一、Tomcat7性能監控與優化

1.   目的

經過優化tomcat提升網站的併發能力。

2.   服務器資源

服務器所能提供CPU、內存、硬盤的性能對處理能力有決定性影響。

3.   優化配置

3.1. 配置tomcat管理員帳戶

在conf/ tomcat-users.xml下添加用戶：

 

<role rolename="manager"/>

<role rolename="manager-gui"/>

<role rolename="admin"/>

<role rolename="admin-gui"/>

<user username="tomcat" password="tomcat" roles="admin-gui,admin,manager-gui,manager"/>

 

啓動tomcat，登陸查看信息：

http://127.0.0.1:8080/

 

3.2. tomcat的3種運行模式

tomcat的運行模式有3種：

一、  bio
默認的模式,性能很是低下,沒有通過任何優化處理和支持.

二、  nio
nio(new I/O)，是Java SE 1.4及後續版本提供的一種新的I/O操做方式(即java.nio包及其子包)。Java nio是一個基於緩衝區、並能提供非阻塞I/O操做的Java API，所以nio也被當作是non-blocking I/O的縮寫。它擁有比傳統I/O操做(bio)更好的併發運行性能。

三、  apr
安裝起來最困難,可是從操做系統級別來解決異步的IO問題,大幅度的提升性能.

3.2.1.   啓動NIO模式

修改server.xml裏的Connector節點,修改protocol爲org.apache.coyote.http11.Http11NioProtocol

 

 

 

3.3. 執行器（線程池）

在tomcat中每個用戶請求都是一個線程，因此可使用線程池提升性能。

 

3.3.1.   開啓而且使用

配置：

 

 

 

 

 

3.3.2.   參數說明

Attribute	Description
threadPriority （優先級）	(int) The thread priority for threads in the executor, the default is 5 (the value of theThread.NORM_PRIORITY constant)
daemon（守護進程）	(boolean) Whether the threads should be daemon threads or not, the default is true
namePrefix（名稱前綴）	(String) The name prefix for each thread created by the executor. The thread name for an individual thread will be namePrefix+threadNumber
maxThreads（最大線程數）	(int) The max number of active threads in this pool, default is 200
minSpareThreads（最小活躍線程數）	(int) The minimum number of threads always kept alive, default is 25
maxIdleTime（空閒線程等待時間）	(int) The number of milliseconds before an idle thread shutsdown, unless the number of active threads are less or equal to minSpareThreads. Default value is 60000(1 minute)
maxQueueSize（最大的等待隊裏數，超過則請求拒絕）	(int) The maximum number of runnable tasks that can queue up awaiting execution before we reject them. Default value is Integer.MAX_VALUE
prestartminSpareThreads （是否在啓動時就生成minSpareThreads個線程）	(boolean) Whether minSpareThreads should be started when starting the Executor or not, the default is false
threadRenewalDelay （重建線程的時間間隔）	(long) If a ThreadLocalLeakPreventionListener is configured, it will notify this executor about stopped contexts. After a context is stopped, threads in the pool are renewed. To avoid renewing all threads at the same time, this option sets a delay between renewal of any 2 threads. The value is in ms, default value is 1000 ms. If value is negative, threads are not renewed. 。重建線程池內的線程時，爲了不線程同時重建，每隔threadRenewalDelay（單位： ms ）重建一個線程。默認值爲1000 ，設置爲負則不重建

3.3.3.   最佳實踐

 

3.4. 鏈接器（Connector）

Connector是Tomcat接收請求的入口，每一個Connector有本身專屬的監聽端口

 

Connector有兩種：HTTP Connector和AJP Connector

3.4.1.   通用屬性（高亮的是重點）

Attribute	Description
allowTrace	A boolean value which can be used to enable or disable the TRACE HTTP method. If not specified, this attribute is set to false. 若是須要服務器可以處理用戶的HAED/TRACE請求，這個值應該設置爲true，默認值是false
asyncTimeout	The default timeout for asynchronous requests in milliseconds. If not specified, this attribute is set to 10000 (10 seconds). 默認超不時候以毫秒爲單位的異步懇求。如果沒有指定，該屬性被設置爲10000（10秒）。
enableLookups	Set to true if you want calls to request.getRemoteHost() to perform DNS lookups in order to return the actual host name of the remote client. Set to false to skip the DNS lookup and return the IP address in String form instead (thereby improving performance). By default, DNS lookups are disabled. 如果你想request.getRemoteHost（）的調用 履行，以便返回的長途客戶端的實際主機名的DNS查詢，則設置爲true。設置爲false時跳過DNS查找，並返回字符串情勢的IP地址（從而提升性能）。默認景象下，禁用DNS查找。
maxHeaderCount	The maximum number of headers in a request that are allowed by the container. A request that contains more headers than the specified limit will be rejected. A value of less than 0 means no limit. If not specified, a default of 100 is used. 容器容許的請求頭字段的最大數目。請求中包含比指定的限制更多的頭字段將被拒絕。值小於0表示沒有限制。若是沒有指定，默認設置爲100。
maxParameterCount	The maximum number of parameter and value pairs (GET plus POST) which will be automatically parsed by the container. Parameter and value pairs beyond this limit will be ignored. A value of less than 0 means no limit. If not specified, a default of 10000 is used. Note that FailedRequestFilter filtercan be used to reject requests that hit the limit. 將被容器自動解析的最大數量的參數和值對（GET加上POST）。參數值對超出此限制將被忽略。值小於0表示沒有限制。若是沒有指定，默認爲10000。請注意， FailedRequestFilter 過濾器能夠用來拒絕達到了極限值的請求。
maxPostSize	The maximum size in bytes of the POST which will be handled by the container FORM URL parameter parsing. The limit can be disabled by setting this attribute to a value less than or equal to 0. If not specified, this attribute is set to 2097152 (2 megabytes). 將被容器以FORM URL參數形式處理的最大長度（以字節爲單位）的POST。經過設置此屬性的值小於或等於0能夠禁用該限制。若是沒有指定，該屬性被設置爲2097152（2兆字節）。
maxSavePostSize	The maximum size in bytes of the POST which will be saved/buffered by the container during FORM or CLIENT-CERT authentication. For both types of authentication, the POST will be saved/buffered before the user is authenticated. For CLIENT-CERT authentication, the POST is buffered for the duration of the SSL handshake and the buffer emptied when the request is processed. For FORM authentication the POST is saved whilst the user is re-directed to the login form and is retained until the user successfully authenticates or the session associated with the authentication request expires. The limit can be disabled by setting this attribute to -1. Setting the attribute to zero will disable the saving of POST data during authentication. If not specified, this attribute is set to 4096 (4 kilobytes). 將被容器在FORM或CLIENT-CERT認證中保存/緩衝的POST的最大尺寸（以字節爲單位）。對於這兩種類型的身份驗證，在用戶身份驗證之 前，POST將被保存/緩衝。對於POST CLIENT-CERT認證，處理該請求的SSL握手和緩衝清空期間，POST將被緩存。對於Form認證，POST將被保存，同時用戶將被重定向到登錄 表單。POST將被一直保留直到用戶成功認證或者認證請求關聯的會話超時。將此屬性設置爲-1能夠禁用此限制。將此屬性設置爲0，POST數據在身份驗證 過程當中將不被保存。若是沒有指定，該屬性設置爲4096（4千字節）。
parseBodyMethods	A comma-separated list of HTTP methods for which request bodies will be parsed for request parameters identically to POST. This is useful in RESTful applications that want to support POST-style semantics for PUT requests. Note that any setting other than POST causes Tomcat to behave in a way that goes against the intent of the servlet specification. The HTTP method TRACE is specifically forbidden here in accordance with the HTTP specification. The default is POST 以逗號分隔的HTTP方法列表，經過方法列表，等同於POST方法，request 正文將被解析成請求參數。這在RESTful應用程序要支持以POST式的語義解析PUT請求中是很是有用的。須要注意的是設置其餘值（不是POST）會致使Tomcat的行爲違反servlet規範的目的。在這裏爲了符合HTTP規範明確禁止HTTP方法TRACE。默認值是POST
port	The TCP port number on which this Connector will create a server socket and await incoming connections. Your operating system will allow only one server application to listen to a particular port number on a particular IP address. If the special value of 0 (zero) is used, then Tomcat will select a free port at random to use for this connector. This is typically only useful in embedded and testing applications. TCP端口號，鏈接器利用該端口號將建立一個服務器套接字，並等待傳入的鏈接。你的操做系統將只容許一個服務器應用程序在一個特定的IP地址偵聽特定的端口號。若是使用特殊值0（零），則Tomcat將爲鏈接器隨機選擇一個空閒的端口。這是一般只用在嵌入式和測試應用程序。
protocol	Sets the protocol to handle incoming traffic. The default value is HTTP/1.1 which uses an auto-switching mechanism to select either a blocking Java based connector or an APR/native based connector. If the PATH (Windows) or LD_LIBRARY_PATH (on most unix systems) environment variables contain the Tomcat native library, the APR/native connector will be used. If the native library cannot be found, the blocking Java based connector will be used. Note that the APR/native connector has different settings for HTTPS than the Java connectors. To use an explicit protocol rather than rely on the auto-switching mechanism described above, the following values may be used: org.apache.coyote.http11.Http11Protocol - blocking Java connector org.apache.coyote.http11.Http11NioProtocol - non blocking Java connector org.apache.coyote.http11.Http11AprProtocol - the APR/native connector. Custom implementations may also be used. Take a look at our Connector Comparison chart. The configuration for both Java connectors is identical, for http and https. For more information on the APR connector and APR specific SSL settings please visit the APR documentation 設置協議來處理傳入流量。默認值是 HTTP/1.1，將使用自動切換機制來選擇阻塞的基於Java的鏈接器或APR /native 爲基礎的鏈接器。若是PATH（Windows）或LD_LIBRARY_PATH（在大多數Unix系統）的環境變量包含在Tomcat的本地庫裏，APR /native 鏈接器將被使用。若是在本地庫中沒法找到，阻斷基於Java的鏈接器將被使用。須要注意的是使用HTTPS比Java鏈接器與APR /native 鏈接器有不一樣的設置。一個明確的協議，而不是依靠上述自動切換機構，可用如下值： org.apache.coyote.http11.Http11Protocol -阻塞式的Java鏈接器 org.apache.coyote.http11.Http11NioProtocol -不阻塞Java鏈接器 org.apache.coyote.http11.Http11AprProtocol的 -的APR / native 鏈接器  也可使用的用戶自定義的實現。看一看在咱們的鏈接器比較圖。Java鏈接器，HTTP和HTTPS，配置是相同的。 APR鏈接器和APR特定的SSL設置的更多信息，請訪問APR文檔
proxyName	If this Connector is being used in a proxy configuration, configure this attribute to specify the server name to be returned for calls to request.getServerName(). See Proxy Support for more information. 若是這個鏈接正在使用的代理服務器配置，配置該屬性指定的服務器的名稱，能夠調用request.getServerName（）返回。有關更多信息，請參見代理支持。
proxyPort	If this Connector is being used in a proxy configuration, configure this attribute to specify the server port to be returned for calls to request.getServerPort(). See Proxy Support for more information. 若是這個鏈接正在使用的代理服務器配置，配置該屬性指定服務器端口，能夠調用request.getServerPort（）返回。有關更多信息，請參見代理支持。
redirectPort	If this Connector is supporting non-SSL requests, and a request is received for which a matching<security-constraint> requires SSL transport, Catalina will automatically redirect the request to the port number specified here. 若是該鏈接器支持非SSL請求，而且接收到的請求爲知足安全約束須要SSL傳輸， Catalina 將自動將請求重定向到指定的端口號。
scheme	Set this attribute to the name of the protocol you wish to have returned by calls torequest.getScheme(). For example, you would set this attribute to "https" for an SSL Connector. The default value is "http". 將該屬性設置爲你想調用request.getScheme（）返回的協議的名稱。例如，對於SSL鏈接器，你會將此屬性設置爲「HTTPS 」。默認值是「 HTTP 」。
secure	Set this attribute to true if you wish to have calls to request.isSecure() to return true for requests received by this Connector. You would want this on an SSL Connector or a non SSL connector that is receiving data from a SSL accelerator, like a crypto card, a SSL appliance or even a webserver. The default value is false. 若是你想調用request.isSecure（）收到此鏈接器的請求返回true，請該該屬性設置爲true。您但願SSL鏈接器或非SSL鏈接器接收數據經過一個SSL加速器，像加密卡，SSL設備，甚至一個web服務器。默認值是假的。
URIEncoding	This specifies the character encoding used to decode the URI bytes, after %xx decoding the URL. If not specified, ISO-8859-1 will be used. 這將指定使用的字符編碼​​，來解碼URI字符。若是沒有指定，ISO-8859-1將被使用。
useBodyEncodingForURI	This specifies if the encoding specified in contentType should be used for URI query parameters, instead of using the URIEncoding. This setting is present for compatibility with Tomcat 4.1.x, where the encoding specified in the contentType, or explicitly set using Request.setCharacterEncoding method was also used for the parameters from the URL. The default value is false. 這指定是否應該用於URI查詢參數，而不是使用URIEncoding contentType中指定的編碼。此設置兼容性Tomcat 4.1.x版（該版在contentType中指定編碼，或者使用request.setCharacterEncoding的方法顯式設置（參數爲 URL傳來的值）。默認值false。
useIPVHosts	Set this attribute to true to cause Tomcat to use the IP address that the request was received on to determine the Host to send the request to. The default value is false. 將該屬性設置爲true會致使Tomcat使用收到請求的IP地址，來肯定將請求發送到哪一個主機。默認值是假的。
xpoweredBy	Set this attribute to true to cause Tomcat to advertise support for the Servlet specification using the header recommended in the specification. The default value is false. 將此屬性設置爲true會致使Tomcat支持使用Servlet規範的通知，（在規範中推薦使用頭字段）。默認值是假的。

 

3.4.2.   標準實現（高亮的是重點）

除了上面列出的常見的鏈接器屬性，標準的HTTP鏈接器（BIO，NIO和APR/native）都支持如下屬性。

 

Attribute	Description
acceptCount	The maximum queue length for incoming connection requests when all possible request processing threads are in use. Any requests received when the queue is full will be refused. The default value is 100. 當全部可能的請求處理線程都在使用時，傳入鏈接請求的最大隊列長度。當隊列滿時收到的任何請求將被拒絕。默認值是100。
acceptorThreadCount	The number of threads to be used to accept connections. Increase this value on a multi CPU machine, although you would never really need more than 2. Also, with a lot of non keep alive connections, you might want to increase this value as well. Default value is 1. 用於接受鏈接的線程的數量。在一個多CPU的機器上，增長該值，雖然你可能不會真正須要超過2個。此外，有不少非保持活動鏈接，您可能須要增長這個值。默認值是 1。
acceptorThreadPriority	The priority of the acceptor threads. The threads used to accept new connections. The default value is 5 (the value of the java.lang.Thread.NORM_PRIORITY constant). See the JavaDoc for the java.lang.Thread class for more details on what this priority means. 接收器線程的優先級。該線程用來接受新的鏈接。默認值是5（java.lang.Thread.NORM_PRIORITY常量）。更多這個優先級是什麼意思的詳細信息，請查看java.lang.Thread的類的JavaDoc 。
address	For servers with more than one IP address, this attribute specifies which address will be used for listening on the specified port. By default, this port will be used on all IP addresses associated with the server. 對於擁有多個IP地址的服務器，該屬性指定哪一個地址將被用於在指定端口上監聽。默認狀況下，該端口將被用於與服務器相關聯的全部IP地址。
bindOnInit	Controls when the socket used by the connector is bound. By default it is bound when the connector is initiated and unbound when the connector is destroyed. If set to false, the socket will be bound when the connector is started and unbound when it is stopped. 控制鏈接器綁定時套接字的使用。缺省狀況，當鏈接器被啓動時套接字被綁定和當鏈接器被銷燬時套接字解除綁定。若是設置爲false，鏈接器啓動時套接字被綁定，鏈接器中止時套接字解除綁定。
compressableMimeType	The value is a comma separated list of MIME types for which HTTP compression may be used. The default value is text/html,text/xml,text/plain. 該值是一個被用於HTTP壓縮的逗號分隔的MIME類型列表。默認值是text / html類型，爲text / xml，text / plain。
compression	The Connector may use HTTP/1.1 GZIP compression in an attempt to save server bandwidth. The acceptable values for the parameter is "off" (disable compression), "on" (allow compression, which causes text data to be compressed), "force" (forces compression in all cases), or a numerical integer value (which is equivalent to "on", but specifies the minimum amount of data before the output is compressed). If the content-length is not known and compression is set to "on" or more aggressive, the output will also be compressed. If not specified, this attribute is set to "off". Note: There is a tradeoff between using compression (saving your bandwidth) and using the sendfile feature (saving your CPU cycles). If the connector supports the sendfile feature, e.g. the NIO connector, using sendfile will take precedence over compression. The symptoms will be that static files greater that 48 Kb will be sent uncompressed. You can turn off sendfile by setting useSendfile attribute of the connector, as documented below, or change the sendfile usage threshold in the configuration of the DefaultServlet in the defaultconf/web.xml or in the web.xml of your web application. 爲了節省服務器帶寬，鏈接器可使用HTTP/1.1 GZIP壓縮。可接受的參數的值是「off 」（禁用壓縮），「on 」（容許壓縮，這會致使文本數據被壓縮），「force 」（強制在全部的狀況下壓縮），或者一個整數值（這是至關於爲「on」，但指定了輸出以前被壓縮的數據最小量）。若是不知道內容長度但被設置爲「on」或更積極的壓縮，輸出的數據也將被壓縮。若是沒有指定，該屬性被設置爲「關」。 注意：這是使用壓縮（節省您的帶寬）和使用sendfile功能（節省你的CPU週期）之間的權衡。若是鏈接器支持sendfile功能，例如NIO鏈接，則使用sendfile將優先於壓縮。症狀是48 KB的靜態文件將未壓縮就發送。你能夠以下文所述經過設置鏈接器的useSendfile屬性來關閉sendfile，或在默認的conf/web.xml或者你的web應用的web.xml中配置DefaultServlet來改變sendfile的使用量閾值。
compressionMinSize	If compression is set to "on" then this attribute may be used to specify the minimum amount of data before the output is compressed. If not specified, this attribute is defaults to "2048". 若是壓縮被設置爲「on」，那麼該屬性能夠用於指定在輸出以前被壓縮的數據的最小量。若是未指定，此屬性默認爲「2048」。
connectionLinger	The number of seconds during which the sockets used by this Connector will linger when they are closed. The default value is -1 which disables socket linger. 鏈接器的套接字被關閉時的逗留秒數。若是沒有指定，將使用默認的JVM。
connectionTimeout	The number of milliseconds this Connector will wait, after accepting a connection, for the request URI line to be presented. Use a value of -1 to indicate no (i.e. infinite) timeout. The default value is 60000 (i.e. 60 seconds) but note that the standard server.xml that ships with Tomcat sets this to 20000 (i.e. 20 seconds). UnlessdisableUploadTimeout is set to false, this timeout will also be used when reading the request body (if any). 在將提交的請求URI行呈現以後，鏈接器將等待接受鏈接的毫秒數。使用值-1表示沒有超時（即無限）。默認值是60000（60秒），但請注意，Tomcat的標準server.xml中，設置爲20000（即20秒）。
connectionUploadTimeout	Specifies the timeout, in milliseconds, to use while a data upload is in progress. This only takes effect if disableUploadTimeout is set to false. 上傳數據過程當中，指定的以毫秒爲單位超時時間。只有在設置disableUploadTimeout爲false有效。
disableUploadTimeout	This flag allows the servlet container to use a different, usually longer connection timeout during data upload. If not specified, this attribute is set to true which disables this longer timeout. 此標誌容許servlet容器在數據上傳時使用不一樣的鏈接超時，一般較長。若是沒有指定，該屬性被設置爲true，禁用上傳超時。
executor	A reference to the name in an Executor element. If this attribute is set, and the named executor exists, the connector will use the executor, and all the other thread attributes will be ignored. Note that if a shared executor is not specified for a connector then the connector will use a private, internal executor to provide the thread pool. 指向Executor元素的引用。若是這個屬性被設置，而且被命名的executor存在，鏈接器將使用這個executor，而其餘全部線程相關屬性將被忽略。請注意共享的executor若是沒有指定到一個鏈接器，則該鏈接器將使用一個私有的，內部的executor來提供線程池。
executorTerminationTimeoutMillis	The time that the private internal executor will wait for request processing threads to terminate before continuing with the process of stopping the connector. If not set, the default is 0 (zero) for the BIO connector and 5000 (5 seconds) for the NIO and APR/native connectors.
keepAliveTimeout	The number of milliseconds this Connector will wait for another HTTP request before closing the connection. The default value is to use the value that has been set for theconnectionTimeout attribute. Use a value of -1 to indicate no (i.e. infinite) timeout. 此鏈接器在關閉鏈接以前將等待另外一個HTTP請求的毫秒數。默認值是使用已設置的connectionTimeout屬性的值。使用值-1表示沒有超時（即無限）。
maxConnections	The maximum number of connections that the server will accept and process at any given time. When this number has been reached, the server will accept, but not process, one further connection. This additional connection be blocked until the number of connections being processed falls below maxConnections at which point the server will start accepting and processing new connections again. Note that once the limit has been reached, the operating system may still accept connections based on the acceptCount setting. The default value varies by connector type. For BIO the default is the value of maxThreads unless anExecutor is used in which case the default will be the value of maxThreads from the executor. For NIO the default is 10000. For APR/native, the default is 8192. Note that for APR/native on Windows, the configured value will be reduced to the highest multiple of 1024 that is less than or equal to maxConnections. This is done for performance reasons. If set to a value of -1, the maxConnections feature is disabled and connections are not counted. 在任何給定的時間服務器接受並處理的最大鏈接數。當這個數字已經達到了，服務器將不會接受任何鏈接，直到鏈接的數量降到低於此值。基於acceptCount的設置，操做系統可能仍然接受鏈接。默認值根據不一樣的鏈接器類型而不一樣。對於BIO，默認的是maxThreads的值，除非使用了Executor，在這種狀況下默認值是executor的maxThreads值 。對於NIO的默認值是10000。APR /native的默認值是8192。 須要注意的是Windows系統的APR/native，所配置的值將減小到小於或等於maxConnections的1024的倍數的最大值。這樣作是出於性能方面的考慮。 若是設置的值-1，maxConnections功能被禁用，並且鏈接數將不作計算。
maxExtensionSize	Limits the total length of chunk extensions in chunked HTTP requests. If the value is -1, no limit will be imposed. If not specified, the default value of 8192 will be used.
maxHttpHeaderSize	The maximum size of the request and response HTTP header, specified in bytes. If not specified, this attribute is set to 8192 (8 KB). 請求和響應的HTTP頭的（以字節爲單位的）最大尺寸。若是沒有指定，該屬性被設置爲8192（8 KB）。
maxKeepAliveRequests	The maximum number of HTTP requests which can be pipelined until the connection is closed by the server. Setting this attribute to 1 will disable HTTP/1.0 keep-alive, as well as HTTP/1.1 keep-alive and pipelining. Setting this to -1 will allow an unlimited amount of pipelined or keep-alive HTTP requests. If not specified, this attribute is set to 100. HTTP請求最大長鏈接個數。將此屬性設置爲1，將禁用HTTP/1.0、以及HTTP/1.1的長鏈接。設置爲-1，不由用。若是沒有指定，該屬性被設置爲100。
maxSwallowSize	The maximum number of request body bytes (excluding transfer encoding overhead) that will be swallowed by Tomcat for an aborted upload. An aborted upload is when Tomcat knows that the request body is going to be ignored but the client still sends it. If Tomcat does not swallow the body the client is unlikely to see the response. If not specified the default of 2097152 (2 megabytes) will be used. A value of less than zero indicates that no limit should be enforced.
maxThreads	The maximum number of request processing threads to be created by this Connector, which therefore determines the maximum number of simultaneous requests that can be handled. If not specified, this attribute is set to 200. If an executor is associated with this connector, this attribute is ignored as the connector will execute tasks using the executor rather than an internal thread pool. 最多同時處理的鏈接數，Tomcat使用線程來處理接收的每一個請求。這個值表示Tomcat可建立的最大的線程數。若是沒有指定，該屬性被設置爲200。若是使用了execute將忽略此鏈接器的該屬性，鏈接器將使用execute，而不是一個內部線程池來處理請求。
maxTrailerSize	Limits the total length of trailing headers in the last chunk of a chunked HTTP request. If the value is -1, no limit will be imposed. If not specified, the default value of 8192will be used. 限制一個分塊的HTTP請求中的最後一個塊的尾隨標頭的總長度。若是該值是-1，沒有限制的被強加。若是沒有指定，默認值是8192。
minSpareThreads	The minimum number of threads always kept running. If not specified, the default of 10 is used. 始終保持運行最小線程數。若是沒有指定，則默認爲10。
noCompressionUserAgents	The value is a regular expression (using java.util.regex) matching the user-agent header of HTTP clients for which compression should not be used, because these clients, although they do advertise support for the feature, have a broken implementation. The default value is an empty String (regexp matching disabled). 該值是一個正則表達式（使用java.util.regex），匹配不該該使用壓縮的HTTP客戶端的用戶代理標頭。由於這些客戶端，雖然他們宣稱支持壓縮功能，但實現不完整。默認值是一個空字符串（正則表達式匹配禁用）。
processorCache	The protocol handler caches Processor objects to speed up performance. This setting dictates how many of these objects get cached. -1 means unlimited, default is 200. If not using Servlet 3.0 asynchronous processing, a good default is to use the same as the maxThreads setting. If using Servlet 3.0 asynchronous processing, a good default is to use the larger of maxThreads and the maximum number of expected concurrent requests (synchronous and asynchronous). 協議處理器緩存Processor對象以提升性能。此設置規定了這些對象有多少能獲得緩存。-1意味着無限制，默認爲200。若是不使用Servlet 3.0的異步處理，一個好的默認是使用maxThreads設置。若是使用Servlet 3.0的異步處理，一個好的默認是使用maxThreads和最大預期的併發請求（同步和異步）的最大值中的較大值。
restrictedUserAgents	The value is a regular expression (using java.util.regex) matching the user-agent header of HTTP clients for which HTTP/1.1 or HTTP/1.0 keep alive should not be used, even if the clients advertise support for these features. The default value is an empty String (regexp matching disabled). 該值是一個正則表達式（使用java.util.regex），匹配用戶代理頭的HTTP瀏覽器將不能使用HTTP/1.1或HTTP/1.0長鏈接，即便該瀏覽器宣稱支持這些功能的。默認值是一個空字符串（正則表達式匹配禁用）。
server	Overrides the Server header for the http response. If set, the value for this attribute overrides the Tomcat default and any Server header set by a web application. If not set, any value specified by the application is used. If the application does not specify a value then Apache-Coyote/1.1 is used. Unless you are paranoid, you won't need this feature. 覆蓋服務器的HTTP響應頭。若是設置了這個屬性的值將覆蓋Web應用程序設置的Tomcat的默認頭和任何服務器頭。若是沒有設置，應用程序指定的任何值將被使用。若是應用程序沒有指定一個值，那麼Apache-Coyote/1.1將被使用。除非你是偏執狂，你將再也不須要此功能。
socketBuffer	The size (in bytes) of the buffer to be provided for socket output buffering. -1 can be specified to disable the use of a buffer. By default, a buffers of 9000 bytes will be used. 爲套接字輸出緩衝而提供的緩衝區的大小（以字節爲單位）。-1能夠被指定來禁止使用的緩衝區。默認狀況下，一個9000個字節的緩衝區將被使用。
SSLEnabled	Use this attribute to enable SSL traffic on a connector. To turn on SSL handshake/encryption/decryption on a connector set this value to true. The default value is false. When turning this value true you will want to set the scheme and the secureattributes as well to pass the correct request.getScheme() and request.isSecure() values to the servlets See SSL Support for more information. 在鏈接器上使用此屬性來啓用SSL加密傳輸。若是要打開SSL握手/加密/解密，請設置true。默認值是false。當設置這個值爲true時，爲了傳遞正確的request.getScheme（）和 request.isSecure（）到servlets，你須要設置scheme和secure屬性。更多信息請查看SSL支持。
tcpNoDelay	If set to true, the TCP_NO_DELAY option will be set on the server socket, which improves performance under most circumstances. This is set to true by default. 若是設置爲true，TCP_NO_DELAY選項將被設置在服務器上的套接字上，在大多數狀況下，這樣能夠提升性能。默認設置爲true。
threadPriority	The priority of the request processing threads within the JVM. The default value is 5(the value of the java.lang.Thread.NORM_PRIORITY constant). See the JavaDoc for thejava.lang.Thread class for more details on what this priority means. 在JVM中請求處理線程的優先級。默認值是5（java.lang.Thread.NORM_PRIORITY常量值）。關於優先級的更多詳細信息，請查看java.lang.Thread的類的JavaDoc 。
upgradeAsyncWriteBufferSize	The default size of the buffer to allocate to for asynchronous writes that can not be completed in a single operation. Data that can't be written immediately will be stored in this buffer until it can be written. If more data needs to be stored than space is available in the buffer than the size of the buffer will be increased for the duration of the write. If not specified the default value of 8192 will be used.

 

3.4.3.    NIO的具體配置

Attribute	Description
pollerThreadCount	(int)The number of threads to be used to run for the polling events. Default value is 1 per processor up to and including version 7.0.27. Default value as of version 7.0.28 is 1 per processor but not more than 2. When accepting a socket, the operating system holds a global lock. So the benefit of going above 2 threads diminishes rapidly. Having more than one thread is for system that need to accept connections very rapidly. However usually just increasing acceptCount will solve that problem. Increasing this value may also be beneficial when a large amount of send file operations are going on. （int）用來處理輪詢事件的線程的數量。在版本7.0.27及之前版本，默認值是每一個處理器1個。版本7.0.28的默認值是每一個處理器1個，但不超過2個。 當接受一個套接字，操做系統擁有全局的鎖。因此超過2個線程的好處而迅速減少。有一個以上的線程是由於系統須要很是迅速地接受鏈接。但一般只要增長acceptCount值就能夠解決這個問題。增長該值也多是有用的，當大量發送文件操做發生的時候。
pollerThreadPriority	(int)The priority of the poller threads. The default value is 5 (the value of thejava.lang.Thread.NORM_PRIORITY constant). See the JavaDoc for the java.lang.Thread class for more details on what this priority means. （int）輪詢線程的優先級。默認值是5（java.lang.Thread.NORM_PRIORITY常量值）。優先級的更多詳細信息，能夠查考java.lang.Thread類的JavaDoc 。
selectorTimeout	(int)The time in milliseconds to timeout on a select() for the poller. This value is important, since connection clean up is done on the same thread, so do not set this value to an extremely high one. The default value is 1000 milliseconds. （int）選擇輪詢器select（）的超時時間（以毫秒爲單位）。這個值很是重要，由於鏈接清理工做也是在同一個線程裏的，因此不要將此值設置爲一個很是高的。默認值是1000毫秒。
useComet	(bool)Whether to allow comet servlets or not. Default value is true. （bool）是否容許Comet servlet。默認值是 true。
useSendfile	(bool)Use this attribute to enable or disable sendfile capability. The default value istrue. （bool）使用此屬性來啓用或禁用sendfile的能力。默認值是true。
socket.directBuffer	(bool)Boolean value, whether to use direct ByteBuffers or java mapped ByteBuffers. Default is false. When you are using direct buffers, make sure you allocate the appropriate amount of memory for the direct memory space. On Sun's JDK that would be something like -XX:MaxDirectMemorySize=256m. （bool）選擇使​​用直接ByteBuffers或Java映射的ByteBuffers。默認是false。 當您使用直接ByteBuffers，請確保你分配適當的內存量給直接內存空間。在Sun的JDK中，配置如-XX：MaxDirectMemorySize = 256M。
socket.appReadBufSize	(int)Each connection that is opened up in Tomcat get associated with a read ByteBuffer. This attribute controls the size of this buffer. By default this read buffer is sized at8192 bytes. For lower concurrency, you can increase this to buffer more data. For an extreme amount of keep alive connections, decrease this number or increase your heap size. （int）在Tomcat中每一個鏈接的開闢鏈接一個讀ByteBuffer。此屬性控制這個緩衝區的大小。默認狀況下，這個讀緩衝區大小爲8192字節。對於較低的併發，你能夠增長這個值以緩衝更多的數據。對於長鏈接數不少的狀況，你須要下降這個數值或者增長堆大小。
socket.appWriteBufSize	(int)Each connection that is opened up in Tomcat get associated with a write ByteBuffer. This attribute controls the size of this buffer. By default this write buffer is sized at8192 bytes. For low concurrency you can increase this to buffer more response data. For an extreme amount of keep alive connections, decrease this number or increase your heap size. The default value here is pretty low, you should up it if you are not dealing with tens of thousands concurrent connections. （int）在Tomcat中每一個鏈接的開闢鏈接一個寫ByteBuffer。此屬性控制這個緩衝區的大小。默認狀況下，這個寫緩衝區大小爲8192字節。對於較低的併發，你能夠增長這個值以緩衝更多的響應數據。對於長鏈接數不少的狀況，你須要下降這個數值或者增長堆大小。 這裏的默認值是至關低的，若是面對的不是幾萬併發鏈接，你應該增大該值。
socket.bufferPool	(int)The NIO connector uses a class called NioChannel that holds elements linked to a socket. To reduce garbage collection, the NIO connector caches these channel objects. This value specifies the size of this cache. The default value is 500, and represents that the cache will hold 500 NioChannel objects. Other values are -1 for unlimited cache and 0 for no cache. （int）NIO鏈接器使用NioChannel這個類來持有連接到一個套接字的元素。爲了減小垃圾收集，NIO鏈接器緩存這些通道的對象。此值指定這個緩存的大小。默認值是500，表示緩存將持有500個 NioChannel的對象。-1表示不限制緩存大小，0表示不緩存。
socket.bufferPoolSize	(int)The NioChannel pool can also be size based, not used object based. The size is calculated as follows: NioChannel buffer size = read buffer size + write buffer size SecureNioChannel buffer size = application read buffer size + application write buffer size + network read buffer size + network write buffer size The value is in bytes, the default value is 1024*1024*100 (100MB). （int）NioChannel池，也能夠是基於尺寸大小，而不是基於對象數的。該大小的計算以下： NioChannel的緩衝區大小=讀取緩衝區大小+寫入緩衝區大小 SecureNioChannel的緩衝區大小=應用程序讀取緩衝區大小+應用程序寫入緩衝區的大小+網絡讀取緩衝區大小+網絡寫入緩衝區的大小 值（以字節爲單位），默認值1024 * 1024 * 100 （100MB）。
socket.processorCache	(int)Tomcat will cache SocketProcessor objects to reduce garbage collection. The integer value specifies how many objects to keep in the cache at most. The default is 500. Other values are -1 for unlimited cache and 0 for no cache. （int）以減小垃圾收集，Tomcat緩存SocketProcessor對象。該值指定保持在緩存中最多有多少個對象。默認值是500。-1表示不限制緩存大小，0表示不緩存。
socket.keyCache	(int)Tomcat will cache KeyAttachment objects to reduce garbage collection. The integer value specifies how many objects to keep in the cache at most. The default is 500. Other values are -1 for unlimited cache and 0 for no cache. （int）以減小垃圾收集，Tomcat緩存KeyAttachment對象。該值指定保持在緩存中最多有多少個對象。默認值是500。-1表示不限制緩存大小，0表示不緩存。
socket.eventCache	(int)Tomcat will cache PollerEvent objects to reduce garbage collection. The integer value specifies how many objects to keep in the cache at most. The default is 500. Other values are -1 for unlimited cache and 0 for no cache. （int）以減小垃圾收集，Tomcat緩存PollerEvent對象。該值指定保持在緩存中最多有多少個對象。默認值是500。-1表示不限制緩存大小，0表示不緩存。
selectorPool.maxSelectors	(int)The max selectors to be used in the pool, to reduce selector contention. Use this option when the command line org.apache.tomcat.util.net.NioSelectorShared value is set to false. Default value is 200. （int）以減小選擇器的爭用，在池中使用的選擇器最大個數。命令行org.apache.tomcat.util.net.NioSelectorShared值設置爲false時，使用此選項。默認值是200。
selectorPool.maxSpareSelectors	(int)The max spare selectors to be used in the pool, to reduce selector contention. When a selector is returned to the pool, the system can decide to keep it or let it be GC'd. Use this option when the command line org.apache.tomcat.util.net.NioSelectorShared value is set to false. Default value is -1 (unlimited). （int）以減小選擇器的爭用，在池中使用的最大備用選擇器個數。當選擇器返回到池中時，系統能夠決定保留它或者讓他垃圾回收。當org.apache.tomcat.util.net.NioSelectorShared 值設置爲false時，使用此選項。默認值是-1（無限制）。
command-line-options	The following command line options are available for the NIO connector: -Dorg.apache.tomcat.util.net.NioSelectorShared=true|false - default is true. Set this value to false if you wish to use a selector for each thread. When you set it to false, you can control the size of the pool of selectors by using the selectorPool.maxSelectors attribute. 下面的命令行選項可用於NIO鏈接器：-Dorg.apache.tomcat.util.net.NioSelectorShared=true|false  默認狀況下是true。若是你想每一個線程使用一個選擇器，將此值設置爲false。當你將它設置爲false，你能夠經過使用selectorPool.maxSelectors屬性控制選擇器池的大小。
oomParachute	(int)The NIO connector implements an OutOfMemoryError strategy called parachute. It holds a chunk of data as a byte array. In case of an OOM, this chunk of data is released and the error is reported. This will give the VM enough room to clean up. The oomParachute represents the size in bytes of the parachute(the byte array). The default value is 1024*1024(1MB). Please note, this only works for OOM errors regarding the Java Heap space, and there is absolutely no guarantee that you will be able to recover at all. If you have an OOM outside of the Java Heap, then this parachute trick will not help. （int）NIO鏈接器實現了一個名叫parachute的OutOfMemoryError錯誤的策略。它擁有一個塊的數據做爲一個字節數組。在一個OOM的狀況下，這個數據塊被釋放，並報告錯誤。這會給VM足夠的空間來清理。oomParachute表明parachute（字節數組）的大小（以字節爲單位）。默認值是 1024 * 1024（1MB）。請注意，這僅適用於關於Java堆空間的OOM錯誤，也不是絕對保證，你將可以恢復全部。若是你有一個Java堆以外OOM的，那麼這個parachute也無濟於事。

3.4.4.   最佳實踐

 

4.   禁用AJP鏈接器

AJP（Apache JServer Protocol）

AJPv13協議是面向包的。WEB服務器和Servlet容器經過TCP鏈接來交互；爲了節省SOCKET建立的昂貴代價，WEB服務器會嘗試維護一個永久TCP鏈接到servlet容器，而且在多個請求和響應週期過程會重用鏈接。

 

 

 

咱們通常是使用Nginx+tomcat的架構，因此用不着AJP協議，因此把AJP鏈接器禁用。

 

 

 

在管理界面中看不到ajp了：

 

 

 

5.   JVM參數的優化

適當調整Tomcat的運行JVM參數能夠提高總體性能。

5.1. JVM內存模型

5.1.1.   Java棧

Java棧是與每個線程關聯的，JVM在建立每個線程的時候，會分配必定的棧空間給線程。它主要用來存儲線程執行過程當中的局部變量，方法的返回值，以及方法調用上下文。棧空間隨着線程的終止而釋放。

5.1.2.   Java堆

Java中堆是由全部的線程共享的一塊內存區域，堆用來保存各類JAVA對象，好比數組，線程對象等。

5.1.3.   Java堆的分區

JVM堆通常又能夠分爲如下三部分：

 

 

 

◆ Young 年輕區（代）

 

Young區被劃分爲三部分，Eden區和兩個大小嚴格相同的Survivor區，其中，Survivor區間中，某一時刻只有其中一個是被使用的，另一個留作垃圾收集時複製對象用，在Eden區間變滿的時候， GC就會將存活的對象移到空閒的Survivor區間中，根據JVM的策略，在通過幾回垃圾收集後，任然存活於Survivor的對象將被移動到Tenured區間。

 

◆ Tenured 年老區

 

Tenured區主要保存生命週期長的對象，通常是一些老的對象，當一些對象在Young複製轉移必定的次數之後，對象就會被轉移到Tenured區，通常若是系統中用了application級別的緩存，緩存中的對象每每會被轉移到這一區間。

 

◆ Perm 永久區

 

Perm代主要保存class,method,filed對象，這部份的空間通常不會溢出，除非一次性加載了不少的類，不過在涉及到熱部署的應用服務器的時候，有時候會遇到java.lang.OutOfMemoryError : PermGen space 的錯誤，形成這個錯誤的很大緣由就有多是每次都從新部署，可是從新部署後，類的class沒有被卸載掉，這樣就形成了大量的class對象保存在了perm中，這種狀況下，通常從新啓動應用服務器能夠解決問題。

 

Virtual區：

最大內存和初始內存的差值，就是Virtual區。

5.1.4.   設置區大小

JVM提供了相應的參數來對內存大小進行配置。正如上面描述，JVM中堆被分爲了3個大的區間，同時JVM也提供了一些選項對Young,Tenured的大小進行控制。

 

 

 

◆ Total Heap

 

-Xms ：指定了JVM初始啓動之後初始化內存

 

-Xmx：指定JVM堆得最大內存，在JVM啓動之後，會分配-Xmx參數指定大小的內存給JVM，可是不必定所有使用，JVM會根據-Xms參數來調節真正用於JVM的內存

 

-Xmx -Xms之差就是三個Virtual空間的大小

 

◆ Young Generation

 

-XX:NewRatio=8意味着tenured 和 young的比值8：1，這樣eden+2*survivor=1/9

 

堆內存

 

-XX:SurvivorRatio=32意味着eden和一個survivor的比值是32：1，這樣一個Survivor就佔Young區的1/34.

 

-Xmn 參數設置了年輕代的大小

 

◆ Perm Generation

 

-XX:PermSize=16M -XX:MaxPermSize=64M

 

Thread Stack

 

-XX:Xss=128K

 

5.2. 經常使用參數

 

修改文件：bin/catalina.sh

 

JAVA_OPTS="-Dfile.encoding=UTF-8 -server -Xms1024m -Xmx1024m -XX:NewSize=512m -XX:MaxNewSize=512m -XX:PermSize=256m -XX:MaxPermSize=256m -XX:NewRatio=2 -XX:MaxTenuringThreshold=50 -XX:+DisableExplicitGC"

 

參數說明：

一、  file.encoding 默認文件編碼

二、  -Xmx1024m  設置JVM最大可用內存爲1024MB

三、  -Xms1024m  設置JVM最小內存爲1024m。此值能夠設置與-Xmx相同，以免每次垃圾回收完成後JVM從新分配內存。

四、  -XX:NewSize  設置年輕代大小

五、  XX:MaxNewSize 設置最大的年輕代大小

六、  -XX:PermSize  設置永久代大小

七、  -XX:MaxPermSize 設置最大永久代大小

八、  -XX:NewRatio=4:設置年輕代（包括Eden和兩個Survivor區）與終身代的比值（除去永久代）。設置爲4，則年輕代與終身代所佔比值爲1：4，年輕代佔整個堆棧的1/5

九、  -XX:MaxTenuringThreshold=0：設置垃圾最大年齡，默認爲：15。若是設置爲0的話，則年輕代對象不通過Survivor區，直接進入年老代。對於年老代比較多的應用，能夠提升效率。若是將此值設置爲一個較大值，則年輕代對象會在Survivor區進行屢次複製，這樣能夠增長對象再年輕代的存活時間，增長在年輕代即被回收的概論。

十、              -XX:+DisableExplicitGC這個將會忽略手動調用GC的代碼使得 System.gc()的調用就會變成一個空調用，徹底不會觸發任何GC

5.3. 在tomcat中設置JVM參數

5.3.1.   windows

修改bin/catalina.bat文件設置參數（第一行）

set JAVA_OPTS=-Dfile.encoding=UTF-8 -server -Xms1024m -Xmx2048m -XX:NewSize=512m -XX:MaxNewSize=1024m -XX:PermSize=256m -XX:MaxPermSize=256m -XX:MaxTenuringThreshold=10 -XX:NewRatio=2 -XX:+DisableExplicitGC

 

 

5.3.2.   linux

修改bin/catalina.sh文件參數（第一行）

JAVA_OPTS="-Dfile.encoding=UTF-8 -server -Xms1024m -Xmx2048m -XX:NewSize=512m -XX:MaxNewSize=1024m -XX:PermSize=256m -XX:MaxPermSize=256m -XX:MaxTenuringThreshold=10 -XX:NewRatio=2 -XX:+DisableExplicitGC"

 

轉載自-- https://www.cnblogs.com/jurendage/p/8426738.html