ns_http - HTTP client functionality
The command ns_http provides HTTP and HTTPS client functionality. It can be used to create, dispatch, wait on and/or cancel requests and process replies from web servers, where NaviServer acts as a web client. This is important, for example, to use web services and REST interfaces.
The command ns_http queue opens a connection to the web server denoted in the url and returns (unless a -donecallback is specified) an id, which might be used later in ns_http wait or ns_http cancel to refer to this request. The command supports both HTTP and HTTPS URIs. The request is run in the default task queue in a dedicated per-queue thread.
Send an HTTP request and wait for the result. The command ns_http run is similar to ns_http queue followed by ns_http wait. The HTTP request is run in the same thread as the caller.
Waits for the queued command specified by the id returned from ns_http queue to complete. Returns a Tcl dictionary with the following keys: status, time, headers. The status contains HTTP/HTTPS status code (200, 201, 400, etc). The time contains elapsed request ns_time. The headers contains the name of the set with response headers. If the request body was given over a Tcl channel, it will add the key body_chan to the result dictionary. If the response was not spooled in the file nor channel, it will return body key with the response data. Otherwise it will return either file if the response was spooled into the named (or temporary) file or outputchan if the request was spooled into a Tcl channel. For HTTPS requests, it will add https with some low-level TLS parameters in a Tcl dictionary format. The specified -timeout specified the maximum duration of the request to complete. The time can be specified in any supported ns_time format.
On success, ns_http wait returns the same dictionary as the ns_http run. On error, leaves a descriptive error message in the interpreter result. On timeout, sets the Tcl variable to NS_TIMEOUT in addition to leaving the error message.
ID of the HTTP request to wait for.
Cancel queued HTTP/HTTPS request by the ID (of the request) as returned by ns_http queue command. The command returns an empty result. The sense behind this command is to be able to terminate runaway requests or requests that have been timed out. Even completed requests can be cancelled if nobody is interested in the request result.
ID of the HTTP request to cancel.
Cancel all pending HTTP/HTTPS requests issued in the current interpreter. At this point, any Tcl channels that have been optionally assigned to a task, will be automatically closed.
If id was specified, returns a single list in form of: "id url status". If id was not specified, returns a list of N elements, where each element is in itself a list in the form of: "id url status". The status can be one of: "done", "running", "error".
Optional ID of the HTTP request to list.
Returns statistics from the currently running request in the form of a list of Tcl dictionaries. If the optional id was specified, just one dictionary containing details about the requested task will be returned, or empty if the task cannot be found. Otherwise, a list of dictionaries will be returned. The returned dictionary contains the following keys: task, url, requestlength, replylength, sent, received, sendbodysize, replybodysize, replysize. The task returns the ID of the HTTP task. The url returns the URL for the given task. The requestlength returns the length of the complete HTTP request, including header line, all the headers plus the optional request body. The replylength returns the value of the Content-Length as returned by the remote. This can be zero if the length of returned data is not known in advance. The member sent returns the number of bytes sent to the remote. This includes the header line, all the headers plus optional request body. The member received contains the number of bytes received from the remote. This includes the status line, all the headers plus the optional reply body. The member sendbodysize returns the number of bytes of the request body sent to the remote so far. The member replybodysize returns the number of bytes of the reply body received from the remote so far. The member replysize returns the number of bytes of the body received from the remote so far. The difference to the replybodysize is that this element tracks the number of body bytes prior to the optional deflate step for compressed contents, whereas the member replybodysize tracks the number of body bytes of the deflated contents. For uncompressed reply content, both replysize and replybodysize will have the same value.
Optional ID of the HTTP request to get statistics for.
First, a minimal GET example:
% ns_http queue http://www.google.com
http0
% ns_http wait http0
status 302 time 0:97095 headers d0 body { ... }
The second example is a code snippet making a request via HTTPS (note that HTTPS is supported only when NaviServer was compiled with OpenSSL support).
% set result [ns_http run https://www.google.com] % dict get $result status 302
If the returned data is too large to be retained in memory, you can use the -spoolsize to control when the content should be spooled to file. The spooled filename is contained in the resulting dict under the key file.
% set result [ns_http run -spoolsize 1kB https://www.google.com] % dict get $result file /tmp/http.83Rfc5
For connecting to a server with virtual hosting that provides multiple certificates via SNI (Server Name Indication) the option -hostname is required.
The third example is a code snippet making a POST requests via HTTPS and provides url-encoded POST data. The example sets a larger timeout on the request, provides requests headers and returns reply-headers.
#######################
# construct POST data
#######################
set post_data [join [lmap {key value} {
q NaviServer
} {
set _ "[ns_urlencode $key]=[ns_urlencode $value]"
}] &]
#######################
# submit POST request
#######################
set requestHeaders [ns_set create headers "Content-type" "application/x-www-form-urlencoded"]
set r [ns_http queue -method POST \
-headers $requestHeaders \
-timeout 10.0 \
-body $post_data \
https://httpbin.org/anything]
#######################
# output results
#######################
ns_log notice "status [dict get $r status]"
ns_log notice "reply [dict get $r ]"
ns_log notice "headers [dict get $r headers]"
The fourth example is a code snippet that sets a larger timeout on the request, provides an ns_set for the reply headers, and spools results to a file if the result is larger than 1000 bytes.
set requestHeaders [ns_set create headers Host localhost]
set h [ns_http queue -timeout 10.0 http://www.google.com]
ns_http wait -result R -headers $requestHeaders -status S -spoolsize 1kB -file F $h
if {[info exists F]} {
ns_log notice "Spooled [file size $F] bytes to $F"
file delete -- $F
} else {
ns_log notice "Got [string length $R] bytes"
}
The next example is for downloading a file from the web into a named file or passed Tcl channel. Note the -spoolsize of zero, which will redirect all received data into the file/channel. Without the -spoolsize set, all the data would be otherwise stored in memory.
% ns_http run -outputfile /tmp/reply.html -spoolsize 0 http://www.google.com status 302 time 0:132577 headers d2 file /tmp/reply.html
% set chan [open /tmp/file.dat w] % ns_http run -outputchan $chan -spoolsize 0 http://www.google.com status 302 time 0:132577 headers d2 outputchan file22 % close $chan
The behavior of ns_http can be influenced by optional settings in the NaviServer configuration file. One can specify the default keep-alive timeout for outgoing HTTP requests, and the logging behavior. When logging is activated, the log file will contain information similar to the access.log of NaviServer (see nslog module), but for HTTP client requests.
#---------------------------------------------------------------------
# HTTP client (ns_http) configuration
#---------------------------------------------------------------------
ns_section ns/server/server1/httpclient {
#
# Set default keep-alive timeout for outgoing ns_http requests
#
ns_param keepalive 5s ;# default: 0s
#
# Configure log file for outgoing ns_http requests
#
ns_param logging on ;# default: off
ns_param logfile ${logroot}/httpclient.log
ns_param logrollfmt %Y-%m-%d ;# format appended to log filename
#ns_param logmaxbackup 100 ;# 10, max number of backup log files
#ns_param logroll true ;# true, should server log files automatically
#ns_param logrollonsignal true ;# false, perform roll on a sighup
#ns_param logrollhour 0 ;# 0, specify at which hour to roll
}