VSL

Shared Memory Logging

OVERVIEW

This document describes the format and content of all the Varnish shared memory logging tags. These tags are used by the varnishlog(1), varnishtop(1), etc. logging tools supplied with Varnish.

VSL tags

Backend - Backend selected

Logged when a connection is selected for handling a backend request.

The format is:

%d %s %s
|  |  |
|  |  +- Backend display name
|  +---- VCL name
+------- Connection file descriptor

BackendClose - Backend connection closed

Logged when a backend connection is closed.

The format is:

%d %s [ %s ]
|  |    |
|  |    +- Optional reason
|  +------ Backend display name
+--------- Connection file descriptor

BackendOpen - Backend connection opened

Logged when a new backend connection is opened.

The format is:

%d %s %s %s
|  |  |  |
|  |  |  +- Remote port
|  |  +---- Remote address
|  +------- Backend display name
+---------- Connection file descriptor

BackendReuse - Backend connection put up for reuse

Logged when a backend connection is put up for reuse by a later connection.

The format is:

%d %s
|  |
|  +- Backend display name
+---- Connection file descriptor

Backend_health - Backend health check

The result of a backend health probe.

The format is:

%s %s %s %u %u %u %f %f %s
|  |  |  |  |  |  |  |  |
|  |  |  |  |  |  |  |  +- Probe HTTP response
|  |  |  |  |  |  |  +---- Average response time
|  |  |  |  |  |  +------- Response time
|  |  |  |  |  +---------- Probe window size
|  |  |  |  +------------- Probe threshold level
|  |  |  +---------------- Number of good probes in window
|  |  +------------------- Probe window bits
|  +---------------------- Status message
+------------------------- Backend name

Begin - Marks the start of a VXID

The first record of a VXID transaction.

The format is:

%s %d %s
|  |  |
|  |  +- Reason
|  +---- Parent vxid
+------- Type ("sess", "req" or "bereq")

BereqAcct - Backend request accounting

Contains byte counters from backend request processing.

The format is:

%d %d %d %d %d %d
|  |  |  |  |  |
|  |  |  |  |  +- Total bytes received
|  |  |  |  +---- Body bytes received
|  |  |  +------- Header bytes received
|  |  +---------- Total bytes transmitted
|  +------------- Body bytes transmitted
+---------------- Header bytes transmitted

BereqHeader - Backend request header

HTTP header contents.

The format is:

%s: %s
|   |
|   +- Header value
+----- Header name

BereqMethod - Backend request method

The HTTP request method used.

BereqProtocol - Backend request protocol

The HTTP protocol version information.

BereqURL - Backend request URL

The HTTP request URL.

BerespHeader - Backend response header

HTTP header contents.

The format is:

%s: %s
|   |
|   +- Header value
+----- Header name

BerespProtocol - Backend response protocol

The HTTP protocol version information.

BerespReason - Backend response response

The HTTP response string received.

BerespStatus - Backend response status

The HTTP status code received.

BogoHeader - Bogus HTTP received

Contains the first 20 characters of received HTTP headers we could not make sense of. Applies to both req.http and beresp.http.

CLI - CLI communication

CLI communication between varnishd master and child process.

Debug - Debug messages

Debug messages can normally be ignored, but are sometimes helpful during trouble-shooting. Most debug messages must be explicitly enabled with parameters.

ESI_BodyBytes - ESI body fragment byte counter

Contains the body byte count for this ESI body fragment. This number does not include any transfer encoding overhead.

The format is:

%d
|
+- Body bytes

ESI_xmlerror - ESI parser error or warning message

An error or warning was generated during parsing of an ESI object. The log record describes the problem encountered.

End - Marks the end of a VXID

The last record of a VXID transaction.

Error - Error messages

Error messages are stuff you probably want to know.

ExpBan - Object evicted due to ban

Logs the VXID when an object is banned.

ExpKill - Object expiry event

Logs events related to object expiry. The events are:

EXP_Rearm

Logged when the expiry time of an object changes.

EXP_Inbox

Logged when the expiry thread picks an object from the inbox for processing.

EXP_Kill

Logged when the expiry thread kills an object from the inbox.

EXP_When

Logged when the expiry thread moves an object on the binheap.

EXP_Expired

Logged when the expiry thread expires an object.

LRU_Cand

Logged when an object is evaluated for LRU force expiry.

LRU

Logged when an object is force expired due to LRU.

LRU_Fail

Logged when no suitable candidate object is found for LRU force expiry.

The format is:

EXP_Rearm p=%p E=%f e=%f f=0x%x
EXP_Inbox p=%p e=%f f=0x%x
EXP_Kill p=%p e=%f f=0x%x
EXP_When p=%p e=%f f=0x%x
EXP_Expired x=%u t=%f
LRU_Cand p=%p f=0x%x r=%d
LRU x=%u
LRU_Fail

Legend:
p=%p         Objcore pointer
t=%f         Remaining TTL (s)
e=%f         Expiry time (unix epoch)
E=%f         Old expiry time (unix epoch)
f=0x%x       Objcore flags
r=%d         Objcore refcount
x=%u         Object VXID

FetchError - Error while fetching object

Logs the error message of a failed fetch operation.

Fetch_Body - Body fetched from backend

Ready to fetch body from backend.

The format is:

%d (%s) %s
|   |    |
|   |    +---- 'stream' or '-'
|   +--------- Text description of body fetch mode
+------------- Body fetch mode

Gzip - G(un)zip performed on object

A Gzip record is emitted for each instance of gzip or gunzip work performed. Worst case, an ESI transaction stored in gzip'ed objects but delivered gunziped, will run into many of these.

The format is:

%c %c %c %d %d %d %d %d
|  |  |  |  |  |  |  |
|  |  |  |  |  |  |  +- Bit length of compressed data
|  |  |  |  |  |  +---- Bit location of 'last' bit
|  |  |  |  |  +------- Bit location of first deflate block
|  |  |  |  +---------- Bytes output
|  |  |  +------------- Bytes input
|  |  +---------------- 'E': ESI, '-': Plain object
|  +------------------- 'F': Fetch, 'D': Deliver
+---------------------- 'G': Gzip, 'U': Gunzip, 'u': Gunzip-test

Examples:

U F E 182 159 80 80 1392
G F E 159 173 80 1304 1314

Hash - Value added to hash

This value was added to the object lookup hash.

NB: This log record is masked by default.

Hit - Hit object in cache

Object looked up in cache. Shows the VXID of the object.

HitPass - Hit for pass object in cache.

Hit-for-pass object looked up in cache. Shows the VXID of the hit-for-pass object.

HttpGarbage - Unparseable HTTP request

Logs the content of unparseable HTTP requests.

Length - Size of object body

Logs the size of a fetch object body.

Link - Links to a child VXID

Links this VXID to any child VXID it initiates.

The format is:

%s %d %s
|  |  |
|  |  +- Reason
|  +---- Child vxid
+------- Child type ("req" or "bereq")

LostHeader - Failed attempt to set HTTP header

Logs the header name of a failed HTTP header operation due to resource exhaustion or configured limits.

ObjHeader - Object header

HTTP header contents.

The format is:

%s: %s
|   |
|   +- Header value
+----- Header name

ObjProtocol - Object protocol

The HTTP protocol version information.

ObjReason - Object response

The HTTP response string received.

ObjStatus - Object status

The HTTP status code received.

PipeAcct - Pipe byte counts

Contains byte counters for pipe sessions.

The format is:

%d %d %d %d
|  |  |  |
|  |  |  +------- Piped bytes to client
|  |  +---------- Piped bytes from client
|  +------------- Backend request headers
+---------------- Client request headers

ReqAcct - Request handling byte counts

Contains byte counts for the request handling. This record is not logged for ESI sub-requests, but the sub-requests' response body count is added to the main request.

The format is:

%d %d %d %d %d %d
|  |  |  |  |  |
|  |  |  |  |  +- Total bytes transmitted
|  |  |  |  +---- Body bytes transmitted
|  |  |  +------- Header bytes transmitted
|  |  +---------- Total bytes received
|  +------------- Body bytes received
+---------------- Header bytes received

ReqHeader - Client request header

HTTP header contents.

The format is:

%s: %s
|   |
|   +- Header value
+----- Header name

ReqMethod - Client request method

The HTTP request method used.

ReqProtocol - Client request protocol

The HTTP protocol version information.

ReqStart - Client request start

Start of request processing. Logs the client IP address and port number.

The format is:

%s %s
|  |
|  +- Port number
+---- IP address

ReqURL - Client request URL

The HTTP request URL.

RespHeader - Client response header

HTTP header contents.

The format is:

%s: %s
|   |
|   +- Header value
+----- Header name

RespProtocol - Client response protocol

The HTTP protocol version information.

RespReason - Client response response

The HTTP response string received.

RespStatus - Client response status

The HTTP status code received.

SessClose - Client connection closed

SessionClose is the last record for any client connection.

The format is:

%s %f
|  |
|  +- How long the session was open
+---- Why the connection closed

SessOpen - Client connection opened

The first record for a client connection, with the socket-endpoints of the connection.

The format is:

%s %d %s %s %s %d
|  |  |  |  |  |
|  |  |  |  |  +- File descriptor number
|  |  |  |  +---- Local TCP port ('-' if !$log_local_addr)
|  |  |  +------- Local IPv4/6 address ('-' if !$log_local_addr)
|  |  +---------- Listen socket
|  +------------- Client TCP socket
+---------------- Client IPv4/6 address

Storage - Where object is stored

Type and name of the storage backend the object is stored in.

The format is:

%s %s
|  |
|  +- Name of storage backend
+---- Type ("malloc", "file", "persistent" etc.)

TTL - TTL set on object

A TTL record is emitted whenever the ttl, grace or keep values for an object is set.

The format is:

%s %d %d %d %d [ %d %d %u %u ]
|  |  |  |  |    |  |  |  |
|  |  |  |  |    |  |  |  +- Max-Age from Cache-Control header
|  |  |  |  |    |  |  +---- Expires header
|  |  |  |  |    |  +------- Date header
|  |  |  |  |    +---------- Age (incl Age: header value)
|  |  |  |  +--------------- Reference time for TTL
|  |  |  +------------------ Keep
|  |  +--------------------- Grace
|  +------------------------ TTL
+--------------------------- "RFC" or "VCL"

The last four fields are only present in "RFC" headers.

Examples:

RFC 60 -1 -1 1312966109 1312966109 1312966109 0 60
VCL 120 10 0 1312966111

Timestamp - Timing information

Contains timing information for the Varnish worker threads.

Time stamps are issued by Varnish on certain events, and show the absolute time of the event, the time spent since the start of the work unit, and the time spent since the last timestamp was logged. See vsl(7) for information about the individual timestamps.

The format is:

%s: %f %f %f
|   |  |  |
|   |  |  +- Time since last timestamp
|   |  +---- Time since start of work unit
|   +------- Absolute time of event
+----------- Event label

VCL_Error - VCL execution error message

Logs error messages generated during VCL execution.

VCL_Log - Log statement from VCL

User generated log messages insert from VCL through std.log()

VCL_acl - VSL ACL check results

Logs VCL ACL evaluation results.

VCL_call - VCL method called

Logs the VCL method name when a VCL method is called.

VCL_return - VCL method return value

Logs the VCL method terminating statement.

VCL_trace - VCL trace data

Logs VCL execution trace data.

The format is:

%u %u.%u
|  |  |
|  |  +- VCL program line position
|  +---- VCL program line number
+------- VCL trace point index

NB: This log record is masked by default.

VSL - VSL API warnings and error message

Warnings and error messages genererated by the VSL API while reading the shared memory log.

WorkThread - Logs thread start/stop events

Logs worker thread creation and termination events.

The format is:

%p %s
|  |
|  +- [start|end]
+---- Worker struct pointer

NB: This log record is masked by default.

TIMESTAMPS

Timestamps are inserted in the log on completing certain events during the worker thread's task handling. The timestamps has a label showing which event was completed. The reported fields show the absolute time of the event, the time spent since the start of the task and the time spent since the last timestamp was logged.

The timestamps logged automatically by Varnish are inserted after completing events that are expected to have delays (e.g. network IO or spending time on a waitinglist). Timestamps can also be inserted from VCL using the std.timestamp() method. If one is doing time consuming tasks in the VCL configuration, it's a good idea to log a timestamp after completing that task. This keeps the timing information in subsequent timestamps from including the time spent on the VCL event.

Request handling timestamps

Start

The start of request processing (first byte received or restart).

Req

Complete client request received.

ReqBody

Client request body processed (discarded, cached or passed to the backend).

Waitinglist

Came off waitinglist.

Fetch

Fetch processing finished (completely fetched or ready for streaming).

Process

Processing finished, ready to deliver the client response.

Resp

Delivery of response to the client finished.

Restart

Client request is being restarted.

Pipe handling timestamps

Pipe

Opened a pipe to the backend and forwarded the request.

PipeSess

The pipe session has finished.

Backend fetch timestamps

Start

Start of the backend fetch processing.

Bereq

Backend request sent.

Beresp

Backend response headers received.

BerespBody

Backend response body received.

Retry

Backend request is being retried.

Error

Backend request failed to vcl_backend_error.

HISTORY

This document was initially written by Poul-Henning Kamp, and later updated by Martin Blix Grydeland.

SEE ALSO

• varnishlog(1)
• varnishhist(1)
• varnishncsa(1)
• varnishtop(1)