I am parsing IIS logs with Logstash and noticed that cookie field is being truncated in some cases (displays "cookie" => "..." instead of the actual value).
I see that other cookies in the events of similar length are being processed correctly. Entire event length does not exceed 4,000 characters, so i suppose everything should fit.
What could have gone wrong?
This seems to be by design. See this post.
Cause This behavior is by design. The length of each IIS log field
value is limited to 4096 bytes (4k). If one of the field values is
greater than 4096 bytes, that value will be replaced with the three
dots. In the above example, the client's Cookie was larger than 4096
bytes and was therefore replaced with (...).
Workaround To workaround this issue, use one of the following options:
Write your own custom logging module that does not have the 4096 byte
field limitation.
OR
Reduce the size of the request or response header values to be logged
so that they are less than 4096 bytes and will therefore not be
replaced by the three dots.
You can instead add a custom field, set it to dump your value from server variables or request header and set the maxCustomFieldLength. However that seems to truncate the data to 4k rather than replacing it with "...". See this post. Slight improvement but not 100% ideal.
Related
Is there an EDI x12 segment that has no character limit? We often use the MSG segment for open text fields but this is capped at 256 characters, so we’re looking for an alternative that can handle 500+ characters.
The short answer
The MTX Text segment allows you to send messages of up to 4096 characters long, which is the longest available in X12. You can’t just swap out an MSG segment for an MTX segment, though. You can only use MTX if it’s included in the transaction set, and that depends on which X12 'release' (version) you're using.
For the 005010 release (one of the more popular ones), here are the transaction sets that MTX appears in:
105 Business Entity Filings
113 Election Campaign and Lobbyist Reporting
150 Tax Rate Notification
155 Business Credit Report
179 Environmental Compliance Reporting
194 Grant or Assistance Application
251 Pricing Support
274 Healthcare Provider Information
284 Commercial Vehicle Safety Reports
500 Medical Event Reporting
620 Excavation Communication
625 Well Information
650 Maintenance Service Order
805 Contract Pricing Proposal
806 Project Schedule Reporting
814 General Request, Response or Confirmation
832 Price/Sales Catalog
836 Procurement Notices
840 Request for Quotation
843 Response to Request for Quotation
850 Purchase Order
855 Purchase Order Acknowledgment
860 Purchase Order Change Request - Buyer Initiated
865 Purchase Order Change Acknowledgment/Request - Seller Initiated
Some additional clarification
Technically, character limits don't apply to X12 segments – what you're referring to is an X12 element. A segment is just a container for elements, and the element you're referring to is the element referenced in MSG01 (the first element of the MSG segment).
Each X12 element references an ID number. For each element, the ID number points to a dictionary that specifies the name, description, type, minimum length, and maximum length. In the case of MSG01, it points to data element [933][1].
Data element 933 – the one you're currently using – actually has a character limit of 264 characters (more than 256 characters, but not by much). Note: the link above is to the 005010 X12 release, but I checked backed to 003010 and up to 008030 and it seems to be 264 characters all the way through.
Now, back to your original question: is there a data element that allows for a larger character payload?
The answer is that there are 8 data elements that accept a payload larger than 264 characters.
Two of them are binary data types, which we can likely eliminate off the bat:
785. Binary Data. A string of octets which can assume any binary pattern from hexadecimal 00 to FF. Note: The maximum length is dependent upon the maximum data value that can be entered in DE 784, which value is 999,999,999,999,999. Max characters: 999999999999999.
1700. Transformed Data. Binary or filtered data having one or more security policy options applied; transformed data may represent compressed, encrypted, or compressed and encrypted plaintext. Max characters: 10000000000000000.
The rest are strings, which is promising:
364. Communication Number. Complete communications number including country or area code when applicable. Max characters: 2048.
1565. Look-up Value. Value used to identify a certificate containing a public key. Max characters: 4096.
1566. Keying Material. Additional material required for decrypting the one-time key. Max characters: 512.
1567. One-time Encryption Key. Hexadecimally filtered encrypted one-time key. Max characters: 512.
1573. Encoded Security Value. Encoded representation of the Security Value specified by the Security Value Qualifier. Max characters: 1.00E+16.
And, last but not least:
1551. Textual Data. To transmit large volumes of message text. Max characters: 4096.
Looks like a winner!
Note that element 1551 appears in only one segment: MTX, which was introduced in the 003060 X12 release. And in the initial 003060 release, it was only included in one X12 Transaction Set: 194 Grant or Assistance Application (which makes sense – a longer field was needed for grant applications).
It seems that as new releases were developed, the MTX segment made its way into more and more transaction sets – likely for exactly the reason you're asking. In 003070, it was included in 5 transaction sets; in 004010, 15; in 005010, 24, and so on.
The MTX segment uses element 1551 in both MTX02 and MTX03, so you can get double the length by using both of them. Note that there's a 'relational condition': If MTX-03 is present, then MTX-02 is required (in other words, you can't use MTX03 if you don't use MTX02 first).
And depending on the transaction set, the MTX segment may be able to be repeated as well.
Long story short: if the MTX segment is in the transaction set / release you're using, you're likely in luck.
Hope this helps.
Use multiple MSGs and trim the data at each to the maximum allowed. You usually have free text segments set with repetitions > 1, so you should be okay. That's how everybody does it.
I'm programming a server that accepts an incoming connection from a client and then reads from it (via net.Conn.Read()). I'm going to be reading the message into a []byte slice obviously and then processing it in an unrelated way, but the question is - how do I find out the length of this message first to create a slice of according length?
It is entirely dependent on the design of the protocol you are attempting to read from the connection.
If you are designing your own protocol you will need to design some way for your reader to determine when to stop reading or predeclare the length of the message.
For binary protocols, you will often find some sort of fixed size header that will contain a length value (for example, a big-endian int64) at some known/discoverable header offset. You can then parse the value at the length offset and use that value to read the correct amount of data once you reach the offset beginning the variable length data. Some examples of binary protocols include DNS and HTTP/2.
For text protocols, when to stop reading will be encoded in the parsing rules. Some examples of text protocols include HTTP/1.x and SMTP. An HTTP/1.1 request for example, declares the protocol to look something like:
METHOD /path HTTP/1.1\r\n
Header-1: value\r\n
Header-2: value\r\n
Content-Length: 20\r\n
\r\n
This is the content.
The first line (where line is denoted as ending with \r\n) must include the HTTP method, followed by the path (could be absolute or relative), followed by the version.
Subsequent lines are defined to be headers, made up of a key and a value.
The key includes any text from the beginning of the line up to, but not including, the colon. After the colon comes a variable number of insignificant space characters followed by the value.
One of these headers is special and denotes the length of the upcoming body: Content-Length. The value for this header contains the number of bytes to read as the body. For our simple case (ignoring trailers, chunked encoding, etc.), we will assume that the end of the body denotes the end of the request and another request may immediately follow.
After the last header comes a blank line denoting the end of the header block and the beginning of the body (\r\n\r\n).
Once you are finished reading all the headers you would then take the value from the Content-Length header you parsed and read the next number of bytes corresponding to its value.
For more information check out:
https://nerdland.net/2009/12/designing-painless-protocols/
http://www.catb.org/esr/writings/taoup/html/ch05s03.html
https://www.ietf.org/rfc/rfc3117.txt
In the end what I did was create a 1024 byte slice, then read the message from the connection, then shorten the slice to the number of integers read.
The solution selected as correct is not good. What happens if the messages is more than 1024 Bytes? You need to have a protocol of the form TLV (Type Length Value) or just LV if you don't have different types of messages. For example, Type can be 2 Bytes and Length can be 2 Bytes. Then you first always read 4 Bytes, then based on the length indicated in Bytes 2 and 3, you will know how many Bytes come later and then you read the rest. There is something else you need to take into account: TCP is stream oriented so in order to read the complete TCP message you might need to read many times. Read this (it is for Java but useful for any language): How to read all of Inputstream in Server Socket JAVA
First of all, this is not language tag spam, but this question not specific to one language in particulary and I think that this stackexchange site is the most appropriated for my question.
I'm working on cache and memory, trying to understand how it works.
What I don't understand is this sentence (in bold, not in the picture) :
In the MIPS architecture, since words are aligned to multiples of four
bytes, the least significant two bits are ignored when selecting a
word in the block.
So let's say I have this two adresses :
[1........0]10
[1........0]00
^
|
same 30 bits for boths [31-12] for the tag and [11-2] for the index (see figure below)
As I understand the first one will result in a MISS (I assume that the initial cache is empty). So one slot in the cache will be filled with the data located in this memory adress.
Now, we took the second one, since it has the same 30 bits, it will result in a HIT in the cache because we access the same slot (because of the same 10 bits) and the 20 bits of the adress are equals to the 20 bits stored in the Tag field.
So in result, we'll have the data located at the memory [1........0]10 and not [1........0]00 which is wrong !
So I assume this has to do with the sentence I quote above. Can anyone explain me why my reasoning is wrong ?
The cache in figure :
In the MIPS architecture, since words are aligned to multiples of four
bytes, the least significant two bits are ignored when selecting a
word in the block.
It just mean that in memory, my words are aligned like that :
So when selecting a word, I shouldn't care about the two last bits, because I'll load a word.
This two last bits will be useful for the processor when a load byte (lb) instruction will be performed, to correctly shift the data to get the one at the correct byte position.
What is the maximum length of the 'name' part in a domain?
I'm referring to the google in http://www.google.com. How long can the google part be without what's before and after it?
Each label may contain up to 63 characters.
"URI producers should use names
that conform to the DNS syntax, even when use of DNS is not
immediately apparent, and should limit these names to no more than
255 characters in length."
https://www.rfc-editor.org/rfc/rfc3986
"The DNS itself places only one restriction on the particular labels
that can be used to identify resource records. That one restriction
relates to the length of the label and the full name. The length of
any one label is limited to between 1 and 63 octets. A full domain
name is limited to 255 octets (including the separators)."
https://www.rfc-editor.org/rfc/rfc2181
The full domain name may not exceed a total length of 253 characters in its external dotted-label specification.
http://en.wikipedia.org/wiki/Domain_Name_System
If you are getting anywhere close to 253 characters, I think you should look for a shorter domain name...
TLDR Answer
Use these limits:
Labels: 61 octets.
Names: 253 octets.
Many applications will work even if you exceed these limits (like Gmail), but there are many older applications that will not.
Source
RFC1035: Domain Names - Implementation And Specification (published November 1987), an accepted Internet Standard, gives the following limits to subdomains and to the entire domain length when viewed in a browser...
Various objects and parameters in the DNS have size limits. They are
listed below. Some could be easily changed, others are more
fundamental.
labels 63 octets [bytes/characters] or less
names 255 octets [bytes/characters] or less
The working level of these are:
Labels: 61 octets.
Names: 253 octets.
That's because RFC821 (published August 1982) defines emails in the format of user#domain.com, and the smallest value for user would be one character. That leaves one character for #, and then you only have 253 characters left for the domain.com part.
This was reconfirmed numerous times...
RFC2181: Clarifications to the DNS Specification (published July 1997) : Only a proposed standard. "A full domain name is limited to 255 octets (including the separators)."
RFC3986: Uniform Resource Identifier (URI): Generic Syntax (published January 2005) : Accepted Internet standard. "URI producers should use names that conform to the DNS syntax, even when use of DNS is not immediately apparent, and should limit these names to no more than 255 characters in length."
RFC5321: Simple Mail Transfer Protocol (published October 2008) : Only a proposed standard. This RFC gives the max length of label or subdomains to be 64, one more than the others of 63. I recommend sticking with 63. "The maximum total length of a domain name or number is 255 octets."
You may have 63 characters per label (or subdomain) and 255 characters per name (this includes the TLD).
Notice that it gives the definition in octets. That's because it's looking at physical bytes, not literal bytes. For instance, \. is interpreted as . (one literal byte), because the \ escapes it, but it is encoded as \. (two physical bytes). These octet limits are physical byte limits.
As a demonstration, this website has a 63 characters domain name, the maximum allowed:
http://63-characters-is-the-longest-possible-domain-name-for-a-website.com
I understand that (for intel) the virtual address translation process is :
1. The incoming virtual address is divided into a page table number, a page number, and an offset.
2. The process desriptor base register (PDBR) in the CPU tells where the directory starts.
3. The page table number is multiplied by four to use as an offset into the directory, and the directory entry is looked up.
4. The directory entry contains the address of the page table, and validity and protection information. If this information says that either the page table isn't present in memory or the protections aren't OK, the translation stops and an exception is raised.
5. The page number is multiplied by four to use as an offset into the page table, and the page table entry is looked up.
6. The page table entry contains the address of the page, and validity and protection information. If this information says that either the page isn't present in memory or the protections aren't OK, the translation stops and an exception is raised.
7. The offset is used as an index into the page.
8. The data is at the address finally arrived at.
And that all makes sense up to step 6 where I get confused because
the table entry format only specifies 20 bits for the physical page frame address which means it can only access up to 1 megabyte, or is it shifted left 12 bits (multiplied by 4096: size of page) to be able to access 4 gigabytes
This is the 32-bit translation process. Each page table entry is 32 bits, but the low 12 bits are used for flags. The upper 20 bits are the page address.