The page describes the node and balancer part of the CONFIG message.
NODE:
| Key | Description | Default | Max size |
|---|---|---|---|
| JvmRoute | See CONFIG in Mod-Cluster Management Protocol | ||
| Domain | See CONFIG in Mod-Cluster Management Protocol | ||
| Host | See CONFIG in Mod-Cluster Management Protocol | ||
| Port | See CONFIG in Mod-Cluster Management Protocol | ||
| Type | See CONFIG in Mod-Cluster Management Protocol | ||
| flushpackets | Tell how to flush the packets. On: Send immediately, Auto wait for flushwait time before sending, Off don't flush. | Off | |
| flushwait | Time in milliseconds to wait before flushing. | 10 | |
| ping | Time in seconds to wait for a pong answer to a ping. 0 means we don't try to ping before sending. | 10 | |
| smax | soft max inactive connection over that limit after ttl are closed. | MPM configuration | |
| ttl | max time in seconds to life for connection above smax. | 60 | |
| Timeout | Max time in seconds httpd will wait for the backend connection. | 0 |
When a field is not present in the CONFIG message the default value is used in mod_cluster.
BALANCER:
| Key | Description | Default | Max size |
|---|---|---|---|
| Balancer | See CONFIG in Mod-Cluster Management Protocol | ||
| StickySession | Yes: use JVMRoute to stick a request to a node No: ignore JVMRoute | Yes | 3 |
| StickySessionCookie | Name of the cookie containing the "sessionid" | JSESSIONID | 30 |
| StickySessionPath | Name of the parameter containing the "sessionid" | jsessionid | 30 |
| StickySessionRemove | Yes: remove the sessionid (cookie or parameter) when the request can't be routed to the right node No: send it anyway | No | 3 |
| StickySessionForce | Yes: Return an error if the request can't be routed according to JVMRoute No: Route it to another node | Yes | 3 |
| WaitWorker | time in seconds to wait for an available worker. "0": no wait. | 0 | |
| Maxattempts | number of attempts to send the request to the backend server. | 1 |
When a field is not present in the CONFIG message the default value is used in mod_cluster.
Notes on node in httpd internals:
The Notes describe how the httpd internal tables are filled with the above node description.
reslist parameters:
| Parameter | Description | Default |
|---|---|---|
| hmax | size of the connection pool (hard max). Use ap_mpm_query(AP_MPMQ_MAX_THREADS) | |
| smax | soft max inactive connection over that limit after ttl are closed | hmax |
| min | min number of connections to have available. Use 0 | |
| acquire | time in milliseconds to wait for an available connection. Use 0 no wait return error | |
| ttl | max time in seconds to life for connection above smax | 60 |
Those are parameters to the apr_reslist_create() that handles the pool of connections.
keepalive behavior:
keepalive: We force keepalive on.
Others
Other field of the proxy_worker structure will be filled with the default values from mod_proxy.
proxy_worker_stat parameters:
| Parameter | Updated by mod_proxy_cluster | Updated by mod_manager |
|---|---|---|
| status | ||
| error_time | ||
| retries | ||
| lbstatus | ||
| lbfactor | ||
| transferred | ||
| read | ||
| elected | ||
| route | ||
| redirect | ||
| busy | ||
| lbset |
status is filled by STATUS commands.
route is JVMRoute it is filled by CONFIG commands.
This information is in shared memory and the proxy_worker_stat uses a part of this shared memory:
proxy_worker_stat structure:
int status; apr_time_t error_time; /* time of the last error */ int retries; /* number of retries on this worker */ int lbstatus; /* Current lbstatus */ int lbfactor; /* dynamic lbfactor */ apr_off_t transferred;/* Number of bytes transferred to remote */ apr_off_t read; /* Number of bytes read from remote */ apr_size_t elected; /* Number of times the worker was elected */ char route[PROXY_WORKER_MAX_ROUTE_SIZ+1]; char redirect[PROXY_WORKER_MAX_ROUTE_SIZ+1]; void *context; /* general purpose storage */ apr_size_t busy; /* busyness factor */ int lbset; /* load balancer cluster set */
Notes on balancer in httpd internals:
The Notes describe how the httpd internal tables are filled with the above balancer description.
The information from the CONFIG message is packed in the shared memory:
StickySessionCookie and StickySessionPath are stored in sticky and separed by a '|'
StickySession, StickySessionRemove and StickySessionForce are stored in sticky_force
The StickySessionForce forces only to the domain (to node belonging to the same domain) when the node corresponding to the sessionid
belongs to a domain.
max_attempts_set: is set if Maxattemps is in the CONFIG message and its value different from 1.
sticky | sticky_force | timeout | max_attempts | max_attempts_set |
That is what is needed to create the balancer to be able to use it.
proxy_balancer structure extract:
const char *sticky; /* sticky session identifier */ int sticky_force; /* Disable failover for sticky sessions */ apr_interval_time_t timeout; /* Timeout for waiting on free connection */ int max_attempts; /* Number of attempts before failing */ char max_attempts_set;
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