Rainer Gerhards, Author at Rainer Gerhards

2010-02-26

syslog normalization

I am working on syslog normalization for quite some years now. A couple of days ago, David Lang talked to me about syslog-ng’s patterndb, an approach to classify log messages and extract properties from it.

I have looked at this approach, and it indeed is promising. One ingredient, though, is missing, that is a directory of standard properties (like bytes sent and received in traffic logs). I know this missing ingredient very well, because we also forgot it until recently.

The aim to normalize log data is far from being new. Actually, I think it is one of the main concerns in log analysis. Probably one of the first folks who thought seriously about it was Marcus Ranum, who coined the concept of “artificial ignorance”, meaning that we can remove those messages from a big pile of logs that we know to be uninteresting. But in order to do that correctly, you need to know how exactly they look. And this is where log normalization comes in. I have written an in-depth paper in 2004, title “On the nature of syslog data“. The version officially published claims “work in progress”, but it still has all the juicy details.

Internally, we implemented this approach in our MonitorWare products a little bit later. For example, it is used inside the “Post Process Action” in WinSyslog (Michael also wrote a nice article on how to parse log messages with this action). While this was a great addition (and is used with great success), I failed to get enough community momentum to build a larger database of log messages that could be used as a basis for large scale log normalization. One such – largely failed for syslog – approach is the event knowledge base.

However, I did not give up on the general idea and proposed it wherever appropriate. The last outcome of this approach is the soon-to-be-released Adiscon LogAnalyzer v3, which uses so-called message parsers to obtain useful information from log entries. Here, I hope we will be able to gain more community involvement. We already got two message parsers contributed. Granted, that’s not much, but the ability to have them is so far little known. With the release of v3, I hope we get more and more momentum.

The syslog-ng patterndb approach brings an interesting idea to this space: as far as I have heard (I generally do NOT look at competing code to prevent polluting my code with things that I should not use), they use radix trees to parse the log messages. That is a clever approach, as it provides a solution for much quicker parsing large amounts of parse templates. This makes the approach suitable for real-time normalization of an incoming stream of syslog data.

Adiscon LogAnalyzer, by contrast, uses a regex-based approach, but that primarily for simplicity in an effort to invite more contributions (WinSyslog has a far more sophisticated approach). In Adiscon LogAnalyzer we began to become serious with identifying what a property actually means. While we have a fixed set of properties, with fixed semantics, in both WinSyslog, MonitorWare Agent and rsyslog, this set is rather limited. The Windows product line supports ease of extension of the properties, but does not provide standard IDs for those properties.

In Adiscon LogAnalyzer, we have fixed IDs for a larger set of properties, now about 50 or so. Still, that set is very small. But we created it with the intention to be able to map various “semantic objects” from different log entries to a single identity. For example, most firewall logs will contain a source and destination IP address, but almost all firewalls will use different log message formats to do that. So we need to have different analyzers to support these native formats, for example in reports. In Adiscon LogAnalyzer, we can now have a message parser “normalize” these syslog entries and map the vendor-specific format to the generic “semantic object”. Thus the upper layers (like views and reports) then work on these normalized semantic objects and do not need to be adopted to each firewall. This needs only be done at the parser level.

Such a directory of semantics objects would be very useful in my humble opinion. We are currently working on making it publicly available, all this in the hope for a community to involve itself ;) If we manage to get a large enough number of log and/or parser contributions, we may potentially be able to make Adiscon LogAnalyzer an even better free tool for system administrators.

And as there is hope that this will finally succeed, I have begun to think about a potential implementation inside rsyslog. It doesn’t sound very hard, but still requires careful thinking. One thing I would like to see is a unified approach that covers at least rsyslog and Adiscon Loganalyzer, and hopefully the Windows tools as well.

Another very good thing is that there already is a standard for providing standard semantical objects: during the IETF syslog standardization effort, I pressed hard for so-called structured data elements. I managed to get them into the final RFC. These structured data elements are now the key for conveying the log information once it is normalized: the corresponding name-value pairs can easily be encoded with it.

I hope we will finally able to succeed on this road, because I think this would be of tremendous benefit for the syslog community.

2010-02-24

phpLogCon becomes Adiscon LogAnalyzer

I have blogged the past days about Adiscon LogAnalyzer. We are now gradually rolling out the new site. So I thought it is a good idea to reproduced my “official announcement” on the blog as well:

As in all things, there is a certain fashion in open source project names as well. For a long time, “php*” was a great name for php-based open source solutions. However, nowadays these somewhat bulky names have been replaced by “more streamlined” names.

I personally think that dropping the “php” part makes it somewhat easier to speak and write about these projects. So we decided it was right to drop “php” from “phpLogCon”. But was “LogCon” the ultimate name for a tool to search, analyze and (starting with v3) report on network event logs? A quick discussion within our group as well as with some external buddies turned out that “LogCon” is probably pretty meaningless. Even if one deciphers “Con” for “Console” – what does it mean to be a “Console” in this context? Not an easy to answer question. Bottom line: “LogCon” is pretty meaningless.

So we thought we do “the right thing” and rename the project before it becomes even more widely spread. The later you do a name change, the more painful it is. That made us think about good names. We ended up with “LogAnalyzer”, because analysis is the dominant use case for this tool (especially if you think of reports as being part of the analysis ;) ). Another quick search made us aware that there are (of course) lots of “LogAnalyzers”. And, of course as well, all second level domains where taken.

Bare of an expensive legal adviser, we made the decision to boldly name the project “Adiscon LogAnalyzer“, aka. “the log analyzer (primarily) written by Adiscon”. With that approach we use our company name (which obviously legally belongs to us) together with the generic term “LogAnalyzer”. That is done in the hope that it will resolve any legal friction that otherwise may occur. For the very same reason you will see us consistently referring to “Adiscon LogAnalyzer”.

We are aware, however, that this implies some other cost: A project with a company name inside it does sound a bit like a purely commercial project. On the other hand, that seems to be no problem with the big players, like “Red Hat Linux” or “SuSe Linux”. So we hope that the company part inside the name will not have a too-bad effect on this project.

We pledge that Adiscon LogAnalyzer will always be a free, open source project. And the GPLv3 we use is your guarantee for that.

In addition to the core Adiscon LogAnalyzer, Adiscon will also provide some non-GPLed components in the future. And we hope that others will do that as well. Our sincere hope is that Adiscon LogAnalyzer will evolve to a framework where many third parties can plug in specific functionality. Consequently, we have added a plugin directory to the new site, and some third-party written message parsers already populate it.

So – phpLogCon has not only a new name and a new site, it is also more active than ever and eager to solve the log analysis and reporting needs for a growing community. Please help spread the word!

2010-02-23

Why is writing good user doc such a problem…?

… for me, I should add. Today, I ran about a post on the rsyslog mailing list where a user (rightfully!) complains that rsyslog documentation is confusing.

I really don’t like the idea that users are having a hard time because they can not get pretty basic things done. Unfortunately, there are a number of reasons for this: one, of course, is lack of time. I am rather busy developing new functionality and besides rsyslog I have also other chores today at Adiscon, like helping with the next and really great release of Adiscon LogAnalyzer, a free and open source solution for searching, analyzing and reporting on network event data and syslog (yeah, and creating buzzwords, of course…). But there is a more subtle issue:

I am doing logging and syslog for over 10 years now (close to 15, if I remember correctly). I have seen so much in the logging world, that I can hardly think of the time when I did not know what PRI or TAG or even MSG was, what are the (disadvantages) or simplex vs. duplex comm modes, and what makes 3195 better (or worse) than 3164 or 5424 ;)

In short: it is pretty hard for me to go back to the roots and envision what somebody new to syslog needs to know AND in what order! I am trying my best, but writing basic-level articles (and documentation) requires considerable effort. A good article, well-thought out (like a 4-page journal article) can easily take 4 to 5 days to create. Even then, I need help from other folks when I need to write for entry level folks (and there is nothing bad with being entry-level: everybody is at some point in time). Here, of course, the time resource problem hits again: I usually can not afford this effort “just” to create doc.

With the rsyslog cookbook I started another approach: there I focus on very specific environments. I don’t really like this idea, because it does not tell people what exactly they are doing. But still the past weeks have proven this to be a useful approach. But I also notice that the cookbook is only useful if the configuration matches exactly what the user wants – otherwise users are lost. I guess that’s due to not really understanding what happens. The good thing about the cookbook is that it requires relatively little effort. Most samples were created within an hour, which seems to be acceptable for something that can be reused.

The ultimate solution would be that users write content themselves. The rsyslog knowledge base (or forum, as you may call it) is most successful in this regard. But it is hard to navigate and hard to find a solution – you often need to wade through various posts before you get to the (often simple) solution. The rsyslog mailing list is another excellent resource, especially as other folks actively help supporting rsyslog. This is a very important for me and the project, and I appreciate it very much. Unfortunately, the con again is that the mailing list makes it hard for new users to find already existing solutions (that is is being mirrored to various aggregators helps a bit, but only so much…).

The ultimate solution, I thought, was the rsyslog wiki and we see some very nice article inside it. Unfortunately, very few users contribute to the wiki. Just think an how enormous knowledge reservoir this could be if only every 5th user who got help would take a few minutes off his time to craft a quick wiki article describing what he does, why, and how it works. Unfortunately, most users seem to not have this time. I can understand that, I guess they have pressing schedules at well. And these schedules may already be stressed by the extra time they needed to find the solution for an obviously simple thing…

So this is not a good situation, but I can currently not do much more than to keep working on the cookbook and ask everyone to contribute documentation. For the long-term success, I think it is vital for rsyslog to make it power available to all users. Good doc is one necessity, a better config format another one (but I won’t elaborate about this in today’s post again ;)).

2010-02-232018-06-11

is a third-level domain suspect to google?

If you follow this blog, you’ve probably already heard that we are doing a name change for phpLogCon: it will soon be known under the name Adiscon LogAnalyzer (with the Adiscon in front of the “real” name to ease potential legal issues).

Among others, that means we need to change the web site. Not surprisingly, no second-level domain with loganalyzer in it was available at the time we searched. Most of them, of course, been taken by domain spammers. So we settled for the loganalyzer.adiscon.com name. As I found out yesterday in Google Webmaster Tools, that this may cause some troubles. Google provides a “Change of Adress” tool that is meant to be used in situation.

However, I discovered that this tool does not work with third-level domains. All I see when I try to use that tool is the message “Setting is restricted to root level domains, only” (as a slight technical side-note, it should say “second level domain” as I don’t think it works for com, net, org, … only ;)).

While browsing the google help forum, I found that others seems to have similar problems. For example, people in the UK, where everything is a third-level domain (for example, .co.uk is what .com is for the international Internet).

Given this stance, I wonder if google punishes third-level domain sites in any other way. If so, our decision to move to the new site may not be a good one. I have posted a question in the Google help forums. I guess I will not get a definite response, but maybe one can read between the lines.

I will keep you posted, also on the overall progress of the name/site switch. We have now entered the “hot phase”, meaning that we actually intend to roll over to the new site within the next couple of days. Stay tuned for more news and more features.

2010-02-19

converting NetApp Filer to syslog – and MS API Changes…

One of the things that is done with EventReporter and MonitorWare Agent is forwarding NetApp Filer event logs via syslog. There are essentially two ways how this can be done: either via backup event log files (*.evt), which NetApp writes in a Windows compatible format or (a newer approach) via an Event Log API Emulation inside the NetApp box. If you’d like to know details, you can find them in our NetApp EventLog to Syslog forwarding paper.

Unfortunately, changes in recent Windows versions cause some trouble with the way the forwarding works. Unfortunately, Microsoft seems to have changed the on-disk format of backup event log files. That’s OK and something that usually can happen. What I find strange is that Microsoft does no longer supply code inside Windows (and its APIs!) to read downlevel event logs. So, for example, on Windows 2008 it is no longer possible to read a backup event log from an older release. This includes the NetApp .evt files, as they are written in the older Windows format.

I do not understand the Microsoft decision. It would not have been hard to preserve backward compatibility – a header flag inside the file plus very few code inside the o
operating system would have been sufficient. But without that, we see trouble that the NetApp .evt files can not be accessed by Windows Event Viewer and, consequently, not yet by our eventlog to syslog tools. Thankfully, though, we support all modes NetApp provides, and so the work-around is to use the NetApp Event Log API emulation, which will also get the necessary information out to syslog. But, again, I do not understand how Microsoft can break backward compatibility in thus an unnecessary way.

Anyhow, things are as they are ;) So far, we are also looking at ways to be able to process the NetApp backup event log files even under these new constraints. And as you know, we are already full of ideas. Of course, I also recommended to opening a support ticket with Microsoft – I am too eager to learn the official response to this situation (and -maybe- a solution)? I’ve been told we’ll open the ticket today, so let’s see what comes out of all that…

2010-02-17

syslog data modeling capabilities

As part of the IETF discussions on a common logging format for sip, I explained some sylsog concepts to the sip-clf working group.

Traditionally, syslog messages contain free-form text, only – aimed at human observers. Of course, today most of the logging information is automatically being processed and the free-form text creates ample problems in that regard.

The recent syslog RFC series has gone great length to improve the situation. Most importantly, it introduced a concept called “Structured Data”, which permits to express information in a well-structured way. Actually, it provides a dual layer approach, with a corase designator at the upper layer and name/value pairs at the lower layer.

However, the syslog RFC do NOT provide any data/information modeling capabilities that come with these structured data elements. Their syntax and semantics is to be defined in separate RFCs. So far, only a few examples exist. One of them is the base RFC5424, which describes some common properties that can be contained in any syslog message. Other than that, RFC5674, which describes a mapping to the Alarm MIB and ITU perceived severities and RFC5675, which describes a mapping to SNMP traps. All of them are rather small. The IHE community, to the best of my knowledge, is currently considering using syslog structured data as an information container, but has not yet reached any conclusion.

Clearly, it would be of advantage to have more advanced data modeling capabilities inside the syslog base RFCs, at least some basic syntax definitions. So why is that not present?

One needs to remember that the syslog standardization effort was a very hard one. There were many different views, “thanks” to the broad variety of legacy syslog, and it was extremely hard to reach consensus (thus it took some years to complete the work…). Next, one needs to remember that there is such an immense variety in message content and objects, that it is a much larger effort to try define some generic syntaxes and semantics (I don’t say it can not be done, but it is far from being easy). In order to get the basics done, the syslog WG deciced to not dig down into these dirty details but rather lay out the foundation so that we can build on it in the future.

I still think this is a good compromise. It would be good if we could complement this foundation with some already existing technology. SNMP MIB encoding is not the right way to go, because it follows a different paradigm (syslog is still meant to be primarily clear text). One interesting alternative which I saw, and now evaluate, is the ipfix data modeling approach. Ideally, we could reuse it inside structured data, saving us the work to define some syslog-specific model of doing so.

The most important task, however, is to think about, and specify, some common “information building blocks”. With these, I mean standard properties, like source and destination ID, mail message id, bytes sent and received and so on. These, together with some standard syntaxes, can greatly relieve problems we face while consolidating and analyzing logs. Obviously, this is an area that I will be looking into in the near future as well.

It may be worth noting that I wrote a paper about syslog parsing back in 2004. It was, and has remained, work in progress. However, Adiscon did implement the concept in MonitorWare Console, which unfortunately never got wider exposure. Thinking about it, that work would benefit greatly from the availability of standardized syslog data models.

2010-02-15

new phplogcon site

Today, I received a first more or less complete link to what will become the new phplogcon site. The site is not yet live, but will provide some of the new features.

If you look at it, you’ll probably notice a couple of things. First of all, the name “phpLogCon” is no longer spelled out. The reason is that we considered a bit bulky and meaningless. “Loganalyzer” is exactly what the tools is about. But, of course, there are a myriad of (trademark) problems related to that name. So we try to avoid all confusion by calling it “Adiscon loganalyzer”, hoping that the company name as dominant part of the product name will rule out all problems. For that very reason, you’ll also see me to refer to Adiscon Loganalyzer in the future. If you wonder why I stress that “Adiscon” part, you now know why.

Secondly, you will notice the fresh design. While I am not a visual guy, I have to say that I like it very much. I think it removes much of the clutter and makes it easier to find the information you need quickly. We also have changed the content management system in the background. The new sites uses WordPress, which seems to be highly approprioate for what the site needs. Of course, the wiki and forum will remain as they are – they have proven to be quite well as they are.

If you look more closely, you will also note that Adiscon LogAnalyzer gets an important new component: a reporting module. I managed to convince my peers at Adiscon to move some of our MonitorWare Console closed source technology into Adiscon LogAnalyzer. My long-term vision is that reporting capabilities will much enhance the utility of this tool. In order for Adiscon to get something back, we will begin to develop some enhanced reports, which will be non-free for commercial users. However, the base product as well as some base reports, will always remain free!

I hope you consider this to be good news, just as I think! Thanks to everyone who made this possible.

2010-02-09

Some thoughts on reliability…

When talking syslog, we often talk about audit or other important data. A frequent question I get is if syslog (and rsyslog in specific) can provide a reliable transport.

When this happens, I need to first ask what level of reliability is needed? There are several flavors of reliability and usually loss of message is acceptable at some level.

For example, let’s assume the process writes out log messages to a text file. Under (allmost?) all modern operating systems and by default, this means the OS accepts the information to write, acks it, does NOT persist it to storage and lets the application continue. The actual data block is usually written a short while later. Obviously, this is not reliable: you can lose log data if an unrecoverable i/o error happens or something else goes fatally wrong.

This can be solved by instructing the operating system to actually persist the information to durable store before returning back from the API. You have to pay a big performance toll for that. This is also a frequent question for syslog data, and many operators do NOT sync and accept a small message loss risk to save themselves from requiring a factor of 10 servers of what they now need.

But even if writes are synchronous, how does the application react? For example: what shall the application do if log data cannot be written? If one really needs reliable logging, the only choice is to shutdown the application when it can no longer log. I know of very few systems that actually do that, even though “reliability” is highly demanded. Here, the cost of shutting down the application may be so high (or even fatal), that the limited risk of log data loss is accepted.

There are a myriad of things when thinking about reliability. So I think it is important to define the level of reliability that is required by the solution and do that in detail. To the best of my knowledge, this is also important for operators who are required by law to do “reliable” logging. If they have a risk matrix, they can define where it is “impossible” (for technical or financial reasons) to achieve full reliability and as of my understanding this is information auditors are looking for.

So for all cases, I strongly recommend to think about which level of reliability is needed. But to provide an answer for the rsyslog case: it can provide very high reliability and will most probably fulfil all needs you may have. But there is a toll in both performance and system uptime (as said above) to go to “full” reliability.

2010-02-082018-06-11

The typical logging problem as viewed from syslog

I run into different syslog use cases from time to time. So I thought it is a good idea to express what I think the typical logging problem is. As I consider it the typical problem, syslog (and WinSyslog and rsyslog in specific) address most needs very well. What they spare is the analysis and correlation part, but other members of the family (like our log analyzer) and third parties care well for that.

So the typical logging problem, as seen from the syslog perspective, is:

there exists events that need to be logged
a single “higher-level” event E may consist of a
number of fine-grained lower level events e_i
each of the e_i’s may be on different
systems / proxies
each e_i consists of a subset of properties
p_j from a set of all possible common properties P
in order to gain higher-level knowledge, the
high-level event E must be reconstructed from
e_i’s obtained from *various* sources
a transport mechanism must exist to move event
e_i records from one system to another, e.g., to
a central correlator
systems from many different suppliers may be involved,
resulting in different syntax and semantic of
the higher-level objects
there is potentially a massive amount of events
events potentially need to be stored for
an extended period of time
quick review of at least the current event data
(today, past week) is often desired
there exists lots of noise data
the data needs to be fed into backend processes,
like billing systems

2010-02-05

on leap seconds and syslog

I was recently asked how syslog handles leap seconds. I thought it would be useful to reproduce my thoughts, initially expressed via private mail, here in the blog.

RFC5424 specifically forbids leap seconds, as during our discussions we found many cases where leap seconds caused grief. I also think the the TAI is considering aborting the use of leap seconds for this reason as well. To the best of my knowledge, GPS also does not use leap seconds. The ultimate reason to abandon UTC leap seconds in syslog was the we failed to identify an operating system that would expose leap seconds to a user process. So a syslogd or any other syslog sender would not even be able to see that one was introduced. From the syslog perspective, a leap second is just like any other second, but time flows “somewhat slower”. I guess we are in the same boat as many operating systems with this perspective.

In RFC5424 we didn’t explicitly state what time stamp should be written during a leap second – because we thought it could actually never happen (why? explained above!). But I would say that “Leap seconds MUST NOT be used” to me means that it should be expressed as the 59th second of said minute. But even if you bump the minute and use the 0 second, I cannot see how this should be problematic. On a single system, time should still evolve serially. For correlating events form multiple systems, the timestamp alone is insufficient in any case. You cannot closely enough synchronize the different real time clocks. So you need a different meachanism (like Lamport clocks) for this in any case.