Table of Contents for
Squid: The Definitive Guide
Squid: The Definitive Guide
Published by
O'Reilly Media, Inc., 2004
- Cover
- Squid: The Definitive Guide
- Squid: The Definitive Guide
- Dedication
- Preface
- 1. Introduction
- 2. Getting Squid
- 3. Compiling and Installing
- 4. Configuration Guide for the Eager
- 5. Running Squid
- 6. All About Access Controls
- 7. Disk Cache Basics
- 8. Advanced Disk Cache Topics
- 9. Interception Caching
- 10. Talking to Other Squids
- 11. Redirectors
- 12. Authentication Helpers
- 13. Log Files
- 14. Monitoring Squid
- 15. Server Accelerator Mode
- 16. Debugging and Troubleshooting
- A. Config File Reference
- http_port
- https_port
- ssl_unclean_shutdown
- icp_port
- htcp_port
- mcast_groups
- udp_incoming_address
- udp_outgoing_address
- cache_peer
- cache_peer_domain
- neighbor_type_domain
- icp_query_timeout
- maximum_icp_query_timeout
- mcast_icp_query_timeout
- dead_peer_timeout
- hierarchy_stoplist
- no_cache
- cache_access_log
- cache_log
- cache_store_log
- cache_swap_log
- emulate_httpd_log
- log_ip_on_direct
- cache_dir
- cache_mem
- cache_swap_low
- cache_swap_high
- maximum_object_size
- minimum_object_size
- maximum_object_size_in_memory
- cache_replacement_policy
- memory_replacement_policy
- store_dir_select_algorithm
- mime_table
- ipcache_size
- ipcache_low
- ipcache_high
- fqdncache_size
- log_mime_hdrs
- useragent_log
- referer_log
- pid_filename
- debug_options
- log_fqdn
- client_netmask
- ftp_user
- ftp_list_width
- ftp_passive
- ftp_sanitycheck
- cache_dns_program
- dns_children
- dns_retransmit_interval
- dns_timeout
- dns_defnames
- dns_nameservers
- hosts_file
- diskd_program
- unlinkd_program
- pinger_program
- redirect_program
- redirect_children
- redirect_rewrites_host_header
- redirector_access
- redirector_bypass
- auth_param
- authenticate_ttl
- authenticate_cache_garbage_interval
- authenticate_ip_ttl
- external_acl_type
- wais_relay_host
- wais_relay_port
- request_header_max_size
- request_body_max_size
- refresh_pattern
- quick_abort_min
- quick_abort_max
- quick_abort_pct
- negative_ttl
- positive_dns_ttl
- negative_dns_ttl
- range_offset_limit
- connect_timeout
- peer_connect_timeout
- read_timeout
- request_timeout
- persistent_request_timeout
- client_lifetime
- half_closed_clients
- pconn_timeout
- ident_timeout
- shutdown_lifetime
- acl
- http_access
- http_reply_access
- icp_access
- miss_access
- cache_peer_access
- ident_lookup_access
- tcp_outgoing_tos
- tcp_outgoing_address
- reply_body_max_size
- cache_mgr
- cache_effective_user
- cache_effective_group
- visible_hostname
- unique_hostname
- hostname_aliases
- announce_period
- announce_host
- announce_file
- announce_port
- httpd_accel_host
- httpd_accel_port
- httpd_accel_single_host
- httpd_accel_with_proxy
- httpd_accel_uses_host_header
- dns_testnames
- logfile_rotate
- append_domain
- tcp_recv_bufsize
- err_html_text
- deny_info
- memory_pools
- memory_pools_limit
- forwarded_for
- log_icp_queries
- icp_hit_stale
- minimum_direct_hops
- minimum_direct_rtt
- cachemgr_passwd
- store_avg_object_size
- store_objects_per_bucket
- client_db
- netdb_low
- netdb_high
- netdb_ping_period
- query_icmp
- test_reachability
- buffered_logs
- reload_into_ims
- always_direct
- never_direct
- header_access
- header_replace
- icon_directory
- error_directory
- maximum_single_addr_tries
- snmp_port
- snmp_access
- snmp_incoming_address
- snmp_outgoing_address
- as_whois_server
- wccp_router
- wccp_version
- wccp_incoming_address
- wccp_outgoing_address
- delay_pools
- delay_class
- delay_access
- delay_parameters
- delay_initial_bucket_level
- incoming_icp_average
- incoming_http_average
- incoming_dns_average
- min_icp_poll_cnt
- min_dns_poll_cnt
- min_http_poll_cnt
- max_open_disk_fds
- offline_mode
- uri_whitespace
- broken_posts
- mcast_miss_addr
- mcast_miss_ttl
- mcast_miss_port
- mcast_miss_encode_key
- nonhierarchical_direct
- prefer_direct
- strip_query_terms
- coredump_dir
- ignore_unknown_nameservers
- digest_generation
- digest_bits_per_entry
- digest_rebuild_period
- digest_rewrite_period
- digest_swapout_chunk_size
- digest_rebuild_chunk_percentage
- chroot
- client_persistent_connections
- server_persistent_connections
- pipeline_prefetch
- extension_methods
- request_entities
- high_response_time_warning
- high_page_fault_warning
- high_memory_warning
- ie_refresh
- vary_ignore_expire
- sleep_after_fork
- B. The Memory Cache
- C. Delay Pools
- D. Filesystem Performance Benchmarks
- E. Squid on Windows
- F. Configuring Squid Clients
- About the Author
- Colophon
- Copyright
Name
sleep_after_fork
Synopsis
Squid uses the fork( ) system call to spawn helper processes, such as redirectors,
authenticators, and DNS resolvers. On some systems, a rapid sequence
of fork( ) calls consumes all available
real and virtual memory. Thus, a fork(
) call may fail with an “out of memory” error. Note that
this isn’t necessarily a fatal error. Squid continues running as long
as at least 50% of helper processes are successfully started.
To alleviate this problem, you can instruct Squid to sleep for a
small amount of time after each fork( ) call. This gives
the recently forked process time to complete its exec( ) call and free up the
memory.
Don’t set this value too high, especially if you have a large number of helper processes. Squid doesn’t service any client requests until all helpers have been started.