varnishd¶
HTTP accelerator daemon¶
- Manual section
1
SYNOPSIS¶
varnishd [-a address[:port][,PROTO]] [-b host[:port]] [-C] [-d] [-F] [-f config] [-h type[,options]] [-i identity] [-j jail[,jailoptions]] [-l vsl[,vsm]] [-M address:port] [-n name] [-P file] [-p param=value] [-r param[,param…]] [-S secret-file] [-s [name=]kind[,options]] [-T address[:port]] [-t TTL] [-V] [-W waiter]
DESCRIPTION¶
The varnishd daemon accepts HTTP requests from clients, passes them on to a backend server and caches the returned documents to better satisfy future requests for the same document.
OPTIONS¶
- -a <address[:port][,PROTO]>
Listen for client requests on the specified address and port. The address can be a host name (“localhost”), an IPv4 dotted-quad (“127.0.0.1”), or an IPv6 address enclosed in square brackets (“[::1]”). If address is not specified, varnishd will listen on all available IPv4 and IPv6 interfaces. If port is not specified, port 80 (http) is used. An additional protocol type can be set for the listening socket with PROTO. Valid protocol types are: HTTP/1 (default), and PROXY. Multiple listening addresses can be specified by using multiple -a arguments.
- -b <host[:port]>
Use the specified host as backend server. If port is not specified, the default is 8080.
- -C
Print VCL code compiled to C language and exit. Specify the VCL file to compile with the -f option.
- -d
Enables debugging mode: The parent process runs in the foreground with a CLI connection on stdin/stdout, and the child process must be started explicitly with a CLI command. Terminating the parent process will also terminate the child.
- -F
Do not fork, run in the foreground.
- -f config
Use the specified VCL configuration file instead of the builtin default. See VCL for details on VCL syntax.
When neither a -f nor a -b argument are given, varnishd will not start the worker process but process cli commands.
- -h <type[,options]>
Specifies the hash algorithm. See Hash Algorithm section for a list of supported algorithms.
- -i identity
Specify the identity of the Varnish server. This can be accessed using
server.identityfrom VCL.- -j <jail[,jailoptions]>
Specify the jailing mechanism to use. See Jail section.
- -l <vsl[,vsm]>
Specifies size of shmlog file. vsl is the space for the VSL records [80M] and vsm is the space for stats counters [1M]. Scaling suffixes like ‘K’ and ‘M’ can be used up to (G)igabytes. Default is 81 Megabytes.
- -M <address:port>
Connect to this port and offer the command line interface. Think of it as a reverse shell. When running with -M and there is no backend defined the child process (the cache) will not start initially.
- -n name
Specify the name for this instance. Amongst other things, this name is used to construct the name of the directory in which varnishd keeps temporary files and persistent state. If the specified name begins with a forward slash, it is interpreted as the absolute path to the directory which should be used for this purpose.
- -P file
Write the PID of the process to the specified file.
- -p <param=value>
Set the parameter specified by param to the specified value, see List of Parameters for details. This option can be used multiple times to specify multiple parameters.
- -r <param[,param…]>
Make the listed parameters read only. This gives the system administrator a way to limit what the Varnish CLI can do. Consider making parameters such as cc_command, vcc_allow_inline_c and vmod_dir read only as these can potentially be used to escalate privileges from the CLI.
- -S secret-file
Path to a file containing a secret used for authorizing access to the management port. If not provided a new secret will be drawn from the system PRNG. To disable authentication use
none.- -s <[name=]type[,options]>
Use the specified storage backend. See Storage Backend section.
This option can be used multiple times to specify multiple storage files. Names are referenced in logs, VCL, statistics, etc.
- -T <address[:port]>
Offer a management interface on the specified address and port. See Management Interface for a list of management commands.
- -t TTL
Specifies the default time to live (TTL) for cached objects. This is a shortcut for specifying the default_ttl run-time parameter.
- -V
Display the version number and exit.
- -W waiter
Specifies the waiter type to use.
- -x optstring
Print the optstring parameter to
getopt(3)to help writing wrapper scripts.
Hash Algorithm¶
The following hash algorithms are available:
- -h critbit
self-scaling tree structure. The default hash algorithm in Varnish Cache 2.1 and onwards. In comparison to a more traditional B tree the critbit tree is almost completely lockless. Do not change this unless you are certain what you’re doing.
- -h simple_list
A simple doubly-linked list. Not recommended for production use.
- -h <classic[,buckets]>
A standard hash table. The hash key is the CRC32 of the object’s URL modulo the size of the hash table. Each table entry points to a list of elements which share the same hash key. The buckets parameter specifies the number of entries in the hash table. The default is 16383.
Storage Backend¶
The following storage types are available:
- -s <malloc[,size]>
malloc is a memory based backend.
- -s <file,path[,size[,granularity]]>
The file backend stores data in a file on disk. The file will be accessed using mmap.
The path is mandatory. If path points to a directory, a temporary file will be created in that directory and immediately unlinked. If path points to a non-existing file, the file will be created.
If size is omitted, and path points to an existing file with a size greater than zero, the size of that file will be used. If not, an error is reported.
Granularity sets the allocation block size. Defaults to the system page size or the filesystem block size, whichever is larger.
- -s <persistent,path,size>
Persistent storage. Varnish will store objects in a file in a manner that will secure the survival of most of the objects in the event of a planned or unplanned shutdown of Varnish. The persistent storage backend has multiple issues with it and will likely be removed from a future version of Varnish.
Jail¶
Varnish jails are a generalization over various platform specific methods to reduce the privileges of varnish processes. They may have specific options. Available jails are:
- -j solaris
Reduce privileges(5) for varnishd and sub-process to the minimally required set. Only available on platforms which have the setppriv(2) call.
- -j <unix[,user=`user`][,ccgroup=`group`][,workuser=`user`]>
Default on all other platforms when varnishd is started with an effective uid of 0 (“as root”).
With the
unixjail mechanism activated, varnish will switch to an alternative user for subprocesses and change the effective uid of the master process whenever possible.The optional user argument specifies which alternative user to use. It defaults to
varnish.The optional ccgroup argument specifies a group to add to varnish subprocesses requiring access to a c-compiler. There is no default.
The optional workuser argument specifies an alternative user to use for the worker process. It defaults to
vcache.- -j none
last resort jail choice: With jail mechanism
none, varnish will run all processes with the privileges it was started with.
Management Interface¶
If the -T option was specified, varnishd will offer a command-line management interface on the specified address and port. The recommended way of connecting to the command-line management interface is through varnishadm(1).
The commands available are documented in varnish(7).
RUN TIME PARAMETERS¶
Run Time Parameter Flags¶
Runtime parameters are marked with shorthand flags to avoid repeating the same text over and over in the table below. The meaning of the flags are:
experimental
We have no solid information about good/bad/optimal values for this parameter. Feedback with experience and observations are most welcome.
delayed
This parameter can be changed on the fly, but will not take effect immediately.
restart
The worker process must be stopped and restarted, before this parameter takes effect.
reload
The VCL programs must be reloaded for this parameter to take effect.
experimental
We’re not really sure about this parameter, tell us what you find.
wizard
Do not touch unless you really know what you’re doing.
only_root
Only works if varnishd is running as root.
Default Value Exceptions on 32 bit Systems¶
Be aware that on 32 bit systems, certain default values are reduced relative to the values listed below, in order to conserve VM space:
workspace_client: 16k
http_resp_size: 8k
http_req_size: 12k
gzip_stack_buffer: 4k
thread_pool_stack: 64k
List of Parameters¶
This text is produced from the same text you will find in the CLI if you use the param.show command:
accept_filter¶
Units: bool
Default: on
Flags: must_restart
Enable kernel accept-filters (if available in the kernel).
acceptor_sleep_decay¶
Default: 0.9
Minimum: 0
Maximum: 1
Flags: experimental
If we run out of resources, such as file descriptors or worker threads, the acceptor will sleep between accepts. This parameter (multiplicatively) reduce the sleep duration for each successful accept. (ie: 0.9 = reduce by 10%)
acceptor_sleep_incr¶
Units: seconds
Default: 0.000
Minimum: 0.000
Maximum: 1.000
Flags: experimental
If we run out of resources, such as file descriptors or worker threads, the acceptor will sleep between accepts. This parameter control how much longer we sleep, each time we fail to accept a new connection.
acceptor_sleep_max¶
Units: seconds
Default: 0.050
Minimum: 0.000
Maximum: 10.000
Flags: experimental
If we run out of resources, such as file descriptors or worker threads, the acceptor will sleep between accepts. This parameter limits how long it can sleep between attempts to accept new connections.
backend_idle_timeout¶
Units: seconds
Default: 60.000
Minimum: 1.000
Timeout before we close unused backend connections.
ban_dups¶
Units: bool
Default: on
Eliminate older identical bans when a new ban is added. This saves CPU cycles by not comparing objects to identical bans. This is a waste of time if you have many bans which are never identical.
ban_lurker_age¶
Units: seconds
Default: 60.000
Minimum: 0.000
The ban lurker will ignore bans until they are this old. When a ban is added, the active traffic will be tested against it as part of object lookup. This parameter holds the ban-lurker off, until the rush is over.
ban_lurker_batch¶
Default: 1000
Minimum: 1
The ban lurker sleeps ${ban_lurker_sleep} after examining this many objects. Use this to pace the ban-lurker if it eats too many resources.
ban_lurker_sleep¶
Units: seconds
Default: 0.010
Minimum: 0.000
How long the ban lurker sleeps after examining ${ban_lurker_batch} objects. Use this to pace the ban-lurker if it eats too many resources. A value of zero will disable the ban lurker entirely.
between_bytes_timeout¶
Units: seconds
Default: 60.000
Minimum: 0.000
We only wait for this many seconds between bytes received from the backend before giving up the fetch. A value of zero means never give up. VCL values, per backend or per backend request take precedence. This parameter does not apply to pipe’ed requests.
cc_command¶
Default: “exec clang -std=gnu99 -g -O2 -Wall -Werror -Wno-error=unused-result t-Werror t-Wall t-Wno-format-y2k t-W t-Wstrict-prototypes t-Wmissing-prototypes t-Wpointer-arith t-Wreturn-type t-Wcast-qual t-Wwrite-strings t-Wswitch t-Wshadow t-Wunused-parameter t-Wcast-align t-Wchar-subscripts t-Wnested-externs t-Wextra t-Wno-sign-compare -fstack-protector -Wno-pointer-sign -Wno-address -Wno-missing-field-initializers -D_THREAD_SAFE -pthread -fpic -shared -Wl,-x -o %o %s”
Flags: must_reload
Command used for compiling the C source code to a dlopen(3) loadable object. Any occurrence of %s in the string will be replaced with the source file name, and %o will be replaced with the output file name.
cli_buffer¶
Units: bytes
Default: 8k
Minimum: 4k
Size of buffer for CLI command input. You may need to increase this if you have big VCL files and use the vcl.inline CLI command. NB: Must be specified with -p to have effect.
cli_limit¶
Units: bytes
Default: 48k
Minimum: 128b
Maximum: 99999999b
Maximum size of CLI response. If the response exceeds this limit, the response code will be 201 instead of 200 and the last line will indicate the truncation.
cli_timeout¶
Units: seconds
Default: 60.000
Minimum: 0.000
Timeout for the childs replies to CLI requests from the mgt_param.
clock_skew¶
Units: seconds
Default: 10
Minimum: 0
How much clockskew we are willing to accept between the backend and our own clock.
clock_step¶
Units: seconds
Default: 1.000
Minimum: 0.000
How much observed clock step we are willing to accept before we panic.
connect_timeout¶
Units: seconds
Default: 3.500
Minimum: 0.000
Default connection timeout for backend connections. We only try to connect to the backend for this many seconds before giving up. VCL can override this default value for each backend and backend request.
critbit_cooloff¶
Units: seconds
Default: 180.000
Minimum: 60.000
Maximum: 254.000
Flags: wizard
How long the critbit hasher keeps deleted objheads on the cooloff list.
debug¶
Default: none
Enable/Disable various kinds of debugging.
- none
Disable all debugging
Use +/- prefix to set/reset individual bits:
- req_state
VSL Request state engine
- workspace
VSL Workspace operations
- waiter
VSL Waiter internals
- waitinglist
VSL Waitinglist events
- syncvsl
Make VSL synchronous
- hashedge
Edge cases in Hash
- vclrel
Rapid VCL release
- lurker
VSL Ban lurker
- esi_chop
Chop ESI fetch to bits
- flush_head
Flush after http1 head
- vtc_mode
Varnishtest Mode
- witness
Emit WITNESS lock records
- vsm_keep
Keep the VSM file on restart
- failresched
Fail from waiting list
default_grace¶
Units: seconds
Default: 10.000
Minimum: 0.000
Flags: obj_sticky
Default grace period. We will deliver an object this long after it has expired, provided another thread is attempting to get a new copy.
default_keep¶
Units: seconds
Default: 0.000
Minimum: 0.000
Flags: obj_sticky
Default keep period. We will keep a useless object around this long, making it available for conditional backend fetches. That means that the object will be removed from the cache at the end of ttl+grace+keep.
default_ttl¶
Units: seconds
Default: 120.000
Minimum: 0.000
Flags: obj_sticky
The TTL assigned to objects if neither the backend nor the VCL code assigns one.
feature¶
Default: none
Enable/Disable various minor features.
- none
Disable all features.
Use +/- prefix to enable/disable individual feature:
- short_panic
Short panic message.
- wait_silo
Wait for persistent silo.
- no_coredump
No coredumps.
- esi_ignore_https
Treat HTTPS as HTTP in ESI:includes
- esi_disable_xml_check
Don’t check of body looks like XML
- esi_ignore_other_elements
Ignore non-esi XML-elements
- esi_remove_bom
Remove UTF-8 BOM
- https_scheme
Also split https URIs
fetch_chunksize¶
Units: bytes
Default: 16k
Minimum: 4k
Flags: experimental
The default chunksize used by fetcher. This should be bigger than the majority of objects with short TTLs. Internal limits in the storage_file module makes increases above 128kb a dubious idea.
fetch_maxchunksize¶
Units: bytes
Default: 0.25G
Minimum: 64k
Flags: experimental
The maximum chunksize we attempt to allocate from storage. Making this too large may cause delays and storage fragmentation.
first_byte_timeout¶
Units: seconds
Default: 60.000
Minimum: 0.000
Default timeout for receiving first byte from backend. We only wait for this many seconds for the first byte before giving up. A value of 0 means it will never time out. VCL can override this default value for each backend and backend request. This parameter does not apply to pipe.
gzip_buffer¶
Units: bytes
Default: 32k
Minimum: 2k
Flags: experimental
Size of malloc buffer used for gzip processing. These buffers are used for in-transit data, for instance gunzip’ed data being sent to a client.Making this space to small results in more overhead, writes to sockets etc, making it too big is probably just a waste of memory.
gzip_memlevel¶
Default: 8
Minimum: 1
Maximum: 9
Gzip memory level 1=slow/least, 9=fast/most compression. Memory impact is 1=1k, 2=2k, … 9=256k.
http_gzip_support¶
Units: bool
Default: on
- Enable gzip support. When enabled Varnish request compressed objects from the backend and store them compressed. If a client does not support gzip encoding Varnish will uncompress compressed objects on demand. Varnish will also rewrite the Accept-Encoding header of clients indicating support for gzip to:
Accept-Encoding: gzip
Clients that do not support gzip will have their Accept-Encoding header removed. For more information on how gzip is implemented please see the chapter on gzip in the Varnish reference.
http_max_hdr¶
Units: header lines
Default: 64
Minimum: 32
Maximum: 65535
Maximum number of HTTP header lines we allow in {req|resp|bereq|beresp}.http (obj.http is autosized to the exact number of headers). Cheap, ~20 bytes, in terms of workspace memory. Note that the first line occupies five header lines.
http_req_hdr_len¶
Units: bytes
Default: 8k
Minimum: 40b
Maximum length of any HTTP client request header we will allow. The limit is inclusive its continuation lines.
http_req_size¶
Units: bytes
Default: 32k
Minimum: 0.25k
Maximum number of bytes of HTTP client request we will deal with. This is a limit on all bytes up to the double blank line which ends the HTTP request. The memory for the request is allocated from the client workspace (param: workspace_client) and this parameter limits how much of that the request is allowed to take up.
http_resp_hdr_len¶
Units: bytes
Default: 8k
Minimum: 40b
Maximum length of any HTTP backend response header we will allow. The limit is inclusive its continuation lines.
http_resp_size¶
Units: bytes
Default: 32k
Minimum: 0.25k
Maximum number of bytes of HTTP backend response we will deal with. This is a limit on all bytes up to the double blank line which ends the HTTP response. The memory for the response is allocated from the backend workspace (param: workspace_backend) and this parameter limits how much of that the response is allowed to take up.
idle_send_timeout¶
Units: seconds
Default: 60.000
Minimum: 0.000
Flags: delayed
Time to wait with no data sent. If no data has been transmitted in this many seconds the session is closed. See setsockopt(2) under SO_SNDTIMEO for more information.
lru_interval¶
Units: seconds
Default: 2.000
Minimum: 0.000
Flags: experimental
Grace period before object moves on LRU list. Objects are only moved to the front of the LRU list if they have not been moved there already inside this timeout period. This reduces the amount of lock operations necessary for LRU list access.
max_restarts¶
Units: restarts
Default: 4
Minimum: 0
Upper limit on how many times a request can restart. Be aware that restarts are likely to cause a hit against the backend, so don’t increase thoughtlessly.
max_retries¶
Units: retries
Default: 4
Minimum: 0
Upper limit on how many times a backend fetch can retry.
nuke_limit¶
Units: allocations
Default: 50
Minimum: 0
Flags: experimental
Maximum number of objects we attempt to nuke in order to make space for a object body.
pcre_match_limit¶
Default: 10000
Minimum: 1
The limit for the number of calls to the internal match() function in pcre_exec().
(See: PCRE_EXTRA_MATCH_LIMIT in pcre docs.)
This parameter limits how much CPU time regular expression matching can soak up.
pcre_match_limit_recursion¶
Default: 20
Minimum: 1
The recursion depth-limit for the internal match() function in a pcre_exec().
(See: PCRE_EXTRA_MATCH_LIMIT_RECURSION in pcre docs.)
This puts an upper limit on the amount of stack used by PCRE for certain classes of regular expressions.
We have set the default value low in order to prevent crashes, at the cost of possible regexp matching failures.
Matching failures will show up in the log as VCL_Error messages with regexp errors -27 or -21.
Testcase r01576 can be useful when tuning this parameter.
ping_interval¶
Units: seconds
Default: 3
Minimum: 0
Flags: must_restart
Interval between pings from parent to child. Zero will disable pinging entirely, which makes it possible to attach a debugger to the child.
pipe_timeout¶
Units: seconds
Default: 60.000
Minimum: 0.000
Idle timeout for PIPE sessions. If nothing have been received in either direction for this many seconds, the session is closed.
pool_req¶
Default: 10,100,10
Parameters for per worker pool request memory pool. The three numbers are:
- min_pool
minimum size of free pool.
- max_pool
maximum size of free pool.
- max_age
max age of free element.
pool_sess¶
Default: 10,100,10
Parameters for per worker pool session memory pool. The three numbers are:
- min_pool
minimum size of free pool.
- max_pool
maximum size of free pool.
- max_age
max age of free element.
pool_vbo¶
Default: 10,100,10
Parameters for backend object fetch memory pool. The three numbers are:
- min_pool
minimum size of free pool.
- max_pool
maximum size of free pool.
- max_age
max age of free element.
prefer_ipv6¶
Units: bool
Default: off
Prefer IPv6 address when connecting to backends which have both IPv4 and IPv6 addresses.
rush_exponent¶
Units: requests per request
Default: 3
Minimum: 2
Flags: experimental
How many parked request we start for each completed request on the object. NB: Even with the implict delay of delivery, this parameter controls an exponential increase in number of worker threads.
send_timeout¶
Units: seconds
Default: 600.000
Minimum: 0.000
Flags: delayed
Send timeout for client connections. If the HTTP response hasn’t been transmitted in this many seconds the session is closed. See setsockopt(2) under SO_SNDTIMEO for more information.
session_max¶
Units: sessions
Default: 100000
Minimum: 1000
Maximum number of sessions we will allocate from one pool before just dropping connections. This is mostly an anti-DoS measure, and setting it plenty high should not hurt, as long as you have the memory for it.
shm_reclen¶
Units: bytes
Default: 255b
Minimum: 16b
Maximum: 4084
Old name for vsl_reclen, use that instead.
shortlived¶
Units: seconds
Default: 10.000
Minimum: 0.000
Objects created with (ttl+grace+keep) shorter than this are always put in transient storage.
sigsegv_handler¶
Units: bool
Default: on
Flags: must_restart
Install a signal handler which tries to dump debug information on segmentation faults, bus errors and abort signals.
tcp_fastopen¶
Units: bool
Default: off
Flags: must_restart
Enable TCP Fast Open extension (if available in the kernel).
tcp_keepalive_intvl¶
Units: seconds
Default: 75.000
Minimum: 1.000
Maximum: 100.000
Flags: experimental
The number of seconds between TCP keep-alive probes.
tcp_keepalive_probes¶
Units: probes
Default: 8
Minimum: 1
Maximum: 100
Flags: experimental
The maximum number of TCP keep-alive probes to send before giving up and killing the connection if no response is obtained from the other end.
tcp_keepalive_time¶
Units: seconds
Default: 7200.000
Minimum: 1.000
Maximum: 7200.000
Flags: experimental
The number of seconds a connection needs to be idle before TCP begins sending out keep-alive probes.
thread_pool_add_delay¶
Units: seconds
Default: 0.000
Minimum: 0.000
Flags: experimental
Wait at least this long after creating a thread.
Some (buggy) systems may need a short (sub-second) delay between creating threads. Set this to a few milliseconds if you see the ‘threads_failed’ counter grow too much.
Setting this too high results in insuffient worker threads.
thread_pool_destroy_delay¶
Units: seconds
Default: 1.000
Minimum: 0.010
Flags: delayed, experimental
Wait this long after destroying a thread.
This controls the decay of thread pools when idle(-ish).
thread_pool_fail_delay¶
Units: seconds
Default: 0.200
Minimum: 0.010
Flags: experimental
Wait at least this long after a failed thread creation before trying to create another thread.
Failure to create a worker thread is often a sign that the end is near, because the process is running out of some resource. This delay tries to not rush the end on needlessly.
If thread creation failures are a problem, check that thread_pool_max is not too high.
It may also help to increase thread_pool_timeout and thread_pool_min, to reduce the rate at which treads are destroyed and later recreated.
thread_pool_max¶
Units: threads
Default: 5000
Minimum: 100
Flags: delayed
The maximum number of worker threads in each pool.
Do not set this higher than you have to, since excess worker threads soak up RAM and CPU and generally just get in the way of getting work done.
thread_pool_min¶
Units: threads
Default: 100
Maximum: 5000
Flags: delayed
The minimum number of worker threads in each pool.
Increasing this may help ramp up faster from low load situations or when threads have expired.
Minimum is 10 threads.
thread_pool_reserve¶
Units: threads
Default: 0
Maximum: 95
Flags: delayed
The number of worker threads reserved for vital tasks in each pool.
Tasks may require other tasks to complete (for example, client requests may require backend requests). This reserve is to ensure that such tasks still get to run even under high load.
Increasing the reserve may help setups with a high number of backend requests at the expense of client performance. Setting it too high will waste resources by keeping threads unused.
Default is 0 to auto-tune (currently 5% of thread_pool_min). Minimum is 1 otherwise, maximum is 95% of thread_pool_min.
thread_pool_stack¶
Units: bytes
Default: 48k
Minimum: 2k
Flags: delayed
Worker thread stack size. This will likely be rounded up to a multiple of 4k (or whatever the page_size might be) by the kernel.
The required stack size is primarily driven by the depth of the call-tree. The most common relevant determining factors in varnish core code are GZIP (un)compression, ESI processing and regular expression matches. VMODs may also require significant amounts of additional stack. The nesting depth of VCL subs is another factor, although typically not predominant.
The stack size is per thread, so the maximum total memory required for worker thread stacks is in the order of size = thread_pools x thread_pool_max x thread_pool_stack.
Thus, in particular for setups with many threads, keeping the stack size at a minimum helps reduce the amount of memory required by Varnish.
On the other hand, thread_pool_stack must be large enough under all circumstances, otherwise varnish will crash due to a stack overflow. Usually, a stack overflow manifests itself as a segmentation fault (aka segfault / SIGSEGV) with the faulting address being near the stack pointer (sp).
Unless stack usage can be reduced, thread_pool_stack must be increased when a stack overflow occurs. Setting it in 150%-200% increments is recommended until stack overflows cease to occur.
thread_pool_timeout¶
Units: seconds
Default: 300.000
Minimum: 10.000
Flags: delayed, experimental
Thread idle threshold.
Threads in excess of thread_pool_min, which have been idle for at least this long, will be destroyed.
thread_pools¶
Units: pools
Default: 2
Minimum: 1
Flags: delayed, experimental
Number of worker thread pools.
Increasing the number of worker pools decreases lock contention. Each worker pool also has a thread accepting new connections, so for very high rates of incoming new connections on systems with many cores, increasing the worker pools may be required.
Too many pools waste CPU and RAM resources, and more than one pool for each CPU is most likely detrimental to performance.
Can be increased on the fly, but decreases require a restart to take effect.
thread_queue_limit¶
Default: 20
Minimum: 0
Flags: experimental
Permitted request queue length per thread-pool.
This sets the number of requests we will queue, waiting for an available thread. Above this limit sessions will be dropped instead of queued.
thread_stats_rate¶
Units: requests
Default: 10
Minimum: 0
Flags: experimental
Worker threads accumulate statistics, and dump these into the global stats counters if the lock is free when they finish a job (request/fetch etc.) This parameters defines the maximum number of jobs a worker thread may handle, before it is forced to dump its accumulated stats into the global counters.
timeout_idle¶
Units: seconds
Default: 5.000
Minimum: 0.000
Idle timeout for client connections. A connection is considered idle, until we have received the full request headers.
timeout_linger¶
Units: seconds
Default: 0.050
Minimum: 0.000
Flags: experimental
How long the worker thread lingers on an idle session before handing it over to the waiter. When sessions are reused, as much as half of all reuses happen within the first 100 msec of the previous request completing. Setting this too high results in worker threads not doing anything for their keep, setting it too low just means that more sessions take a detour around the waiter.
vcc_unsafe_path¶
Units: bool
Default: on
Allow ‘/’ in vmod & include paths. Allow ‘import … from …’.
vcl_cooldown¶
Units: seconds
Default: 600.000
Minimum: 0.000
How long a VCL is kept warm after being replaced as the active VCL (granularity approximately 30 seconds).
vcl_dir¶
Default: /usr/local/etc/varnish
Directory (or colon separated list of directories) from which relative VCL filenames (vcl.load and include) are to be found.
vmod_dir¶
Default: /usr/local/lib/varnish/vmods
Directory (or colon separated list of directories) where VMODs are to be found.
vsl_buffer¶
Units: bytes
Default: 4k
Minimum: 267
Bytes of (req-/backend-)workspace dedicated to buffering VSL records. Setting this too high costs memory, setting it too low will cause more VSL flushes and likely increase lock-contention on the VSL mutex.
The minimum tracks the vsl_reclen parameter + 12 bytes.
vsl_mask¶
Default: -VCL_trace,-WorkThread,-Hash,-VfpAcct
Mask individual VSL messages from being logged.
- default
Set default value
Use +/- prefix in front of VSL tag name, to mask/unmask individual VSL messages.
vsl_reclen¶
Units: bytes
Default: 255b
Minimum: 16b
Maximum: 4084b
Maximum number of bytes in SHM log record.
The maximum tracks the vsl_buffer parameter - 12 bytes.
vsl_space¶
Units: bytes
Default: 80M
Minimum: 1M
Flags: must_restart
The amount of space to allocate for the VSL fifo buffer in the VSM memory segment. If you make this too small, varnish{ncsa|log} etc will not be able to keep up. Making it too large just costs memory resources.
vsm_free_cooldown¶
Units: seconds
Default: 60.000
Minimum: 10.000
Maximum: 600.000
How long VSM memory is kept warm after a deallocation (granularity approximately 2 seconds).
vsm_space¶
Units: bytes
Default: 1M
Minimum: 1M
Flags: must_restart
The amount of space to allocate for stats counters in the VSM memory segment. If you make this too small, some counters will be invisible. Making it too large just costs memory resources.
workspace_backend¶
Units: bytes
Default: 64k
Minimum: 1k
Flags: delayed
Bytes of HTTP protocol workspace for backend HTTP req/resp. If larger than 4k, use a multiple of 4k for VM efficiency.
workspace_client¶
Units: bytes
Default: 64k
Minimum: 9k
Flags: delayed
Bytes of HTTP protocol workspace for clients HTTP req/resp. If larger than 4k, use a multiple of 4k for VM efficiency.
workspace_session¶
Units: bytes
Default: 0.50k
Minimum: 0.25k
Flags: delayed
Allocation size for session structure and workspace. The workspace is primarily used for TCP connection addresses. If larger than 4k, use a multiple of 4k for VM efficiency.
workspace_thread¶
Units: bytes
Default: 2k
Minimum: 0.25k
Maximum: 8k
Flags: delayed
Bytes of auxiliary workspace per thread. This workspace is used for certain temporary data structures during the operation of a worker thread. One use is for the io-vectors for writing requests and responses to sockets, having too little space will result in more writev(2) system calls, having too much just wastes the space.
EXIT CODES¶
Varnish and bundled tools will, in most cases, exit with one of the following codes
0 OK
1 Some error which could be system-dependent and/or transient
2 Serious configuration / parameter error - retrying with the same configuration / parameters is most likely useless
The varnishd master process may also OR its exit code
with 0x20 when the varnishd child process died,
with 0x40 when the varnishd child process was terminated by a signal and
with 0x80 when a core was dumped.
HISTORY¶
The varnishd daemon was developed by Poul-Henning Kamp in cooperation with Verdens Gang AS and Varnish Software.
This manual page was written by Dag-Erling Smørgrav with updates by Stig Sandbeck Mathisen <ssm@debian.org>, Nils Goroll and others.
COPYRIGHT¶
This document is licensed under the same licence as Varnish itself. See LICENCE for details.
Copyright (c) 2007-2015 Varnish Software AS