

It is also possible to use httprsp to return an array. The simplest way to return an array is to subscript the result with 1,2,3, etc. For example:

set httprsp(1)="Mary has"
set httprsp(2)="a little"
set httprsp(3)="lamb"
set httprsp("mime")="text/plain; charset=utf-8"

To transfer a large amount of data, a YottaDB global variable may be preferable, e.g.:

set httprsp=$name(^temp($job))
set @httprsp@(1)="Mary has"
set @httprsp@(2)="a little"
set @httprsp@(3)="lamb"
; Set more array entries...
set @httprsp@("mime")="text/plain; charset=utf-8"

For example, consider the xml label in the %ydbwebapi routine, which uses a global variable:

xml ; GET /test/xml XML sample
    set httprsp("mime")="text/xml"
    set httprsp(1)="<?xml version=""1.0"" encoding=""UTF-8""?>"
    set httprsp(2)="<note>"
    set httprsp(3)="<to>Tovaniannnn</to>"
    set httprsp(4)="<from>Jani</from>"
    set httprsp(5)="<heading>Reminders</heading>"
    set httprsp(6)="<body>Don't forget me this weekend!</body>"
    set httprsp(7)="</note>"


Above we demonstrated how to access the web server using HTTP GET requests. Now, we'll take a look at POST and a PUT requests.

Assume we'd like to store text data in a YottaDB global variable named ^text. Each data entry can be subscripted by an entry number, with the matching text stored as the node value under that subscript. For example:

^text(3,1)="It was the best of times"
^text(3,3)="It was the worst of times."

To access this data, let's create two methods on the server, one for POST and one for PUT requests.

The POST method will add text to the next available entry, while the PUT method will add or replace text for a specific entry. For completeness, a GET handler is also included in _ydbweburl.m:

;;POST /text post^text
;;PUT /text/{ien} put^text
;;GET /text/{ien} get^text

Next, let's write a routine for these methods:

text ; ven/smh - post and put data into global ^text;2014-11-28  7:37 PM
post ; handles POST /text/
    new ien
    set ien=$o(^text(""),-1)+1  ; last sub + 1
    new i for i=0:0 set i=$order(httpreq("body",i)) quit:'i  set ^text(ien,i)=httpreq("body",i) ; put data into text
    set ^text(ien)=$o(^text(ien," "),-1) ; make header node the last sub number in the text
    set httprsp("mime")="text/html; charset=utf-8"
    set httprsp="/text/"_ien
put ; handles PUT /text/{ien}
    new ien set ien=$g(args("ien"))
    if ien<1 do setError^%ydbwebutils(400,"invalid ien") quit ""
    kill ^text(ien) ; bye bye. We are replacing you.
    new i for i=0:0 set i=$order(httpreq("body",i)) quit:'i  set ^text(ien,i)=httpreq("body",i) ; put data into text
    set ^text(ien)=$o(^text(ien," "),-1) ; make header node the last sub number in the text
    set httprsp("mime")="text/html; charset=utf-8"
    set httprsp="/text/"_ien
get ; handles GET /text/{ien}
    new ien set ien=$g(args("ien"))
    if ien<1 do setError^%ydbwebutils(400,"invalid ien") quit
    if '$data(^text(ien)) do setError^%ydbwebutils("404","No such entry exists") quit
    new i for i=1:1:^text(ien) set httprsp(i)=^text(ien,i)
    set httprsp("mime")="text/html"

By default, the web server will read 4000 characters per node. For simplicity's sake, we will not parse them according to newline characters.

To test the routine, put some text files into a temporary directory so that they can later be accessed using requests sent via curl. For example:

$ ls /tmp/*.txt
/tmp/gettysburg_address.txt  /tmp/oratio_in_l_catilinam_para.txt  /tmp/varsari_da_vinci.txt

First, try a POST request, e.g.:

$ curl -X POST --data-binary @gettysburg_address.txt http://localhost:9081/text

HTTP/1.1 201 Created
Date: Sat, 29 Nov 2014 00:50:29 GMT
Location: https://localhost:9081/text/1
Content-Type: application/json; charset=utf-8
Content-Length: 7


This will result in the following additions to the YottaDB database:

^text(1,1)="Four score and seven years ago our fathers brought forth on this con
                  tinent a new nation, conceived in liberty, and dedicated to the propos
                  ition that all men are created equal."_$C(10,10)_"Now we are engaged i
                  n a great civil war, testing whether that nation, or any nation so con
                  ceived and so dedicated, can long endure. We are met on a great battle
                  field of that war. We have come to dedicate a portion of that field, a

Next, try a PUT request:

$ curl -X PUT --data-binary @varsari_da_vinci.txt http://localhost:9081/text/5

HTTP/1.1 201 Created
Date: Sat, 29 Nov 2014 00:56:23 GMT
Location: https://localhost:9081/text/5
Content-Type: application/json; charset=utf-8
Content-Length: 7


This will result in the following database additions:

^text(5,1)=" LIFE OF LEONARDO DA VINCI: Painter and Sculptor of Florence"_$C(10,10)_"The greatest gifts are often seen, in the course of nature, rained by celestial influences on human creatures; and sometimes, in supernatural fashion, beauty, grace, and talent are united beyond measure in.... and I have one, a head drawn with"
^text(5,2)=" the style in chiaroscuro, which is divine."_$C(10,10)_"And there was infused in that brain such grace from God, and a power of expression in such sublime accord with the intellect and memory that served it, and he knew so well how to express his conceptions by draughtmanship, that he vanquished with his discourse, and confuted with his reasoning... him, not thinking himself capable of imagining features that should"
^text(5,3)=" represent the countenance of him who, after so many benefits received, had a mind so cruel as to resolve to betray his Lord, the Creator of the world. However, he would seek out a model for the latter; but if in the end he could not find a better, he should not want that of th...."

The new URL of the saved data is returned with each POST or PUT request. Each new URL can then be used with GET, e.g.:

$ curl http://localhost:9081/text/5

LIFE OF LEONARDO DA VINCI: Painter and Sculptor of Florence

The greatest gifts are often seen, in the course of nature, rained by celestial influences on human creatures; ...

Continuing with the example, let's try to store Cicero's speech using a POST request, which we expect will go into slot 6, since the last entry was stored in slot 5 using PUT request:

$ curl -X POST --data-binary @oratio_in_l_catilinam_para.txt http://localhost:9081/text

HTTP/1.1 201 Created
Date: Sat, 29 Nov 2014 01:07:23 GMT
Location: https://localhost:9081/text/6
Content-Type: application/json; charset=utf-8
Content-Length: 7


The database will now contain these nodes:

^text(6,1)=" [1] I. Quo usque tandem abutere, Catilina, patientia nostra?
quam diu etiam furor iste tuus nos eludet? quem ad finem sese effrenata iactabit
audacia? Nihilne te nocturnum praesidium Palati, nihil urbis vigiliae, nihil
timor populi, nihil con cursus bonorum omnium, nihil hic munitissimus habendi
senatus locus, nihil horum ora voltusque moverunt? Patere tua consilia non
sentis, constrictam iam horum omnium scientia teneri coniurationem tuam non
vides? Quid proxima, quid superiore noct...

Now, let's try an error case by attempting to GET data that doesn't exist:

$ curl http://localhost:9081/text/10
{"apiVersion":1.1,"error":{"code":404,"errors":[{"errname":"Unknown error","message":"150379354,filesys+12^%ydbwebapi,%YDB-E-DEVOPENFAIL, Error opening \/tmp\/text\/10,%SYSTEM-E-ENO2, No such file or directory","reason":500},{"errname":"Not Found","message":"Not Found","reason":404}],"request":"GET \/text\/10 ","toperror":"Not Found"}}

The server in this case returns a 404 error as expected. Now, try to PUT to an invalid location:

$ curl -X PUT --data-binary @varsari_da_vinci.txt http://localhost:9081/text

HTTP/1.1 404 Not Found
Date: Sat, 29 Nov 2014 01:15:47 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 156

{"apiVersion":1.1,"error":{"code":404,"errors":[{"errname":"Unknown error","message":"150379354,filesys+12^%ydbwebapi,%YDB-E-DEVOPENFAIL, Error opening \/tmp\/text,%SYSTEM-E-ENO2, No such file or directory","reason":500},{"errname":"Not Found","message":"Not Found","reason":404}],"request":"PUT \/text ","toperror":"Not Found"}}

This also results in a 404 error, as expected.


Automated Testing

%ydbwebtest is the main testing routine. Note that it requires the libcurl plugin.

The testing system requires some set-up; it's easiest to do it via the Dockerfile like this:

$ docker build -t mws .
$ docker run -v $PWD/src:/mwebserver/r --rm mws tests
 -------------------------------- %ydbwebtest --------------------------------
tstartagain - Start again on the same port--------------------  [OK]  104.514ms
tdebug - Debug Entry Point------------------------------------  [OK]  125.257ms
thome - Test Home Page----------------------------------------  [OK]    7.989ms
tgetr - Test Get Handler Routine------------------------------  [OK]    5.443ms
tputr - Put a Routine-----------------------------------------  [OK]    9.604ms
tgetxml - Test Get Handler XML--------------------------------  [OK]    4.628ms
tdecodeutf8 - Test Decode UTF-8 URL---------------------------  [OK]    4.474ms
tencdecutf8 - Encode and Decode UTF-8-------------------------  [OK]    0.198ms
tencdecx - Encode and Decode an excepted character------------  [OK]    0.046ms
tpostutf8 - Post UTF8 data, expect parts of url post data back  [OK]    5.640ms
tgzip - Test gzip encoding------------------------------------  [OK]  130.423ms
tnogzip - Test the default nogzip-----------------------------  [OK]    8.432ms
temptynogzip - Empty response with no gzip encoding-----------  [OK]    4.935ms
temptygzip - Empty response with gzip-------------------------  [OK]    4.851ms
tping - Ping--------------------------------------------------  [OK]    5.873ms
terr - generating an error------------------------------------  [OK]    6.098ms
terr2 - crashing the error trap-------------------------------  [OK]    4.460ms
tcustomError - Custom Error-----------------------------------  [OK]    5.330ms
tlong - get a long message------------------------------------  [OK]    5.441ms
tDC - Test Disconnecting from the Server w/o talking----------  [OK]  100.330ms
tInt - ZInterrupt---------------------------------------------  [OK]  113.296ms
tLog1 - Set httplog to 1--------------------------------------  [OK]  221.629ms
tLog2 - Set httplog to 2--------------------------------------  [OK]  118.528ms
tLog3 - Set httplog to 3--------------------------------------  [OK]  225.367ms
tDCLog - Test Log Disconnect----------------------------------  [OK]  212.880ms
tOptionCombine - Test combining options (#113)----------------  [OK]  123.547ms
tWebPage - Test Getting a web page----------------------------  [OK]  122.532ms
tHomePage - Getting index.html page---------------------------  [OK]  120.029ms
CORS - Make sure CORS headers are returned--------------------  [OK]    8.040ms
login - Test that logging in/tokens/logging out works---------  [OK]  940.353ms
tTokenCleanup - Test Token Cleanup with timeout---------------  [OK] 1461.319ms
tLoginNoTimeout - Test Logins with no Timeouts----------------  [OK]  460.297ms
tLoginMultipleServers - Test login with multiple servers------  [OK]  682.582ms
tusersNoFile - Test --auth-file with a file that doesn't exist  [OK]   24.636ms
tusersInvalidJSON - Test --auth-file with a invalid JSON------  [OK]   25.151ms
tusersValidJSONInvalidKeys - Test --auth-file with bad keys---  [OK]   15.090ms
tsodiumerror - Test crashing libsodium runtime----------------  [OK]   10.344ms
tauthMode - /api/auth-mode------------------------------------  [OK]  241.926ms
tpost - simple post-------------------------------------------  [OK]    8.399ms
tgetjson - Get simple JSON (tests auto-encoder)---------------  [OK]    5.573ms
tpostmalformed - Malformed post-------------------------------  [OK]    5.862ms
tTLS - Start with TLS and testPort 55730 is currently being used.
Checking if it is the YDB-Web-Server.
Using TLS. $DEVICE: 0
HTTP/1.1 200 OK
Server running at 386
Now going to stop it...
STOP issued to process 386
Deleting tokens database files (if present)
--------------------------------------------------------------  [OK]  440.622ms
tEtag1 - Test caching with Etag-------------------------------  [OK]    9.201ms
tReadWrite - Test read-write flag-----------------------------  [OK]  125.115ms
tVersion - version--------------------------------------------  [OK]    8.435ms
tUppercase - uppercase HTTP variables-------------------------  [OK]    7.357ms
tGlobalDir - Custom Global Directory using X-YDB-Global-Directory
 -------------------------------------------------------------  [OK]   43.380ms
tStop - Stop the Server. MUST BE LAST TEST HERE.Port 55728 is currently being used.
Checking if it is the YDB-Web-Server.
HTTP/1.1 200 OK
Server running at 20
Now going to stop it...
STOP issued to process 20
Deleting tokens database files (if present)
--------------------------------------------------------------  [OK]  109.430ms

 --------------------------- %ydbwebjsonEncodeTest ---------------------------
numeric - is numeric function---------------------------------  [OK]    0.076ms
nearzero - encode of numbers near 0---------------------------  [OK]    0.188ms
jsonesc - create JSON escaped string--------------------------  [OK]    0.134ms
basic - encode basic object as JSON---------------------------  [OK]    0.909ms
vals - encode simple values only object as JSON---------------  [OK]    0.289ms
long - encode object with continuation nodes for value--------  [OK]    0.825ms
pre - encode object where parts are already JSON encoded------  [OK]    0.190ms
wp - word processing nodes inside object----------------------  [OK]    0.757ms
ltzero - leading / trailing zeros get preserved---------------  [OK]    0.128ms
strings - force encoding as string----------------------------  [OK]    0.099ms
labels - unusual labels---------------------------------------  [OK]    0.216ms
example - encode samples that are on JSON.ORG-----------------  [OK]    3.957ms
keyesc - keys should be escaped-------------------------------  [OK]    0.060ms
extarray - No top object; first level is an array-------------  [OK]    0.157ms

 --------------------------- %ydbwebjsonDecodeTest ---------------------------
jsonues - unescape JSON encoded string------------------------  [OK]    0.036ms
splita - JSON input with escaped characters on single line (uses build)
 -------------------------------------------------------------  [OK]    0.458ms
splitb - multiple line JSON input with lines split across tokens (uses builda)
 -------------------------------------------------------------  [OK]    0.115ms
splitc - multiple line JSON input with lines split inside boolean value
 -------------------------------------------------------------  [OK]    0.151ms
splitd - multiple line JSON input with key split--------------  [OK]    0.056ms
long - long document that must be saved across extension nodes  [OK] 51044.846ms
frac - multiple lines with fractional array elements----------  [OK]    0.135ms
valonly - passing in value only -- not array------------------  [OK]    0.144ms
numeric - passing in numeric types and strings----------------  [OK]    0.070ms
nearzero - decoding numbers near 0----------------------------  [OK]    0.072ms
badquote - poorly formed JSON (missing close quote on LABEL)--  [OK]    0.134ms
badslash - poorly formed JSON (non-escaped backslash)---------  [OK]    0.130ms
badbrace - poorly formed JSON (Extra Brace)-------------------  [OK]    0.046ms
badcomma - poorly formed JSON (Extra Comma)-------------------  [OK]    0.038ms
psnum - subjects that look like a numbers shouldn't be encoded as numbers
 -------------------------------------------------------------  [OK]    0.137ms
numlabel - label that begins with numeric---------------------  [OK]    0.242ms
purenum - label that is purely numeric------------------------  [OK]    0.409ms
strtypes - strings that may be confused with other types------  [OK]    0.062ms
estring - a value that looks like an exponents, other numerics  [OK]    0.213ms
sam1 - decode sample 1 from JSON.ORG--------------------------  [OK]    0.195ms
sam2 - decode sample 2 from JSON.ORG--------------------------  [OK]    1.747ms
sam3 - decode sample 3 from JSON.ORG--------------------------  [OK]    1.398ms
sam4 - decode sample 4 from JSON.ORG--------------------------  [OK]   21.893ms
sam5 - decode sample 5 from JSON.ORG--------------------------  [OK]    2.636ms
maxnum - encode large string that looks like number-----------  [OK]    0.420ms
escq - escaped quote across lines-----------------------------  [OK]    0.125ms
keyquote - keys with quotes-----------------------------------  [OK]    0.058ms

Ran 3 Routines, 89 Entry Tags
Checked 300 tests, with 0 failures and encountered 0 errors.

Debugging code written for the YottaDB Web Server

The YottaDB Web Server provides a --debug option for setting breakpoints to assist in debugging web application code. --debug sets a breakpoint at the specified label name, such that web server execution will break and present an interactive YottaDB prompt when that label is about to be executed. For example:

Window 1$ yottadb -r %ydbwebreq --debug ping^%ydbwebapi
Starting Server at port 9080 in directory /home/sam/work/gitlab/MWS/ at logging level 0 in debug mode stopping at ping^%ydbwebapi
Window 2$ curl localhost:9080/api/ping
Window 1:
%YDB-I-BREAKZBA, Break instruction encountered during ZBREAK action
                At M source location ping+1^%ydbwebapi
%YDB-W-NOTPRINCIO, Output currently directed to device /dev/null

YDB>u 0

HTTPREQ("header","accept-encoding")="gzip, deflate"
HTTPREQ("header","user-agent")="Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/116.0"
httpreq("header","accept-encoding")="gzip, deflate"
httpreq("header","user-agent")="Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/116.0"

YDB>u "/dev/null"

Window 1: {"self":"23984","server":"23984"}

Utility routines for debugging

The YottaDB Web server also provides two utility routines for help when debugging API code:

do stdoutzw^%ydbwebutils("myvariable")  ; ZWRITEs the contents of the given M variable, e.g. `myvariable`.
; Prints the given string to stdout. M variables may be output by being passed directly or by concatenating them to the string with the `_` operator.
do stdout^%ydbwebutils("String to print")

To print various levels of application logging to standard output, you can combine the above with the httplog variable, which corresponds to --log n sent via the command line, where n is 0 to 4.

Using the YDB Web Server with Systemd


The YDB web server starts and runs in the foreground until a signal 2 (CTRL-C) or a signal 15, i.e. MUPIP STOP is received. To run it in the background, you can use your shell's job control or systemd.

Systemd Set-up

To run the YDB Web Server in the background using Systemd, first create a /lib/systemd/system/ydb-web-server.service file like this:

Description=YottaDB Web Server

Environment='ydb_routines=$ydb_dist/plugin/o/_ydbmwebserver.so $ydb_dist/libyottadbutil.so'
ExecStart=/usr/bin/env "${ydb_dist}/yottadb" -run start^%%ydbwebreq --directory /var/www --port 9080 --log 1
ExecStop=/usr/bin/env "${ydb_dist}/yottadb" -run stop^%%ydbwebreq --port 9080

Replace the paths with paths appropriate to your system. Note that there are many other ways to do this, e.g. using EnvironmentFile for YottaDB environment variables or offloading the entire setup process to a script.

After creating the ydb-web-server.service file, do the following:

systemctl daemon-reload
systemctl enable ydb-web-server
systemctl is-enabled ydb-web-server
systemctl status ydb-web-server
systemctl start ydb-web-server
systemctl status ydb-web-server

This will to load the service file, enable the service (i.e. start it on reboot), check whether the service is enabled, start it, then check whether it was started successfully.

You can also try the following as well:

systemctl stop ydb-web-server
systemctl restart ydb-web-server
journalctl -xeu ydb-web-server

TLS Set-up on YottaDB

Setting up TLS can be difficult. The following instructions are provided as a guide, though they are not guaranteed to work in any particular case.


Follow the instructions for YDBEncrypt.

Certificate Set-up

# Go to your database
cd /data

# Create your certificate with a key that has a password. I know from previous
# interaction with the GT.M developers is that they don't allow passwordless keys
# for business reasons. Here's is how I did it; but you may already have a
# certificate. I moved all the files into a cert directory after this.
openssl genrsa -aes128 -passout pass:monkey1234 -out ./mycert.key 2048
openssl req -new -key ./mycert.key -passin pass:monkey1234 -subj '/C=US/ST=Washington/L=Seattle/CN=www.smh101.com' -out ./mycert.csr
openssl req -x509 -days 365 -sha256 -in ./mycert.csr -key ./mycert.key -passin pass:monkey1234 -out ./mycert.pem
mkdir certs
mv mycert.* certs/

# Create a file (name doesn't matter) called ydbcrypt_config.libconfig with the
# following contents. Note the section called server. This can be called anything.
# It lets you put a pair of cert/key for each environment you need to configure.
# Note the "client" section. This allows you to use the self-signed certificate
# by telling YottaDB about it.
cat ydbcrypt_config.libconfig
tls: {
  server: {
    format: "PEM";
    cert: "/data/certs/mycert.pem";
    key:  "/data/certs/mycert.key";
  client: {
    CAfile: "/data/certs/mycert.pem";

# In your file that sets up the YottaDB environment, add set the env variable
# ydbcrypt_config to be the path to your config file:
export ydbcrypt_config="/data/ydbcrypt_config.libconfig"

# Find out the hash of your key password using the maskpass utility
$ydb_dist/plugin/ydbcrypt/maskpass <<< 'monkey1234' | cut -d ":" -f2 | tr -d ' '

# In your environment file, ydbtls_passwd_{section name} to be that hash. For me, it's:
export ydbtls_passwd_server="30A22B54B46618B4361F"

# Run the server like this, substituting the {section name} appropriately. Here it is server. See how to stop it below (although you can CTRL-C here and stop it).
$ydb_dist/yottadb -run ^%ydbwebreq --port 9080 --tlsconfig server

# Test the server like this (cacert to supply curl with the self-signed Certificate)
curl --cacert /data/certs/mycert.pem https://localhost:9080

Then, from M, you can connect to the server like this, implicitly using the self-signed certificate from via the client.CAfile in the section above:

set port=9080
open "porttest":(connect=""_port_":TCP":delim=$char(13,10):attach="client"):0:"SOCKET"
write /tls("client",,"client")
set d=$device ; check d to see if it is positive--in that case, TLS failed.
write "GET /api/ping HTTP/1.1"_$char(13,10)
write "Host: localhost:"_options("port")_$char(13,10)
write "User-Agent: "_$zposition_$char(13,10)
write "Accept: */*"_$char(13,10)_$char(13,10)
new httpstatus read httpstatus
; etc.

Log output will look something like this:

Starting Server at port 9080 using TLS configuration server
::ffff: - - [15/SEP/2022 01:19:52 PM] Starting Child at PID 13 from parent 1
::ffff: - - [15/SEP/2022 01:19:52 PM] TLS Connection Data:
::ffff: - - [15/SEP/2022 01:19:52 PM]             $DEVICE: 1,Connection reset by peer
::ffff: - - [15/SEP/2022 01:19:52 PM]                $KEY: ESTABLISHED|h1663247992000|::ffff:
::ffff: - - [15/SEP/2022 01:19:52 PM]               $TEST: 0
::ffff: - - [15/SEP/2022 01:19:52 PM] Disconnect/Halt 13
::ffff: - - [15/SEP/2022 01:19:58 PM] Starting Child at PID 15 from parent 1
::ffff: - - [15/SEP/2022 01:19:58 PM] TLS Connection Data:
::ffff: - - [15/SEP/2022 01:19:58 PM]             $DEVICE: 0
::ffff: - - [15/SEP/2022 01:19:58 PM]                $KEY: ESTABLISHED|h1663247998000|::ffff:
::ffff: - - [15/SEP/2022 01:19:58 PM]               $TEST: 1
::ffff: - - [15/SEP/2022 01:19:58 PM] GET / HTTP/1.1
::ffff: - - [15/SEP/2022 01:19:58 PM] Disconnect/Halt 15

To stop TLS, use --tlsconfig client, e.g.:

$ydb_dist/yottadb -run stop^%ydbwebreq --port 9080 --tlsconfig client

Authentication and Authorization

Before starting, note that libsodium-devel must be installed on your server in order to use the features here. If libsodium-devel wasn't installed it prior to installing the YottaDB Web Server, please install it and then reinstall the Web Server.


When you start the server with start^%ydbwebreq, the server will not require any authentication, and all web services will be accessible by anyone with access to your network. To protect your web services, enable authentication.

Note that file system pages are NEVER protected by authentication: only web services defined in your _ydbweburl.m file are protected. This is the default configuration, since file pages must be served in order to prompt users to log in.

There are currently two ways to add authentication:

  1. Using the --auth-stdin flag.

    • Prompts for a username, password, and role. Multiple users may be entered if desired.

    • Users will be saved into a users.json file in the current directory, which can then be used with the --auth-file </path/to/filename.json> flag.

  2. Using the --auth-file </path/to/filename.json> option.

    • Loads the users in /path/to/filename.json. The file has JSON content and the path can be absolute or relative.

      • Passwords in this file cannot start with a $, since that character is used to identify hashed passwords (this restriction does not apply when using the --auth-stdin flag).

      • Any file at /path/to/filename.json must be in the following format if created manually:

        "username": "user1",
        "password": "plaintext-password1",
        "authorization": "RW"
        "username": "user2",
        "password": "plaintext-password2",
        "authorization": "RO"

When the server starts up and reads the newly created JSON file, the passwords will be hashed and the plain-text passwords will no longer exist.

For example:

$ydb_dist/yottadb -r %ydbwebreq --auth-stdin

Please enter usernames, passwords, authorization at the prompts:
Enter enter without entering a username to quit from the loop.

Username: sam
Password: foo
Authorization: RW

Username: <enter>
Saving users to file users.json with passwords hashed
Starting Server at port 9080 in directory xxx at logging level 0 using authentication


$ydb_dist/yottadb -r %ydbwebreq --auth-file users.json
Starting Server at port 9080 in directory xxx at logging level 0 using authentication

If you manually create a users.json file as shown above, you will get a message about each password getting hashed:

$ydb_dist/yottadb -r %ydbwebreq --auth-file myusers.json
Hashing password for user user1
Hashing password for user user2
Starting Server at port 9080 in directory xxx at logging level 0 using authentication

Login/Token/Logout workflow

Once authentication is enabled, all REST endpoints defined in the _ydbweburl.m file will be protected. However, these endpoints are always available from the server at these addresses:

  • /api/ping

  • /api/version

  • /api/login

  • /api/logout

  • /api/auth-mode

Attempts to call any other end point without authentication or with a bad token will result in an error. For example:

curl -Ss localhost:9080/test/json | jq
  "apiVersion": 1.1,
  "error": {
    "code": 403,
    "errors": [
        "errname": "Forbidden",
        "message": "Forbidden",
        "reason": 403
    "request": "GET /test/json ",
    "toperror": "Forbidden"

To login, POST a JSON of the format: { "username": "xxx", "password": "xxx" } to /api/login. The server will return a token in the body of the request in the format: { "token": "xxx", "authorization": "RO", timeout:900 }. It will return 401 Unauthorized if the username and password are not specified correctly.

For example:

curl -H 'Content-Type: application/json' -d '{ "username": "sam", "password": "foo" }' localhost:9080/api/login

To terminate the session and invalidate the token, log out by sending the token back in the Authorization request header using a GET call.

$ curl -H 'Authorization: Bearer F3joHQj0kyt1Df8ZglOp40' localhost:9080/api/logout

It is possible to log out again and receive an HTTP 200 in response, but the status will say token not found.

If a token timed out, you will get an HTTP 408 back, with a message of "Token timeout". By default, each token will time out in 15 minutes from its last use.

Tokens are cleaned at 10 times the timeout. In the default case, they will be cleaned in 150 minutes from the last time the token is used. In this case, you will get a 403 with a message of "Forbidden".

The default timeout can be changed by using --token-timeout. See below for more details.


Currently, nothing is done with the authorization of RO or RW except to populate the HTTPREADWRITE variable. It's the responsibility of the end application choose how to handle the value of this variable. If authorizations other than "RW" are used, HTTPREADWRITE will remain zero.

Miscellaneous considerations

Using --token-timeout {n}

The --token-timeout {n} flag can be used to specify when tokens obtained via a log-in exchange will expire. n is the number of seconds.

The default token timeout is 15 minutes. Specifying --token-timeout 0 will run the server with no timeouts. This can be useful for machine-to-machine communication where no timeout behavior is desired.

Debugging token issues in development

The YottaDB Web Server supports a --log option for logging web server activity during operation. --log supports five levels of verbosity using the values 0 through 4:

  1. 0: No output except first line mentioning the server and its start-up settings, including, importantly, the port number.

  2. 1: Worker process start, TLS connection information, HTTP requests, HTTP Continues, Worker process stop, Use of alternate global directory, working directory, or environment variables, token database location

  3. 2: Log headers, periodic token clean-up message

  4. 3: Log all input and output from server, print out authentication tokens

  5. 4: Single line stepping (experimental)

Each successive verbosity level includes all output from preceding verbosity levels. For example:

Log level 1 show the location of the created database:

<PARENT> - - [14/APR/2023 12:08:08 PM] Created database - global directory: /tmp/yottadb/r999_x86_64/ydbgui94468.gld
<PARENT> - - [14/APR/2023 12:08:08 PM]                  - database file   : /tmp/yottadb/r999_x86_64/ydbgui94468.dat

Log level 2 additionally shows every timeout interval (15 minutes by default) before each request:

<PARENT> - - [14/APR/2023 12:19:28 PM] Cleaning Tokens

Log level 3 additionally shows sensitive information on all user hashes and tokens after every 10 seconds of inactivity:

<PARENT> - - [14/APR/2023 12:11:08 PM] Users
<PARENT> - - [14/APR/2023 12:11:08 PM] Tokens

Note that passwords and password-hashes are never printed, since they are not actually stored anywhere.

Log level 4 prints the M lines that the server executes:

sstep+4^%ydbwebutils: open parentStdout use parentStdout
sstep+5^%ydbwebutils: write !,"Stepping STARTED",!

The –readwrite flag

If the server is started with users, the --readwrite flag no longer applies and the HTTPREADWRITE variable is set only if the authorization is "RW".

You are free to have different authorizations which you can obtain at runtime using the API $$getAuthorizationFromToken^%ydbwebusers(token).

Running the YDB Web Server with Docker

To build a YDB Web Server Docker image and run tests, run:

docker build -t mws .

Various options can be used to change the behavior of this command:

# Run Server on port 9080
docker run -v $PWD/src:/mwebserver/r --rm -it -p 9080:9080 mws server

# Run Server on port 9080 with level 2 verbosity
docker run -v $PWD/src:/mwebserver/r --rm -it -p 9080:9080 mws server 2

# Run Tests
docker run -v $PWD/src:/mwebserver/r --rm mws tests

# Run Bash
docker run -v $PWD/src:/mwebserver/r --rm -it -p 9080:9080 mws bash

# Run debugger (starts server on 9080, and you need to zstep into)
docker run --rm -it -p 9080:9080 mws debug

# Run Server TLS on port 9080:
docker run -p 9080:9080 -v $PWD/src:/mwebserver/r --rm -it mws server-tls

# Run Debug TLS on port 9080:
docker run -p 9080:9080 -v $PWD/src:/mwebserver/r --rm -it mws debug-tls

Since you are passing the src directory in Docker run as a volume, you can modify the routines on the host and see the changes in the container right away.


The primary input and output format for the web services is JSON. In the preceding sections, most examples sent text output to web service calls.

Now, let's demonstrate how to use JSON for web service I/O as well as a few other helpful resources and techniques, including:

  • API calls that help verify that all required data is sent

  • How to parse text by new lines

  • How to send error messages back to the client


Both JSON encoding and decoding are done automatically by the YottaDB web server if the accept-encoding request header is "application/json" or the content-type response reader is "application/json". You can also use the JSON encoding/decoding APIs directly if you wish.

How to use Auto Encoding of JSON

Encoding is done automatically when sending data from M to the browser. For example, in _ydbweburl.m:

;;GET test/json getjson^myjson

In myjson.m:

getjson ; GET /test/json JSON sample
    set httprsp("foo",1)="boo"
    set httprsp("foo",2)="doo"
    set httprsp("foo",3)="loo"
curl -sS localhost:9080/test/json | jq

curl will then return the following output:

    "foo": [ "boo", "doo", "loo" ]

How to use Auto Decoding of JSON

Data received from the browser is automatically decoded and converted to an M array in httpreq("json"). For example, consider the posttest label mapped in _ydbweburl.m:

;;POST test/post posttest^%ydbwebapi

The label in the myjson.m M routine:

posttest ; POST /test/post Simple test for post
    set httprsp("mime")="text/plain; charset=utf-8" ; Character set of the return URL
    set httprsp="/path/"_httpreq("json","random")_"/1" ; Stored URL
    set httploc=httprsp ; Set the path to your data and return

This label is accessible via the URL /test/post, e.g.:

curl -X POST -H "Content-Type: application/json" localhost:9080/test/post -d '{ "random": "foo" }'

curl will then return the output /path/foo/1.

Direct API


Encoding is done using:


The encode^%ydbwebjson label handles the complexities of JSON encoding, including prefixing 0s to M numeric values less than 0, escaping quotes, etc. Also, the encode^%ydbwebjson label always succeeds, so passing an error array is unnecessary.

For example:

S X("myObj","booleanT")="true"
S X("myObj","booleanF")="false"
S X("myObj","numeric")=3.1416
S X("myObj","nullValue")="null"
S X("myObj","array",1)="one"
S X("myObj","array",2)="two"
S X("myObj","array",3)="three"
S X("myObj","subObject","fieldA")="hello"
S X("myObj","subObject","fieldB")="world"
D encode^%ydbwebjson("X","JSON")

> zwrite JSON

Decoding is done using:


The first two arguments are required. The third argument is optional; if omitted, error messages will be dumped into %ydbwebjsonerr.

An array input by name consists of a database variable subscripted by array index intengers, e.g.:


Such an array can be passed to a routine like this:

DO decode^%ydbwebjson("MYLOCAL","ARRAY","LOCALERR")


DO decode^%ydbwebjson("MYLOCAL",$NAME(ARRAY),"LOCALERR")

Note that the label uses name indirection to access the array elements.

For example:

{"title":"my array of stuff", "count":3, "items": [
{"name":"red", "rating":"ok"},
{"name":"blue", "rating":"good"},
{"name":"purple", "rating":"outstanding"}

YDB>D decode^%ydbwebjson($NA(JSON),$NA(OUT),$NA(ERR))

OUT("title")="my array of stuff"

%YDB-E-UNDEF, Undefined local variable: ERR

Now, let's try an error case by deleting the last brace in the JSON array:

JSON(1)="{""title"":""my array of stuff"", ""count"":3, ""items"": ["
JSON(2)="{""name"":""red"", ""rating"":""ok""},"
JSON(3)="{""name"":""blue"", ""rating"":""good""},"
JSON(4)="{""name"":""purple"", ""rating"":""outstanding""}"

YDB>S JSON(5)="]"


YDB>D decode^%ydbwebjson($NA(JSON),$NA(OUT),$NA(ERR))

OUT("title")="my array of stuff"

ERR(1)="Stack mismatch - exit stack level was  1"

Other Utilities

Check for unwanted arguments

The $$unkargs^%ydbwebutils label can be used to check whether any input arguments are missing. If so, the caller must QUIT. In that case, the HTTP error code is set to 111 automatically.

For example:

I $$unkargs^%ydbwebutils(.httpargs,"file,iens,field,screen,match") Q  ; Is any of these not passed?

In this example , the code checks that all input variables to a Fileman call are present. If not, it returns an error code of 111. There's no need to set the error manually. Note also that the arguments are passed by reference and the list of fields is passed as a literal.

Converting long lines to an arrays

A single long line of text can be converted to an array using $C(13,10) (CR/LF). For instance, this method can be used to convert the body of a POST or PUT request into a linear array.

For example, passing the input and output by reference:

D parse10^%ydbwebutils(.BODY,.PARSED) ; Parser

Given this value of BODY:


parse10^%ydbwebutils yields:


To reverse the transformation, again passing input by reference:

D addcrlf^%ydbwebutils(.RESULTS) ; crlf the result

This is useful when line breaks between word processing fields must be preserved in a given format, e.g. the Fileman format, wherein a CRLF must be added to each line of the result.

Sending an HTTP error back to the client

In case an error is encountered while executing server-side code, an HTTP error code can be sent and execution terminated. The general format for doing this is:

D setError^%ydbwebutils(HTTP code,error description) QUIT

For example:

D setError^%ydbwebutils("400","Input parameters not correct") Q