# VSL

## Varnish Shared Memory Logging

Manual section: | 7

### 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

      NOTE: This tag is currently not in use in the Varnish log.
      It is mentioned here to document legacy versions of the log,
      or reserved for possible use in future versions.

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 %s %s
      |  |  |  |  |  |
      |  |  |  |  |  +- Local port
      |  |  |  |  +---- Local address
      |  |  |  +------- 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

BackendStart - Backend request start

  Start of backend processing. Logs the backend IP address and port number.

  The format is:

      %s %s
      |  |
      |  +- Backend Port number
      +---- Backend IP4/6 address

Backend_health - Backend health check

  The result of a backend health probe.

  The format is:

      %s %s %s %s %u %u %u %f %f %s
      |  |  |  |  |  |  |  |  |  |
      |  |  |  |  |  |  |  |  |  +- Probe HTTP response / error information
      |  |  |  |  |  |  |  |  +---- Average response time
      |  |  |  |  |  |  |  +------- Response time
      |  |  |  |  |  |  +---------- Probe window size
      |  |  |  |  |  +------------- Probe threshold level
      |  |  |  |  +---------------- Number of good probes in window
      |  |  |  +------------------- Probe window bits
      |  |  +---------------------- "healthy" or "sick"
      |  +------------------------- "Back", "Still" or "Went"
      +---------------------------- Backend name

  Probe window bits are:

      '4': Good IPv4
      '6': Good IPv6
      'U': Good UNIX
      'x': Error Xmit
      'X': Good Xmit
      'r': Error Recv
      'R': Good Recv
      'H': Happy

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.

  Debug messages may be added, changed or removed without prior notice and shouldn’t be considered stable.

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.

  Error messages should be self-explanatory, yet the http connection(HTC) class of errors is reported with these symbols:

  > - junk (-5): Received unexpected data
  > - close (-4): Connection closed
  > - timeout (-3): Timed out
  > - overflow (-2): Buffer/workspace too small
  > - eof (-1): Unexpected end of input
  > - empty (0): Empty response
  > - more (1): More data required
  > - complete (2): Data complete (no error)
  > - idle (3): Connection was closed while idle

  Notice that some HTC errors are never emitted.

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

Filters - Body filters

  List of filters applied to the body.

  > NOTE: This tag is currently not in use in the Varnish log. It is mentioned here to document legacy versions of the log, or reserved for possible use in future versions.

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

H2RxBody - Received HTTP2 frame body
  Binary data
H2RxHdr - Received HTTP2 frame header
  Binary data
H2TxBody - Transmitted HTTP2 frame body
  Binary data
H2TxHdr - Transmitted HTTP2 frame header
  Binary data
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.

  The format is:

      %u %f %f %f
      |  |  |  |
      |  |  |  +- Keep period
      |  |  +---- Grace period
      |  +------- Remaining TTL
      +---------- VXID of the object

HitMiss - Hit for miss object in cache.

  Hit-for-miss object looked up in cache.

  The format is:

      %u %f
      |  |
      |  +- Remaining TTL
      +---- VXID of the object

HitPass - Hit for pass object in cache.

  Hit-for-pass object looked up in cache.

  The format is:

      %u %f
      |  |
      |  +- Remaining TTL
      +---- VXID of the 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.
Notice - Informational messages about request handling
  Informational log messages on events occured during request handling. Lines are prefixed with either [core] or [<VMOD name>]. See the NOTICE MESSAGES section below or the individual VMOD manual pages for detailed information of notice messages.
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

Proxy - PROXY protocol information

  PROXY protocol information.

  The format is:

      %d %s %d %s %d
      |  |  |  |  |
      |  |  |  |  +- server port
      |  |  |  +---- server ip
      |  |  +------- client port
      |  +---------- client ip
      +------------- PROXY protocol version

      All fields are "local" for PROXY local connections (command 0x0)

ProxyGarbage - Unparseable PROXY request
  A PROXY protocol header was unparseable.
ReqAcct - Request handling byte counts

  Contains byte counts for the request handling. The body bytes count includes transmission overhead (ie: chunked encoding). ESI sub-requests show the body bytes this ESI fragment including any subfragments contributed to the top level 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 address, port number and listener endpoint name (from the -a command-line argument).

  The format is:

      %s %s %s
      |  |  |
      |  |  +-- Listener name (from -a)
      |  +----- Client Port number (0 for Unix domain sockets)
      +-------- Client IP4/6 address (0.0.0.0 for UDS)

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

  SessClose is the last record for any client connection.

  The format is:

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

SessError - Client connection accept failed

  Accepting a client connection has failed.

  The format is:

      %s %s %s %d %d %s
      |  |  |  |  |  |
      |  |  |  |  |  +- Detailed error message
      |  |  |  |  +---- Error Number (errno) from accept(2)
      |  |  |  +------- File descriptor number
      |  |  +---------- Local TCP port / 0 for UDS
      |  +------------- Local IPv4/6 address / 0.0.0.0 for UDS
      +---------------- Socket name (from -a argument)

      NOTE: This tag is currently not in use in the Varnish log.
      It is mentioned here to document legacy versions of the log,
      or reserved for possible use in future versions.

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
      |  |  |  +------- Local IPv4/6 address
      |  |  +---------- Socket name (from -a argument)
      |  +------------- Remote TCP port
      +---------------- Remote 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 as well as whether the object is cacheable or not.

  The format is:

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

  The four optional fields are only present in “RFC” headers.

  Examples:

      RFC 60 10 -1 1312966109 1312966109 1312966109 0 60 cacheable
      VCL 120 10 0 1312966111 uncacheable
      HFP 2 0 0 1312966113 uncacheable

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 the TIMESTAMPS section below for information about the individual time stamps.

  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 - VCL 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:

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

  NB: This log record is masked by default.

VCL_use - VCL in use

  Records the name of the VCL being used.

  The format is:

      %s [ %s %s ]
      |    |  |
      |    |  +- Name of label used to find it
      |    +---- "via"
      +--------- Name of VCL put in use

VSL - VSL API warnings and error message
  Warnings and error messages generated by the VSL API while reading the shared memory log.
VfpAcct - Fetch filter accounting

  Contains name of VFP and statistics.

  The format is:

      %s %d %d
      |  |  |
      |  |  +- Total bytes produced
      |  +---- Number of calls made
      +------- Name of filter

  NB: This log record is masked by default.

Witness - Lock order witness records
  Diagnostic recording of locking order.
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.

### NOTICE MESSAGES

Notice messages contain informational messages about the handling of a request. These can be exceptional circumstances encountered that causes deviation from the normal handling. The messages are prefixed with [core] for core Varnish generated messages, or with [<VMOD name>] for VMOD generated messages. The [core] messages are described in detail below, see the individual VMOD documentation for messages from VMODs.

[core] Conditional fetch wait for streaming object
  The backend answered 304 Not Modified on a conditional fetch using an object that has not yet been fully fetched as the stale template object. This can only happen when the TTL of the object is less than the time it takes to fetch it. The fetch is halted until the stale object is fully fetched, upon which the new object is created as normal. While waiting, any grace time on the stale object will be in effect.

### HISTORY

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

### SEE ALSO

- varnishhist
- varnishlog
- varnishncsa
- varnishtop

### COPYRIGHT

This document is licensed under the same licence as Varnish itself. See LICENCE for details.

- Copyright (c) 2006 Verdens Gang AS
- Copyright (c) 2006-2015 Varnish Software AS