Usage:

	logformat <name> <format specification>

	Defines an access log format.

	The <format specification> is a string with embedded % format codes

	% format codes all follow the same basic structure where all
	components but the formatcode are optional and usually unnecessary,
	especially when dealing with common codes.

		% [encoding] [-] [[0]width] [{arg}] formatcode [{arg}]

		encoding escapes or otherwise protects "special" characters:

			"	Quoted string encoding where quote(") and
				backslash(\) characters are \-escaped while
				CR, LF, and TAB characters are encoded as \r,
				\n, and \t two-character sequences.

			[	Custom Squid encoding where percent(%), square
				brackets([]), backslash(\) and characters with
				codes outside of [32,126] range are %-encoded.
				SP is not encoded. Used by log_mime_hdrs.

			#	URL encoding (a.k.a. percent-encoding) where
				all URL unsafe and control characters (per RFC
				1738) are %-encoded.

			/	Shell-like encoding where quote(") and
				backslash(\) characters are \-escaped while CR
				and LF characters are encoded as \r and \n
				two-character sequences. Values containing SP
				character(s) are surrounded by quotes(").

			'	Raw/as-is encoding with no escaping/quoting.

			Default encoding: When no explicit encoding is
			specified, each %code determines its own encoding.
			Most %codes use raw/as-is encoding, but some codes use
			a so called "pass-through URL encoding" where all URL
			unsafe and control characters (per RFC 1738) are
			%-encoded, but the percent character(%) is left as is.

		-	left aligned

		width	minimum and/or maximum field width:
			    [width_min][.width_max]
			When minimum starts with 0, the field is zero-padded.
			String values exceeding maximum width are truncated.

		{arg}	argument such as header name etc. This field may be
			placed before or after the token, but not both at once.

	Format codes:

		%	a literal % character

		byte{value}	Adds a single byte with the given value (e.g., %byte{10}
			adds an ASCII LF character a.k.a. "new line" or "\n"). The value
			parameter is required and must be a positive decimal integer not
			exceeding 255. Zero-valued bytes (i.e. ASCII NUL characters) are
			not yet supported.

		sn	Unique sequence number per log line entry
		err_code    The ID of an error response served by Squid or
				a similar internal error identifier.

		err_detail  Additional err_code-dependent error information. Multiple
			details are separated by the plus sign ('+'). Admins should not
			rely on a particular detail listing order, the uniqueness of the
			entries, or individual detail text stability. All those properties
			depend on many unstable factors, including external libraries.

		note	The annotation specified by the argument. Also
			logs the adaptation meta headers set by the
			adaptation_meta configuration parameter.
			If no argument given all annotations logged.
			The argument may include a separator to use with
			annotation values:
                            name[:separator]
			By default, multiple note values are separated with ","
			and multiple notes are separated with "\r\n".
			When logging named notes with %{name}note, the
			explicitly configured separator is used between note
			values. When logging all notes with %note, the
			explicitly configured separator is used between
			individual notes. There is currently no way to
			specify both value and notes separators when logging
			all notes with %note.
		master_xaction  The master transaction identifier is an unsigned
			integer. These IDs are guaranteed to monotonically
			increase within a single worker process lifetime, with
			higher values corresponding to transactions that were
			accepted or initiated later. Due to current implementation
			deficiencies, some IDs are skipped (i.e. never logged).
			Concurrent workers and restarted workers use similar,
			overlapping sequences of master transaction IDs.

	Connection related format codes:

		>a	Client source IP address
		>A	Client FQDN
		>p	Client source port
		>eui	Client source EUI (MAC address, EUI-48 or EUI-64 identifier)
		>la	Local IP address the client connected to
		>lp	Local port number the client connected to
		>qos    Client connection TOS/DSCP value set by Squid
		>nfmark Client connection netfilter packet MARK set by Squid

		transport::>connection_id Identifies a transport connection
			accepted by Squid (e.g., a connection carrying the
			logged HTTP request). Currently, Squid only supports
			TCP transport connections.

			The logged identifier is an unsigned integer. These
			IDs are guaranteed to monotonically increase within a
			single worker process lifetime, with higher values
			corresponding to connections that were accepted later.
			Many IDs are skipped (i.e. never logged). Concurrent
			workers and restarted workers use similar, partially
			overlapping sequences of IDs.

		la	Local listening IP address the client connection was connected to.
		lp	Local listening port number the client connection was connected to.

		<a	Server IP address of the last server or peer connection
		<A	Server FQDN or peer name
		<p	Server port number of the last server or peer connection
		<la	Local IP address of the last server or peer connection
		<lp     Local port number of the last server or peer connection
		<qos	Server connection TOS/DSCP value set by Squid
		<nfmark Server connection netfilter packet MARK set by Squid

		>handshake Raw client handshake
			Initial client bytes received by Squid on a newly
			accepted TCP connection or inside a just established
			CONNECT tunnel. Squid stops accumulating handshake
			bytes as soon as the handshake parser succeeds or
			fails (determining whether the client is using the
			expected protocol).

			For HTTP clients, the handshake is the request line.
			For TLS clients, the handshake consists of all TLS
			records up to and including the TLS record that
			contains the last byte of the first ClientHello
			message. For clients using an unsupported protocol,
			this field contains the bytes received by Squid at the
			time of the handshake parsing failure.

			See the on_unsupported_protocol directive for more
			information on Squid handshake traffic expectations.

			Current support is limited to these contexts:
			- http_port connections, but only when the
			  on_unsupported_protocol directive is in use.
			- https_port connections (and CONNECT tunnels) that
			  are subject to the ssl_bump peek or stare action.

			To protect binary handshake data, this field is always
			base64-encoded (RFC 4648 Section 4). If logformat
			field encoding is configured, that encoding is applied
			on top of base64. Otherwise, the computed base64 value
			is recorded as is.

	Time related format codes:

		ts	Seconds since epoch
		tu	subsecond time (milliseconds)
		tl	Local time. Optional strftime format argument
				default %d/%b/%Y:%H:%M:%S %z
		tg	GMT time. Optional strftime format argument
				default %d/%b/%Y:%H:%M:%S %z
		tr	Response time (milliseconds)
		dt	Total time spent making DNS lookups (milliseconds)
		tS	Approximate master transaction start time in
			<full seconds since epoch>.<fractional seconds> format.
			Currently, Squid considers the master transaction
			started when a complete HTTP request header initiating
			the transaction is received from the client. This is
			the same value that Squid uses to calculate transaction
			response time when logging %tr to access.log. Currently,
			Squid uses millisecond resolution for %tS values,
			similar to the default access.log "current time" field
			(%ts.%03tu).

		busy_time	Time spent in transaction-related code (nanoseconds)
			This cumulative measurement excludes periods of time when the
			transaction was waiting (e.g., for a server or helper response)
			while Squid worked on other transactions or was engaged in
			transaction-unrelated activities (e.g., generating a cache index).
			In other words, this measurement represents the total amount of
			physical time when Squid was busy working on this transaction.

			WARNING: This measurement relies on Squid transaction context
			tracking features that currently have known context leak bugs and
			coverage gaps. Until those features are fully implemented, logged
			values may significantly understate or exaggerate actual times.
			Do not use this measurement unless you know it works in your case.

	Access Control related format codes:

		et	Tag returned by external acl
		ea	Log string returned by external acl
		un	User name (any available)
		ul	User name from authentication
		ue	User name from external acl helper
		un	A user name. Expands to the first available name
			from the following list of information sources:
			- authenticated user name, like %ul
			- user name supplied by an external ACL, like %ue
			- SSL client name, like %us
		credentials Client credentials. The exact meaning depends on
			the authentication scheme: For Basic authentication,
			it is the password; for Digest, the realm sent by the
			client; for NTLM and Negotiate, the client challenge
			or client credentials prefixed with "YR " or "KK ".

	HTTP related format codes:

	    REQUEST

		[http::]rm	Request method (GET/POST etc)
		[http::]>rm	Request method from client
		[http::]<rm	Request method sent to server or peer

		[http::]ru	Request URL received (or computed) and sanitized

				Logs request URI received from the client, a
				request adaptation service, or a request
				redirector (whichever was applied last).

				Computed URLs are URIs of internally generated
				requests and various "error:..." URIs.

				Honors strip_query_terms and uri_whitespace.

				This field is not encoded by default. Encoding
				this field using variants of %-encoding will
				clash with uri_whitespace modifications that
				also use %-encoding.

		[http::]>ru	Request URL received from the client (or computed)

				Computed URLs are URIs of internally generated
				requests and various "error:..." URIs.

				Unlike %ru, this request URI is not affected
				by request adaptation, URL rewriting services,
				and strip_query_terms.

				Honors uri_whitespace.

				This field is using pass-through URL encoding
				by default. Encoding this field using other
				variants of %-encoding will clash with
				uri_whitespace modifications that also use
				%-encoding.

		[http::]<ru	Request URL sent to server or peer
		[http::]>rs	Request URL scheme from client
		[http::]<rs	Request URL scheme sent to server or peer
		[http::]>rd	Request URL domain from client
		[http::]<rd	Request URL domain sent to server or peer
		[http::]>rP	Request URL port from client
		[http::]<rP	Request URL port sent to server or peer
		[http::]rp	Request URL path excluding hostname
		[http::]>rp	Request URL path excluding hostname from client
		[http::]<rp	Request URL path excluding hostname sent to server or peer
		[http::]rv	Request protocol version
		[http::]>rv	Request protocol version from client
		[http::]<rv	Request protocol version sent to server or peer

		[http::]>h	Original received request header.
				Usually differs from the request header sent by
				Squid, although most fields are often preserved.
				Accepts optional header field name/value filter
				argument using name[:[separator]element] format.
		[http::]>ha	Received request header after adaptation and
				redirection (pre-cache REQMOD vectoring point).
				Usually differs from the request header sent by
				Squid, although most fields are often preserved.
				Optional header name argument as for >h

	    RESPONSE

		[http::]<Hs	HTTP status code received from the next hop
		[http::]>Hs	HTTP status code sent to the client

		[http::]<h	Reply header. Optional header name argument
				as for >h

		[http::]mt	MIME content type


	    SIZE COUNTERS

		[http::]st	Total size of request + reply traffic with client
		[http::]>st	Total size of request received from client.
				Excluding chunked encoding bytes.
		[http::]<st	Total size of reply sent to client (after adaptation)

		[http::]>sh	Size of request headers received from client
		[http::]<sh	Size of reply headers sent to client (after adaptation)

		[http::]<sH	Reply high offset sent
		[http::]<sS	Upstream object size

		[http::]<bs	Number of HTTP-equivalent message body bytes
				received from the next hop, excluding chunked
				transfer encoding and control messages.
				Generated FTP listings are treated as
				received bodies.

	    TIMING

		[http::]<pt	Peer response time in milliseconds. The timer starts
				when the last request byte is sent to the next hop
				and stops when the last response byte is received.
		[http::]<tt	Total time spent forwarding to origin servers or
				cache_peers (milliseconds).

				The timer starts when Squid decides to forward the request (to
				an origin server or cache_peer) and peer selection begins. The
				timer stops when relevant forwarding activities (including any
				retries) end.

				Between those two timer events, Squid may perform DNS lookups,
				query external ACL helpers, adapt responses using pre-cache
				RESPMOD services, and participate in other concurrent
				secondary activities. Most secondary activities increase
				peering time. In some cases, a secondary activity may start
				before the timer starts or end after the timer stops, leading
				to misleading results of simple computations like %<tt - %dt.

				If this logformat %code is used before its timer starts, the
				corresponding measurement has no value (and the %code expands
				to a single dash ("-") character).

				If this code is used while its timer is running, the time
				spent so far is used as the measurement value.

				When Squid re-forwards the request (e.g., after certain cache
				revalidation failures), the timer may restart. In this case,
				the new measurement is added to the value accumulated from
				previous forwarding attempts. The time interval between
				forwarding attempts is not added to the final result.

	Squid handling related format codes:

		Ss	Squid request status (TCP_MISS etc)
		Sh	Squid hierarchy status (DEFAULT_PARENT etc)

		[http::]request_attempts	Number of request forwarding attempts

			See forward_max_tries documentation that details what Squid counts
			as a forwarding attempt. Pure cache hits log zero, but cache hits
			that triggered HTTP cache revalidation log the number of attempts
			made when sending an internal revalidation request. DNS, ICMP,
			ICP, HTCP, ICAP, eCAP, helper, and other secondary requests
			sent by Squid as a part of a master transaction do not increment
			the counter logged for the received request.

	SSL-related format codes:

		ssl::bump_mode	SslBump decision for the transaction:

				For CONNECT requests that initiated bumping of
				a connection and for any request received on
				an already bumped connection, Squid logs the
				corresponding SslBump mode ("splice", "bump",
				"peek", "stare", "terminate", "server-first"
				or "client-first"). See the ssl_bump option
				for more information about these modes.

				A "none" token is logged for requests that
				triggered "ssl_bump" ACL evaluation matching
				a "none" rule.

				In all other cases, a single dash ("-") is
				logged.

		ssl::>sni	SSL client SNI sent to Squid.

		ssl::>cert_subject
				The Subject field of the received client
				SSL certificate or a dash ('-') if Squid has
				received an invalid/malformed certificate or
				no certificate at all. Consider encoding the
				logged value because Subject often has spaces.

		ssl::>cert_issuer
				The Issuer field of the received client
				SSL certificate or a dash ('-') if Squid has
				received an invalid/malformed certificate or
				no certificate at all. Consider encoding the
				logged value because Issuer often has spaces.

		ssl::<cert_subject
				The Subject field of the received server
				TLS certificate or a dash ('-') if this is
				not available. Consider encoding the logged
				value because Subject often has spaces.

		ssl::<cert_issuer
				The Issuer field of the received server
				TLS certificate or a dash ('-') if this is
				not available. Consider encoding the logged
				value because Issuer often has spaces.

		ssl::<cert
				The received server x509 certificate in PEM
				format, including BEGIN and END lines (or a
				dash ('-') if the certificate is unavailable).

				WARNING: Large certificates will exceed the
				current 8KB access.log record limit, resulting
				in truncated records. Such truncation usually
				happens in the middle of a record field. The
				limit applies to all access logging modules.

				The logged certificate may have failed
				validation and may not be trusted by Squid.
				This field does not include any intermediate
				certificates that may have been received from
				the server or fetched during certificate
				validation process.

				Currently, Squid only collects server
				certificates during step3 of SslBump
				processing; connections that were not subject
				to ssl_bump rules or that did not match a peek
				or stare rule at step2 will not have the
				server certificate information.

				This field is using pass-through URL encoding
				by default.

		ssl::<cert_errors
				The list of certificate validation errors
				detected by Squid (including OpenSSL and
				certificate validation helper components). The
				errors are listed in the discovery order. By
				default, the error codes are separated by ':'.
				Accepts an optional separator argument.

		%ssl::>negotiated_version The negotiated TLS version of the
				client connection.

		%ssl::<negotiated_version The negotiated TLS version of the
				last server or peer connection.

		%ssl::>received_hello_version The TLS version of the Hello
				message received from TLS client.

		%ssl::<received_hello_version The TLS version of the Hello
				message received from TLS server.

		%ssl::>received_supported_version The maximum TLS version
				supported by the TLS client.

		%ssl::<received_supported_version The maximum TLS version
				supported by the TLS server.

		%ssl::>negotiated_cipher The negotiated cipher of the
				client connection.

		%ssl::<negotiated_cipher The negotiated cipher of the
				last server or peer connection.

	If ICAP is enabled, the following code becomes available (as
	well as ICAP log codes documented with the icap_log option):

		icap::tt Total ICAP "blocking" time for the HTTP transaction. The
				timer ticks while Squid checks adaptation_access and while
				ICAP transaction(s) expect ICAP response headers, including
				the embedded adapted HTTP message headers (where applicable).
				This measurement is meant to estimate ICAP impact on HTTP
				transaction response times, but it does not currently account
				for slow ICAP response body delivery blocking HTTP progress.

				Once Squid receives the final ICAP response headers (e.g.,
				ICAP 200 or 204) and the associated adapted HTTP message
				headers (if any) from the ICAP service, the corresponding ICAP
				transaction stops affecting this measurement, even though the
				transaction itself may continue for a long time (e.g., to
				finish sending the ICAP request and/or to finish receiving the
				ICAP response body).

				When "blocking" sections of multiple concurrent ICAP
				transactions overlap in time, the overlapping segment is
				counted only once.

				To see complete ICAP transaction response times (rather than
				the cumulative effect of their blocking sections) use the
				%adapt::all_trs logformat code or the icap_log directive.

	If adaptation is enabled the following codes become available:

		adapt::<last_h	The header of the last ICAP response or
				meta-information from the last eCAP
				transaction related to the HTTP transaction.
				Like <h, accepts an optional header name
				argument.

		adapt::sum_trs Summed adaptation transaction response
				times recorded as a comma-separated list in
				the order of transaction start time. Each time
				value is recorded as an integer number,
				representing response time of one or more
				adaptation (ICAP or eCAP) transaction in
				milliseconds.  When a failed transaction is
				being retried or repeated, its time is not
				logged individually but added to the
				replacement (next) transaction. Lifetimes of individually
				listed adaptation transactions may overlap.
				See also: %icap::tt and %adapt::all_trs.

		adapt::all_trs All adaptation transaction response times.
				Same as %adapt::sum_trs but response times of
				individual transactions are never added
				together. Instead, all transaction response
				times are recorded individually.

	You can prefix adapt::*_trs format codes with adaptation
	service name in curly braces to record response time(s) specific
	to that service. For example: %{my_service}adapt::sum_trs

	Format codes related to the PROXY protocol:

		proxy_protocol::>h PROXY protocol header, including optional TLVs.

				Supports the same field and element reporting/extraction logic
				as %http::>h. For configuration and reporting purposes, Squid
				maps each PROXY TLV to an HTTP header field: the TLV type
				(configured as a decimal integer) is the field name, and the
				TLV value is the field value. All TLVs of "LOCAL" connections
				(in PROXY protocol terminology) are currently skipped/ignored.

				Squid also maps the following standard PROXY protocol header
				blocks to pseudo HTTP headers (their names use PROXY
				terminology and start with a colon, following HTTP tradition
				for pseudo headers): :command, :version, :src_addr, :dst_addr,
				:src_port, and :dst_port.

				Without optional parameters, this logformat code logs
				pseudo headers and TLVs.

				This format code uses pass-through URL encoding by default.

				Example:
					# relay custom PROXY TLV #224 to adaptation services
					adaptation_meta Client-Foo "%proxy_protocol::>h{224}"

				See also: %http::>h

	The default formats available (which do not need re-defining) are:

logformat squid      %ts.%03tu %6tr %>a %Ss/%03>Hs %<st %rm %ru %[un %Sh/%<a %mt
logformat common     %>a - %[un [%tl] "%rm %ru HTTP/%rv" %>Hs %<st %Ss:%Sh
logformat combined   %>a - %[un [%tl] "%rm %ru HTTP/%rv" %>Hs %<st "%{Referer}>h" "%{User-Agent}>h" %Ss:%Sh
logformat referrer   %ts.%03tu %>a %{Referer}>h %ru
logformat useragent  %>a [%tl] "%{User-Agent}>h"

	NOTE: When the log_mime_hdrs directive is set to ON.
		The squid, common and combined formats have a safely encoded copy
		of the mime headers appended to each line within a pair of brackets.

	NOTE: The common and combined formats are not quite true to the Apache definition.
		The logs from Squid contain an extra status and hierarchy code appended.