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<HTML><HEAD>
<TITLE>C Examples -- Example 4: stats</TITLE>
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<a name="16333">
</a><h3>Example 4: stats</h3>
<p><a name="16348">
</a>The following example provides several cooperating facilities to implement a simple connection statistics system. The module includes a trace to collect the statistics on each connection, a scheduled procedure to aggregate the statistics, the /NS/Stat request function to print the statistics, and a Tcl command to access the statistics in a script.</p>
<p><a name="16335">
</a>This example can be found in the <code>examples/c/stats</code> directory.</p>
<pre> <a name="15846"></a>
<a name="16371"></a>/*
<a name="16376"></a> * stat.c - Example C module.
<a name="16377"></a> *
<a name="16378"></a> * This example incorporates many of the features of the AOLserver
<a name="16379"></a> * C API in a single simple, but useful, statistics gathering module.
<a name="16380"></a> * The module maitains statistics on the number of connections and
<a name="16381"></a> * bytes sent by a server. The data is stored in a simple
<a name="16382"></a> * `StatContext' structure which is allocated when the module is
<a name="16383"></a> * loaded. The StatContext stores the current, last, and total numbers
<a name="16384"></a> * and is updated after each connection by the `StatTrace' connection
<a name="16385"></a> * trace procedure. At a regular interval (the interval in seconds
<a name="16386"></a> * is configurable), the `StatUpdate' funcation is called to log the
<a name="16387"></a> * current and total number to the AOLserver log file and then
<a name="16388"></a> * makes the current data the last data. Access to these data is
<a name="16389"></a> * provided in two forms:
<a name="16390"></a> *
<a name="16391"></a> * 1. A simple C request function, `StatRequest', will return the
<a name="16392"></a> * current data as a simple notice page. The StatRequest function
<a name="16393"></a> * is registered at the GET /NS/Stat URL of the server.
<a name="16394"></a> *
<a name="16395"></a> * 2. The `ns_stat' Tcl command is added to each Tcl interpreter
<a name="16396"></a> * of the server interpreter pool. This allows a Tcl script
<a name="16397"></a> * to access the current, last, or total data at any time.
<a name="16398"></a> *
<a name="16399"></a> * Because the AOLserver is completely multithreaded, the statistics
<a name="16400"></a> * data can be updated and queried simultaneously. An Ns_Mutex is
<a name="16401"></a> * included in the ServerContext structure to keep multiple threads
<a name="16402"></a> * from accessing the data at the same time.
<a name="16403"></a> *
<a name="16404"></a> * Finally, on shutdown, the `StatShutdown' function is called to
<a name="16405"></a> * print out a final tally and clean up the ServerContext structure.
<a name="16406"></a> *
<a name="16407"></a> * Note that all the features of this module are specific to the
<a name="16408"></a> * server it is loaded into. The server handle, `hServer',
<a name="16409"></a> * is used to makes sure the trace, request, Tcl command, and
<a name="16410"></a> * shutdown functions are all run in the context of the single
<a name="16411"></a> * server. Other virtaul servers may ignore or load the
<a name="16412"></a> * stat module as well and the AOLserver guarantees the data
<a name="16413"></a> * will be keep separate for each server.
<a name="16417"></a>*/
<a name="16418"></a>
<a name="16419"></a>
<a name="16420"></a>
<a name="16421"></a>#include "ns.h"
<a name="16422"></a>#include "nstcl.h"
<a name="16423"></a>
<a name="16424"></a>/*
<a name="16425"></a> * The default statistics update interval is 1 minute or 60 seconds.
<a name="16426"></a> */
<a name="16427"></a>#define DEFAULT_INTERVAL 60
<a name="16428"></a>
<a name="16429"></a>/*
<a name="16430"></a> * Definitions of the StatContext structure which is allocated
<a name="16431"></a> * on a per-server basis.
<a name="16432"></a> */
<a name="16433"></a>typedef struct {
<a name="16434"></a> int bytes;
<a name="16435"></a> int conns;
<a name="16436"></a>} StatData;
<a name="16437"></a>
<a name="16438"></a>typedef struct {
<a name="16439"></a> Ns_Mutex lock;
<a name="16440"></a> int interval;
<a name="16441"></a> char *hServer;
<a name="16442"></a> StatData current;
<a name="16443"></a> StatData last;
<a name="16444"></a> StatData total;
<a name="16445"></a>} StatContext;
<a name="16446"></a>
<a name="16447"></a>
<a name="16448"></a>/*
<a name="16449"></a> * Forward declarations of functions which will be referenced
<a name="16450"></a> * in the stat module initialization function.
<a name="16451"></a> */
<a name="16452"></a>static Tcl_CmdProc StatCmd;
<a name="16453"></a>static Ns_TclInterpInitProc StatTclInit;
<a name="16454"></a>static Ns_TraceProc StatTrace;
<a name="16455"></a>static Ns_Callback StatUpdate;
<a name="16456"></a>static Ns_Callback StatShutdown;
<a name="16457"></a>static Ns_OpProc StatRequest;
<a name="16458"></a>
<a name="16459"></a>/*
<a name="16460"></a> * The Ns_ModuleVersion exported integer is used to verify
<a name="16461"></a> * this module version when loaded. For AOLserver 2.0,
<a name="16462"></a> * 1 (one) is the only valid value for this variable.
<a name="16463"></a> */
<a name="16464"></a>int Ns_ModuleVersion = 1;
<a name="16465"></a>
<a name="16466"></a>/*
<a name="16467"></a> * The Ns_ModuleInit function is the function the AOLserver
<a name="16468"></a> * will call each time the module is loaded into a
<a name="16469"></a> * server. The function is passed two parameters:
<a name="16470"></a> *
<a name="16471"></a> * hServer: The server `handle' as a string. This is the
<a name="16472"></a> * short name given to the virutal server such
<a name="16473"></a> * as `server1'.
<a name="16474"></a> *
<a name="16475"></a> * hModule: The module `handle' as a string. This is the
<a name="16476"></a> * short name given to the module such as `stat'
<a name="16477"></a> *
<a name="16478"></a> * For example, if this module is known as `stat' and loaded
<a name="16479"></a> * into the `server1' server with entries similar to the following
<a name="16480"></a> * in the nsd.ini file:
<a name="16481"></a> *
<a name="16482"></a> * [ns\servers]
<a name="16483"></a> * server1=My First Server
<a name="16484"></a> *
<a name="16485"></a> * [ns\server1\modules]
<a name="16486"></a> * stat=stat.dll
<a name="16487"></a> *
<a name="16488"></a> * This function would be called with "server1" and "stat" as
<a name="16489"></a> * its arguments.
<a name="16490"></a> *
<a name="16491"></a> */
<a name="16492"></a>int
<a name="16493"></a>Ns_ModuleInit(char *hServer, char *hModule)
<a name="16494"></a>{
<a name="16495"></a> char *configPath;
<a name="16496"></a> StatContext *ctx;
<a name="16497"></a>
<a name="16498"></a>
<a name="16499"></a> /*
<a name="16500"></a> * Create and initalize the statistics context.
<a name="16501"></a> */
<a name="16502"></a> ctx = ns_malloc(sizeof(StatContext));
<a name="16503"></a> Ns_InitializeMutex(&ctx->lock);
<a name="16504"></a> ctx->hServer = hServer;
<a name="16505"></a> ctx->current.bytes = 0;
<a name="16506"></a> ctx->current.conns = 0;
<a name="16507"></a> ctx->last.bytes = 0;
<a name="16508"></a> ctx->last.conns = 0;
<a name="16509"></a> ctx->total.bytes = 0;
<a name="16510"></a> ctx->total.conns = 0;
<a name="16511"></a>
<a name="16512"></a> /*
<a name="16513"></a> * Determine the statistics interval from the config file.
<a name="16514"></a> * The Ns_ConfigGetPath function will expand to the
<a name="16515"></a> * `server module specific' configuration section, e.g.,
<a name="16516"></a> * [ns\server1\module\stat].
<a name="16517"></a> */
<a name="16518"></a> configPath = Ns_ConfigGetPath(hServer, hModule, NULL);
<a name="16519"></a> if (!Ns_ConfigGetInt(configPath, "Interval", &ctx->interval)) {
<a name="16520"></a> ctx->interval = DEFAULT_INTERVAL;
<a name="16521"></a> }
<a name="16522"></a>
<a name="16523"></a> /*
<a name="16524"></a> * Register the trace to accumulate the statistics.
<a name="16525"></a> */
<a name="16526"></a> Ns_RegisterServerTrace(hServer, StatTrace, ctx);
<a name="16527"></a>
<a name="16528"></a> /*
<a name="16529"></a> * Register the statistics update function to run at
<a name="16530"></a> * regular intervals.
<a name="16531"></a> */
<a name="16532"></a> Ns_ScheduleProc(StatUpdate, ctx, 0, ctx->interval);
<a name="16533"></a>
<a name="16534"></a> /*
<a name="16535"></a> * Add the GET /NS/Stat request function.
<a name="16536"></a> */
<a name="16537"></a> Ns_RegisterRequest(hServer, "GET", "/NS/Stat", StatRequest,
<a name="16758"></a> NULL, ctx, 0);
<a name="16538"></a>
<a name="16539"></a> /*
<a name="16540"></a> * Add the Tcl "ns_stat" command to the interpreter pool.
<a name="16541"></a> * Note how the context is passed to StatTclInit which
<a name="16542"></a> * then passes it to the Tcl_CreateCommand function.
<a name="16543"></a> */
<a name="16544"></a> Ns_TclInitInterps(hServer, StatTclInit, ctx);
<a name="16545"></a>
<a name="16546"></a> /*
<a name="16547"></a> * Register the statistics shutdown procedure which
<a name="16548"></a> * cleans up the context on server shutdown.
<a name="16549"></a> */
<a name="16550"></a> Ns_RegisterServerShutdown(hServer, StatShutdown, ctx);
<a name="16551"></a>
<a name="16552"></a> return NS_OK;
<a name="16553"></a>}
<a name="16554"></a>
<a name="16555"></a>
<a name="16556"></a>
<a name="17884"></a>
<a name="17885"></a>
<a name="17886"></a>
<a name="18826"></a>
<a name="18827"></a>
<a name="17887"></a>
<a name="17888"></a>/*
<a name="16557"></a> * StatTrace is called after each connection and accumulates the
<a name="16558"></a> * statistics.
<a name="16559"></a> */
<a name="16560"></a>static void
<a name="16561"></a>StatTrace(void *ctx, Ns_Conn *conn)
<a name="16562"></a>{
<a name="16563"></a> StatContext *sc;
<a name="16564"></a> int bytes;
<a name="16565"></a>
<a name="16566"></a> sc = (StatContext *) ctx;
<a name="16567"></a> Ns_LockMutex(&sc->lock);
<a name="16568"></a> bytes = Ns_ConnResponseLength(conn);
<a name="16569"></a> sc->current.bytes += bytes;
<a name="16570"></a> sc->total.bytes += bytes;
<a name="16571"></a> ++sc->current.conns;
<a name="16572"></a> ++sc->total.conns;
<a name="16573"></a> Ns_UnlockMutex(&sc->lock);
<a name="16574"></a>}
<a name="16575"></a>
<a name="16576"></a>
<a name="16577"></a>/*
<a name="16578"></a> * StatUpdate aggregates the statistics and logs the data to
<a name="16579"></a> * the AOLserver server log.
<a name="16580"></a> */
<a name="16581"></a>static void
<a name="16582"></a>StatUpdate(void *ctx)
<a name="16583"></a>{
<a name="16584"></a> StatContext *sc;
<a name="16585"></a>
<a name="16586"></a> sc = (StatContext *) ctx;
<a name="16587"></a>
<a name="16588"></a> Ns_LockMutex(&sc->lock);
<a name="16589"></a> Ns_Log(Notice,
<a name="16759"></a> "StatUpdate(%s): Last: conns %d, bytes %d Total: conns %d, bytes %d",
<a name="16590"></a> sc->hServer, sc->current.conns, sc->current.bytes,
<a name="16591"></a> sc->total.conns, sc->total.bytes);
<a name="16592"></a> sc->last.conns = sc->current.conns;
<a name="16593"></a> sc->last.bytes = sc->current.bytes;
<a name="16594"></a> sc->current.conns = 0;
<a name="16595"></a> sc->current.bytes = 0;
<a name="16596"></a> Ns_UnlockMutex(&sc->lock);
<a name="16597"></a>}
<a name="16598"></a>
<a name="16599"></a>
<a name="16600"></a>
<a name="17889"></a>
<a name="17890"></a>
<a name="17891"></a>
<a name="17892"></a>/*
<a name="16601"></a> * StatTclInit is called once for each Tcl interpreter
<a name="16602"></a> * in the virutal server's Tcl interpreter pool.
<a name="16603"></a> */
<a name="16604"></a>static int
<a name="16605"></a>StatTclInit(Tcl_Interp *interp, void *ctx)
<a name="16606"></a>{
<a name="16607"></a> Tcl_CreateCommand(interp, "ns_stat", StatCmd, ctx, NULL);
<a name="16608"></a> return NS_OK;
<a name="16609"></a>}
<a name="16610"></a>
<a name="16611"></a>
<a name="16612"></a>/*
<a name="16613"></a> * StatCmd implements the Tcl "ns_stat" command.
<a name="16614"></a> */
<a name="16615"></a>static int
<a name="16616"></a>StatCmd(ClientData ctx, Tcl_Interp *interp, int argc, char **argv)
<a name="16617"></a>{
<a name="16618"></a> StatContext *sc;
<a name="16619"></a> StatData *sd;
<a name="16620"></a>
<a name="16621"></a> sc = (StatContext *) ctx;
<a name="16622"></a> if (argc != 2) {
<a name="16623"></a> Tcl_AppendResult(interp, "wrong # args: should be \"",
<a name="16624"></a> argv[0], " command\"", NULL);
<a name="16625"></a> return TCL_ERROR;
<a name="16626"></a> }
<a name="16627"></a> if (strcmp(argv[1], "current") == 0) {
<a name="16628"></a> sd = &sc->current;
<a name="16629"></a> } else if (strcmp(argv[1], "last") == 0) {
<a name="16630"></a> sd = &sc->last;
<a name="16631"></a> } else if (strcmp(argv[1], "total") == 0) {
<a name="16632"></a> sd = &sc->total;
<a name="16633"></a> } else {
<a name="16634"></a> Tcl_AppendResult(interp, "unknown command \"",
<a name="16635"></a> argv[1], "\": should be current, last, or total", NULL);
<a name="16636"></a> return TCL_ERROR;
<a name="16637"></a> }
<a name="16638"></a>
<a name="16639"></a> Ns_LockMutex(&sc->lock);
<a name="16640"></a> sprintf(interp->result, "%d %d", sd->conns, sd->bytes);
<a name="16641"></a> Ns_UnlockMutex(&sc->lock);
<a name="16642"></a> return TCL_OK;
<a name="16643"></a>}
<a name="16644"></a>
<a name="16645"></a>
<a name="16646"></a>
<a name="17893"></a>
<a name="17894"></a>
<a name="17895"></a>/*
<a name="16647"></a> * StatRequest is a simple AOLserver request function which returns
<a name="16648"></a> * the current data in a simple HTML page. The page is generated
<a name="16649"></a> * with the Ns_ConnReturnNotice() function which is used throughout the
<a name="16650"></a> * AOLserver to generate simple HTML page responses with the
<a name="16651"></a> * AOLserver banner logo. Ns_ConnReturnNotice() takes a string as
<a name="16652"></a> * the HTML page content. We use an Ns_DString to quickly build
<a name="16653"></a> * up the string - Ns_DString's grow as needed so we don't have
<a name="16654"></a> * to worry about buffer overflow. The HTML page is a simple
<a name="16655"></a> * HTML3 <TABLE> which formats the current, last, and total
<a name="16656"></a> * statistics for the server.
<a name="16657"></a> */
<a name="16658"></a>static int
<a name="16659"></a>StatRequest(void *ctx, Ns_Conn *conn)
<a name="16660"></a>{
<a name="16661"></a> StatContext *sc;
<a name="16662"></a> Ns_DString ds;
<a name="16663"></a> int retcode;
<a name="16664"></a>
<a name="16665"></a> sc = (StatContext *) ctx;
<a name="16666"></a> Ns_DStringInit(&ds);
<a name="16668"></a> /*
<a name="16669"></a> * Build up the HTML3 <TABLE> with the latest data.
<a name="16670"></a> */
<a name="16671"></a> Ns_DStringAppend(&ds, "<table border cellpadding=\"10\">");
<a name="16672"></a> Ns_DStringVarAppend(&ds, "<tr><th>", sc->hServer, "</th>", NULL);
<a name="16673"></a> Ns_DStringAppend(&ds,
<a name="16760"></a> "<th>Current</th><th>Last</th><th>Total</th></tr>");
<a name="16674"></a> Ns_LockMutex(&sc->lock);
<a name="16675"></a> Ns_DStringPrintf(&ds,
<a name="16761"></a> "<tr><th># connections</th><td>%d</td><td>%d</td><td>%d</td></tr>",
<a name="16676"></a> sc->current.conns, sc->last.conns, sc->total.conns);
<a name="16677"></a> Ns_DStringPrintf(&ds,
<a name="16762"></a> "<tr><th># bytes</th><td>%d</td><td>%d</td><td>%d</td></tr>",
<a name="16678"></a> sc->current.bytes, sc->last.bytes, sc->total.bytes);
<a name="16679"></a> Ns_UnlockMutex(&sc->lock);
<a name="16680"></a> Ns_DStringAppend(&ds, "</table>");
<a name="16682"></a> /*
<a name="16683"></a> * Return the HTML page using Ns_ConnReturnNotice().
<a name="16684"></a> */
<a name="16685"></a> retcode = Ns_ConnReturnNotice(conn, 200, "Server Statistics",
ds.string);
<a name="16687"></a> /*
<a name="16688"></a> * Don't forget to free the dstring!
<a name="16689"></a> */
<a name="16690"></a> Ns_DStringFree(&ds);
<a name="16691"></a>
<a name="16692"></a> return retcode;
<a name="16693"></a>}
<a name="16694"></a>
<a name="16695"></a>
<a name="16696"></a>/*
<a name="16697"></a> * StatShutdown simple prints a final statistics entry to the
<a name="16698"></a> * server log and then cleans up the StatContext structure.
<a name="16699"></a> */
<a name="16700"></a>static void
<a name="16701"></a>StatShutdown(void *ctx)
<a name="16702"></a>{
<a name="16703"></a> StatContext *sc;
<a name="16704"></a>
<a name="16705"></a> sc = (StatContext *) ctx;
<a name="16706"></a> Ns_Log(Notice, "StatShutdown(%s): Total: conns %d, bytes %d.",
<a name="16707"></a> sc->hServer, sc->total.conns, sc->total.bytes);
<a name="16708"></a> Ns_DestroyMutex(&sc->lock);
<a name="16709"></a> ns_free(ctx);
<a name="16710"></a>}
<a name="16711"></a>
</pre><p>
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