Home > Articles > Programming

  • Print
  • + Share This
This chapter is from the book

Put simply, the ACE Logging Service is a configurable two-tier replacement for UNIX syslog. Both syslog and the Windows Event Logger are pretty good at what they do and can even be used to capture messages from remote hosts. But if you have a mixed environment, they simply aren't sufficient.

Table 3.7. ACE_Log_Record Attributes




The log record type from Table 3.1


Synonym for type


The log record's priority name


The length of the log record, set by the creator of the log record


The timestamp—generally, creation time—of the log record; set by the creator of the log record


ID of the process that created the log record instance


The textual message of the log record


Length of the msg_data attribute

The ACE netsvcs logging framework has a client/server design. On one host in the network, you run the logging server that will accept logging requests from any other host. On that and every host in the network where you want to use the distributed logger, you invoke the logging client. The client acts somewhat like a proxy by accepting logging requests from clients on the local system and forwarding them to the server. This may seem to be a bit of an odd design, but it helps prevent pounding the server with a huge number of client connections, many of which may be transient. By using the proxy approach, the proxy on each host absorbs a little bit of the pounding, and everyone is better off.

To configure our server and client proxy, we will use the ACE Service Configurator framework. The Service Configurator is an advanced topic that is covered in Chapter 19. We will show you just enough here to get things off the ground. Feel free to jump ahead and read a bit more about the Service Configurator now, or wait and read it later.

To start the server, you need to first create a file server.conf with the following content:

dynamic Logger Service_Object * ACE:_make_ACE_Logging_Strategy() "-s foobar -f
graphics/ccc.gif STDERR|OSTREAM|VERBOSE"
   dynamic Server_Logging_Service Service_Object * netsvcs:_make_ACE_Server_Logging_Acceptor
   graphics/ccc.gif() active "-p 20009"

Note these lines are wrapped for readability. Your server.conf should contain only two lines, each beginning with the word dynamic. The first line defines the logging strategy to write the log output to standard error and the output stream attached to a file named foobar. This line also requests verbose log messages instead of a more terse format. (Section 3.8 discusses more ways to use this service.) The second line of server.conf causes the server to listen for client connections at TCP (Transmission Control Protocol) port 200091 on all network interfaces available on your computer. You can now start the server with:

$ACE_ROOT/netsvcs/servers/main -f server.conf

The next step is to create the configuration file for the client proxy and start the proxy. The file could be named client.conf and should look something like this:

dynamic Client_Logging_Service Service_Object * netsvcs:_make_ACE_Client_Logging_Acceptor
graphics/ccc.gif() active "-p 20009 -h localhost"

Again, that's all on one line. The important parts are -p 20009, which tells the proxy which TCP port the server will be listening to—this should match the -p value in your server.conf—and -h localhost, which sets the host name where the logging server is executing. For our simple test, we are executing both client and server on the same system. In the real world, you will most likely have to change localhost to the name of your real logging server.

Although we provide the port on which the server is listening, we did not provide a port value for clients of the proxy. This value is known as the logger key, and its form and value change, depending on the capabilities of the platform the client logger is built on. On some platforms, it's a pipe; where that's not possible, it's a loopback TCP socket at address localhost:20012. If you want your client proxy to listen at a different address, you can specify that with the -k parameter in client.conf.

You can now start the client logger with:

$ACE_ROOT/netsvcs/servers/main -f client.conf

Using the logging service in one of our previous examples is trivial:

#include "ace/Log_Msg.h"

int ACE_TMAIN (int, ACE_TCHAR *argv[])
  ACE_LOG_MSG->open (argv[0],

  ACE_TRACE (ACE_TEXT ("main"));

  ACE_DEBUG ((LM_DEBUG, ACE_TEXT ("%IHi Mom\n")));
  ACE_DEBUG ((LM_INFO, ACE_TEXT ("%IGoodnight\n")));

  return 0;

As with the syslog example, we must use the open() method when we want to use the logging service; set_flags() isn't sufficient. Note also the open() parameter ACE_DEFAULT_LOGGER_KEY. This has to be the same logger key that the client logger is listening at; if you changed it with the -k option in client.conf, you must specify the new value to open().

To summarize: On every machine on which you want to use the logging service, you must execute an instance of the client logger. Each instance is configured to connect to a single instance of the logging server somewhere on your network. Then, of course, you execute that server instance on the appropriate system.

For the truly adventurous, your application can communicate directly with the logging server instance. This approach has two problems:

  1. Your program is now more complicated because of the connection and logging logic.

  2. You run the risk of overloading the server instance because you've removed the scaling afforded by the client proxies.

However, if you still want your application to talk directly to the logging server, here's a way to do so:

#include "ace/Log_Msg.h"
#include "Callback-3.h"

int ACE_TMAIN (int, ACE_TCHAR *[])
  Callback *callback = new Callback;

  ACE_LOG_MSG->set_flags (ACE_Log_Msg::MSG_CALLBACK);
  ACE_LOG_MSG->clr_flags (ACE_Log_Msg::STDERR);
  ACE_LOG_MSG->msg_callback (callback);

  ACE_TRACE (ACE_TEXT ("main"));

  ACE_DEBUG ((LM_DEBUG, ACE_TEXT ("%IHi Mom\n")));
  ACE_DEBUG ((LM_INFO, ACE_TEXT ("%IGoodnight\n")));

  return 0;

This looks very much like our previous callback example. We use the callback hook to capture the ACE_Log_Record instance that contains our message. Our new Callback object then sends that to the logging server:

#include "ace/streams.h"
#include "ace/Log_Msg.h"
#include "ace/Log_Msg_Callback.h"
#include "ace/Log_Record.h"
#include "ace/SOCK_Stream.h"
#include "ace/SOCK_Connector.h"
#include "ace/INET_Addr.h"

#define LOGGER_PORT 20009

class Callback : public ACE_Log_Msg_Callback
  Callback ()
      this->logger_ = new ACE_SOCK_Stream;
      ACE_SOCK_Connector connector;

      if (connector.connect (*(this->logger_), addr) == -1)
          delete this->logger_;
          this->logger_ = 0;

  virtual ~Callback ()
      if (this->logger_)
          this->logger_->close ();
      delete this->logger_;

  void log (ACE_Log_Record &log_record)
      if (!this->logger_)
            (ACE_TEXT (""), ACE_Log_Msg::VERBOSE, cerr);

      size_t len = log_record.length();
      log_record.encode ();

      if (this->logger_->send_n ((char *) &log_record, len) == -1)
          delete this->logger_;
          this->logger_ = 0;

  ACE_SOCK_Stream *logger_;

We've introduced some things here that you won't read about for a bit. The gist of what we're doing is that the callback object's constructor opens a socket to the logging service. The log() method then sends the ACE_Log_Record instance to the server via the socket. Because several of the ACE_Log_Record attributes are numeric, we must use the encode() method to ensure that they are in a network-neutral format before sending them. Doing so will prevent much confusion if the byte ordering of the host executing your application is different from that of the host executing your logging server.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020