Squid_ The Definitive Guide - Duane Wessels [153]
Stale: by default
Squid considers the cached response stale by default, because it didn't meet any of the other criteria.
Following the HTTP histogram, you'll see the same data for ICP, HTCP, Cache Digests, and On Store.
The On Store table represents freshness checks for responses that are coming into Squid's cache (i.e., cachable misses). Note, however, that Squid does store stale responses (as long as they have a cache validator). Don't be alarmed if you see some stale responses in the On Store histogram.
delay: Delay Pool Levels
This page displays the Delay Pool statistics. Squid has three classes of pools (1, 2, 3) and three types of buckets (aggregate, individual, and network). A class 1 pool has only an aggregate bucket, a class 2 pool has both aggregate and individual, and a class 3 pool has all three.
An aggregate bucket looks like this:
Aggregate:
Max: 16384
Restore: 4096
Current: 6144
The values are all in bytes. Max is the size of the bucket, which is the number of bytes the bucket can hold. Restore is the number of bytes added to the bucket each second. Current is the number of bytes currently in the bucket. If nobody uses the bytes, the bucket fills until it reaches the maximum size.
An individual bucket is almost the same:
Individual:
Max: 20000
Restore: 5000
Current: 1:18760 9:4475 14:20000
The only difference is that the Current line displays a number of different values, one for each host number. The host number is defined as the last octet of an IPv4 address. In this example, the host numbers are 1, 9, and 14. In a class 2 delay pool, the host numbers from different networks share the same bucket. For example, 192.168.0.1 and 192.168.44.1 both share the bucket for host number 1. In a class 3 pool, however, each network number (third octet) has its own array of individual buckets. Thus, for a class 3 pool, the individual buckets appear this way:
Individual:
Max: 20000
Rate: 5000
Current [Network 0]: 1:12000
Current [Network 44]: 1:17000
A network bucket (for class 3 pools only) is similar as well:
Network:
Max: 30000
Rate: 15000
Current: 0:3912 7:30000
In this case, the Current line shows the current level for each network number (third octet). See Appendix C for more information about Delay Pools.
forward: Request Forwarding Statistics
The table on this page shows how many attempts were made to forward each request, with their results. Upon receiving some status codes, Squid gives up immediately. For others, however, Squid keeps trying. Each row of the table is a different HTTP status code (200, 401, 404, etc.). Each column is the number of forwarding attempts. The value in each cell is how many requests were forwarded that many times, resulting in the corresponding status code. This information helps developers understand whether or not it makes sense to retry a request after receiving certain types of responses. Here is an example:
Status try#1 try#2 try#3 try#4 try#5 try#6 try#7 try#8 try#9 try#10
0 1 0 0 0 0 0 0 0 0 0
200 3970083 111015 51185 29002 18242 12097 8191 6080 4490 6140
201 57 0 0 0 0 0 0 0 0 0
202 162 0 0 0 0 0 0 0 0 0
204 1321 11 0 0 0 0 0 0 0 0
206 624288 453 25 9 4 3 0 1 0 0
207 147 0 0 0 0 0 0 0 0 0
300 23 0 0 0 0 0 0 0 0 0
301 23500 25 2 0 0 0 1 0 0 0
302 339332 3806 153 26 6 4 2 3 0 1
303 101 1 0 0 0 0 0 0 0 0
304 772831 3510 125 21 7 8 8 5 3 2
307 7 0 0 0 0 0 0 0 0 0
400 529 1 0 0 0 0 0 0 0 0
401 1559 0 0 0 0 0 0 0 0 0
403 5098 30 1 1 0 0 0 0 0 0
404 100800 216 25 6 7 1 2 4 1 5
405 1 0 0 0 0 0 0 0 0 0
...
A value of 29,002 in the cell under try#4 and in the row for status 200 means that there were 29,002 times when Squid finally got a successful response after 4 forwarding attempts. If you look at the table, you may see some unknown status codes. Squid keeps track of all status codes up to 600, even those it doesn't know about. See Table 13-1 for the list of codes that Squid does know about.
client_list: