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.TH "TSHTTPHOOKADD" "3ts" "Mar 08, 2019" "7.1" "Apache Traffic Server"
.SH NAME
TSHttpHookAdd \- intercept Traffic Server events
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.SH SYNOPSIS
.sp
\fI#include <ts/ts.h>\fP
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.TP
.B void TSHttpHookAdd(TSHttpHookID\fI\ id\fP, TSCont\fI\ contp\fP)
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.INDENT 0.0
.TP
.B void TSHttpSsnHookAdd(TSHttpSsn\fI\ ssnp\fP, TSHttpHookID\fI\ id\fP, TSCont\fI\ contp\fP)
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.TP
.B void TSHttpTxnHookAdd(TSHttpTxn\fI\ txnp\fP, TSHttpHookID\fI\ id\fP, TSCont\fI\ contp\fP)
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.SH DESCRIPTION
.sp
Hooks are points in Apache Traffic Server transaction HTTP processing
where plugins can step in and do some work. Registering a plugin
function for callback amounts to adding the function to a hook. You
can register your plugin to be called back for every single
transaction, or for specific transactions only.
.sp
HTTP transaction hooks are set on a global basis using the function
\fI\%TSHttpHookAdd()\fP\&. This means that the continuation specified
as the parameter to \fI\%TSHttpHookAdd()\fP is called for every
transaction. \fI\%TSHttpHookAdd()\fP is typically called from
\fBTSPluginInit()\fP or \fBTSRemapInit()\fP\&.
.sp
\fI\%TSHttpSsnHookAdd()\fP adds \fIcontp\fP to
the end of the list of HTTP session hooks specified by \fIid\fP\&.
This means that \fIcontp\fP is called back for every transaction
within the session, at the point specified by the hook ID. Since
\fIcontp\fP is added to a session, it is not possible to call
\fI\%TSHttpSsnHookAdd()\fP from the plugin initialization routine;
the plugin needs a handle to an HTTP session.
.sp
\fI\%TSHttpTxnHookAdd()\fP adds \fIcontp\fP
to the end of the list of HTTP transaction hooks specified by
\fIid\fP\&. Since \fIcontp\fP is added to a transaction, it is
not possible to call \fI\%TSHttpTxnHookAdd()\fP from the plugin
initialization routine but only when the plugin has a handle to an
HTTP transaction.
.SH RETURN VALUES
.sp
None. Adding hooks is always successful.
.SH EXAMPLES
.sp
The following example demonstrates how to add global, session and
transaction hooks:
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.INDENT 3.5
.sp
.nf
.ft C
#include <ts/ts.h>

static int
handler(TSCont contp, TSEvent event, void *edata)
{
    TSHttpSsn ssnp;
    TSHttpTxn txnp;

    switch (event){
    case TS_EVENT_HTTP_SSN_START:
        ssnp = (TSHttpSsn) edata;
        // Add a session hook ...
        TSHttpSsnHookAdd(ssnp, TS_HTTP_TXN_START_HOOK, contp);
        TSHttpSsnReenable(ssnp, TS_EVENT_HTTP_CONTINUE);
        return 0;
    case TS_EVENT_HTTP_TXN_START:
        txnp = (TSHttpTxn) edata;
        // Add a transaction hook ...
        TSHttpTxnHookAdd(txnp, TS_HTTP_READ_REQUEST_HDR_HOOK, contp);
        TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);
        return 0;
    default:
         break;
    }

    return 0;
}

void
TSPluginInit (int argc, const char *argv[])
{
    TSCont contp;
    contp = TSContCreate(handler, NULL);
    TSHttpHookAdd(TS_HTTP_SSN_START_HOOK, contp);
}
.ft P
.fi
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.SH SEE ALSO
.sp
\fBTSAPI(3ts)\fP,
\fBTSContCreate(3ts)\fP,
\fBTSLifecycleHookAdd(3ts)\fP
.SH COPYRIGHT
2019, dev@trafficserver.apache.org
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