OCI8 and DTrace Dynamic Tracing

Installing OCI8 with DTrace Support

To enable DTrace support in PHP OCI8, build OCI8 as a shared extension after setting PHP_DTRACE.

$ export PHP_DTRACE=yes
$ pecl install oci8

Edit php.ini, set extension_dir to the directory with the created oci8.so and also enable the extension by adding:

extension=oci8.so

If you install PHP OCI8 from PECL using phpize and configure (instead of pecl), you will still need to set PHP_DTRACE=yes. This is because the --enable-dtrace option will be ignored by the limited configure script of a PECL bundle.

See Installation of PECL extensions for general PECL installation instructions.

DTrace Static Probes in PHP OCI8

These probes are useful for tracing OCI8 scripts.

The connection and statement are the pointers to internal structures used for tracking PHP connections and executed statements.

The client_id is the value set by oci_set_client_identifier().

Core PHP also has static probes. See DTrace Static Probes in Core PHP.

These probes are useful for OCI8 maintainers. Refer to the OCI8 source code for arguments and to see when the will fire.

Listing DTrace Static Probes in PHP OCI8

To list available probes, start a PHP process and then run:

# dtrace -l

The output will be similar to:

   ID   PROVIDER            MODULE                          FUNCTION NAME
   [ . . . ]
   17 phpoci22116           oci8.so   php_oci_dtrace_check_connection oci8-check-connection
   18 phpoci22116           oci8.so                php_oci_do_connect oci8-connect-entry
   19 phpoci22116           oci8.so         php_oci_persistent_helper oci8-connect-expiry
   20 phpoci22116           oci8.so             php_oci_do_connect_ex oci8-connect-lookup
   21 phpoci22116           oci8.so  php_oci_pconnection_list_np_dtor oci8-connect-p-dtor-close
   22 phpoci22116           oci8.so  php_oci_pconnection_list_np_dtor oci8-connect-p-dtor-release
   23 phpoci22116           oci8.so                php_oci_do_connect oci8-connect-return
   24 phpoci22116           oci8.so             php_oci_do_connect_ex oci8-connect-type
   25 phpoci22116           oci8.so          php_oci_connection_close oci8-connection-close
   26 phpoci22116           oci8.so                     php_oci_error oci8-error
   27 phpoci22116           oci8.so         php_oci_statement_execute oci8-execute-mode
   28 phpoci22116           oci8.so              php_oci_create_spool oci8-sesspool-create
   29 phpoci22116           oci8.so            php_oci_create_session oci8-sesspool-stats
   30 phpoci22116           oci8.so            php_oci_create_session oci8-sesspool-type
   31 phpoci22116           oci8.so          php_oci_statement_create oci8-sqltext

The Provider column values consist of phpoci and the process id of the currently running PHP process.

The Function column refers to PHP's internal C implementation function names where each provider is located.

If a PHP process is not running, then no PHP probes will be shown.

DTrace with PHP OCI8 Example

This example shows the basics of the DTrace D scripting language.

#!/usr/sbin/dtrace -Zs

#pragma D option quiet

php*:::oci8-connect-entry
{
    printf("%lld: PHP connect-entry\n", walltimestamp);
    printf("  credentials=\"%s@%s\"\n", arg0 ? copyinstr(arg0) : "", arg1 ? copyinstr(arg1) : "");
    printf("  charset=\"%s\"\n", arg2 ? copyinstr(arg2) : "");
    printf("  session_mode=%ld\n", (long)arg3);
    printf("  persistent=%d\n", (int)arg4);
    printf("  exclusive=%d\n", (int)arg5);
}

php*:::oci8-connect-return
{
    printf("%lld: PHP oci8-connect-return\n", walltimestamp);
    printf("  connection=0x%p\n", (void *)arg0);
}

php*:::oci8-connection-close
{
    printf("%lld: PHP oci8-connect-close\n", walltimestamp);
    printf("  connection=0x%p\n", (void *)arg0);
}

php*:::oci8-error
{
    printf("%lld: PHP oci8-error\n", walltimestamp);
    printf("  status=%d\n", (int)arg0);
    printf("  errcode=%ld\n", (long)arg1);
}

php*:::oci8-check-connection
{
    printf("%lld: PHP oci8-check-connection\n", walltimestamp);
    printf("  connection=0x%p\n", (void *)arg0);
    printf("  client_id=\"%s\"\n", arg1 ? copyinstr(arg1) : "");
    printf("  is_open=%d\n", arg2);
    printf("  errcode=%ld\n", (long)arg3);
    printf("  server_status=%lu\n", (unsigned long)arg4);
}

php*:::oci8-sqltext
{
    printf("%lld: PHP oci8-sqltext\n", walltimestamp);
    printf("  connection=0x%p\n", (void *)arg0);
    printf("  client_id=\"%s\"\n", arg1 ? copyinstr(arg1) : "");
    printf("  statement=0x%p\n", (void *)arg2);
    printf("  sql=\"%s\"\n", arg3 ? copyinstr(arg3) : "");
}

php*:::oci8-execute-mode
{
    printf("%lld: PHP oci8-execute-mode\n", walltimestamp);
    printf("  connection=0x%p\n", (void *)arg0);
    printf("  client_id=\"%s\"\n", arg1 ? copyinstr(arg1) : "");
    printf("  statement=0x%p\n", (void *)arg2);
    printf("  mode=0x%x\n", arg3);
}

This script uses the -Z option to dtrace, allowing it to be run when there is no PHP process executing. If this option were omitted the script would immediately terminate when no PHP executable was running because it knows none of the probes to be monitored are in existence.

On multi-CPU machines the probe ordering might not appear to be sequential. This depends on which CPU was processing the probes, and how threads migrate across CPUs. Displaying probe time stamps helps reduce confusion.

The script traces all user-level PHP OCI8 static probe points throughout the duration of a running PHP script. Run the D script:

# ./user_oci8_probes.d

Run a PHP script or application. The monitoring D script will output each probe's arguments as it fires. For example, a simple PHP script that queries a table might produce the following trace output:

1381794982092854582: PHP connect-entry
  credentials="hr@localhost/pdborcl"
  charset=""
  session_mode=0
  persistent=0
  exclusive=0
1381794982183158766: PHP oci8-connect-return
  connection=0x7f4a7907bfb8
1381794982183594576: PHP oci8-sqltext
  connection=0x7f4a7907bfb8
  client_id="Chris"
  statement=0x7f4a7907c2a0
  sql="select * from employees"
1381794982183783706: PHP oci8-execute-mode
  connection=0x7f4a7907bfb8
  client_id="Chris"
  statement=0x7f4a7907c2a0
  mode=0x20
1381794982444344390: PHP oci8-connect-close
  connection=0x7f4a7907bfb8

When monitoring is complete, the D script can be terminated with a CTRL+C.

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• DTrace Dynamic Tracing