add $postgres_error variable

Author: niquola

src/ngx_postgres_module.c

@@ -141,6 +141,10 @@ static ngx_http_variable_t ngx_postgres_module_variables[] = {
       ngx_postgres_variable_query, 0,
       NGX_HTTP_VAR_NOCACHEABLE|NGX_HTTP_VAR_NOHASH, 0 },
 
+    { ngx_string("postgres_error"), NULL,
+      ngx_postgres_variable_error, 0,
+      NGX_HTTP_VAR_NOCACHEABLE|NGX_HTTP_VAR_NOHASH, 0 },
+
     { ngx_null_string, NULL, NULL, 0, 0, 0 }
 };
 

src/ngx_postgres_module.h

@@ -169,6 +169,7 @@ typedef struct {
     ngx_int_t                           var_rows;
     ngx_int_t                           var_affected;
     ngx_str_t                           var_query;
+    ngx_str_t                           var_error;
     ngx_array_t                        *variables;
     ngx_int_t                           status;
 } ngx_postgres_ctx_t;

src/ngx_postgres_processor.c

@@ -290,6 +290,9 @@ ngx_postgres_upstream_get_result(ngx_http_request_t *r, ngx_connection_t *pgxc,
     ExecStatusType   pgrc;
     PGresult        *res;
     ngx_int_t        rc;
+    ngx_postgres_ctx_t  *pgctx;
+    u_char *errormsg;
+    u_char *errorvar;
 
     dd("entering");
 
@@ -331,10 +334,20 @@ ngx_postgres_upstream_get_result(ngx_http_request_t *r, ngx_connection_t *pgxc,
     pgrc = PQresultStatus(res);
     if ((pgrc != PGRES_COMMAND_OK) && (pgrc != PGRES_TUPLES_OK)) {
         dd("receiving result failed");
+
+        pgctx = ngx_http_get_module_ctx(r, ngx_postgres_module);
+
+        errormsg = PQerrorMessage(pgdt->pgconn);
+
         ngx_log_error(NGX_LOG_ERR, pgxc->log, 0,
                       "postgres: failed to receive result: %s: %s",
                       PQresStatus(pgrc),
-                      PQerrorMessage(pgdt->pgconn));
+                      errormsg);
+
+        errorvar = ngx_palloc(r->pool, strlen(errormsg));
+        strcpy(errorvar, errormsg);
+        pgctx->var_error.len = strlen(errorvar);
+        pgctx->var_error.data = errorvar;
 
         PQclear(res);
 

src/ngx_postgres_variable.c

@@ -152,6 +152,32 @@ ngx_postgres_variable_query(ngx_http_request_t *r,
     return NGX_OK;
 }
 
+ngx_int_t
+ngx_postgres_variable_error(ngx_http_request_t *r,
+    ngx_http_variable_value_t *v, uintptr_t data)
+{
+    ngx_postgres_ctx_t  *pgctx;
+
+    dd("entering: \"$postgres_error\"");
+
+    pgctx = ngx_http_get_module_ctx(r, ngx_postgres_module);
+
+    if ((pgctx == NULL) || (pgctx->var_error.len == 0)) {
+        v->not_found = 1;
+        dd("returning NGX_OK (not_found)");
+        return NGX_OK;
+    }
+
+    v->valid = 1;
+    v->no_cacheable = 0;
+    v->not_found = 0;
+    v->len = pgctx->var_error.len;
+    v->data = pgctx->var_error.data;
+
+    dd("returning NGX_OK");
+    return NGX_OK;
+}
+
 ngx_int_t
 ngx_postgres_variable_get_custom(ngx_http_request_t *r,
     ngx_http_variable_value_t *v, uintptr_t data)

src/ngx_postgres_variable.h

@@ -42,6 +42,8 @@ ngx_int_t  ngx_postgres_variable_affected(ngx_http_request_t *,
                ngx_http_variable_value_t *, uintptr_t);
 ngx_int_t  ngx_postgres_variable_query(ngx_http_request_t *,
                ngx_http_variable_value_t *, uintptr_t);
+ngx_int_t  ngx_postgres_variable_error(ngx_http_request_t *,
+               ngx_http_variable_value_t *, uintptr_t);
 ngx_int_t  ngx_postgres_variable_get_custom(ngx_http_request_t *,
                ngx_http_variable_value_t *, uintptr_t);
 ngx_str_t  ngx_postgres_variable_set_custom(ngx_http_request_t *r,